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The collapse of Diporeia spp. and invasions of dreissenid mussels (zebra, Dreissena polymorpha; quagga, D. bugensis) and round goby (Neogobius melanostomus) have been associated with declines in abundance of native benthic fishes in the Great Lakes, including historically abundant slimy sculpin (Cottus cognatus). We hypothesized that as round goby colonized deeper habitat, slimy sculpin avoided habitat competition, predation, and aggression from round goby by shifting to deeper habitat. Accordingly, we predicted increased depth overlap of slimy sculpin with both round goby and deepwater sculpin (Myoxocephalus thompsonii) that resulted in habitat squeeze by both species. We used long-term bottom trawl data from Lakes Michigan, Huron, and Ontario to evaluate shifts in slimy sculpin depth and their depth overlap with round goby and deepwater sculpin. Lake Huron most supported our hypotheses as slimy sculpin shifted to deeper habitat coincident with the round goby invasion, and depth overlap between slimy sculpin and both species recently increased. Slimy sculpin depth trends in Lakes Michigan and Ontario suggest other ecological and environmental factors better predicted sculpin depth in these lakes.

A comprehensive study based on molecular marker and karyotype analyses has provided evidence for the monophyly of the subfamily Myoxocephalinae, which includes the genera Myoxocephalus, Megalocottus, Microcottus, Porocottus, Enophrys and Argyrocottus. In addition, the karyotype of the threadfoot sculpin Argyrocottus zanderi Herzenstein 1892 has been studied for the first time. Marker traits of karyotypes identified 13 species among six cottid genera. As the molecular genetic results confirmed, the subfamily is divided into two groups corresponding to Enophrys and Myoxocephalus. The molecular genetic data did not support the formation of tribes within the subfamily Myoxocephalinae, as proposed earlier based on morphological characters. Moreover, the genera Trichocottus and Taurocottus should be excluded from the Myoxocephalinae. The evolutionary transformations of karyotypes in cottid fish tended towards a reduction in the number of chromosomes and chromosome arms.

A molecular genetic and karyological study of the frog sculpin Myoxocephalus stelleri Tilesius, 1811 was carried out on an extensive sample from a large area of the species’ range. A total of 42 specimens was sampled from the Sea of Japan, Sea of Okhotsk, and coastal waters off the southern Kuril Islands, which makes this sampling scheme the most comprehensive to date. The level of mtDNA polymorphism was found to be low. The haplotypes of the species formed three phylogenetic groups. The unique M. stelleri haplotype from the coast of Shikotan Island linked all the studied groups, indicating that it is likely ancestral. Robertsonian polymorphism was identified in the species. In all five cytotypes (I – 2n = 44, II – 2n = 43, III – 2n = 42, IV – 2n = 41, V – 2n = 40; NF = 44+2) were identified, all of which were present in the Sea of Japan. Only one (cytotype I) was found in the Sea of Okhotsk, which is probably the closest to the ancestral karyotype. The significant chromosomal polymorphism and the presence of common haplotypes in the studied samples indicate their recent origin from a common ancestor and/or relatively recent contacts within the range. The discrepancies between mtDNA and karyotypes in assigning the ancestral M. stelleri to the coastal waters off Shikotan Island (southern Kuril Islands) and the Sea of Okhotsk, respectively, can be explained by the different inheritance mechanisms and the rates of evolution of molecular genetic and karyological traits.

While decreases in Arctic sea ice affect all marine communities in the Arctic Basin, the effects are greatest on the cryopelagic ecosystem and species with critical life history stages dependent on the presence of sea ice. During the recent and ongoing period of rapid sea ice loss these species have been subject to spatial and temporal disruptions requiring behavioural plasticity. Mandt’s Black Guillemots (Cepphus grylle mandtii) is one of the few ice-obligate Arctic seabirds. Polar cod (Boreogadus saida) is their preferred prey. We monitored their prey selection and diving behaviour during the annual period of chick provisioning from 2011 to 2017, to assess their ability to respond to the now common seasonal loss of sea ice and increased water temperature in their nearshore foraging area. The percentage of polar cod fed to nestlings decreased with increasing SST, with fourhorn sculpin (Myoxocephalus quadricornis), a nearshore demersal, becoming common (20% of deliveries) with SST > 2.0 °C and comprising more than half of the prey when SST > 3.4 °C. This prey-switch coincided with a marked increase in dives and time underwater per day and a decrease in dive duration as birds switched to nearshore, benthic habitats. Sea ice is declining and SST increasing throughout the Arctic Basin and other upper-trophic level predators dependent on polar cod could be expected to be exhibiting similar prey-switching and modifications in foraging effort.

Karyological and molecular genetic study of the sculpins of the genus Myoxocephalus is conducted. Molecular genetic analysis demonstrates that the genus is heterogeneous in the contemporary composition and is divided into Pacific and Arctic-Atlantic groups. In the Pacific group, a close phylogenetic relationship is found between the species M. stelleri, M. polyacanthocephalus, and M. jaok. The representative of the Arctic-Atlantic group, M. quadricornis, is monotypic and sister to Megalocottus platycephalus. Close relations of M. scorpius and the sculpins of the Pacific group are revealed on the basis of the molecular genetic and karyological data. Analysis of M. brandtii, M. ochotensis, and M. jaok from different parts of their habitats shows the absence of karyological variability. The degree and direction of the divergence of the karyotypes in Pacific species M. brandtii, M. ochotensis, M. jaok, M. polyacanthocephalus, M. stelleri, and M. scorpius are established.

Four lake trout, Salvelinus namaycush, Walbaum 1792 morphs occur in Lake Superior: lean, siscowet, humper, and redfin. Diets of lean and siscowet have been relatively well described. However, less is known about diets of humper and redfin, and overall few studies have been conducted at offshore shoals. We compared gut content data among mature (357–867 mm) sympatric lake trout morphs caught at two offshore shoals in Lake Superior, Stannard Rock and Superior Shoal, in 2013 and 2014 (total n = 416). All morphs were caught in shallow ( 100 m) strata. Invertebrates made up a greater portion of the stomach contents than did fish for all morphs by both percent occurrence and proportional biomass, and Mysis was the primary invertebrate consumed by all morphs at both sites. Coregonus spp. and deepwater sculpin, Myoxocephalus thompsonii were the most commonly consumed fish. Humper had the highest average proportional biomass of deepwater sculpin and had no other identifiable species of fish in their guts. Biomass of fish in redfin guts was highest for Coregonus spp., followed by similar amounts of deepwater sculpin and burbot, Lota lota. Diet overlap among morphs was high, and differences in prey consumption between sites are likely related to prey availability. Additional study is needed to determine if differences in trophic ecology between humper and other morphs are sufficient to support concurrent stocking of multiple morphs, particularly in light of recent declines in native prey fishes, especially Coregonus spp., in the Laurentian Great Lakes.

The karyotype of the brightbelly sculpin Microcottus sellaris (Gilbert, 1896) (family Cottidae) from the Sea of Japan and Sea of Okhotsk has been studied for the first time. The karyotype is stable; it includes 42 chromosomes (2 metacentric, 2 submetacentric, 32 subtelocentric, and 6 acrocentric chromosomes); the number of chromosome arms is 46. A comparative analysis of the basic karyotype traits was carried out for M. sellaris and for the Far Eastern species of the genus Myoxocephalus (M. stelleri from the Sea of Japan and Sea of Okhotsk, M. brandtii, M. jaok, M. ochotensis, and M.polyacanthocephalus). The traits that allow differentiation of M. sellaris from species of the genus Myoxocephalus, as well as the common traits indicating their relationship, are identified.

Myoxocephalus quadricornis (Linnaeus, 1758). Fourhorn Sculpin. To 36.5 cm (14.4 in) TL (Mecklenburg et al. 2016). Circumpolar; Arctic coasts of Russia to Gulf of Anadyr; Alaska from Beaufort Sea to Saint Lawrence Island, and northern Bristol Bay, Bering Sea (Mecklenburg et al. 2016). Coastal marine and estuarine waters and ascends rivers as far up as 100 km (62 mi) (Mecklenburg et al. 2016); benthic; depth: at least as shallow as 5 m (16 ft) to 55 m (180 ft) (min.: Personal communication: University of Washington, Burke Museum of Natural History and Culture Fish Collection, Seattle, Washington; max.: Mecklenburg et al. 2016). While recognized in the genus Triglopsis by some authors, genetic data supports classification in Myoxocephalus (Mecklenburg et al. 2018)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 123, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Mecklenburg, C. W., Mecklenburg, T. A., Sheiko, B. A. & Steinke, D. (2016) Pacific Arctic Marine Fishes. Conservation of Arctic Flora and Fauna, Akureyri.","Mecklenburg, C. W., Lynghammar, A., Johannesen, E., Byrkjedal, I., Christiansen, J. S., Dolgov, A. V., Karamushko, O. V., Mecklenburg, T. A., Moller, P. R., Steinke, D. & Wienerrolther, R. M. (2018) Marine Fishes of the Arctic Region. Conservation of Arctic Flora and Fauna, Akureyrl."]}

Myoxocephalus jaok (Cuvier, 1829). Plain Sculpin. To 75 cm (29.5 in) TL (Spies et al. 2012). Seas of Japan and Okhotsk to western and eastern Bering Sea to western Beaufort Sea at least to 71��15���N, 153��07���W to eastern Aleutian Islands, and Limestone Inlet, south-eastern Alaska (Mecklenburg et al. 2016). Benthic; depth: intertidal to 680 m (2,231 ft) (min.: Mecklenburg et al. 2016; max.: Sheiko and Fedorov 2000)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 123, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Spies, I., Ormseth, O. A. & TenBrink, T. T. (2012) Bering Sea and Aleutian Island Sculpins. North Pacific Fisheries Management Council, 2012 North Pacific Groundfish Stock Assessment and","Mecklenburg, C. W., Mecklenburg, T. A., Sheiko, B. A. & Steinke, D. (2016) Pacific Arctic Marine Fishes. Conservation of Arctic Flora and Fauna, Akureyri.","Sheiko, B. A. & Fedorov, V. V. (2000) Chapter 1. Class Cephalaspidomorphi - Lampreys. Class Chondrichthyes - Cartilaginous fishes. Class Holocephali - Chimaeras. Class Osteichthyes - Bony fishes. In: Catalog of Vertebrates of Kamchatka and Adjacent Waters. Kamchatsky Pechatny Dvor, Petropavlovsk-Kamchatsky, Russia, pp. 7 - 69 [In Russian.]"]}

Myoxocephalus niger (Bean, 1881). Warthead Sculpin. To 27 cm (10.6 in) TL (Mecklenburg et al. 2002). Coasts of Sea of Okhotsk, and northern Sea of Japan to Commander���Aleutian Chain, and Pribilof Islands, southern Bering Sea to Sanak and Shumagin Islands, western Gulf of Alaska (Mecklenburg et al. 2002). Benthic; depth: intertidal to 50 m (164 ft) (min.: Mecklenburg et al. 2002; max: Federov et al. 2003)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 123, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Federov, V. V., Chereshnev, I. A., Nazarkin, M. V., Shestakov, A. V. & Volubuev, V. V. (2003) Catalog of Marine and Freshwater Fishes of the Northern Part of the Sea of Okhotsk. Vladivostok, Dolnauka [In Russian]."]}

Myoxocephalus scorpioides (Fabricius, 1780). Arctic Sculpin. To 36.5 cm (14.3 in), SL, 43.5 cm (17.1 in) TL (Personal communication: University of Washington, Burke Museum of Natural History and Culture Fish Collection, Seattle, Washington). Coasts of East Siberian and Chukchi Seas to Gulf of Anadyr, and Norton Sound, Bering Sea, to Beaufort Sea, and along Arctic Canada coasts to Greenland and Gulf of Saint Lawrence in Atlantic (Mecklenburg et al. 2002). Also confirmed 19 th Century records from Bristol Bay (eastern Bering Sea) and Chignik Bay (Gulf of Alaska) (Mecklenburg et al. 2011). Benthic; marine and brackish waters (Fricke et al. 2020); depth: shallow waters near shore to 40 m (131 ft) (Mecklenburg et al. 2016). A much deeper maximum record of 280 m (918 ft) (Coad in Coad and Reist 2018) is without documentation. Male Myoxocephalus scorpius (Linnaeus, 1758) in breeding coloration have often been incorrectly identified (e.g., in museum collections) as M. scorpioides (Catherine W. Mecklenburg, unpubl. data). Boreocottus axillaris Gill, 1859 is a junior synonym (Mecklenburg et al. 2018)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 123, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Mecklenburg, C. W., Moller, P. R. & Steinke, D. (2011) Biodiversity of arctic marine fishes: taxonomy and zoogeography. Marine Biodiversity, 41, 109 - 140. https: // doi. org / 10.1007 / s 12526 - 010 - 0070 - z","Fricke, R., Eschmeyer, W. N. & van der Laan, R. (Eds). 2020. Eschmeyer's Catalog of Fishes: Genera, Species, Reference. Available from: http: // researcharchive. calacademy. org / research / ichthyology / catalog / fishcatmain. asp (accessed 17 April 2021).","Mecklenburg, C. W., Mecklenburg, T. A., Sheiko, B. A. & Steinke, D. (2016) Pacific Arctic Marine Fishes. Conservation of Arctic Flora and Fauna, Akureyri.","Coad, B. W. & Reist, J. D. (Eds.). (2018) Marine Fishes of Arctic Canada. University of Toronto Press, Toronto.","Mecklenburg, C. W., Lynghammar, A., Johannesen, E., Byrkjedal, I., Christiansen, J. S., Dolgov, A. V., Karamushko, O. V., Mecklenburg, T. A., Moller, P. R., Steinke, D. & Wienerrolther, R. M. (2018) Marine Fishes of the Arctic Region. Conservation of Arctic Flora and Fauna, Akureyrl."]}

* Myoxocephalus stelleri Tilesius, 1811. Frog Sculpin. To 62 cm (24.4 in) FL (Kulik et al. 2016). Sea of Japan coast of South Korea to Sea of Okhotsk, east coast of Kamchatka, and Commander Islands. A species endemic to the north-western Pacific (Mecklenburg et al. 2015), only unconfirmed records from Arctic and Alaska (Mecklenburg et al. 2011). Benthic; marine, brackish, and fresh waters (Dyldin and Orlov 2017); depth: intertidal to 65 m (213 ft) (min.: Mecklenburg et al. 2002; max.: Panchenko et al. 2016). Off North America, both Myoxocephalus scorpius and M. polyacanthocephalus have been mistaken for this species (Mecklenburg et al. 2015). Various records of this species in U.S. waters (e.g., Personal communication: University of Washington, Burke Museum of Natural History and Culture Fish Collection, Seattle, Washington) are of other species (Katherine Maslenikov)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 124, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Kulik, V. V. & Gerasimov, N. N. (2016) Length-weight and length-length relationships of 11 fish species fromthe Sea of Okhotsk. Journal of Applied Ichthyology, 32, 1326 - 1328. https: // doi. org / 10.1111 / jai. 13225","Mecklenburg, C. W. & Anderson, M. E. (2015) Reassessment of multiple species of Gymnelus (Teleostei: Zoarcidae) in Pacific Arctic and boreal regions. Zootaxa, 3948, 263 - 278. https: // doi. org / 10.11646 / zootaxa. 3964.2.11","Mecklenburg, C. W., Moller, P. R. & Steinke, D. (2011) Biodiversity of arctic marine fishes: taxonomy and zoogeography. Marine Biodiversity, 41, 109 - 140. https: // doi. org / 10.1007 / s 12526 - 010 - 0070 - z","Dyldin, Yu. V. & Orlov, A. M. (2017) Ichthyofauna of fresh and brackish waters of Sakhalin Island: an annotated list with taxonomic comments: 3. Gadidae - Cruptacanthodidae families. Journal of Ichthyology, 57, 53 - 88. https: // doi. org / 10.1134 / s 0032945217010039","Panchenko, V. V., Kalchugin, P. V. & Solomatov, S. F. (2016) Specification of the habitation depths and maximum sizes for the demersal fish species in the Russian territorial waters of the Sea of Japan. Journal of Ichthyology, 56, 348 - 367. https: // doi. org / 10.1134 / s 0032945216030127"]}

Myoxocephalus polyacanthocephalus (Pallas, 1814). Great Sculpin. To 91.5 cm (36 cm) TL (Datsky 2017). Seas of Japan and Okhotsk to Kamchatka to Commander���Aleutian Chain to northern Chukchi Sea (70��20���N, 163��06���W) (Mecklenburg et al. 2018) to Puget Sound, Washington (Eschmeyer and Herald 1983); northern California (43��05���N) (NWFSC-FRAM). Benthic; depth: intertidal to 825 m (2,707 ft) (min.: Eschmeyer and Herald 1983; max.: Kim 2001). Myoxocephalus ensiger Jordan & Starks, 1904, classified as either a subspecies or junior synonym, may be a valid species (Mecklenburg et al. 2007)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 123, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Datsky, A. V. (2017) Biological features of the common fish species in Olyutorsky-Navarin Region and the adjacent waters of the Bering Sea: 4. Family sculpins (Cottidae). Journal of Ichthyology, 57, 341 - 353. https: // doi. org / 10.1134 / s 0032945217030031","Mecklenburg, C. W., Lynghammar, A., Johannesen, E., Byrkjedal, I., Christiansen, J. S., Dolgov, A. V., Karamushko, O. V., Mecklenburg, T. A., Moller, P. R., Steinke, D. & Wienerrolther, R. M. (2018) Marine Fishes of the Arctic Region. Conservation of Arctic Flora and Fauna, Akureyrl.","Eschmeyer, W. N. & Herald, E. S. (1983) A Field Guide to Pacific Coast Fishes of North America from the Gulf of Alaska to Baja California. Houghton Mifflin, Boston.","Kim, S. T. (2001) Winter migrations of shelf fish to the continental slope of the southwestern Sakhalin. Journal of Ichthyology, 41, 564 - 574.","Mecklenburg, C. W., Stein, D. L., Sheiko, B. A., Chernova, N. V., Mecklenburg, T. A. & Holladay, B. A. (2007) Russian-American long-term census of the Arctic: benthic fishes trawled in the Chukchi Sea and Bering Sea, August 2004. Northwestern Naturalist, 88, 168 - 187. https: // doi. org / 10.1898 / 1051 - 1733 (2007) 88 [168: rlcota] 2.0. co; 2"]}

Myoxocephalus scorpiu s (Linnaeus, 1758). Shorthorn Sculpin or Warty Sculpin. To at least 60 cm (18.3 in) TL (Eriksen et al. 2020) or, but without documention, to 90 cm (35.4 in) TL (Coad and Reist 2004). Circumpolar; Laptev Sea to East Siberian, Chukchi, and Beaufort Seas to Greenland, and northern North Atlantic, and Arctic seas of Europe; Sea of Okhotsk off south-western Kamchatka, Commander, and Aleutian Islands to Bering Sea, and northern British Columbia (Mecklenburg et al. 2016). Benthic; depth: intertidal (McAllister 1975), adults as shallow as 3 m (10 ft) or less (Ennis 1970) to 550 m (1,804 ft) (Mecklenburg et al. 2018). All information other than maximum length and maximum depth from Mecklenburg et al. (2002). Includes records formerly attributed to Myoxocephalus verrucosus (Bean, 1881), as a junior synonym of M. scorpius (Mecklenburg et al. 2002, 2007, 2011; Eschmeyer 2005)., Published as part of Love, Milton S., Bizzarro, Joseph J., Cornthwaite, Maria, Frable, Benjamin W. & Maslenikov, Katherine P., 2021, Checklist of marine and estuarine fishes from the Alaska-Yukon Border, Beaufort Sea, to Cabo San Lucas, Mexico, pp. 1-285 in Zootaxa 5053 (1) on page 123, DOI: 10.11646/zootaxa.5053.1.1, http://zenodo.org/record/5578008, {"references":["Eriksen, E., Benzik, A. N., Dolgov, A. V., Skjoldal, H. R., Vihtakari, M., Johannesen, E., Prokhorova, T. A., Keulder-Stenvik, F., Prokochuk, I. & Strand, S. (2020) Diet and trophic structure of fishes in the Barents Sea: The Norwegian-Russian program \" Year of stomachs \" 2015 - Establishing a baseline. Progress in Oceanography, 183, 102262 https: // doi. org / 10.1016 / j. pocean. 2019.102262","Coad, B. W. & Reist, J. D. (2004) Annotated list of the arctic marine fishes of Canada. Canadian Manuscript Report of Fisheries and Aquatic Sciences, 2674.","Mecklenburg, C. W., Mecklenburg, T. A., Sheiko, B. A. & Steinke, D. (2016) Pacific Arctic Marine Fishes. Conservation of Arctic Flora and Fauna, Akureyri.","McAllister, D. E. (1975) Ecology of the marine fishes of Arctic Canada. Proceedings of the Circumpolar Conference on Northern Ecology. National Research Council of Canada, pp. 49 - 65.","Ennis, G. P. (1970) Reproduction and associated behaviour in the shorthorn sculpin, Myoxocephalus scorpius in Newfoundland waters. Journal of the Fisheries Research Board of Canada, 27, 2037 - 2045.","Mecklenburg, C. W., Lynghammar, A., Johannesen, E., Byrkjedal, I., Christiansen, J. S., Dolgov, A. V., Karamushko, O. V., Mecklenburg, T. A., Moller, P. R., Steinke, D. & Wienerrolther, R. M. (2018) Marine Fishes of the Arctic Region. Conservation of Arctic Flora and Fauna, Akureyrl.","Eschmeyer, W. N. (Ed.). (2005) Catalog of Fishes Online. California Academy of Sciences, San Francisco. www. calacademy. org / research / ichthyology"]}

Myoxocephalus quadricornis lonnbergi Berg, 1916 (Fig. 13) Holotype: ZIN 20691, Lake Ladoga, 45 km north of Konevets Island, July 26, 1905, collected by A.S. Skorikov. Current status: synonym of Myoxocephalus quadricornis (Linnaeus, 1758) (Kottelat, 1997). Counts: D1 8, D2 14, A 15, P 15, C 29, vert. 40 (abdominal 13, caudal 27), pleural ribs absent. Diagnosis: bumps on the upper side of head are poorly developed, posterior bumps are larger than the front ones. Row of bony plates is located closer to dorsal side of body; from occiput to end of first dorsal fin, plates are arranged in one row, then 2 rows which reach vertical in middle of caudal peduncle. Proportional measurements as percentages of standard length (108.7 mm): predorsal length 38.1, preanal length 57.1, maximum body depth 17.4, length of caudal peduncle 14.9, depth of caudal peduncle 5.0, length of first dorsal-fin base 19.4, length of second dorsal-fin base 27.2, length of anal-fin base 23.6, length of longest first dorsal-fin ray 14.3, length of longest second dorsal-fin ray 25.7, length of longest anal-fin ray 13.2, pectoral-fin length 31.5, pelvic-fin length 18.8, distance between first and second dorsal fins 5.4, head length 35.9, postorbital length 18.7, head depth 17.0, head width 36.6, eye horizontal diameter 7.4, snout length 11.9, interorbital width 5.1, upper jaw length 17.1, length of gill slit 21.0., Published as part of Sideleva, Valentina G. & Zhidkov, Zakhar V., 2021, An annotated type catalogue of freshwater sculpins (Cottoidei) described by Lev Berg, pp. 229-242 in Zootaxa 5016 (2) on page 240, DOI: 10.11646/zootaxa.5016.2.4, http://zenodo.org/record/5222048, {"references":["Berg, L. S. (1916) The fishes of fresh waters of the Russian Empire. Izd-vo Departamenta Zemledeliya, Moscow, 563 pp. [in Russian]","Linnaeus, C. (1758) Systema naturae: per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. L. Salvii, Holmiae, 824 pp. https: // doi. org / 10.5962 / bhl. title. 542","Kottelat, M. (1997) European freshwater fishes. An heuristic checklist of the freshwater fishes of Europe (exclusive of former USSR), with an introduction for non-systematists and comments on nomenclature and conservation. Biologia, Bratislava, 52 (5), 1 - 271."]}

Myoxocephalus quadricornis onegensis Berg et Popov, 1932 (Fig. 14) Holotype: ZIN 9026 а, Lake Onega, near city of Petrozavodsk, 1887, collected by A. G��nther. Paratype: ZIN 3842, Lake Onega, 1875, collected by I.S. Polyakov. Counts: D1 8, D2 14, A 14, P 15, C 29, vert. 39 (abdominal 13, caudal 26), one-pair of pleural ribs. Current status: synonym of Myoxocephalus quadricornis (Linnaeus, 1758) (Kottelat, 1997). Diagnosis: bumps on head and bony plates on body are poorly developed or absent. Proportional measurements as percentages of standard length (88.3 mm): predorsal length 38.3, preanal length 59.7, maximum body depth 17.0, length of caudal peduncle 15.3, depth of caudal peduncle 5.5, length of first dorsal-fin base 15.6, length of second dorsal-fin base 25.2, length of anal-fin base 23.5, length of longest first dorsal-fin ray 8.5, length of longest second dorsal-fin ray 13.4, length of longest anal-fin ray 8.9, pectoral-fin length 27.2, pelvic-fin length 13.2, distance between first and second dorsal fins 8.5, head length 35.7, postorbital length 18.2, head depth 16.0, head width 25.6, eye horizontal diameter 8.8, snout length 8.3, interorbital width 3.5, upper jaw length 15.8, length of gill slit 21.2. In this paper, we present for the first time information on the type specimens of cottoid fishes described by Lev S. Berg in 1900-1932. The information given in the catalog can be used for accurate identification and comparative analysis of freshwater cottoid fish in Russia., Published as part of Sideleva, Valentina G. & Zhidkov, Zakhar V., 2021, An annotated type catalogue of freshwater sculpins (Cottoidei) described by Lev Berg, pp. 229-242 in Zootaxa 5016 (2) on page 241, DOI: 10.11646/zootaxa.5016.2.4, http://zenodo.org/record/5222048, {"references":["Berg, L. S. & Popov, A. M. (1932) A review of the forms of Myoxocephalus quadricornis (L.). Reports of the Academy of Science of the U. S. S. R., 1932 (6), 152 - 160.","Linnaeus, C. (1758) Systema naturae: per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. L. Salvii, Holmiae, 824 pp. https: // doi. org / 10.5962 / bhl. title. 542","Kottelat, M. (1997) European freshwater fishes. An heuristic checklist of the freshwater fishes of Europe (exclusive of former USSR), with an introduction for non-systematists and comments on nomenclature and conservation. Biologia, Bratislava, 52 (5), 1 - 271."]}

Foraging characteristics of siscowet lake trout (Salvelinus namaycush siscowet) on deepwater sculpin (Myoxocephalus thompsonii) were studied under ecologically relevant downwelling light intensities (9.0 × 108 to 1.62 × 1011 photons m−2 s−1) and emission spectrum (500–510 nm) on varying substrates (gravel, sand, and black fabric). Siscowet reaction distance within our trials increased with light intensity up to 6.0 × 109 photons m−2 s−1, after which reaction distance remained constant with additional increases in light intensity following the Michaelis–Menten saturation function. Reaction distances were not affected by substrate type under any light intensity. The number of prey captures also increased with increasing light intensity, with most orientations toward prey occurring within the siscowet’s forward sector (± 0°–60°, where 0° represents the tip of the siscowet rostrum). Finally, the overall probability of prey capture was positively related to reaction distance at each light intensity. Results suggest that siscowet can visually forage on benthic prey at great depth in Lake Superior, and reaction distance (≤ 27 cm) to sculpin may not diminish until depths exceed 200 m (6.00 × 109 photons m−2 s−1).

Rapid environmental changes occurring in the Arctic nearshore are expected to have significant effects on food web structures. Land-fast ice cover limits the effectiveness of monitoring methods during winter months, precluding understanding of how seasonal Arctic nearshore food webs operate. Tissue-dependent stable isotope analysis (SIA) offers an efficient and cost-effective approach to monitoring changes in food webs during ice-covered months but requires controlled laboratory experiments to determine isotopic turnover rates and trophic discrimination factors (TDFs) of different tissues. We propose that Arctic Sculpin (Myoxocephalus scorpioides) be used to investigate Arctic nearshore trophodynamics given its opportunistic feeding habits and consistent residence within nearshore Arctic habitats. We present the first tissue-dependent SIA experiment on an Arctic marine fish species and show that δ15N values of fin (or liver) and muscle of Arctic Sculpin may be used to identify shifts in low-trophic-level resource availability between 56 and 122 days before sacrifice. Furthermore, TDFs were determined for carbon isotopes (1.87‰), but results for nitrogen (1.23‰ to 3.23‰) suggest that TDFs in Arctic fish may be highly dependent on lipid content of their diet. We observed similar turnover rates between liver and fin tissues (56 and 58 days, respectively), and suggest it may not be necessary to sample both, making it possible to use Arctic Sculpin for tissue dependent analyses with potentially non-lethal sampling of fin and muscle tissues. The use of Arctic Sculpin as an indicator species can increase the understanding of food web structure and aid in monitoring changes to lower-trophic level prey availability as ecosystem dynamics are affected by climate change.

Organisms ingest microplastics directly from environments and indirectly from food sources. Ingesting microplastics can lead to an organism accumulating plastic-derived chemicals. However, the relative contributions of the two exposure routes (direct ingestion vs. indirect ingestion) to plastic-derived chemical accumulation in an organism are unknown. Using microplastics containing different types of plastic additives, we performed exposure experiments to compare chemical accumulation patterns in fish (Myoxocephalus brandti) between the exposure from the water and prey (Neomysis spp.). We found significantly higher brominated flame retardant concentrations in fish fed microplastic-contaminated prey than fish exposed to microplastics suspended in the water. The results indicate that prey-mediated ingestion of microplastics can be a more significant route for organisms accumulating plastic-derived chemicals, suggesting that organisms at higher trophic levels are more exposed to microplastics and associated chemicals than organisms at lower trophic levels.

Offshore wind farms (OWFs) act as artificial reefs, attracting high abundances of fish, which could potentially increase their local production. This study investigates the feeding ecology of fish species that abundantly occur at artificial habitats, such as OWFs, by examining the short- and the long-term dietary composition of five species: the benthopelagic Gadus morhua and Trisopterus luscus, the pelagic Scomber scombrus and Trachurus trachurus, and the benthic Myoxocephalus scorpioides. We conducted combined stomach content and stable isotope analyses to examine the short- and the time-integrated dietary composition, respectively. Our results indicated that benthopelagic and benthic species utilize artificial reefs, such as OWFs, as feeding grounds for a prolonged period, since both analyses indicated that they exploit fouling organisms occurring exclusively on artificial hard substrates. Trachurus trachurus only occasionally uses artificial reefs as oases of highly abundant resources. Scomber scombrus does not feed on fouling fauna and therefore its augmented presence in OWFs is probably related to reasons other than the enhanced food availability. The long-termed feeding preferences of benthic and benthopelagic species contribute to the hypothesis that the artificial reefs of OWFs could potentially increase the fish production in the area. However, this was not supported for the pelagic species.

Predators ingest microplastics directly from the environment and indirectly via trophic transfer, yet studies have not investigated the contribution of each pathway to microplastic ingestion in fish. We assessed the relative importance of the two exposure routes using mysids (Neomysis spp.) and a benthic fish (Myoxocephalus brandti) as a model prey-predator system. We first exposed the mysids to fluorescent polyethylene beads (27-32 mu m) at concentrations of 200 and 2000 mu g/L. We then exposed the fish to water containing the same concentrations of polyethylene beads or to nine mysids pre-exposed to polyethylene beads. We quantified the size and overall mass of polyethylene beads in mysids and in fish to assess polyethylene beads fragmentation by the mysids. Mysids ingested 2-3 more polyethylene beads from water containing the higher concentration, and fish ingested 3-11 times more polyethylene beads via trophic transfer than from the water column. The percentage of fragmented particles was higher in mysids and in fish fed bead-exposed mysids, suggesting that the mysids can fragment polyethylene beads. Our experiments demonstrate that trophic transfer is a major route of microplastic ingestion by fish and that prey such as mysids can fragment microplastics. Small particles can translocate from the digestive system into tissues and exert adverse physiological effects. Trophic transfer of microplastics may therefore pose more serious threats to organisms at higher trophic levels. (C) 2021 Elsevier Ltd. All rights reserved.

18-28_rDNA_Sculpins.meg: The nucleotide sequences of the rDNA genes. COI_Sculpins: The nucleotide sequences of the COI gene. mt_Genomes_Sculpins: The nucleotide sequences of the complete mitochondrial genomes. Table S1: Sites of specimen collection. Table S2: Species names and GenBank accession numbers. Table S3: The best model of substitution under the maximum likelihood criterion. Text S1: Values of log likelihood, standard deviations of split frequencies, and convergence diagnostic for the rDNA and COI genes.

Relative abundance, diet composition and feeding strategy were determined for three benthic fish, the native deepwater sculpin Myoxocephalus thompsonii (Girard, 1851) and slimy sculpin Cottus cognatus (Richardson, 1836), and the invasive round goby Neogobius melanostomus (Pallas, 1814), along a nearshore to offshore gradient in southeastern Lake Michigan during March–December 2010, 2015, and 2016. Round goby were most abundant in the nearshore ( 75 m). Despite a large degree of spatial separation, some species did overlap, with slimy and deepwater sculpin occurring in sympatry throughout the year in the offshore and transitional zones, and round goby overlapping with both sculpin species seasonally in the transitional zone. Deepwater sculpin exhibited specialization on Mysis diluviana in all depth regions. Slimy sculpin in the offshore reduced diet overlap with deepwater sculpin by specializing on fish eggs during spring and fall, whereas in the transitional depth zone, there was considerable overlap between sculpin species due to the high importance of Mysis in diets. The invasive round goby had a mixed diet, with some diet overlap with native sculpin, especially slimy sculpin, in the transitional zone. In the nearshore zone, round goby displayed a generalized diet with many prey contributing to the diet, but the average contribution of any prey was generally low. Spatial separation and variable feeding strategies help reduce, but not eliminate shared resource use amongst these benthic fish in Lake Michigan.

Fourhorn sculpins (Myoxocephalus quadricornis) and shorthorn sculpins (Myoxocephalus scorpius) have been considered suitable local bioindicators for environmental monitoring studies in the Arctic. Because these species share many characteristics, data from the two species have previously been pooled when assessing marine metal contamination. A chemical and histological study was conducted on fourhorn and shorthorn sculpins collected around a contaminated lead-zinc mine at East Greenland to investigate whether there were any differences in the residues of metals, histopathology and parasites in liver and gills between the two sculpin species. The results demonstrated that concentrations of copper (Cu), zinc (Zn), mercury (Hg) and lead (Pb) were significantly higher in the fourhorn sculpins (p

The karyotype of the great sculpin, Myoxocephalus polyacanthocephalus (Pallas, 1814) (Pisces: Cottidae) from the Sea of Okhotsk and the Sea of Japan has been studied for the first time. The karyotype is stable; it consists of 40 chromosomes (4 metacentric, 2 submeta-subtelocentric, 20 subtelocentric, and 14 acrocentric chromosomes); the number of chromosomal arms is 44 + 2. Nucleolar organizer regions (NOR) are found in the telomeric region of the arm in one homologue of a pair of small metacentric chromosomes, using the Ag-NOR banding technique. A comparative analysis of the karyotype of M. polyacanthocephalus and the karyotypes of other Myoxocephalus species (M. stelleri, M. brandtii, M. jaok, M. ochotensis, and M. scorpius) has been carried out based on the main karyotype characters, as well as on the number and localization of NORs. The identified differences make it possible to differentiate the studied species, whereas the general traits indicate their taxonomic proximity.

Monitoring changes in diets of fish is essential to understanding how food web dynamics respond to changes in native prey abundances. In the Great Lakes, Diporeia, a benthic macroinvertebrate and primary food of native benthivores, declined following the introduction of invasive Dreissena mussels and these changes were reflected in fish diets. We examined the diets of deepwater sculpin Myoxocephalus thompsonii collected in bottom trawls during 2010–2014 in the main basin of Lake Huron, and compared these results to an earlier diet study (2003–2005) to assess if their diets have continued to change after a prolonged period of Dreissena mussel invasion and declined Diporeia densities. Diporeia, Mysis, Bythotrephes, and Chironomidae were consumed regularly and other diet items included ostracods, copepods, sphaerid clams, and fish eggs. The prey-specific index of relative importance calculated for each prey group indicated that Mysis importance increased at shallow (≤55 m) and mid (64–73 m) depths, while Diporeia importance increased offshore (≥82 m). The average number of Diporeia consumed per fish increased by 10.0% and Mysis decreased by 7.5%, while the frequency of occurrence of Diporeia and Mysis remained comparable between time periods. The weight of adult deepwater sculpin (80 mm and 100 mm TL bins) increased between time periods; however, the change in weight was only significant for the 80 mm TL group (p

Non-indigenous species (NIS) can alter food web structure and function in many ways. While the predatory and competitive roles of NIS in aquatic environments are commonly studied, their role as a prey item for native predators is often overlooked. As the northern Baltic Sea lacks native crabs, the omnivorous estuarine Harris mud crab (Rhithropanopeus harrisii) is a novel invader to the system and provides an opportunity to observe how the species enters the prey field of predatory fish. In fall 2013, 1185 stomachs from 17 fish species were dissected and analyzed for the presence of R. harrisii. Fishermen had previously reported finding crabs mostly in the stomachs of perch (Perca fluviatilis), a frequent catch in recreational and commercial fisheries, but our study also found large numbers of crabs in four-horned sculpins (Myoxocephalus quadricornis) and small numbers in other species’ stomachs (Rutilus rutilus, Leuciscus ide, Gymnocephalus cernuus, and Blicca bjoerkna). In the study area occupied by R. harrisii, four-horned sculpins were the most frequent predator, with 83% having at least one crab in their stomach. In comparison, 7% of perch and roach had consumed R. harrisii. Most crabs eaten were 10–12 mm (carapace width), despite broader size range available (1–26 mm). Predation on R. harrisii in this system may be limited by the predators’ gape size (i.e., physical feeding restriction). These results highlight the need to understand the role of novel invasive species as prey items for native species, ultimately increase understanding of whether native predators can control NIS populations. peerReviewed

Many marine species inhabiting icy seawater produce antifreeze proteins (AFPs) to prevent their body fluids from freezing. The sculpin species of the superfamily Cottoidea are widely found from the Arctic to southern hemisphere, some of which are known to express AFP. Here we clarified DNA sequence encoding type I AFP for 3 species of 2 families (Cottidae and Agonidae) belonging to Cottoidea. We also examined antifreeze activity for 3 families and 32 species of Cottoidea (Cottidae, Agonidae, and Rhamphocottidae). These fishes were collected in 2013–2015 from the Arctic Ocean, Alaska, Japan. We could identify 8 distinct DNA sequences exhibiting a high similarity to those reported for Myoxocephalus species, suggesting that Cottidae and Agonidae share the same DNA sequence encoding type I AFP. Among the 3 families, Rhamphocottidae that experience a warm current did not show antifreeze activity. The species inhabiting the Arctic Ocean and Northern Japan that often covered with ice floe showed high activity, while those inhabiting Alaska, Southern Japan with a warm current showed low/no activity. These results suggest that Cottoidea acquires type I AFP gene before dividing into Cottidae and Agonidae, and have adapted to each location with optimal antifreeze activity level.

Seasonal thermal remodelling (acclimatization) and laboratory thermal remodelling (acclimation) can induce different physiological changes in ectothermic animals. As global temperatures are changing at an increasing rate, there is urgency to understand the compensatory abilities of key organs such as the heart to adjust under natural conditions. Thus, the aim of the present study was to directly compare the acclimatization and acclimatory response within a single eurythermal fish species, the European shorthorn sculpin (Myoxocephalus scorpio). We used current- and voltage-clamp to measure ionic current densities in both isolated atrial and ventricular myocytes from three groups of fish: (1) summer-caught fish kept at 12°C (‘summer-acclimated’); (2) summer-caught fish kept at 3°C (‘cold acclimated’); and (3) fish caught in March (‘winter-acclimatized’). At a common test temperature of 7.5°C, action potential (AP) was shortened by both winter acclimatization and cold acclimation compared with summer acclimation; however, winter acclimatization caused a greater shortening than did cold acclimation. Shortening of AP was achieved mostly by a significant increase in repolarizing current density (IKr and IK1) following winter acclimatization, with cold acclimation having only minor effects. Compared with summer acclimation, the depolarizing L-type calcium current (ICa) was larger following winter acclimatization, but again, there was no effect of cold acclimation on ICa. Interestingly, the other depolarizing current, INa, was downregulated at low temperatures. Our further analysis shows that ionic current remodelling is primarily due to changes in ion channel density rather than current kinetics. In summary, acclimatization profoundly modified the electrical activity of the sculpin heart while acclimation to the same temperature for >1.5 months produced very limited remodelling effects. © 2019. Published by The Company of Biologists Ltd. Russian Foundation for Basic Research, RFBR: 18-315-20049 The study was supported by the Russian Foundation for Basic Research (18-315-20049 to D.V.A.).

The study was aimed to determine the diversity and species identification of trematodes family Opecoelidae (Digenea) in sculpins living in shallow waters of Billefjord (Svalbard). Second aim was to determine the affinity between the partenogenetic parasitic larval stages living in whelks (Buccinidae) and adult stages living in sculpins to describe their life cycle. During the work, there were used molecular methods using DNA and phylogeny analysis to identify the species of collected trematodes.

For many years, the sculpin has been utilized as a sentinel monitoring species for anthropogenic impacts on the marine environment. To further develop its potential as a screening model body burden of several trace elements, including cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and selenium (Se), were investigated. In addition, histopathology in shorthorn sculpins (Myoxocephalus scorpius; n = 20) and fourhorn sculpins (Myoxocephalus quadricornis; n = 10) were examined at three sites around the Scoresby Sound settlement in Central East Greenland. Fourhorn sculpins caught at the most distant site from the settlement, contained significantly higher hepatic Cu and Cd concentrations as well as significantly elevated gill Pb levels compared to the shorthorn sculpins collected at two other sites closer to the settlement. Histological examinations showed that fish with significantly higher concentrations of hepatic Cd and Se exhibited greater nuclear alterations, interstitial hyperplasia/hypertrophy, interstitial mononuclear infiltrations and granulomas. Further, fish with higher Cd and Cu gill tissue levels displayed a significantly higher number of cytoplasmic alterations and lamellar epithelium lifting, hypertrophic and hyperplastic epithelium along with mucus cell hyperplasia. While the presence of liver lesions were not species or sex-specific, the presence of gill lesions decreased in the order female fourhorn sculpins > female shorthorn sculpins > male fourhorn sculpins > male shorthorn sculpins. Hepatic Hg concentrations exceeded known lowest observable effect doses (LOED) for fish (0.1–0.5 μg g−1 ww) in 27% of fish, while liver Cd residues in 80% exceeded LOED (0.42–1.8 μg g−1 ww). Based upon these results, data suggest that using the sculpin as a valuable sentinel fish species histopathology may serve as a reliable tool for assessing marine ecosystem exposure to trace metals. However, confounding physiological and ecological factors also need to be considered.

Sculpin fishes belonging to the family Cottidae represent a large and complex group, inhabiting a wide range of freshwater, brackish-water, and marine environments. Numerous studies based on analysis of their morphology and genetic makeup frequently provided controversial results. In the present work, we sequenced complete mitochondrial (mt) genomes and fragments of nuclear ribosomal DNA (rDNA) of the fourhorn sculpin Myoxocephalus quadricornis and some related cottids to increase the power of phylogenetic and taxonomic analyses of this complex fish group. A comparison of the My. quadricornis mt genomes obtained by us with other complete mt genomes available in GenBank has revealed a surprisingly low divergence (3.06 &plusmn, 0.12%) with Megalocottus platycephalus and, at the same time, a significantly higher divergence (7.89 &plusmn, 0.16%) with the species of the genus Myoxocephalus. Correspondingly, phylogenetic analyses have shown that My. quadricornis is clustered with Me. platycephalus but not with the Myoxocephalus species. Completely consistent patterns of divergence and tree topologies have been obtained based on nuclear rDNA. Thus, the multi-gene data in the present work indicates obvious contradictions in the relationships between the Myoxocephalus and Megalocottus species studied. An extensive phylogenetic analysis has provided evidence for a closer affinity of My. quadricornis with the species of the genus Megalocottus than with the species of the genus Myoxocephalus. A recombination analysis, along with the additional GenBank data, excludes introgression and/or incorrect taxonomic identification as the possible causative factors responsible for the observed closer affinity between the two species from different genera. The above facts necessitate realignment of the genera Myoxocephalus and Megalocottus. The genetic data supports the two recognized genera, Myoxocephalus and Megalocottus, but suggests changing their compositions through transferring My. quadricornis to the genus Megalocottus. The results of the present study resolve the relationships within a complex group of sculpin fishes and show a promising approach to phylogenetic systematics (as a key organizing principle in biodiversity research) for a better understanding of the taxonomy and evolution of fishes and for supplying relevant information to address various fish biodiversity conservation and management issues.

Due to a mistake during the production process, the online/HTML version of the original article was published under the terms of the Creative Commons Attribution 4.0 International License. The article is not open access and no special license applies. The original article has been corrected.

Gene expression of antifreeze proteins (AFPs) facilitates various species of fish to survive in near-freezing seawater. The marine sculpin genus Myoxocephalus (Teleostei; Perciformes) is widely distributed from Arctic to Subarctic and is known to express type I AFP. Here, we clarify gene structures and the antifreeze activity of three Myoxocephalus species and discuss their cold adaptation and their geographic movements across a global-level time scale. These fishes were collected during winter in 2014–2015 at Hokkaido and Alaska. A total of 14–16 amino acid sequences were determined as type I AFP, some of which exhibit the same amino acid sequence among species. The Subarctic species contains many amino acid sequences, and the antifreeze activities are lowest. In contrast, the Arctic species contains a few active proteins. Mitochondrial DNA analysis suggests that the Atlantic and Arctic species migrated to those oceans 7.9 and 3.0 million years ago (Mya), respectively. Since the AFP sequences of Myoxocephalus are similar to each other regardless of their difference in the timing of migration, the ancestral species of this genus may have developed the AFP gene(s) approximately 7.9 Mya, before speciation within the genus. It is speculated that these sculpins survived the cold environment in the Arctic Ocean during the Pliocene–Pleistocene by acquisition of the type I AFP in their body fluids.

There is inadequate morphological nomenclature and definition of organ pathology when using wild fish in biomonitoring of environmental pollution. The aim of this investigation was to provide a guide that assesses histology of Shorthorn (Myoxocephalus scorpius) and Fourhorn (Myoxocephalus quadricornis) sculpins obtained from a study using these two fish species as bioindicator organisms to evaluate environmental impact attributed to a dumpsite located in East Greenland. Specific histopathological lesions were quantified on the basis of Bernet et al. and all lesions were photomicrographed, evaluated, and placed into specific categories of five reaction patterns. These were circulatory disturbances, regressive changes, progressive alterations, inflammation, and tumors based on anatomical location, type, and severity. This method is postulated to enable an objective assessment of the histological integrity of fish gills and liver; thus, making it possible to compare sculpin pathology and reaction patterns at different locations. Data suggest that this updated histological guide might be used for identification and quantification of histological lesions when applying sculpins in biomonitoring programs in Greenland and other Arctic regions.

The former lead-zinc mine at Mestersvig, Greenland, continues to contaminate the surrounding environment despite its operations ceasing over 50 years ago. Elevated concentrations of heavy metals are found in water, sediment and biota in the terrestrial, freshwater and marine environments. To shed light on the present contamination and its potential effects on local fish we investigated gill and liver histology of sculpins (Myoxocephalus spp.) around the former mining area. Two species of sculpins were caught; shorthorn sculpins (M. scorpius; n = 16) and fourhorn sculpins (M. quadricornis; n = 17) at a contaminated site, Nyhavn, and shorthorn sculpins (M. scorpius; n = 25) at the reference site. In a previous study we found histopathological changes in the tissues of the sculpins, and we suspected this to be related to elevated heavy metal tissue concentrations. Concentrations of Fe, Hg, Mn, Pb, Se and Zn were significantly higher in sculpins at Nyhavn compared to the reference site. Reference NOED and LOEC thresholds for biochemistry, tissue lesions, growth, survival and reproduction for hepatic Hg, As, Cd and Pb from the ERED database were exceeded in both sculpin species. Histopathological investigations of the sculpins gills revealed significant increases in the prevalence of hyperplastic epithelium, inflammation, intensity of neutral and total mucus cells and chloride cells along with an increased infection of colonial Peritricha. At the contaminated Nyhavn site, fourhorn sculpins had a significantly higher prevalence of chondroplastic tissue and intensity of neutral, mixed and total mucus cells in the gills compared to the shorthorn sculpins. The data indicate that both sculpin species could be useful indicator species for environmental monitoring of metal pollution in Arctic areas. However, confounding effects of gender and species should be investigated further. Effects on other biomarkers as well as baseline measurements should be included in future environmental monitoring efforts around mining activities in Greenland.

During periods of environmental stress a number of different anuran species employ adaptive strategies to promote survival. Our study found that in response to dehydration (i.e., loss of total body water content), the African clawed frog (Xenopus laevis) increased the expression of a novel gene (drp10) that encodes a structural homolog of the freeze-responsive FR10 protein found in wood frogs. Similar to FR10, the DRP10 protein was found to also contain a highly conserved N-terminal cleavable signal peptide. Furthermore, DRP10 was found to have high structural homology to the available crystal structures of type A and E apolipoproteins in Homo sapiens, and a type IV LS-12 anti-freeze protein in the longhorn sculpin, Myoxocephalus octodecemspinosis. In response to dehydration, the transcript expression of drp10 was found to increase 1.52 ± 0.16-fold and 1.97 ± 0.11-fold in response to medium (15%) and high (30%) dehydration stresses in the liver tissue of X. laevis, respectively, while drp10 expression increased 2.12 ± 0.12-fold and 1.46 ± 0.16-fold in kidney tissue. Although the molecular function of both dehydration-responsive DRP10 and the freeze-responsive FR10 have just begun to be elucidated, it is likely that both are frog-specific proteins that likely share a similar purpose during water-related stresses. J. Exp. Zool. 323A: 375–381, 2015. © 2015 Wiley Periodicals, Inc.

Using various available time series for Lake Michigan, we examined changes in the Lake Michigan food web following the dreissenid mussel invasions and identified those changes most likely attributable to these invasions, thereby providing a synthesis. Expansion of the quagga mussel ( Dreissena rostriformis bugensis ) population into deeper waters, which began around 2004, appeared to have a substantial predatory effect on both phytoplankton abundance and primary production, with annual primary production in offshore (> 50 m deep) waters being reduced by about 35% by 2007. Primary production likely decreased in nearshore waters as well, primarily due to predatory effects exerted by the quagga mussel expansion. The drastic decline in Diporeia abundance in Lake Michigan during the 1990s and 2000s has been attributed to dreissenid mussel effects, but the exact mechanism by which the mussels were negatively affecting Diporeia abundance remains unknown. In turn, decreased Diporeia abundance was associated with reduced condition, growth, and/or energy density in alewife ( Alosa pseudoharengus ), lake whitefish ( Coregonus clupeaformis ), deepwater sculpin ( Myoxocephalus thompsonii ), and bloater ( Coregonus hoyi ). However, lake-wide biomass of salmonines, top predators in the food web, remained high during the 2000s, and consumption of alewives by salmonines actually increased between the 1980–1995 and 1996–2011 time periods. Moreover, abundance of the lake whitefish population, which supports Lake Michigan's most valuable commercial fishery, remained at historically high levels during the 2000s. Apparently, counterbalancing mechanisms operating within the complex Lake Michigan food web have enabled salmonines and lake whitefish to retain relatively high abundances despite reduced primary production.

In Lake Michigan, diets of planktivorous and benthivorous fishes have varied over the past decades, in part owing to food web changes. To update diet information and compare them to a similar effort in 1994–1995, we analyzed the diets of seven benthivorous and planktivorous fish species collected along two northern Lake Michigan transects that spanned nearshore (18 m), intermediate (46 m), and offshore (91, 110, 128 m) bottom depths during spring, summer, and autumn of 2010. Calanoid copepods (e.g., Limnocalanus macrurus, Leptodiaptomus sicilis, and Senecella calanoides) comprised a majority of the diets in at least one season for all sizes of alewife (Alosa pseudoharengus), bloater (Coregonus hoyi), and rainbow smelt (Osmerus mordax). Similarly, Mysis diluviana was the highest proportion in at least one season for large sizes of alewife, bloater, and rainbow smelt, as well as slimy sculpin (Cottus cognatus) and deepwater sculpin (Myoxocephalus thompsonii). The diets of the remaining two species, ninespine stickleback (Pungitius pungitius) and round goby (Neogobius melanostomus), were dominated by herbivorous cladocerans or dreissenid mussels, respectively. Interspecific diet overlap was minimal at 18 and 46 m. In offshore waters, however, overlap was relatively high, driven by frequent consumption of Mysis. Relative to 1994–1995, 2010 diets revealed increased feeding on calanoid copepods and Mysis, with corresponding declining consumption of Diporeia spp. and herbivorous cladocerans. Relative diet weight was also higher in 1994–1995 than in 2010 for small and large bloater and both sculpin species. We hypothesize that the shifts in diets are reflective of community-level changes in invertebrate prey availability.

The phylogenetic relationships among five species of sculpins, including Myoxocephalus stelleri, M. brantii, M. jaok, M. ochotensis, and Megalocottus platycephalus, were estimated from the sequence vari� ability of the mtDNA cytochrome b (cytb) and cytochrome oxidase 1 (CO1) genes. Analysis of the topologies of combined phylogenetic trees showed that all of the morphologically described species from different gen� era represented monophyletic groups with high support of branch robustness. Haplotypes with different kary� otypes from different geographical localities with an intragroup nucleotide diversity of 0.42% were combined into the M. stelleri clade. All of the species (except for M. stelleri from the Sea of Japan and the Okhotsk Sea coast of the Hokkaido Island) were characterized by relatively low values of the intragroup variation, along with high values of interspecific variation of mtDNAencoded markers. Studies of the M. stelleri karyotypes using Agbanding showed that karyotypes of the indivi duals from the Sea of Japan and Okhotsk differed not only in the number of chromosomes (2n) but also in the number of active nucleolus organizers (NO) and stained NO blocks, calling into question whether they belong to a single species. The observed discrepancy between the phylogenetic topologies and karyological data is discussed in relation to the informative capacity of mtDNA fragments and the phenomenon of intraspecific chromosomal polymorphism.

Freshwater sculpins, grouped by their common ecological characteristic of freshwater habitats, comprise the species from the genera Cottus, Trachidermus, Mesocottus and Myoxocephalus as well as the Baikal sculpins. These fishes are typically coldwater-adapted, having probably originated polyphyletically from ancestral species of marine sculpins. Gottus, the most speciose taxonomic group, includes at least 64 species and is distributed throughout the fresh waters of the northern part of the Northern Hemisphere. Indinidual species have diverse life histories, such as fluvial, lacustrine, catadromous, and freshwater amphidromous. The second most abundant group, the Baikal sculpins, includes 33 species in 12 genera representing 3 families, and comprises many benthic, and a few bentho-pelagic and pelagic species. The freshwater sculpins belonging to Trachidermus, Mesocottus and Myoxocephalus include only one or two species in each genus. Recent molecular phylogenetic analyses of Cottus species, Baikal sculpins and their relatives have demonstrated mainly that (1) Cottus kazika is a sister taxon to Trachidermus fasciatus (designated lineage A), (2) Cottus species, except for C. kazika, and the Baikal sculpins are monophyletic, (3) on the basis of (1) and (2), Cottus as presently recognized is not monophyletic, and (4) the Major monophyletic lineages include 7 lineages: lineage B from Eurasia, lineages C and D from East Asia, the Cottopsis clade (sensu Copeia 2005:303–311, 2005) from the west coast of North America, the Cottus clade from the Circum-Arctic sea, the monophyletic Baikal sculpins, and the Uranidea clade. These findings suggested that the monophyletic freshwater sculpins that comprise the lineage A and the 7 other lineages may undergone two major radiations, one having occurred in the fresh water Cottus species in the northern part of the Northern Hemisphere, and the other in the Baikal sculpins in the Lake Baikal, the world’s oldest freshwater lake. Through these adaptive radiations, a tremendous diversity of morphological, ecological, physiological and life historical traits now exists in the freshwater sculpins.

This study deals with the karyotype of the flathead sculpin Megalocottus platycephalus platycephalus (Pallas, 1814) (family Cottidae) from Odyan Bay of the Sea of Okhotsk. The karyotype is stable: 2n = 42 (2 metacentric, 2 submeta-subtelocentric, 30 subtelocentric, and 8 acrocentric chromosomes), NF = 44 + 2. The nucleolar organizers (NOs) were identified using Ag-banding in the telomere parts of the short arms of two large subtelocentric chromosomes. Variations in the number of nucleolar organizer chromosomes and in the number of NO-staining blocks were found. Comparison of the karyotype of M. p. platycephalus with the karyotypes of previously studied species of the genus Myoxocephalus from the Sea of Japan and the Sea of Okhotsk revealed their significant similarity in the main features and difference in the number and localization of NORs.

Deepwater sculpins ( Myoxocephalus thompsonii ) are an important link in deepwater benthic foodwebs of the Great Lakes. Little information exists about deepwater sculpin spawning habits and early life history ecology due to difficulty in sampling deep offshore habitats. Larval and age-0 deepwater sculpins collected in northern Lake Huron and the Detroit River during 2007 were used to improve our understanding of their habitat use, diet, age, and growth. Peak larval density reached 8.4/1000 m 3 in the Detroit River during April and was higher than that in Lake Huron. Offshore bottom trawls at DeTour and Hammond Bay first collected benthic age-0 deepwater sculpins in early September when fish were ≥ 25 mm TL. Otolith analysis revealed that hatch dates for pelagic larvae occurred during late March and larvae remained pelagic for 40 to 60 days. Diet of pelagic larvae (10–21 mm TL) was dominated by calanoid copepods at all sample locations. Diets of benthic age-0 fish varied by location and depth: Mysis and chironomids were prevalent in fish from Hammond Bay and the 91 m site at DeTour, but only chironomids were found in fish from the 37 m DeTour site. This work showed that nearshore epilimnetic sites were important for pelagic larvae and an ontogenetic shift from pelagic planktivore to benthivore occurred at about 25 mm TL in late summer. Age analysis showed that larvae remained pelagic long enough to be transported through the St. Clair–Detroit River system, Lake Erie, and the Niagara River, potentially contributing to populations in Lake Ontario.

Using a 37-year recruitment time series, we uncovered a field pattern revealing a strong, inverse relationship between bloater Coregonus hoyi recruitment success and slimy sculpin Cottus cognatus biomass in Lake Michigan (United States), one of the largest freshwater lakes of the world. Given that slimy sculpins (and deepwater sculpin Myoxocephalus thompsonii) are known egg predators that spatiotemporally overlap with incubating bloater eggs, we used recently published data on sculpin diets and daily ration to model annual bloater egg consumption by sculpins for the 1973–2010 year-classes. Although several strong year-classes were produced in the late 1980s when the proportion of eggs consumed by slimy sculpins was extremely low (i.e., 0.10–1.0), egg predation failed to explain why recruitment was weak for the 1995–2005 year-classes when the proportion consumed was also low (i.e.

The acute toxicity of physically and chemically dispersed crude oil and the dispersant Corexit 9500 were evaluated for key Arctic species. The copepod Calanus glacialis, juvenile Arctic cod (Boreogadus saida), and larval sculpin (Myoxocephalus sp.) were tested under conditions representative of the Beaufort and Chukchi Seas during the ice-free season. The toxicity of 3 water-accommodated fractions (WAF) of Alaska North Slope crude oil was examined with spiked, declining exposures. A dispersant-only test was conducted with the copepod C. glacialis. Each preparation with oil (WAF, breaking wave WAF [BWWAF], and chemically enhanced WAF [CEWAF]) produced distinct suites of hydrocarbon constituents; the total concentrations of oil were lowest in WAF and highest in CEWAF preparations. The relative sensitivity for the different species and age classes was similar within each WAF type. Median lethal concentration values based on total petroleum hydrocarbons ranged from 1.6 mg/L to 4.0 mg/L for WAF and BWWAF treatments and from 22 mg/L to 62 mg/L for CEWAF. For Corexit 9500 exposures, median lethal concentration values ranged from 17 mg/L to 50 mg/L. The differences in the relative toxicity among the accommodated fractions indicated that the majority of petroleum hydrocarbons in the CEWAF are in less acutely toxic forms than the components that dominate the WAF or BWWAF. Further evaluation showed that the parent polycyclic aromatic hydrocarbon compounds, specifically naphthalene, were highly correlated to acute toxicity. Environ Toxicol Chem 2013;32:2284–2300.

Accurate estimates of fish consumption are required to understand trophic interactions and facilitate ecosystem-based fishery management. Despite their importance within the food-web, no method currently exists to estimate daily consumption for Great Lakes slimy ( Cottus cognatus ) and deepwater sculpin ( Myoxocephalus thompsonii ). We conducted experiments to estimate gastric evacuation (GEVAC) and collected field data from Lake Michigan to estimate index of fullness [(g prey/g fish weight)100%) to determine daily ration for water temperatures ranging 2–5 °C, coinciding with the winter and early spring season. Exponential GEVAC rates equaled 0.0115/h for slimy sculpin and 0.0147/h for deepwater sculpin, and did not vary between 2.7 °C and 5.1 °C for either species or between prey types ( Mysis relicta and fish eggs) for slimy sculpin. Index of fullness varied with fish size, and averaged 1.93% and 1.85% for slimy and deepwater sculpins, respectively. Maximum index of fullness was generally higher (except for the smallest sizes) for both species in 2009–2010 than in 1976 despite reductions in a primary prey, Diporeia spp. Predictive daily ration equations were derived as a function of fish dry weight. Estimates of daily consumption ranged from 0.2 to 0.8% of their body weight, which was within the low range of estimates from other species at comparably low water temperatures. These results provide a tool to estimate the consumptive demand of sculpins which will improve our understanding of benthic offshore food webs and aid in management and restoration of these native species in the Great Lakes.

Understanding the invasibility of marine species with complex life cycles requires examination of the ecology of both larval and adult stages. The goal of our study was to determine whether several species of coastal fish native to the western North Atlantic Ocean can consume megalopae of the nonindigenous Asian shore crab Hemigrapsus sanguineus and, if so, whether megalopae can respond to chemicals from potential fish predators by either molting faster to a benthic crab stage or exhibiting avoidance behaviors. Laboratory predation experiments showed that all fish species tested (cunner, Tautogolabrus adspersus ; tautog, Tautoga onitis ; grubby, Myoxocephalus aeneus ; scup, Stenotomus chrysops ; and mummichog, Fundulus heteroclitus ) consumed H. sanguineus megalopae. When megalopae were reared in seawater in which fish or adult crabs had been housed, fish chemical cues had no effect on molting rate whereas chemicals from adult conspecific crabs accelerated molting. Behavioral responses of H. sanguineus megalopae to chemicals from fish and crabs were tested in still and flowing water. In still water, megalopae moved away from chemicals from T. adspersus and M. aeneus . In flowing water, chemicals from T. onitis caused a behavioral reaction that led to enhanced movement away from the source of the cue. All 3 species are related to fishes present in the native range of H. sanguineus . In contrast, chemicals from adult crabs and F. heteroclitus had no effect on behavior of megalopae. Behavioral responses of H. sanguineus megalopae to chemical cues from coastal fish species might function as antipredator strategies that enhance survival of this nonindigenous species.