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Lattice organs on the dorsal part of the carapace were examined by scanning electron microscopy (SEM) in females, males, and/or cypridiform ascothoracid-larvae (in the ascothoracid-larva I stage, for the first time ever) of six species of Ascothoracida representing four genera and three families: Waginella sandersi (Newman, 1974), W. ?metacrinicola (Okada, 1926), and Gorgonolaureus muzikaeGrygier, 1981 (family Synagogidae); BaccalaureusBroch 1929, unidentified species (Lauridae); and Ascothorax gigasWagin, 1968 and A. synagogoides (Wagin, 1964) (Ascothoracidae). All were of the “keel in a trough” or “tube in a trough” type, but they varied even more than those of previously studied ascothoracidans in number, form, orientation, and terminal pore position. Such extensive variability, summarized graphically herein, limits the potential utility of Ascothoracida (parasites of anthozoans and echinoderms) as an out-group for polarizing lattice organ character-state variation in Cirripedia (free-living and parasitic barnacles). While the ground-pattern of lattice organs in Thecostraca (comprising Ascothoracida, Cirripedia, and Facetotecta, or “y-larvae”) includes two anterior and three posterior pairs, ascothoracid-larvae and males of AscothoraxDjakonov, 1914 and DendrogasterKnipovich, 1890 (family Dendrogastridae) have only two posterior pairs; evidence as to which pair is missing is discussed. The hypothesis that dorsal setae in thecostracan nauplii are the precursors of lattice organs in later developmental stages is reexamined; one-to-one positional matching of such setae to lattice organs is difficult in Ascothoracida. Newly characterized structures of unknown function, termed “reticulated pore-plates”, exist along the hinge line in a juvenile male of G. muzikae. The “pits” reported earlier along the anterior valve margin in ascothoracid-larva II of A. synagogoides are actually clusters of pores that may be homologous to these pore-plates. Potentially homologous pore-fields in other ascothoracidans are reviewed from the literature or described anew using SEM.

The relationship between carapace width (CW) and weight (W) of the blue swimmer crab Portunus armatus (A. Milne-Edwards, 1861) was determined for southwestern Australian populations using measurements collected over two decades from a range of nearshore marine and estuarine environments. A strong and significant positive linear relationship occurred between the natural logarithm (ln) of CW and ln(W) for both sexes overall and individually for males and females (R2 = 0.985–0.987; P < 0.001). The relationships were: overall ln(W) = −10.2262 + 3.1708 ln(CW); males ln(W) = −10.4641 + 3.234 ln(CW), and females ln(W) = −10.0595 + 3.1246 ln(CW). Significant differences in the relationship were detected between sexes, decadal sampling periods, environments, and seasons (P < 0.001), with sex and decadal period being most influential. Males were heavier than females at any given CW, which was most apparent at larger (>100 mm CW) sizes. Crabs were also generally heavier at CW in a recent sampling period (2014–2019) than historically (1995–2000), with the greatest decadal differences occurring in the estuarine environment. These relationships have direct applicability for use in stock assessments of this valuable fishery species. Moreover, observed changes in the CW-W relationships over time highlight the importance of regularly reviewing biological parameters used in fisheries assessments, particularly in response to climate change as in the case of southwestern Australia.

The caridean shrimp Heterocarpus chani Li, 2006 (Pandalidae), is widely distributed along the Indian coasts, and is commercially exploited by deep-sea fisheries in southern India. There is limited information on its reproductive biology. A total of 3,122 specimens were collected from commercial bottom trawlers with a 25–30 mm mesh cod-end at depths of 200–300 m between November 2013 and December 2015. There was no significant difference (P < 0.05) in the sex ratio, and size at first maturity with regard to the carapace length was estimated as 22.2 mm in females and 21 mm in males in Arabian Sea specimens and 22 mm and 20.8 mm, respectively, in Bay of Bengal samples. Ovigerous females were observed through the entire fishing season, which indicates year-round breeding, with three stages identified in the development of eggs (early, middle, and late stages). The estimated absolute and relative fecundity in ovigerous females ranged 830–45,650 eggs and 160–2,871 eggs g–1, respectively. The maximum of 45,650 eggs is the highest number so far reported for any pandalid species. The relationship between carapace length and fecundity revealed b values of 3.31 to 6.33, indicating positive allometry with the coefficient of determination (r2) of 0.21–0.37. Knowledge of the reproductive biology of the species can be further extrapolated aiming for the sustainable management of this resource.

The Arabian red shrimp, Aristeus alcocki Ramadan, 1938, is one of the targets of commercial trawlers operating since 2000 along the Indian coasts at depths of 200–850 m. We report for the first time on the reproductive biology, insemination frequency, ovarian maturation, gonadosomatic index (GSI), size at maturity, and fecundity of A. alcocki investigated macroscopically and validated histologically using monthly trawl samples from the southwestern coast of India. Females have an open thelycum with five gonad developmental stages (I to V) and two stages (I and II) in males. A total of 4,170 specimens were examined and 68.6% of the females had been inseminated (carapace length (CL) 22.0–53.0 mm), predominantly during January to May. Females in stage I (immature) measured on average CL 25.5 ± 0.87 mm, those in stages IV and V (mature) CL 41.5 ± 0.62 mm. Immature males were smaller, mean CL 20.5 ± 0.5 mm. Size at first sexual maturity for females was estimated as CL 35.07 mm (total length (TL) 120–170 mm) and the inseminated specimens (CL50is) were mature at CL 31.45 mm using a non-linear method. The smallest mature female was CL 35 mm, whereas the size at maturity (CL50ms) of males was estimated as CL 19.6 mm (TL 75–96 mm). We also report synchronous oocyte development and continuous spawning activity with a peak during January to April. Information on the reproduction of this deep-water shrimp will help fishery managers estimate the stock sustainability and develop resource management measures.

The freshwater crab Potamon elbursi Pretzmann, 1962 is widely distributed in northwestern Iran, occurring in two separate hydrographic systems, one draining into the Caspian Sea and a second into Namak Lake. A total of 192 specimens from the two drainage systems were analyzed: 122 specimens from the Caspian drainage and 70 specimens from the Namak Lake drainage. Fourteen measurements of body dimensions were taken for traditional morphometric analyses, and eight landmarks and two semi-landmarks from the carapace were used for geometric-morphometric analyses. Morphometric analyses were performed with the aid of SPSS ver. 22 and geometric analyses using PAST ver. 2.14 and MorphoJ ver. 1.06d software. Adults and juveniles were separated using the K-means method, and puberty-size calculations revealed females reach morphometric puberty at smaller sizes than males. Sexual size dimorphism (SSD) and allometric growth findings revealed that males have longer carapaces, higher body height, and larger chelae, probably due to optimizing mating with females, whereas females have broader pleonal somites and a wider posterior carapace, likely because of more energy investment in egg care and reproduction. Although separate comparison of sexes between the two drainages showed no significant differences between females (in traditional morphometry), population comparisons (excluding pleonal characters) provide evidence for a significant distinction with partial overlapping. Poor dispersal ability and philopatric behaviour, as often known to occur in freshwater crabs, is probably responsible for such intraspecific differentiation in P. elbursi.

The assessment of life history traits can help to better understand the population dynamics of the respective species. We present some life history traits of the freshwater crab Potamon ibericum (Bieberstein, 1809) from the western Alborz Mountains, Iran. Carapace size at the onset of morphometric maturity was estimated using the breakpoint of the relative growth of the chela and abdomen in males and females, respectively, by implementing piecewise linear regressions. In order to quantify variations in the estimated breakpoint, a bootstrap resampling method was applied. Allometric trajectories of chelar dimensions were also applied to juveniles and adults. Sexual size dimorphism was evaluated using the dimensions of the carapace and chelae, and patterns of the carapace shape dimorphism were investigated by implementing geometric morphometric analysis. The results showed that females reach morphometric maturity at smaller sizes than males, which could be of advantage in the fluctuating environment of their freshwater habitat in order to mate as soon as possible and increase fecundity. Positive allometric trends in the length of the major chela was observed in adults of both sexes, and the possible adaptive forces on the evolution of this pattern are discussed. Results of sexual dimorphism analyses confirmed male-biased sexual size dimorphism and functional adaptation of carapace shape in both sexes.

Reproduction, including ovarian maturation, size at sexual maturity, and spawning season of Parapenaeus fissuroides Crosnier, 1985 (Decapoda: Penaeidae), were studied using females collected from Kagoshima Bay, Kyushu, Japan. The ovaries of individuals were examined by histological observations to estimate the degree of ovarian maturation. Ovarian maturity stages were classified into four categories based on the developmental stage of the most advanced oocytes in the ovary as follows: undeveloped, developing, nearly ripe, and ripe. The mature females were defined as those having nearly ripe or ripe ovaries containing cortical granules in the peripheral region of the oocytes. The gonadosomatic index (GSI) significantly increased with progress of ovarian maturation and most of the females with GSI ⩾ 6% were mature. The size at sexual maturity of female P. fissuroides was estimated to be 23.5 mm in carapace length. The spawning season of this species was estimated to last from July to February with a peak during October and November.

Potamid freshwater crabs are characterised by mandibular palps possessing three segments with the terminal lobe simple. A new genus and new species of semi-terrestrial crab, Gempala bilobata , is here described from Peninsular Malaysia that possesses a 3-segmented mandibular palp having a bilobed terminal segment, a hitherto unknown condition. In addition, the carapace of the new genus is unusually high. Comparisons with allied potamid genera from Malaysia are also made and the affinities of the genus discussed.

Data of the life history of Cambarus ( Puncticambarus ) theepiensis Loughman, Foltz, Garrison and Welsh, 2013 was collected monthly from May 2012 through April 2013 from two sites within the Twelvepole Creek watershed in southwestern West Virginia, USA. Mature females showed signs of glair development in early May. Egg extrusion was noted in early June, with first- through third-stage juveniles occurring from July to August, before becoming free-living juveniles in late August and September. Evidence for possible overwintering with young was found as a mature female with free-living juveniles was collected in early April. Mature female total carapace length (TCL) ranged from 29.7-52.4 mm. Support for the hypothesis that form change occurs in female cambarid crayfishes was found in female C. theepiensis . Form I males were collected throughout the year, but reached their highest densities in May through August. Size cohorts, determined through histograms, demonstrate six size cohorts existed between both streams, following appearance of young of the year (YOY) in late summer. Cambarus theepiensis appears to have life history characteristics similar to other Cambarus species, displaying K-selected life history traits.

The western Pacific pinnotherid crab, Fabia obtusidentata Dai, Feng, Song and Chen, 1980, which lives in the saucer scallop, Amusium (Pectinidae), is found not to belong to Fabia Dana, 1851 s. str. or Pinnotheres Bosc, 1802. In contrast to these two genera, F. obtusidentata possesses a carapace not having longitudinal grooves, a third maxilliped in which the dactylus is slender and inserted one-third from the proximal end of the conical propodus, and a prominently elongated right third ambulatory leg with a long dactylus. It is here referred to its own genus, Amusiotheres gen. nov. Pinnotheres hanumantharaoi Devi and Shyamasundari, 1989, from India, is also transferred to the new genus.

The mathildellid crab genus Neopilumnoplax Serene in Guinot, 1969 was originally proposed for several deep-sea species previously placed in Pilumnoplax Stimpson, 1858, including P. sinclairi Alcock and Anderson, 1899 from the Bay of Bengal. Further revision led to creation of Mathildella Guinot and Richer de Forges, 1981, which differed chiefly from Neopilumnoplax in having one instead of two pairs of endostomial ridges, and in the width of the anterior abdominal somites. Most species of both genera are relatively well known, but N. sinclairi , until now, was known with certainty only from the type description and figure of the female holotype housed in the collections of the Zoological Survey of India. Examination of the holotype of Pilumnoplax sinclairi , facilitated by the late Michael Turkay, revealed P. sinclairi to belong to Mathildella instead of Neopilumnoplax . Moreover, comparison of M. sinclairi with M. kyushupalauensis Takeda and Watabe, 2004 from Komahashi Seamount off Japan revealed that the two nominal species may well be synonyms. We defer synonymising the two species, however, until male M. sinclairi can be studied. We also clarify selected historical records of “ Pilumnoplax ” species from Indonesia and mainland Japan, from which we confirm the occurrence of Mathildella serrata (Sakai, 1974) and M. kyushupalauensis , respectively. In addition, we recognise an additional character separating Neopilumnoplax from Mathildella in the respective presence or absence of epibranchial ridges on the carapace. Neopilumnoplax michalis sp. nov. from the Southwest Indian Ocean Ridge is described and compared with its nearest congener, N. heterochir (Studer, 1883) from off southern Africa. The identity of Pseudorhombilia ( Pilumnoplax ) normani Miers in Tizzard, Moseley, Buchanan and Murray, 1885 from Nightingale Island (Tristan da Cunha) and Agulhas Bank, off South Africa, is fixed by lectotype designation as a junior synonym of N. heterochir .

We studied the ontogenetic allometry pattern in the freshwater brachyuran crab Potamon fluviatile (Herbst, 1785) to describe some new sexual dimorphic features on the ontogenic trajectories of the chelae. We surveyed carapace width, chela length and width, dactylus length, and propodus length of both chelae of 93 females and 114 males to the nearest 0.05 mm using a vernier caliper. Our main result was the identification of morphological biometry showing a variability of the chela linked to growth allometry, with some different between-sex ontogenic trajectories. Specifically, we emphasized how the morphometric features of the chelae change during body-size growth with different increasing rates. Particularly, the observed significant shape changes are mainly due to positive allometries in both sexes, although negative allometries (the latter visible only in the propodus length of females) and isometries were observed as well. Our study confirms that a form of sexual dimorphism exists in the ontogenetic allometric trajectories of P. fluviatile in both the large and small chelae, these trajectories being related to mechanical aspects in predation, food manipulation, mate acquisition, and between-sex differences in aggressiveness during antagonistic fights.

Declining ambient calcium (Ca 2+ ) concentrations in boreal, soft-water lakes of North America and Europe is one of many threats facing their biotic assemblages such as crayfish populations. We examined the specific exoskeleton calcium (Ca) concentration in Astacus astacus (Linnaeus, 1758) populations from a wide range of ambient Ca 2+ concentrations to determine a possible correlation between the amount of Ca accumulated in their carapaces and the ambient Ca 2+ concentrations. Exoskeleton Ca was the major constituent of the crayfish A. astacus carapaces in this survey (21.2 to 25.8% Ca of dry weight (DW)), whereas magnesium (Mg) displayed a disproportionately low constituent. The strong correlation between mineral contents of dry weight (DW) and ash weight (AW) ( r = 0 . 98 ) allowed us to refer mineral contents consequently to DW. A linear model using gender, length and ambient Ca 2+ concentration (log transformed) explained 82% of the variation in carapace Ca content (as % DW). Astacus astacus females were slightly more calcified than males (0.4% of DW, when adjusted for ambient Ca 2+ and body length). Large-bodied populations were slightly, but significantly more heavily calcified than those with smaller bodies: carapace Ca content increased by 0.2% DW for each cm increase in body length. The strong logarithmic effect of ambient Ca 2+ implies that carapace Ca content increases by 1.7 × log(2) = 1.2% DW for every doubling of the Ca 2+ concentration in the water.

Identifying ontogenetic shifts in habitat use by aquatic organisms is necessary for improving conservation strategies; however, our ability to designate life stages based on surrogate metrics (i.e., length) is questionable without validation. This study identified growth patterns of age-0 western painted crayfish Orconectes palmeri longimanus (Faxon, 1898) reared in the laboratory, provided support for field-based designations of age-0 lengths, and identified microhabitat factors important to adult and juvenile presence from field collections. Two growth periods of a laboratory crayfish population were described using a broken line model: a rapid, early-growth period (weeks 2-20, slope = 0.81 ± 0.03SE), and a slower, late-growth period (weeks 22-50, slope = 0.13 ± 0.03SE). A smoothed curve was generated to represent the size distribution of juveniles from our laboratory population to determine the probability that an age-0 crayfish from our laboratory population had a carapace length (CL) similar to that found in previous field studies using onset of maturity (22.4 mm CL). We determined that the probability of the age-0 crayfish in our summer laboratory population exceeding 22.4 mm CL was 0.06. The threshold between the lower 0.95 and upper 0.05 probabilities was 22.9 mm CL, confirming previous field observations of onset at maturity. We used this threshold to identify juveniles and adults from our field collections, and found that both life stages were positively associated with coarse substrate and negatively associated with water depth. Adults, however, were negatively related to gravel, whereas juveniles showed a positive relationship. This result is reflective of the relationship between crayfish body size and refuge use within the interstitial spaces of substrates, whereby adult crayfish are unable to seek refuge in the small interstitial spaces of gravel.

The blue swimmer crab, Portunus pelagicus (Linnaeus, 1758), is an important component of the crustacean fisheries in Egypt. This fishery occurs mainly in two salt-water lakes in the Eastern Mediterranean, the coastal Lakes Bardaweel and Timsah, which is located about 100 km further south. We investigated for the first time the applicability of using growth band counts in thin sections of two gastric mill ossicles (mesocardiac and zygocardiac) as age indicator in the blue swimmer crab collected from the two lakes. There was no significant difference in band counts in thin sections of the two ossicles, although the zygo-cardiac ossicles were easier to process. Three growth bands were observed in the ossicles suggesting three years as the species life span. Meanwhile, size modal analysis suggested that the longevity of the species in the two lakes is only two years. Mean carapace width (mm) of the first two presumed year-classes obtained from the band counts and size modal analysis ( y 1 72.8 and 76.2 mm and y 2 91.5 and 97.8 mm, respectively) were not significantly different in Lake Timsah. In Lake Bardaweel, however, the mean size observed at the first two years was different ( y 1 78.5 and 102.2 mm and y 2 94.5 and 128.0 mm for the band count and size modal analysis, respectively). Sex-specific size-at-band counts (estimated age) was demonstrated for the species in both lakes. The models were fitted by power equations and there was no significant difference in the growth models between sexes in the two lakes. Further validation needs to be done to confirm the annual deposition of the growth bands before using the results on a routine basis.

We describe the reproductive cycle, population structure, growth and longevity of Aegla schmitti Hobbs, 1978 from the Betari River, at the Alto Ribeira Tourist State Park (24°31′57″S, 48°42′09″W), on the southern portion of state of Sao Paulo. A total of 1528 specimens (1204 males and 324 females) were sampled from September 2010 to December 2011. Carapace length excluding rostrum (CL) was measured in all individuals, and females were inspected for late developing ovaries or eggs attached to the pleopods. Growth curve equations were CL t = 28 . 358 ( 1 − e − 0 . 058 ( t + 1 . 127 ) ) for males and CL t = 21 . 69 ( 1 − e − 0 . 060 ( t + 1 . 468 ) ) for females. Average longevity was estimated to be 34.03 and 38.40 months for males and females, respectively. Size at the onset of functional maturity of females was estimated as 12.92 mm of CL. Aegla schmitti from the Betari River has two reproductive cycles during the expected lifespan. Each reproductive cycle extends for 9 months and can be subdivided in two sequential periods of similar duration: a first, from April to July, characterized by higher reproductive intensity and including the hatching of most of the juveniles in July, and a second, from August to December, with less intense reproductive activity. We discuss regional variations in water flow velocity as a selective pressure that regulates the timing of juvenile hatching in Aegla schmitti as well as in other aeglid species.

Benthesicymus tanneri Faxon, 1893 (Benthesicymidae) is a poorly known benthopelagic shrimp dominant in the lower oxygen minimum zone (OMZ) boundary in the Mexican Pacific. Its bathymetric distribution and diet were studied off the Mexican Pacific continental slope at depths of 710-2309 m, and the potential environmental drivers were analyzed. A total of 187 specimens were collected between 772 and 2010 m, although most were found between 1008 and 1620 m. This represents a wide bathymetric distribution compared to other species inhabiting lower OMZ boundaries. The size of individuals (carapace length, CL) ranged from 11.2 to 53.3 mm with no clear bathymetric patterns in the size distribution of the species. The sex ratio (males:females, M:F) changed with depth from M:F = 1:1 at 700-1000 m to M:F = 1:5 at 1300-1600 m. The main prey of B. tanneri in all the samples analyzed was the pelagic red crab Pleuroncodes planipes (Munididae Ahyong, Baba, Macpherson and Poore, 2010), and secondary preys were benthopelagic and bathypelagic fishes and shrimp-like decapod crustaceans. Only 15% of the stomachs were empty. Specimens of P. planipes captured simultaneously to B. tanneri were measured as an indicator of the size of available prey and 90% of individuals measured 11.1-14.8 mm CL. Benthesicymus tanneri was collected within wide ranges of values of the different environmental variables considered, and statistical analyses did not provide solid relationships between the patterns of distribution and the environmental factors (Spearman R and Generalized Linear Models). We hypothesize that B. tanneri is a eurytopic species whose swimming capacity allows for temporal vertical migrations into the water column.

Harpiosquilla harpax , a mantis shrimp, serves an important role in both commercial fisheries and benthic food webs in tropical and subtropical marine areas. Yet its population biology and ecology remain poorly understood. In this study, seasonal, independent surveys were conducted in August 2010, November 2010, February 2011 and May 2011 in the Beibu Gulf (formerly the Gulf of Tonkin), South China Sea. It was observed that H. harpax dominated the Stomatopoda catch, accounting for more than 80% of the total mantis shrimp caught in the survey areas. Spatial-temporal patterns of H. harpax trophic ecology, reproduction, and distribution were examined. The carapace length (CL), body length (BL) and body weight (BW) were compared between the sexes and among seasons and sites. The weight-length relationships of females and males were identified and allometric growth patterns were observed. Study findings showed that sex ratios varied among seasons. Half of the female specimens had a BL of 202.5 mm by sexual maturity. Crustacean, Pisces, and Cephalopoda were the three major taxonomic groups in the stomach content of H. harpax . The dietary patterns of H. harpax were significantly different among seasons, but not between sexes or across sites. Its feeding intensity peaked in fall and declined to a minimum in winter. H. harpax spawned year-round, peaking in summer when the gonad somatic index and sea surface temperature (SST) were highest. H. harpax density was positively correlated with SST and negatively correlated with salinity and phytoplankton density, respectively. Seasonal and latitudinal factors were important in determining the distribution of H. harpax .

The amphidromous shrimp Xiphocaris elongata (Guerin-Meneville, 1855) has a long rostrum in the presence of predatory fishes and a short rostrum above steep waterfalls where predatory fishes are absent, i.e., typically above waterfalls. Prior experiments showed that elongated rostrum in X. elongata is induced by chemical signals from the predatory fish Agonostomus monticola . We tested the hypothesis that in addition to rostrum length there are other morphometric differences between long-rostrum (LR) and short-rostrum (SR) X. elongata . We measured the post-orbital carapace length and pleon length of LR and SR shrimp and weighed both shrimp morphs. LR shrimp have significantly longer and heavier pleons than the SR shrimp. These allometric differences may affect the behavior of X. elongata shrimp in ways that, in turn, affect their interactions with predators and the environment. Our study demonstrates the importance of taking pleon measurements when studying crustaceans given that these measurements have been mostly overlooked, and may provide insight of environmental influences on crustacean morphology and behavior. This research provides data of the differences between prey phenotypes, which may alter their life-histories and interactions with the environment.

A new specimen of a basal echinocaridid phyllocaridan is noted from the Lower Devonian sediments of the Izdebno IG-1 borehole of central-eastern Poland. The description and reconstruction are based on a three-dimensionally preserved incomplete left carapace valve. The unique characters of the valve surface, mainly in the form of the number and location of nodes, places this specimen within Ptychocaris . However, the unique arrangement of nodes on its carapace allows us to erect a new species, Ptychocaris sheldoni n. sp. The parallel and longitudinal ridges (‘striae’) preserved on the carapace suggest the ability of a fast burial into the muddy seafloor.

Growth of Antarctic krill Euphausia superba Dana, 1850 is commonly calculated using the Instantaneous Growth Rate (IGR) method based on the difference between the uropod lengths of the moulted exoskeleton and the uropod lengths after moulting. To date, this method has not accounted for sex-dependent differences in body proportion, relying only upon uropod measurements. We measured the carapace, uropod, and total body lengths of gravid females, non-gravid females, males, and juvenile krill from the Indian Sector of the Southern Ocean. Growth rates derived using a combination of the carapace and uropod measurements for gravid females were different from those derived through the traditional uropod-only based IGR, whereas non-gravid females, male, and juvenile growth rates showed no significant difference between methods. The refined method we propose successfully reflects dimorphism in growth between the sexes of krill, with gravid females having enlarged carapaces during the reproductive season. The interaction between growth and reproduction must be considered to improve the reliability of predictions from krill life history models, which is possible through the use of sex-dependent IGR measurements. We propose that, whenever possible, measurements of carapace and total length should be made along with uropod measurements. Together with assessments of maturity stages of krill that did not moult during experiments, these measurements will aid in further informing krill stock assessments.

Sosiocaris schramin. gen. n. sp., is described from the Permian Sosio Limestone (Lercara Formation) of the Sosio Valley, Palermo Province, Italy. Sosiocaris schramiis attributed to Pygocephalomorpha incertae sedis. The brachyuran-like carapace morphology of S. schramisuggests that its overall morphology might have been convergent on that of brachyurans, an evolutionary trend that has also been observed in other pygocephalomorphs. Sosiocaris schramirepresents the first occurrence of a pygocephalomorph from the Sosio Limestone, an assemblage of Permian-aged limestone olistoliths from which several unusual crustaceans have been described.

Cyzicus altus n. sp. and Leptestheria kunmingensis n. sp. are described and diagnosed from Yunnan Province, China. Cyzicus altus can be distinguished from all other species of Cyzicus by the form of the telson and cercopods, and the lack of carapace setation. Leptestheria kunmingensis is separated from all other known Leptestheria by the form of the head (in the males) and the form of the telson and cercopods. Both species are so far known only from their type localities, and the sole wild population of L. kunmingensis has been destroyed by human activities. The known large branchiopod species of Yunnan and the general status of Chinese spinicaudatan clam shrimp taxonomy and diversity are briefly discussed.

Spinicaudata (colloquially ‘the clam shrimp’) are freshwater branchiopod crustaceans that occur worldwide in lakes and temporary pools. The spinicaudatans are easily recognizable by their bivalved carapace which is unusual among arthropods in that it is subject to only partial molting. During ecdysis (molting), the outer surface of the carapace is not shed, resulting in the retention of the ontogenetic record of an individual through distinct growth-rings representing each molt. When this unusual feature is considered alongside the interesting chemical properties of the carapace, “clam shrimp” present an interesting biological material not seen anywhere else: a multi-laminar calcium-phosphate-chitin composite. In addition, the carapace survives numerous destructive taphonomic processes (including transport, decay, compaction, and desiccation) to become the dominant body component of Spinicaudata preserved in their 380 million year fossil record. Understanding the mechanical properties and chemical composition of this structure may not only aid in a better understanding of the evolutionary history of this group but also facilitate efforts to develop novel materials that retain functional material properties even in harsh aquatic conditions. Therefore, this study aims to provide quantitative information about the composition and mechanics of this unique and interesting biological material and help predict possible biases in the fossilization of different species of Spinicaudata to aid future palaeontological research.

The effect of water temperature on the growth of juvenile snow crabs Chionoecetes opilio (Fabricius, 1788) was investigated in laboratory culture experiments. Laboratory-born juveniles were cultured from instar I to VIII at four temperatures (approximately 1, 3, 5 and 8°C). The growth indices (size increments at moulting in mm and in % of premoult carapace width) were significantly higher in crabs reared at 5°C than in those reared at other temperatures. The relationship between the mean temperature (T) and intermoult period (D) of each instar was described by the heat summation theory equation: D=K∕(T−α). The thermal constant K is the summation of the effective temperature for development (above the threshold temperature, α) up to a selected biological end point. The thermal constant tended to increase and the threshold temperature tended to decrease with increasing mean premoult carapace width of each instar, reaching asymptotes of 1573 day-degrees and −4.7°C, respectively. Size- and temperature-dependent growth models were developed for snow crab juveniles.

Nephrops norvegicus (Linnaeus, 1758) is a decapod crustacean of high economic importance found across the northeast Atlantic. Little is currently known about the variation in stomach morphology with body size. In this study, a novel two-stage endocasting technique was used to determine stomach volume in relation to carapace length. Scanning electron microscope images of the teeth of the gastric mill were analysed to determine the changes in gastric mill size and structure with growth. Correlation analysis revealed strong positive relationships between both carapace length and stomach volume, and the size of the gastric mill. These changes are thought to facilitate an increase in size and range of prey species.

Portunus sanguinolentus (Herbst, 1783) is commercially important in China, but its yields have declined in recent years. Here, the morphometric characteristics and organ indices are analysed to obtain baseline information about the population structure, sexual maturity, and fecundity of this species. Specimens were collected monthly from the waters of Honghai Bay, off the South China Sea. A 1.26:1 male:female sex ratio was recorded. Male crabs reached sexual maturity at a carapace width (CW) of 74-87 mm, while this CW range was 76-92 mm for females. Fifty percent of males and females were mature at a CW of 76.4 and 82.2 mm, respectively. Spawning peaked in February (53.4%), while the smallest and largest berried female crabs were 77.1 mm CW and 139.6 mm CW, respectively. A total of 58,600 to 565,000 eggs was attached to the pleopods of berried females, with female fecundity being significantly correlated to CW. The assimilated information is expected to help improve the sustainability of this crab fishery in China.

A thompsoniid rhizocephalan parasite, Diplothylacus sinensis (Keppen, 1877), was discovered in the semi-open Honghai Bay in the South China Sea, occurring in 26.4% of 1852 (934 males and 918 females) Portunus sanguinolentus (Herbst, 1783) (Decapoda: Portunidae) collected monthly between November 2012, and October 2013. Of the sampled crabs, 243 males and 246 females were infected with externae of D. sinensis or bore attachment scars on the body surface, giving an overall prevalence of infection of 26.0% and 26.8% in male and female crabs, respectively. The infection rate changed monthly with the highest prevalence in December (50.6%) and the lowest in June (1.3%). New externae filled with eggs or embryos were observed throughout the year, which indicates a year-round reproductive cycle, but virgin externae were more commonly present in late spring or early summer. Carapace width and wet weight of infected crabs of both sexes were significantly smaller than those of uninfected crabs. Compared to normal crabs, the pleon of infected females was significantly wider and the first pleopod of parasitized males was shorter. On addition, crabs infected by the rhizocephalan parasite were more susceptible to other epibionts, which included Octolasmis warwickii Gray, 1825 (10.1%), Chelonibia patula (Ranzani, 1818) (6.8%), Obelia spp. (7.2%) and Membranipora membranacea (6.5%) on the carapace surface, and Octolasmis bullata (Aurivillius, 1894) (64.7%) on the gills.

The evolution of reproductive systems is of critical importance to evolution and yet has been difficult to examine using paleontological information. Recent studies on freshwater “clam shrimp” in both extant and fossil populations have demonstrated that sex can be inferred by quantifying morphological differences of the carapaces. However, the extent of morphological continuity between juveniles and mature phenotypes remains unclear, which, if extensive, would confound the determination of sex ratios from fossil specimens. Herein, we report studies of clam shrimp ontogeny using quantitative morphometric techniques to assess carapace shape change through juvenile and early adult development. Intra- and inter-species ontogenetic variance was captured in three species from two families (Limnadiidae, Cyzicidae), three genera (Paralimnadia, Eulimnadia and Cyzicus), and three breeding systems (dioecy, androdioecy and hermaphroditism) using geometric morphometric analyses to identify and characterize discrete phenotypic stages during ontogeny. With this approach, we successfully discriminated juvenile, male and female/hermaphrodite phenotypes. Additionally, we generated models that described the ontogenetic trajectory of carapace shape as species developed into sexually mature phenotypes. These findings verify the ability of these morphometric techniques to distinguish sex ratios using only carapace shape and, thus, validate the use of fossil spinicaudatans for studies of reproductive system evolution in deep time.

The mud crab Scylla serrata (Forskal, 1775) (Portunidae) is a commercial species in the Indo-West-Pacific. Despite its high fishery value, the microhabitat of its early juvenile stages remains unknown. We studied microhabitat use by the ‘early benthic stage’ (EBS, between 3 and 30 mm carapace width, CW) at two sites in eastern Australia by two types of artificial benthic collectors and baited traps. 92% of EBS mud crabs were captured in muddy areas, compared to 8% on sandy habitats. The majority of the EBS mud crabs (87%) was found in intertidal areas within the mangrove fringe, only few individuals (13%) were found on unvegetated mud flats seawards to the mangroves. EBS from the mudflat (including first instars of 3-4 mm CW) were significantly smaller (p

In an effort to better understand juvenile growth in the first year and to determine potential effects of hatchery larval rearing, we compared growth of juvenile red king crab, Paralithodes camtschaticus (Tilesius, 1815), in the field and under laboratory-rearing conditions. Glaucothoe were obtained from the Alutiiq Pride Shellfish Hatchery and field; once molted to first stage juveniles, both sets were raised individually in the laboratory under ambient conditions (hereafter called hatchery/laboratory-reared and wild/laboratory-reared, respectively) and measured at each molt. Field-surveyed juveniles were observed and measured monthly in the intertidal in Juneau, AK, USA. Size, molt interval, cumulative molt interval, and molt increment did not differ significantly between hatchery/laboratory-reared and wild/laboratory-reared crab or between male and female crab over one year. Crab reached an average size ± SD of 13.6 ± 2.1 mm CL after 10-11 molts/year with 24% average molt increment at ambient temperatures. Carapace lengths of hatchery/laboratory-reared, wild/laboratory-reared, and field-surveyed juveniles were not significantly different in five of eight months from January through August, with small differences in January, February, and May, likely resulting from differences in hatch timing. Spine lengths differed from January through March but not from April through August. Spine lengths of hatchery/laboratory-reared crab were significantly larger than field-surveyed crab from January through March. Wild/laboratory-reared crab had significantly longer spine lengths than field-surveyed crab in February and March. In conclusion, growth did not differ significantly among juveniles reared in the laboratory and from the field.

Primary burrowing crayfish make up 15% of total crayfish species, but account for 32% of those imperiled. Primary burrowers are also much less studied as compared to secondary and tertiary burrowers. The purpose of this study was to observe the annual life cycles, and morphometric and morphological characteristics of two primary burrowing crayfish species: Cambarus (Lacunicambarus) diogenes Girard, 1852 and C. (Tubericambarus) polychromatus Thoma et al., 2005. Sampling occurred adjacent to two streams near Troy, AL, using hand excavation at one-month intervals from February 2011 to March 2012. A total of 195 C. diogenes (sex ratio = 1.3) and 194 C. polychromatus (sex ratio = 0.85) were collected. For a given size, C. diogenes had a broader carapace than C. polychromatus ( p< 0.001), and males had larger chelae than females for both species (p = 0.01 and p = 0.001, respectively). Minimum carapace length at sexual maturity (smallest form I) was 32.7 mm for C. diogenes males, 41.2 mm for C. diogenes females, 27.4 mm for C. polychromatus males, and 32.2 for C. polychromatus females. The proportion of form I males for both species increased in summer and remained at an increased level through winter, though C. polychromatus males remained reproductively active longer than C. diogenes. Females of both species were reproductively active only in winter except for one form I C. polychromatus female. Four ovigerous C. diogenes and three ovigerous C. polychromatus were collected in March, and five young of the year of C. polychromatus were found in burrows in June, July, and September.

A new genus, Eneosesarma, is created for a new species of sesarmid crab, E. azizi, from Saso Island, Farasan Archipelago, Saudi Arabia. The new species shows close affinities with species of the sesarmid genera Sesarmoides Serene and Soh, 1970 and Karstarma Davie and Ng, 2007, but differs from these in regard to carapace shape, morphology of male G1, and absence of stridulatory organ.

Shell disease is the progressive degradation of a crustacean’s exoskeleton through the secretion of chitinases and other enzymes from a suite of microorganisms. It affects a number of crustacean fisheries worldwide, through increased pre-capture mortality and rendering many individuals unsalable or with a reduced market value. The European edible crab (also known as the brown crab), Cancer pagurus Linnaeus, 1758, is highly susceptible to shell disease, but while intertidal populations have been comprehensively assessed, there has been little attention from a commercial fishery perspective. This study assessed the prevalence (% of catch infected) and severity (% cover of lesions on the carapace) of shell disease in the fishery around the Isle of Man for C. pagurus, in the Irish Sea. Shell disease was assessed in relation to sex and size, and the pattern of infection on ventral and dorsal surfaces described. A total of 2361 individuals was sampled between June and August 2012. Almost 25% of crabs were infected to some degree and of those infected an average of just over 2% of the carapace was covered by lesions. The proportion of individuals infected and the severity of infections was found to increase with size and was greater in males and those exhibiting limb losses. Differences in the pattern of lesions on the carapace between sexes suggest behavioural differences between genders can result in different patterns of individual infection. Both prevalence and severity of the disease varied considerably around the Isle of Man. Based on assessment of eight different fishing grounds, prevalence varied from as low as 15% of the population to as high as 35%, while the severity of infection varied between 0.8% to almost 3%. These findings not only suggest that shell disease syndrome could be causing a significant economic loss in the fishery, but also that environmental factors may be driving the condition. However, further investigation is required to fully elucidate the environmental drivers of this syndrome.

Decapod crustaceans from the Early Jurassic of southern Germany have been described since the middle of the 19th century, often based on isolated chelae. Among them, the taxon Glyphea amalthei Quenstedt, 1854 from the Late Pliensbachian, has been interpreted in rather different ways and in fact, the original specimens belong to four different decapod crustacean species: a glypheid, an erymid, a ‘thalassinoid’ and a paguroid (hermit crab). The complicated taxonomy of this material is clarified here. New material of chelae and even of an almost complete specimen from Franconia, Germany, allows the description of a new family, genus, and species for the paguroid. Carapace morphology the outline of the chelae and the characteristic occlusal dentition of the fingers make it significantly distinct from all other previously described Jurassic paguroids. One specimen shows a remarkably anomaly, unique in fossil decapods so far: a small chela developed at the outer margin of a bigger one. One more paguroid represented by a few incomplete chelae and a cheliped co-occurring with Schobertella simonsenetlangi n. gen., n. sp. is described here as Cryptopagurus svenhofmanni n. gen., n. sp. A further new species, Schobertella hoelderi, comes from the Angulatenton Formation of southern Germany and extends the fossil record of paguroids now back to the Late Hettangian. The previously described Venipagurus mariae Collins, 2011 from the Sinemurian of Dorset, which was supposed to be the oldest hermit crab is here considered as dubiously placed within paguroids and perhaps could represent a stomatopod. All records of Schobertella n. gen. and Cryptopagurus n. gen. come from claystones or detritic limestones representing non-reefal but well-oxygenated to slightly dysoxic habitats. The paguroid genus Orhomalus Etallon, 1861, is recorded from the Early Jurassic by isolated chelae of two new species, Orhomalus arpi from the uppermost Toarcian of southern Germany, and O. dubrullei from the Upper Pliensbachian of northern France, thus expanding the previously known stratigraphical range of this genus significantly.

In an ecologically oriented paper, Maruzzo et al. (2012) illustrate six developmental phases from the freshly settled cyprid larvae to the sessile juvenile in the barnacle, Amphibalanus amphitrite (Darwin, 1854), and in an evolutionarily oriented paper Hoeg et al. (2012) do likewise for Megabalanus rosa (Pilsbry, 1916). Both video-based studies illustrate 5 unadorned increasingly sac-like phases leading up to the sessile juvenile (Phase 6). In both species, Phase 5 is not only illustrated as sac-like, it resides outside the protective canopy of the cyprid shell, and this is reminiscent of the situation described by Bernard and Lane (1962, Fig. 24A). However, it has been long known that not only is the metamorphosing balanoid larva within the cyprid carapace divided into a capitulum and peduncle, but the anlagen of plates can seen with light microscopy through the largely transparent cyprid carapace (Runnstrom, 1925; Walley, 1969; Gusenbauer, 2003), and primordial plates appear in SEMs in Phase 5, after the carapace has been shed (Glenner and Hoeg, 1993; Gusenbauer, 2003). Maruzzo et al. and Hoeg et al. neither recognize such plates nor do they recognize the peduncle in any of the phases. Yet it is largely the peduncle that is involved in the struggle to shed the cyprid carapace in the transition to semi-sessile Phase 5, which they describe and illustrate as a “bag-like body shape.” Maruzzo et al. claim this phase persists for as much as 24 hours before becoming fully sessile (Phase 6), and they call for studies to assess its contribution to differential mortality. But Phase 5 has generally been observed to persist for less than three hours. Thus, the significantly longer duration being reported is either an artifact resulting from in vitro conditions and manipulations and/or failure to determine when the wall plates they illustrate in Phase 6 began to form. On the other hand, SEMs of Glenner and Hoeg, and more recently Gusenbauer, show that semi-sessile Phase 5 is by and large comparable to that illustrated by Runnstrom (1925) and, therefore, an unadorned sac-like form surely does not exist. Thus, Phase 5 of Maruzzo et al. and Hoeg et al., like that of Bernard and Lane (Fig. 14A), is most certainly an artifact.

This study provides information on the population structure, reproductive biology, growth, and mortality of Lepidophthalmus siriboia Felder and Rodrigues, 1993 on Algodoal Island in northern Brazil. Each month between June 2007 and May 2008, approximately 100 specimens were collected from a sand-muddy beach. In the laboratory, the specimens were wet weighed, measured – carapace length (CL) and length of the major chela (ChL) – and sexed. The ovigerous females were classified according to the stage of embryonic development. A total of 1268 individuals were analyzed (753 males, 515 females). Females were significantly larger than males throughout most of the year. Males reached sexual maturity at 6 mm and females at 7 mm. The observed overall sex ratio (1.5 male:1 female) was significantly different to the expected sex ratio of 1:1 ( χ 2 = 44 . 3 ; df = 1; p < 0 . 01 ; n = 1268 ). There was a significant female bias (0.7:1) in the specimens with a carapace length of over 10 mm ( χ 2 = 7 . 9 ; df = 1; p < 0 . 01 ; n = 313 ). Ovigerous females occurred throughout the study period, peaking in July, January, and April. The smallest ovigerous female had a carapace length of 7.5 mm. Fecundity was positively and significantly related to carapace length and body weight. Females had a higher maximum asymptotic carapace length and longevity (females: L ∞ = 15 . 3 mm carapace length, longevity = 1.4 years; males: L ∞ = 14 . 9 mm carapace length, longevity = 1.3 years). Males grow faster ( K = 0 . 009 ) than females ( K = 0 . 007 ) before reaching sexual maturity, but as adults, growth rates are similar in both sexes. Estimates of mortality rates varied among methods, but were invariably higher for males.

Abundance trends, population structure, and biology of the langoustine Metanephrops mozambicus (Macpherson, 1990) were investigated, based on commercial logbook information (1988-2010; 49 990 trawls) and biological samples collected off eastern South Africa. A generalized linear model (GLM) framework was used to model variation in catch rates, carapace length (CL), sex ratio, and maturation size. Standardized catch rates were inversely related to fishing effort, gradually increasing between 2002 and 2010, when fishing effort was lower. Catch rates were greatest in trawls made at 300 to 599 m depth and between June and December. Langoustines ranged in size from 17.5 to 72.6 mm CL, and the mean CL decreased with increasing depth. Males predominated in November, but equal numbers of males and females were observed in other months. The smallest egg-bearing female had a CL of 33.5 mm, and L50 was estimated at 49.4 mm, based on the incidence of external eggs. Females with freshly spawned eggs were most abundant in August, and the incidence of egg-bearing remained high until March, where after it declined. Eggs about to hatch occurred mainly in May. Growth parameter estimates (L∞ and K) were 65.5 mm and 0.7 year−1 for sexes combined, based on modal progression and the standard von Bertalanffy growth function, and longevity was estimated to be 3-4 years. Combining analyses of fisheries data with biological samples yielded insights into spatio-temporal population trends, as well as the correlation of reproduction and moulting in M. mozambicus.

The spatial and temporal distribution of the green crab, Carcinus maenas (Linnaeus, 1758) was studied in two New Hampshire estuaries, NW Atlantic, over a one-year period from November 2009 to October 2010 using baited traps. Green crab catch peaked in December and March in the Great Bay Estuary (GBE), and in November and April in the Hampton-Seabrook Estuary (HSE). Catch per unit effort was higher in the HSE than in the GBE, and more than 14 times as many green crabs were captured in the HSE (n = 35 788) than in the GBE (n = 2337). Catch of green crabs generally rose with increasing distance up-estuary in the HSE, while in the GBE, catch peaked mid-estuary. Quantity and species diversity of by-catch was greater in the GBE than in the HSE. In the HSE, sex ratios were skewed toward females in summer and female catch was maximized in salinities 30-31 ppt. In both estuaries, sex ratios favored male crabs most in the spring (March-April). Male and female green crabs in the GBE were larger (carapace size, weight), on average, than those in the HSE. This is the first study to compare seasonal green crab populations throughout and between NH estuaries.

Distocambarus crockeri Hobbs and Carlson, 1983 (piedmont prairie burrowing crayfish) burrows were excavated monthly from April through July 2005 and September 2005 through June 2006 at a terrestrial site in South Carolina. Crayfish were counted, measured (carapace length in mm, CL), sexed, and life stage determined. Number, size and life stage of crayfish per burrow varied within and among months. Burrow excavation yielded ovigerous females in spring and a new cohort of young-of-the-year (YOY) crayfish in June 2005 and 2006. Burrows contained both sexes of adult (≥27 mm CL) and juvenile (

The order Stomatopoda comprises a large number of modern representatives but only a relatively small number of fossil representatives. This low number of fossil mantis shrimp could be attributed to the fact that, in general, they have a poorly calcified cuticle, and their body is highly articulated and flexible, as compared to decapods, which may lead to a high rate of disarticulation and decomposition. A new genus, and species of Cretaceous stomatopod is described from a clastic, shallow water environment, of what today is north-east Texas. Nodosculda fisherorum n. gen. n. sp. is a relatively small mantis shrimp characterized by strong, defensive ornament on the carapace, thorax, and pleon. Although preserved in clastic sediments, these specimens show a remarkably good state of preservation. Articulated pleopods with attached setae, and muscle fibers have been identified on the pleon.

The molting growth pattern of the Japanese mitten crab Eriocheir japonica (de Haan, 1835) was investigated under laboratoryreared conditions. Crabs were individually reared in freshwater for 5 years in a constant temperature room at 23–25°C. The age after metamorphosis and instar number were recorded for each molt, and the intermolt period was calculated for each crab. Carapace width (CW) was measured and the percentage molt increment was calculated. Eleven crabs reached a CW > 10 mm. Each growth curve (ageCW relationship) had two phases in the juvenile stage. Growth rate gradually decreased in the younger phase before changing to nearly constant in the older phase. During the younger phase, the percentage molt increment decreased from 25.0%–38.1% to 6.0%–26.2% (ca. 2–10 mm CW, 1st to 11th instars), and the intermolt period increased from 4–9 days to 40–300 days (ca. 2–20 mm CW, first to thirteenth instars). During the older phase, both parameters became broadly flat but showed marked fluctuation...

Freshwater ecosystems are characterized by a high spatial complexity. This heterogeneity affects the distribution of aquatic organisms in riverine landscapes. Morphological variation in natural populations is driven by evolutionary forces. In crustaceans, morphological variations have been observed between different basins, environments, or developmental sequences along their geographical distribution. In this study, we assessed the possible effects of spatial scale on the phenotype of Aegla plana Buckup and Rossi, 1977 using geometric morphometrics. We examined 110 adult specimens from three river basins in southern Brazil. We used 13 morphological landmarks for the dorsal view of the carapace; the coordinates were superimposed using a generalized Procrustean analysis. We used a multivariate analysis to test the morphological variation in crabs from different basins, and we employed the Mantel test to assess the relationship of spatial and environmental factors with the principal components matrix for the carapace shape. Populations from different river basins differed significantly in carapace centroid size. Carapace shapes also differed significantly among the river-basin populations, and the interaction between sex and populations was also significant. The environmental and geographical matrices were correlated with the carapace shape matrix. This morphological variation shows an association with the geographical distribution of microbasins, which suggests a biogeographical effect on the distribution of A. plana.

The reliability of population dynamics and stock assessment models hinges on accurate life-history information. Mark-recapture studies represent a commonly used technique to investigate crustacean growth, mortality, and migrations. We evaluated tagging by coded microwire tags for the American lobster, Homarus americanus H. Milne Edwards, 1837, in a controlled study to determine tag retention and any influence on growth increment, intermolt duration, or survival. Microwire tags were injected into the propodus of the second right walking leg and two size classes (12-19.6 and 19.7-30 mm carapace length [CL]) were tested by two individual taggers. Overall tag retention was 96%. Tag retention after first ecdysis was 95% for the 12-19.6 mm CL and 92.5% for the 19.7-30 mm CL size class. There was no significant difference in tag retention between taggers, growth between tagged and untagged lobsters, or intermolt duration between tagged and untagged lobsters (P > 0.05 for all tests). Tag-induced mortality did not occur. These results support the further use of coded microwire tags to explore life-history variables for juvenile lobsters in the wild.

Raninoida, also known as “frog crabs,” is a clade of extant true crabs (Brachyura) characterized by a fusiform carapace (raninid-type), narrow thoracic sternum, pleon partially exposed dorsally, and paddle-like limbs, all of which are well suited to their cryptic burrowing lifestyle. However, the most basal raninoids from the Cretaceous were morphologically different, with ornamented carapaces that were wider than long (necrocarcinid-type), a broader thoracic sternum, and the pleon fitting between the legs assisted by pleonal locking mechanisms. During Albian times (∼112 to 99.6 Ma.) both body plans flourished worldwide. In contrast, pre-Albian (older than ∼112 Ma.) fusiform families have not yet been reported. The discovery of Notopocorystes kerri n. sp., a fusiform crab from the upper Aptian (∼115 Ma.) of Colombia, South America, and the re-examination of Planocarcinus olssoni (Rathbun, 1937) n. comb., a necrocarcinid-like crab from the same age and locality, extend the record of the two body plans back into the Aptian of the equatorial Neotropics. Notopocorystes kerri is the oldest fusiform raninoid known to date, revealing that the morphological innovation of a fusiform carapace was already evolved in Raninoida before the rapid radiation experienced during Albian times. Our findings are suggestive of a still unresolved Palaeocorystidae, containing the rootstock for the post-Aptian Raninidae/Symethidae clade, with the most basal palaeocorystids lying in proximity to, and possibly derived from, a necrocarcinid-like ancestor.

Studies in the western Atlantic have relied primarily on the key of Cook (1966) to identify and discriminate early life stages (ELS) of Xiphopenaeus kroyeri (Heller, 1862) and Rimapenaeus spp. Perez-Farfante and Kensley, 1997, even though larvae had not been reared successfully past the zoea phase at that time. We surveyed the penaeid literature for descriptions of reared mysis stages of X. kroyeri and Rimapenaeus, compared characters with those of Cook (1966), and found that Cook had reversed illustrations and criteria to discriminate taxa. We also examined plankton-collected mysis stages and identified new characters and previously unrecognized differences between taxa. Mysis stages of X. kroyeri have a slender median spine laterally near the posterior margin of pleomere five, not those of Rimapenaeus, although some early first myses of Rimapenaeus may have a vestigial spine laterally on pleomere five. Rimapenaeus has single dorsomedian spines on pleomeres four through six with the spine on pleomeres five and six >40% (usually about 50%) of fifth pleomere length as measured along the dorsal midline. Rimapenaeus lacks a pterygiostomial spine, although a spine on the distal margin of the developing antennal peduncle near the ventrolateral border of the carapace can be confused with a pterygiostomial spine. Xiphopenaeus kroyeri has a pterygiostomial spine and single dorsomedian spines on pleomeres four through six with the spine on pleomeres five and six

Milnepanopeus n. gen. is proposed to accommodate the western Atlantic brachyuran crab, Hexapanopeus lobipes. Characters of the carapace, sternal groove, carpus of the ambulatory pereiopods, and male first gonopod define this presently monospecific genus. Recent molecular analyses support removal of H. lobipes from Hexapanopeus, and segregate this genus as a distinct lineage of Panopeidae Ortmann, 1893. The species is redescribed as Milnepanopeus lobipes, n. comb., on the basis of the holotype and supplementary material from deep banks in the Gulf of Mexico. Variations in morphology are addressed along with morphological comparisons to related genera of the family.