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Major ecological disturbance events can provide opportunities to assess multispecies responses to upheaval. In particular, catastrophic disturbances that regionally extirpate habitat-forming species can potentially influence the genetic diversity of large numbers of codistributed taxa. However, due to the rarity of such disturbance events over ecological timeframes, the genetic dynamics of multispecies recolonization processes have remained little understood. Here, we use single nucleotide polymorphism (SNP) data from multiple coastal species to track the dynamics of cocolonization events in response to ancient earthquake disturbance in southern New Zealand. Specifically, we use a comparative phylogeographic approach to understand the extent to which epifauna (with varying ecological associations with their macroalgal hosts) share comparable spatial and temporal recolonization patterns. Our study reveals concordant disturbance-related phylogeographic breaks in two intertidal macroalgal species along with two associated epibiotic species (a chiton and an isopod). By contrast, two codistributed species, one of which is an epibiotic amphipod and the other a subtidal macroalga, show few, if any, genetic effects of palaeoseismic coastal uplift. Phylogeographic model selection reveals similar post-uplift recolonization routes for the epibiotic chiton and isopod and their macroalgal hosts. Additionally, codemographic analyses support synchronous population expansions of these four phylogeographically similar taxa. Our findings indicate that coastal paleoseismic activity has driven concordant impacts on multiple codistributed species, with concerted recolonization events probably facilitated by macroalgal rafting. These results highlight that high-resolution comparative genomic data can help reconstruct concerted multispecies responses to recent ecological disturbance.

Biotic interactions can determine species distributions and range limits, but little theoretical background exists regarding variation in commensalistic associations across latitudes. We estimated the geographic variation of the epibiont limpet Scurria parasitica’s association with its obligate host chiton species Enoplochiton niger across their distribution from Peru to northern Chile (12-30°S), to test the influence of host size variation on epibiont occurrence, individual spatial distribution, and body size. We analyzed the contribution of chiton body size to the pattern of abundance and distribution of occupancy of the epibiont limpet. We also examined the relationship between limpet shell size, coverage, and incidence probability function and chiton body size across latitudes. For some localities across the range edge of the host grazer’s distribution (i.e. 28-30°S), incidence and densities of the epibiont limpet were higher on larger chitons. Unoccupied host chiton proportions decreased at the poleward edge of the host-epibiont species range compared with sites located to the north. Increased variation in the epibiont limpet distribution on the host chiton plates suggests that limpets’ spatial segregation may have a role in lessening intraspecific interference competition with the host species at southern latitudes. Therefore, local and large-scale processes seem to contribute to modify the host-epibiont association pattern. Further studies are necessary to determine if this association shifts from commensalistic to antagonistic across the distributional range of both species.

Rocky intertidal zones are some of the most thermally stressful environments on earth, where ectotherms deal with tidally driven fluctuations in air and water temperatures that can exceed their maximum thermal tolerance. However, not all intertidal ectotherms face the same exposure risk. In northern regions of the eastern Pacific, summertime low tides occur during midday, exposing ectotherms to potentially stressful temperatures, whereas cooler pre-dawn low tides in southern regions buffer ectotherms from thermal stress. Gumboot chitonsCryptochiton stelleriare thermally sensitive intertidal grazers that range from southern California to Alaska, exposing them to a mosaic of thermal stresses. We quantified chiton thermal performance limits in the laboratory by testing the effects of elevated air and water temperatures on grazing. We also compared the thermoregulation efficiency of chitons from thermally benign northern California sites with those from thermally stressful San Juan Island, Washington sites, using 3 components: (1) biomimetic thermal models deployed intertidally, (2) chiton body temperatures in the field, and (3) chiton thermal preference in a laboratory-based thermal gradient. We found that chiton grazing performance was greatly reduced at 18°C in water, and they reached their grazing performance limit after exposure to 20°C in air, confirming previous work documenting thermal limits on chiton respiration. Chitons preferred body temperatures within 3°C of their thermal performance limits, but they rarely achieved body temperatures that would maximize grazing in the field. This suggests that chitons are not thermoregulating efficiently with respect to maximizing grazing performance, but instead are minimizing exposure to temperatures that would be detrimental to their performance.

Onithochiton neglectus is a morphologically variable, brooding chiton inhabiting coastal reefs throughout New Zealand and its Sub-Antarctic Islands. Southern O. neglectus populations are typically associated with buoyant kelp (Durvillaea spp.) and are potentially connected via kelp-rafting. Northern O. neglectus populations are less likely to raft, due to lower numbers of Durvillaea in northern New Zealand. To test for the impact of kelp-rafting on the spatial distribution of variation in O. neglectus, we undertook a combined analysis of morphological and genetic variation across the range of the species. Geometric morphometrics were used to assess shell shape. We detected a northern vs. southern split in shell shape, corresponding to the frequency of the O. neglectus/Durvillaea spp. association. To assess O. neglectus genetic patterns across New Zealand, we estimated phylogenetic trees with nuclear (ITS) and mitochondrial (COI and 16S) markers, which revealed distinct northern and southern lineages, and an additional lineage in central New Zealand. Neither the morphological nor genetic groups match existing O. neglectus subspecies, but are concordant with the patterns of association of O. neglectus with Durvillaea. We suggest that shell shape may be linked to O. neglectus’ regionally variable ecological association with kelp holdfasts.

The chiton Liolophura japonica (Lischke 1873) is distributed in intertidal areas of the northwestern Pacific. Using COI and 16S rRNA, we found three genetic lineages, suggesting separation into three different species. Population genetic analyses, the two distinct COI barcoding gaps albeit one barcoding gap in the 16S rRNA, and phylogenetic relationships with a congeneric species supported this finding. We described L. koreana, sp. nov. over ca. 33°24′ N (JJ), and L. sinensis, sp. nov. around ca. 27°02′–28°00′ N (ZJ). We confirmed that these can be morphologically distinguished by lateral and dorsal black spots on the tegmentum and the shape of spicules on the perinotum. We also discuss species divergence during the Plio-Pleistocene, demographic expansions following the last interglacial age in the Pleistocene, and augmentation of COI haplotype diversity during the Pleistocene. Our study sheds light on the potential for COI in examining marine invertebrate species discrimination and distribution in the northwestern Pacific.

Many shell-bearing gastropods exhibit pre-capture behaviors when encountering predatory asteroid sea stars. As shown in this meta-analysis of 48 studies on 24 sea star and 100 gastropod and chiton species, almost three-quarters of prey escape by moving or tumbling away, whereas the remaining species clamp tightly to the substratum or otherwise resist. The aim of the present paper is to correlate these behaviors with predicted shell traits, including those with gravitational stability for species that escape on the substratum and those that clamp, and those with a strongly sculptured shell in species that resist sea star attacks. Escaping species and those that clamp have gravitationally stable shells, with the center of gravity located above the broad aperture and large foot. Species that resist have significantly more sculptured shells. All of these traits would also work well in encounters with other slow-moving predators, such as gastropods and planarians. Although the sea stars are generalist predators, and the gastropods have many enemies besides sea stars, cool-water gastropods are well adapted to predatory sea stars on temperate and polar coasts, where most hard-bottom sea stars with molluscan diets occur. The prominence of escape among cool-water gastropods seems contradictory, given that locomotor speed rises with increasing temperature; but tropical gastropods rely more on armor than on escape, because of the prevalence of faster, more powerful predators in warm water. The black pigment of shells of many temperate prey species of sea stars might confer crypsis against these predators.

Compared to stable reef habitats, dynamic boulder-reefs (commonly called boulder-fields when intertidal) host many habitat specialist species. Most occur underneath boulders where they are largely ...

Things without names are difficult to rationalise, and so species that go without names are difficult to conserve or protect. This is a case study in resolving conflicts in historical taxonomy and ‘real’ species (identifiable and evolutionarily relevant groupings) using an approach including population genetics, natural history, and pragmatism. We report the observation that populations of a shallow-water chiton species from Washington and British Columbia demonstrate extremely high site fidelity and patchy distribution. Their limited dispersal potential and isolation could be explained by a brooding life history. This stands in direct contrast with the supposedly wide distribution of this “species”, Leptochiton rugatus (Carpenter in Pilsbry, 1892) sensu lato, from the Sea of Japan to Baja California. But this lineage has previously been suggested to comprise several cryptic species. Indeed, a haplotype network analysis using 61 individual sequences of the cytochrome oxidase c subunit I gene for L. rugatus s.l. revealed four discrete clusters which correspond to different parts of the geographic range. We infer these to represent four distinct species, at least two of which are likely novel. Leptochiton rugatus sensu stricto is herein reinterpreted as restricted to California and Baja California, and the new name L. cascadiensis sp. nov. is established for the lineage with a distribution in the Cascadia coastal bioregion from the panhandle of Alaska to Oregon. There are minor morphological differences among these species in the L. rugatus species complex, but genetic data or morphological observations alone would not have been sufficient to definitively recognise these groups as species-level lineages. The observation that different species within the complex may have different life history strategies provides important support for interpreting different populations as genuinely separate species.

Indexación: Scopu Intertidal communities’ composition and diversity usually exhibit strong changes in relation to environmental gradients at different biogeographical scales. This study represents the first comprehensive diversity and composition description of polyplacophoran assemblages along the Peruvian Province (SE Pacific, 12°S–39°S), as a model system for ecological latitudinal gradients. A total of 4,775 chitons from 21 species were collected on twelve localities along the Peruvian Province. This sampling allowed us to quantitatively estimate the relative abundance of the species in this assemblage, and to test whether chitons conform to elementary predictions of major biogeographic patterns such as a latitudinal diversity gradient. We found that the species composition supported the division of the province into three ecoregional faunal groups (i.e. Humboldtian, Central Chile, and Araucanian). Though chiton diversity did not follow a clear latitudinal gradient, changes in species composition were dominated by smaller scale variability in salinity and temperature. Body size significantly differed by ecoregions and species, indicating latitudinal size-structure assamblages. In some localities body size ratios differed from a random assemblage, evidencing competition at local scale. Changes in composition between ecoregions influence body size structure, and their overlapping produce vertical size segregation, suggesting that competition coupled with environmental conditions structure these assemblages. © 2019, The Author(s). https://www-nature-com.recursosbiblioteca.unab.cl/articles/s41598-019-52395-z

Environmental heterogeneity is one of the main hypotheses promoting changes in species diversity. Several abiotic and biotic factors that promote environmental heterogeneity generate physical and biological microhabitats, where organisms may find refuge from environmental stress. The abundance, species richness and body size structure of chiton assemblages were estimated in different intertidal microhabitats. These microhabitats (physical: crevices, pools, and boulders; biological: mussel beds, arborescent algae, and crustose algae) were sampled in six sites of the southern Chilean coast during the austral spring of 2016. The results of our study exhibited the species Chiton granosus as the most abundant, followed by C. magnificus and Tonicia chilensis. Species richness and abundance were higher in physical microhabitats, with boulders and crevices showing the highest values, respectively. The multivariate analyses revealed three groups with high similarities within them; the first group represented by crevices, pools, and mussel beds; the second group composed of arborescent and crustose algae; and the third group comprised by boulders. Mussel beds were considered “nursery grounds” for harbouring a high abundance of juveniles of C. granosus ( 10 mm), whilst physical microhabitats and algae host the biggest specimens of both C. magnificus and T. chilensis ( > 30 mm). We suggest that in biological microhabitats, the patterns of species richness and abundance and body size structure would be determined by a relation of functional specificity derived from feeding habits; and, in physical microhabitats, these patterns would be explained by a relation of behavioural specificity derived from negative phototactism.

Homing behaviour is frequently observed in marine intertidal invertebrate species. This behaviour may help species to deal with the environmental variability of the intertidal, providing shelter during low tides and areas to explore and search for food during high tides. The capacity of individuals to show fidelity behaviour should be an adaptive trait, due to the uncertainty that finding a new shelter in each tidal cycle implies. Chiton granosus is a common polyplacophora of the Southeastern Pacific rocky intertidal zone. During high tides, individuals move throughout the substratum in search of food; meanwhile, they are found within crevices in groups of variable sizes during low tides. According to previous works, this species shows some degree of fidelity to these shelters. Using field and laboratory experiments, we herein evaluate the factors determining the degree of site fidelity in C. granosus, taking into account the distance travelled from the shelter and food availability. Also, we evaluated the importance that chemical signs from the pedal mucus have in aiding C. granosus to return to its refuge. Field observations showed that C. granosus presents variable levels of site fidelity covering a maximum distance of 50 cm from its shelter. Laboratory results suggested that fidelity to shelters is related to the proximity of food sources. Chemical cues from the pedal mucus could be used to find the shelter after exploratory activities during high tides.

Sixteen deep-sea polyplacophoran species are reported in this article, fifteen of which were found for the first time in the waters of Taiwan. Two of these species, Leptochiton taiwanensis n. sp. and L. wui n. sp., are described as new to science. Several of these species are distributed near Japan and in other areas of the western Pacific Ocean. Eight of the reported species live and feed on sunken wood. A survey of the polyplacophorans of Taiwan has also been conducted. The updated list of chitons collected near Taiwan at all depths contains 34 species. Seventeen of these species are shallow-water and seventeen species are deep-water chitons.

Chitons are very common molluscs on European rocky shores. They are common prey of fish and crabs and often display several colour morphs within a given habitat. Predation is one of the potential mechanisms accounting for chiton colour polymorphism. The colour variation is considered to provide a camouflage protection through a match with the substratum surface typology. However, the effectiveness of chiton polymorphism as a predation defence requires further investigation. Previously we found a relationship between chiton colour morphs and substrate characteristics, with chitons most commonly found on substrates that were of similar colour to their shells. Here, we examined whether each morph displayed an active choice for matching the substratum. Next, we assessed if the predation success of the intertidal common crab Carcinus maenas varied significantly with the absence/presence of an apparent camouflage effect created between the chiton colour morph and the substratum type. The present study indicates that chiton colour morphs probably actively choose substratum types where they blend in. Carcinus maenas was able to prey on all Lepidochitona cinereus colour morphs, regardless of the substrate camouflage effect. Surprisingly, the predation frequency was higher on camouflaged chitons than on contrasting chitons. It was concluded that chiton camouflage is probably not a defence mechanism against predation by the crab C. maenas, and that chiton colour polymorphism is probably promoted by other, more visual predators.

Polyplacophoran molluscs show low morphological diversity compared to other marine invertebrate clades, yet chitons are ecologically important grazers that occupy a range of distinct ecological niches. We investigated a potential functional correlate of niche separation in three species of co-occurring mopallid chitons that have total ranges across differing environments (Mopalia muscosa, Mopalia lignosa, Katharina tunicata). We found that the force needed to fracture the protective valves varied significantly among species. K. tunicata, whose valves have a relatively reduced exposed dorsal surface, was significantly more resistant to fracture than the two Mopalia species (mean force: K. tunicata = 31.9 ± 4.5 N; M. lignosa = 12.5 ± 0.8 N; M. muscosa = 20.2 ± 0.8 N). In Mopalia spp., the terminal valves were significantly stronger than intermediate valves (i.e. higher force to fracture), whereas all valves in K. tunicata appeared to be functionally equivalent. To assess whether future chemical changes predicted under ocean acidification (OA) will affect these species differently, we measured the force to fracture of valves after 10 days of exposure to elevated pCO2 (control = 8.0 pH [407 ± 104, pCO2], elevated = 7.5 pH [1544 ± 249, pCO2]) for both live animals and dissected individual valves. Although previous experimental OA work found significant impacts of elevated pCO2 on adult mollusc shells over similar timescales, we saw no reduction in total strength related to treatment. Our data demonstrate that diversity in chiton valve morphology has functional implications and that physical changes in local topology and wave exposure may have stronger impacts on adult chitons than changes in ocean chemistry under future climate change.

The chiton Calloplax vivipara was previously considered as ovoviviparous [40]. However, six females of C. vivipara found on Chilean coast brooded both ova and juveniles in their pallial grooves. Therefore, the data of Plate [39, 40] about ovoviviparity in C. vivipara are to be considered incorrect. The present study discusses four methods of reproduction in chitons: (1) free spawning of separate eggs into the water; (2) spawning of eggs as a mucous mass or a mucous string on the bottom; (3) spawning of eggs into the pallial groove of a female, where eggs and larvae are brooded; and (4) spawning of eggs with hulls (capsules) on macroalgal thalli. Tables with lists of brooding species of chitons are included in the paper. Four brooding species have been recorded for the first time, thus increasing the number of brooding species of chitons to 41.

Most species ofIschnochitonare habitat specialists and are almost always found underneath unstable marine hard-substrata such as boulders. The difficulty of experimenting on these chitons without causing disturbance means little is known about their ecology despite their importance as a group that often contributes greatly to coastal species diversity. In the present study we measured among-boulder distributional patterns ofIschnochiton smaragdinus, and used time-lapse photography to quantify movement behaviours within different habitat types (pebble substrata and rock-platform). In intertidal rock-pools in South Australia,I. smaragdinuswere significantly overdispersed among boulders, as most boulders had few individuals but a small proportion harboured large populations.I. smaragdinusindividuals emerge from underneath boulders during nocturnal low-tides and move amongst the inter-boulder matrix (pebbles or rock-platform). Seventy-two percent of chitons in the pebble matrix did not move from one pebble to another within the periods of observation (55–130 min) but a small proportion moved across as many as five pebbles per hour, indicating a capacity for adults to migrate among disconnected habitat patches. Chitons moved faster and movement paths were less tortuous across rock-platform compared to pebble substrata, which included more discontinuities among substratum patches. Overall, we show that patterns of distribution at the boulder-scale, such as the observed overdispersion, must be set largely by active dispersal of adults across the substratum, and that differing substratum-types may affect the degree of adult dispersal for this and possibly other under-boulder chiton species.

The plesiomorphic state of the molluscan scleritome remains ambiguous. Chitons are significant because they show a mix of characters considered diagnostic in both aplacophorans and conchiferans, with both shell plates and small calcified girdle elements on an elongate body, and there is no consensus on the homology of structures involved in chiton plate calcification with those in conchiferan shells. Using light, scanning, and transmission microscopy, the present study examined the structure and formation of the cuticle and underlying epithelium in five chiton species collected over several years in southeast Spain and in California, USA. The cuticular matrix in chitons is similar to the translucent layer of the bivalve periostracum, although there are differences in the orientation of the densely spaced laminae with respect to the mantle surface. The cuticle arises in the accessory fold of the ventral girdle mantle. There is full continuity between the outermost layer of the cuticle and the thin outer layer of the tegmentum, suggesting that the latter is derived from the cuticular wedge permanently lying on the plate margins. A homology is proposed between the cuticle/associated girdle mantle epithelium of Polyplacophora and the periostracum/inner side of the outer mantle fold of the Bivalvia. Nevertheless, while the bivalve periostracum slides over the mantle epithelium during growth, the polyplacophoran cuticle remains stationary. The configuration of the cuticle, which overlaps the plate margins, allows it to efficiently close the plate biomineralization compartment, in a way comparable to that of the periostracum of conchiferans.

Drillholes represent direct evidence of ecological interactions in the fossil record. Most of them have been interpreted as predatory in origin and enable the analysis of behavioral information of both predator and prey. Drillholes have been found in a variety of fossil organisms, but this is the first report of a bored fossil chiton plate. It was found in the La Coronilla deposit, a Late Pleistocene invertebrate assemblage from southeastern Uruguay. The drillhole belongs to the ichnospecies Oichnus simplex and is attributed to a muricid gastropod, which could likely have been the ocenebrinid Urosalpinx haneti, recorded in the fossil assemblage. The drillhole features all traits for a predatory origin. However, the rareness of this particular interaction between chitons and gastropods in the fossil record and in the recent, could signify an event of arbitrary drilling. The reported occurrence here raises the question as to whether this behavior represents an understudied ecological interaction between polyplacophorans and gastropods. Fil: Rojas, Alejandra. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Verde, Mariano. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Urteaga, Diego Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Scarabino, Fabrizio. Ministerio de Ganadería, Agricultura y Pesca; Uruguay Fil: Martínez, Sergio. Universidad de la República. Facultad de Ciencias; Uruguay

Sea urchins provide habitat for many other invertebrates and fish which live in association with the spines or tests of the urchins. In boulder-fields in New South Wales, Australia, there is a large suite of chitons of the genus Ischnochiton, most of which show very overdispersed patterns of abundance among boulders, with many individuals aggregated onto few boulders. Most species are too sparse to manipulate experimentally to test hypotheses about their strong patterns of association with particular boulders, but the most common species, Ischnochiton australis, is strongly associated with the urchin, Heliocidaris erythrogramma, at two spatial scales. The two species occurred together on boulders more than expected by chance and, on boulders occupied by both species, abundances were positively correlated. In addition, I. australis were predominantly found under the spines and tests of the urchins. These patterns were general in time and space. Despite the relative rarity of the chiton, experiments were done to test hypotheses about the presence of each species influencing dispersal among boulders of the other species. Sample size was necessarily small because the chitons are not widespread among the boulders and not all experimental treatments and procedural controls could be included due to limited habitat containing chitons and urchins. Nevertheless, replicate small experiments showed that chitons decreased in abundance under boulders from which urchins had been removed, more than under boulders with chitons, although not all tests were significant. Urchins, in contrast, showed no effects of removal of chitons. Thus, it is likely that urchins provide habitat for chitons, rather than the reverse. Therefore, removal of urchins from these habitats by harvesting could have large negative effects on abundances of this relatively rare intertidal chiton, which appears to be a habitat-specialist. These experiments should offer insight into responses to habitat-needs for other rare molluscs and provide guidance on the value of experimental tests of habitat-specificity for rare species, even when rarity itself reduces the scope of the experimental treatments that can be used.

Marine Priority Region No. 33 (MPR 33) lies in the State of Guerrero, where the National Commission for Knowledge and Use of Biodiversity has declared a lack of information on marine species, Class POLYPLACOPHORA among others. This program was carried out on the rocky intertidal zone of MPR 33 with the objectives to: 1) determine species richness, 2) community composition based on families represented, 3) estimate the density, 4) index of diversity, 5) analyze body proportions and 6) geographic distribution of species. Three surveys on five sites were conducted during 2009 and 2012, using one mt2 quadrant for systematic sampling procedure; collecting all POLYPLACOPHORA specimens found within the quadrants, then proceeding with their preservation. 441 organisms were analyzed where 17 species were identified, on nine genera within six families. Fifteen new species were recorded for the MPR 33. Family ISCHNOCHITONIDAE Dall, 1889 was the best represented in species richness and CHITONIDAE Rafinesque, 1815 in abundance. Density of 8.82 organisms/m2, the H′ index was 2.38 bits/individuals and J′ = 0.57. The species Chiton (Chiton) articulatus Sowerby, 1832 showed the highest density, greater size and was found in all five collection sites. Three species, (Chiton (C.) articulatus, Ischnochiton (Ischnochiton) muscarius (Reeve, 1847) and Chiton (Chiton) alboli-neatus Broderip & Sowerby, 1829), were considered wide. Intertidal species richness was associated with habitat stability and wave intensity; the more unstable sites had greater richness while most stable sites lower. Species inventory and understanding the communities’ interactions of the marine fauna of the State of Guerrero are important; therefore these efforts must be continued.

Through histological analyses, this study reveals an unusually high incidence of hermaphroditism in Chiton articulatus. Specimens were sampled every 30 days between September 2010 and September 2011 at two locations (Las Brisas and Jaramillo beaches, Acapulco) on the tropical eastern Pacific coast of Mexico. At both sites, hermaphroditism was found throughout the year, although in varying proportions. Higher percentages of hermaphroditism were found during the pre-spawning summer months (Las Brisas Beach 63%, Jaramillo Beach 68%). Two different kinds of hermaphroditic gonads were found, showing a preponderance of either male or female tissues but, commonly, female tissues occupied the greatest part of the gonad cross sections. Similar to other species of polyplacophorans, there was a predominance of males, although M:F sex ratios ranged from 0.7 to 4.5: 1 at Las Brisas Beach and 0.3-8: 1 at Jaramillo Beach. Fil: Ramírez Álvarez, Citlalith. Universidad Autónoma de Guerrero; México Fil: Vélez Arellano, Nurenskaya. Instituto Politécnico Nacional. Centro Interdisciplinario de Ciencias Marinas; México Fil: García Domínguez, Federico Andrés. Instituto Politécnico Nacional. Comisión de Fomento y Actividades Académicas; México. Instituto Politécnico Nacional. Centro Interdisciplinario de Ciencias Marinas; México Fil: García Ibáñez, Sergio. Instituto Politécnico Nacional. Centro Interdisciplinario de Ciencias Marinas; México Fil: Ituarte, Cristian Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina

At present, over 300 species of marine alien Mollusc are reported from the European waters (Streftaris et al. 2005; Zenetos et al. 2010). However, only three alien polyplacophoran have been recorded: Chaetopleura angulata (Spengler, 1797), Acanthopleura gemmata (Blainville, 1825) and Chiton hululensis (E. A. Smith, 1903); the latter is considered as “questionable” (Zenetos et al. 2010). These polyplacophoran constituting about 1% of the alien marine mollusc reported from Europe. Here we present the first record of Tonicia atrata (Sowerby, 1840) and Chiton cumingsii Frembly, 1827 in European waters, constituting the first evidence of their presence outside their native range. Furthermore, we give brief notes on the taxonomy and distribution of T. atrata and C. cumingsii , and discuss the potential pathways for introduction toEurope.

The rock type of hard substrata marine habitats can affect numerous benthic invertebrates, but little is known of the effects on molluscan assemblages, for example, the chitons often found under intertidal boulders. We compared chiton assemblage composition, abundance, species richness, and patterns of frequency distribution in 10 boulder fields containing either hard metamorphic/igneous boulders or soft limestone boulders in two geographical areas in South Australia. Similar species richness occurred in both types of boulder fields, but hard rock boulder fields had greater overall abundances, because of particularly large abundances of some common species. Differences in abundances of common species also resulted in significantly different assemblages occurring between the boulder field types. Some species appeared aggregated among boulders, but this pattern was variable between boulders in differing areas and of differing rock type. In one area, a common species had variable aggregation that caused freq...

The polyplacophoran Chiton articulatus Sowerby, 1832, is distributed along the tropical Pacific coast of Mexico and has been collected for generations in an artisanal manner for bait or as a complement in domestic cookery of coastal inhabitants; nevertheless, recently, some restaurants are offering this chiton to the tourists as a gourmet and aphrodisiac food, thus becoming of potential economic interest. This study explores in a population of C. articulatus adults from Oaxaca, southern Mexican Pacific, the changes in morphometry and in somatic and reproductive indices throughout one year, reporting on five reproductive indices, five somatic indices, body shape (BS), and length-weight relationships. An attempt is made to elucidate the energetic trade-off between somatic and reproductive tissues, including an assessment of whether these can be estimated from noninvasive indices. Somatic indices diminished considerably as gonad development proceeded, thus showing an inverse relationship with repro...

Most species of Polyplacophora are found in shallow, coastal water, and their distribution and ecology is generally well known. On the contrary, information related with distribution, biology and ecology of deep-sea chitons is scarce. Specimens of the deep-sea mollusks fauna were obtained during sampling operations of western Mexico (TALUD project) aimed at the study of invertebrate fauna occurring under the Oxygen Minimum Zone (OMZ). The material reported herein is part of the Polyplacophora fauna collected with a benthic sledge off the west coast of the Baja California Peninsula, in the eastern Pacific, Mexico. The deep-sea chiton Tripoplax cf. balaenophila Schwabe & Sellanes 2004 was collected in 530–625 m depth, in the following environmental conditions: dissolved oxygen

Polyplacophoran molluscs (chitons) are phylogenetically ancient and morphologically constrained, yet multiple living species are often found co-occurring within widely overlapping ecological niches. This study used two sets of experiments to compare interspecific variation among co-occurring species in the North Atlantic (Ireland) and separately in the North Pacific (British Columbia, Canada) chiton faunas. A complementary review of historical literature on polyplacophoran physiology provides an overview of the high level of metabolic variability in this group of ‘living fossils’. Species examined in de novo experiments showed significant variation in oxygen consumption both under air-saturated water conditions (normoxia), and in response to decreasing oxygen availability (hypoxia). Some species demonstrate an ability to maintain constant oxygen uptake rates despite hypoxia (oxyregulators), while others oxyconform, with uptake rate dependent on ambient oxygen tension. These organisms are often amalgamated in studies of benthic communities, yet show obvious physiological difference that may impact their response or tolerance to environmental change.

Few studies have documented chiton growth rates, and lifespans for most chiton species remain unknown. This study presents the first size-at-age and longevity estimates for Cryptochiton stelleri and Katharina tunicata, two of the largest known species of chitons. Age estimates were based on growth ring counts obtained by cross-sectioning and polishing valves. This process alone showed clear growth rings in shell plates of K. tunicata. Valves of C. stelleri did not show conspicuous growth rings in cross section, so the acetate peel technique was used to highlight growth bands. Linear growth in terms of body length and shell width approached an asymptote in both species and was described with the von Bertalanffy growth function. Both C. stelleri and K. tunicata displayed indeterminate growth with regard to tissue weight and shell weight, continuing to maintain a steady growth rate throughout their lifespans. The oldest K. tunicata specimen was estimated to be 17 years old. The oldest C. stelleri was estimated to be 40 years old, making it the longest-lived chiton species known.

The coast of Acapulco is located within the Marine Priority Region No. 32 (MPR No. 32) at the State of Guerrero, Mexico. The National Commission for the Knowledge and Use of Biodiversity has stated the lack of information on marine species that live there, among which are the Class Polyplacophora. This study aimed to: 1) determine species richness, 2) the community structure based on the representative families, 3) estimate the density, 4) locate species distribution, 5) determine their degree of occurrence (hierarchical position) within the community, 6) analyze the structure of length and width across the populations and 7) estimate the diversity index. The intertidal rocky substrate at seven beaches was sampled from 2009 to 2012. The sampling unit 1 m2, while the area sampled was 10 m2. It was analyzed 2.548 specimens of Polyplacophora, with 20 species identified. Tonicellidae and Ischnochitonidae were the Families better represented inspecies richness and Chitonidae in abundance. Lepidochitona flectens is a new record for the Mexican Tropical Pacific and Stenoplax mariposa for MPR. No. 32. The density was 25.48 specimens/m2. Eight dominant species were determined. Chiton albolineatus had the highest density. Ischnochiton muscarius, Chaetopleura unilineata, Chiton albolineatus and Chiton articulatus presented wide distribution. Chiton articulatus showed the largest size in length and width. H’ = 2.01 bits/ individual. Numerous dominant species were present with broad and regular distribution, probably due to Polyplacophora body design, which allows for better adaptation to the rigorous environmental conditions of the rocky intertidal.

Rafting has long been invoked as a key marine dispersal mechanism, but biologists have thus far produced little genetic evidence to support this hypothesis. We hypothesize that coastal species associated with buoyant seaweeds should experience enhanced population connectivity owing to rafting. In particular, invertebrates strongly associated with the buoyant bull-kelp Durvillaea antarctica might be expected to have lower levels of population-genetic differentiation than taxa mainly exploiting nonbuoyant substrates. We undertook a comparative genetic study of two codistributed, congeneric chiton species, assessing population connectivity at scales of 61-516 km, using ≥ 186 polymorphic AFLP loci per species. Consistent with predictions, population-genetic differentiation was weaker in the kelp-associated Sypharochiton sinclairi than in the rock-associated S. pelliserpentis. Additionally, while we found a significant positive correlation between genetic and oceanographic distances in both chiton species, the correlation was stronger in S. pelliserpentis (R(2) = 0.28) than in S. sinclairi (R(2) = 0.18). These data support the hypothesis that epifaunal taxa can experience enhanced population-genetic connectivity as a result of their rafting ability.

We present a phylogeographic study of the New Zealand andAustralian intertidal chiton Sypharochiton pelliserpentis that was conducted to ascertain levels of population connectivity and to investigate the effect of previously hypothesized general phylogeographic boundaries. The analysis incorporated both cytochrome oxidase subunit 1 sequence data (approximately 700 bp) and RFLP data from 29 populations around New Zealand, and from one Australian population, for a total of N = 472. The major population structure observed was a strong disjunction between northern and southern populations (FST = 0.47), with the genetic breaks located at Cloudy/Clifford Bay and Farewell Spit, at the northern tip of the South Island. This finding corresponds with a common phylogeographic barrier observed in a number of other marine invertebrates, highlighting its significance and ubiquity.Athird barrier to gene flow was identified between Spirits Bay and Ahipara, around the northern tip of the North Island. All three of these areas that exhibit significant population disjunctions have strong near-shore upwelling along with water current movement offshore, and these features are prevalent during the time of year when S. pelliserpentis spawns. That these seasonal hydrographic patterns contribute to the population structuring of S. pelliserpentis is supported by comparison with other phylogeographic studies of marine invertebrates, where the strength of this barrier seems to correlate with spawning season. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 552‐563.

Among the diverse patterns of energy allocation to the offspring of gastropods, the presence of egg capsules to protect embryos is common. Females of the edible snail Zidonadufresnei attach egg capsules to hard substrates in shallow Argentine Patagonian waters (40°45′S, 64°56′W) during spring-summer. Embryonic development takes about 30 days at 22°C. In this study, three likely capsule predator species and the marks left by each on egg capsule walls were identified in laboratory experiments in February 2010. Abundances of predators and egg capsules with evidence of predation were assessed in the field in the summers of 2010 and 2011. Under laboratory conditions (N = 10 replicates per treatment and control), the predation rate by the chiton Chaetopleuraisabellei was the highest (up to 90%), followed by the gastropod Tegulapatagonica and the crab Neohelicegranulata (~20% each). Nearly 60% of 41 capsules found in the field showed signs of predation. According to the marks identified in the laboratory, C. isabellei was responsible for 79% of this predation, and T. patagonica for the rest. Predation appears to be important during the encapsulated early life and could be an agent for selecting for resistant capsule walls and a relatively shorter development time.

This paper focuses on five species of Polyplacophora (Mollusca) collected from Lavanono, southern Madagascar. Ischnochiton sirenkoi is described as a new species and is compared with the two Ischnochiton species known from Madagascar, I. yerburyi (E.A. Smith, 1891) and I. sansibarensis Thiele, 1909, and with all known Indian Ocean Ischnochiton species. Findings for the other species here discussed provide a significant extension of previously known geographical range. Chaetopleura chelazziana Ferreira, 1983 is reported for the first time in the chiton fauna of Madagascar. The taxonomic status of Callistochiton ashbyi (Barnard, 1963), previously considered a synonym of C. crosslandi Sykes, 1907, is discussed. This taxon, which was described from a unique intermediate valve from South Africa, is re-evaluated and recognized as a valid species, differing from C. crosslandi in several significant characters. We also present an unusual feature detected in almost all the specimens of Cryptoplax dupuisi Ashby, 1931, which are characterized by the absence of dorsal girdle spicules on the first four valves, a feature never reported in other chiton species. Type material of Callistochiton madagassicus Thiele, 1909, Chiton ashbyi (Barnard, 1963) is figured.

Many species are aggregated at some spatial scale but for some species, due to habitat or behaviour, aggregation can be difficult to assess quantitatively. Here, aggregation of chiton species (Polyplacophora; Neoloricata; Ischnochitonina; Ischnochitonidae; Ischnochitoninae; Ischnochiton) living under boulders in intertidal boulder fields was investigated at several relatively small spatial scales. Closely related species were found to be aggregated at the level of individual boulders, but evidence for grouping at the larger scale of patches of boulders varied. When organisms are mobile, dispersal can have an important influence on spatial patterns. Some organisms, such as marine invertebrates, have a highly dispersive larval phase that can influence spatial patterns of adults, particularly where the adult is sessile or relatively sedentary. Aggregation was compared in two species to test whether different modes of larval development influence spatial pattern. There was some evidence that species with a planktonic larva were even more aggregated than expected, in contrast to predictions based on this mode of development. Both types of larval development (planktonic and non-planktonic) produce larvae with short development times in these species, so one possible explanation for the grouping habit of these chitons is that they do not disperse, at all, from their natal boulder. The complexity of the boulder field habitat and the cryptic behaviour of these chitons may also contribute to a lack of dispersal. A simple application of a genetic method indicated, however, that philopatry at this scale is unlikely.

Cryptochiton stelleri is the largest herbivore in the intertidal and subtidal zone throughout its North Pacific range, but its larval development and metamorphosis have not been well documented. A description of larval development for specimens in Hokkaido, Japan, has been used in multiple textbooks yet shows many features atypical of chiton development. In the present study in Oregon, C. stelleri larvae were raised in culture and displayed developmental stages similar to other chitons, very different from the previous description. Plate development began 3 days after hatching. Larvae were competent beginning 3 days posthatching and metamorphosed in response to extract from encrusting coralline algae. Larvae survived for over a month without metamorphosing and did not metamorphose in response to increased temperature, presence of adults or the addition of algal foods of adults or juveniles. Juvenile C. stelleri were discovered in the field and grew c. 4 mm per month in captivity. Juveniles had exposed shell plates and fed on the red alga Cryptopleura.

The intertidal chiton Acanthopleura gemmata (Blainville) is a central place forager which rests in a dug scar and moves at nocturnal low tide. The fraction of chitons abandoning the home during each potential foraging phase is reduced after experimental overcrowding. On the contrary, reduced crowding in the natural population increases number of active chitons. Feeding excursions after increasing or reducing crowding are shorter than in control chitons. Also the orientation of migration is scattered after manipulation. Animals sharing their home with a conspecific suppress migrations, but local overcrowding when body-contact is lacking also reduces activity. Rest zonation in overcrowded areas shifts upward, and most imported chitons fail to home. Induced home co-ownership is followed by overt aggressive patterns and by a “waiting war”. Conflicts are resolved according to size ratio between contestants.

In the Red Sea, pearl oyster banks occur most extensively around the Dahlak and the Farasan Islands. Pearl oysters (Pinctada, Pteriidae) form extended beds by attaching themselves to hard substrates. Such beds attract a diverse bio-fouling fauna. Most dominant are the molluscs, but little is known about the associated biota of pearl oyster beds, their distributional abundance, and the structure of this community. In this study, the macro-molluscan fauna living on pearl oyster beds in the Red Sea around the Farasan Islands was studied using a quantitative survey of the by-catch left by pearl oyster divers. Bivalvia represented 99.6% of the malaco-fauna on pearl oyster beds around the Farasan Islands, while gastropods and chitons represented only 0.4%. In total, 33 mollusc species were identified (24 bivalves, 7 prosobranch gastropods, one basomatophore gastropod and one chiton), with Brachidontes variabilis, a species which is not found on Arabian Gulf pearl oyster beds, the most common bivalve (7...

As a social activity in “Korea and Japan Joint Symposium on Biology of Tidal Flats 2009” held in Sucheon, Jeollanam-do, the southern part of South Korea, most of the participants to the symposium joined the surveys with the purpose of making a list of macrobenthic fauna that occur on Suncheon Bay Tidal Flats with approximately 1,200 ha in total area between June 21 and 23, 2009. In this survey, sixteen species of bivalves, twenty species of gastropods, one species of chiton, fourteen species of polychaetes, eight species of crabs, and three species of other animals were collected, and identified by the participants. Among these sixty-one species, two species of macrobenthic invertebrate animals including gastropod, Ellobium chinense, and crab, Sesarmops intermedius, are listed in the latest Red List of the Ministry of Environment of the Republic of Korea, and eight species of them including five species of potamidid gastropods are listed in that of the Ministry of Environment, Japan. The results of this survey indicate that the ecosystem on the tidal flats in Suncheon Bay are still healthy, and preserved almost in their original conditions, due to the serious efforts of the people in Suncheon City and the municipal authorities.

We present data on sponge species found to serve as substrate and prey to the chiton Hanleya nagelfar in Northern Scandinavian waters and describe a recently discovered sponge–sponge–chiton association. A specimen of H. nagelfar was found to display selective feeding and homing behaviour on a massive sponge covered by an encrusting sponge. The nature of this three-fold association is discussed.

In the early twentieth century, Dwight Blaney (1865–1944) and William Procter (1872–1951), two men of disparate genteel backgrounds, congregated in the summers with many of America's social elite in Maine's Bar Harbor region. Not prone to idleness, Blaney and Procter dredged the waters of Frenchman Bay for marine mollusks, Blaney in 1901–1909 and Procter in 1926–1932. Blaney collected 149 species: 6 chitons, 62 bivalves, 2 scaphopods, and 79 gastropods. Two of the mollusks were new species that were named after him: Tonicella blaneyi (a chiton) and Oenopota blaneyi (a gastropod). In 1904, Blaney made a survey of the land snails of Ironbound Island, his home in Frenchman Bay, finding 19 species. This survey remains the definitive study of the island. In 1916, Blaney and paleontologist Frederic Brewster Loomis extricated 23 marine mollusks from the Pleistocene clays of Mount Desert Island. Nine of these species were no longer living in Frenchman Bay, but had presumably moved to more northern climes...

Epibiotic foraminifers selectively settle on the most food-rich area of the host substrate, even when the species acts as a facultative ectoparasite in later life stages. In 398 specimens examined of the deep-sea chiton Leptochiton arcticus from Iceland, 46% show evidence of infestation by foraminifers, with many showing extensive shell damage from present and past bioeroding epibionts. Disturbances to the inner layer of the host shell are indicative of parasitism, as evidenced both by wound healing calcification and protrusions of the foraminiferan tubules. The epibionts employ different feeding strategies at different stages of their life cycle, taking advantage of nutrient availability from the posterior respiration currents and excrement of the chitons as juveniles, and feeding parasitically as adults. Epibiont persistence on individual hosts – through successive generations, or long-term continuous bioerosion by epibionts – allow larger adult parasitic foraminifers of Hyrrokkin sarcophaga to...

This study investigated the taxonomy and distribution of the deep‐sea polyplacophoran mollusc Nierstraszella Sirenko, 1992 in the Indo‐West Pacific, based on a collection of 516 specimens collected in the Philippines and Solomon Islands. Although seven species names have historically been proposed in this group of chitons, all have been considered as synonyms of the monotypic N. lineata (Nierstrasz, 1905). Morphological examination of this new material reveals the presence of two species. N. lineata is distinct from N. andamanica (Smith, 1906), based on morphological characters given in the original species description and very distinctly different morphology of aesthete pores in the shell surface. Furthermore, populations of N. andamanica in the Philippines and Solomon Islands are locally colonized with the epibiotic (ectoparasitic) bryozoan Pseudobathyalozoon profundum d'Hondt, 2006. These bryozoans attach ventrally to the girdle of the host chiton and the erect zooids feed within the pallial cavity, am...

The chiton fossil record is richer than previously reported in the literature. A newly compiled database comprised of Cambrian to Pleistocene fossil chitons totals 2594 occurrences of 900 species. Of the 900, 430 are named species known only as fossils, 123 are extant species that also have a fossil record, and 247 are indeterminate taxa. Most of the database (61%) consists of fossil chiton occurrences reported from localities other than type localities. A preliminary analysis of the data using the collector curve method suggests that the chiton fossil record has not been adequately sampled by geographic regions or geologic time. The fossil record of chitons is incomplete, sporadic, and geographically limited because the sampling record has been incomplete, sporadic, and geographically limited. The current database comprises enough information to discern diversity patterns throughout geologic time, but whether the patterns are real or artifacts of sampling inadequacy remains to be investigated.

The present study describes the species composition and vertical distribution of chitons in tide pools and on exposed rock areas of the intertidal zone of Samara, Guanacaste, Pacific Costa Rica. Nine different species of chitons were recorded, and their densities and sizes were determined using quadrate sampling. Physical (period of emersion, temperature and salinity range) and biotic (presence and diversity of food resources) factors were examined to assess their influence on distribution and abundance of each species.Ischnochiton disparwas the predominant species with densities of up to 200 ind m−2, representing 85.4% of all sampled individuals (N = 4193). The size ofI. disparwas positively correlated with the size of the inhabited boulders. Two species (I. disparandStenoplax limaciformis) showed segregation in size:I. disparbeing negatively andS. limaciformispositively correlated to the distance from the shore. Two of the nine species (Chiton stokesiiandAcanthochitona hirundiniformis) occurred mainly on rocky areas outside the tide pools with variable amounts of exposure to air during each tidal cycle. In both species the tide pool specimens were significantly smaller than those collected in the rocky areas. Distribution of all other species was restricted to the tide pools and species had their peak abundance in the zones with more moderate conditions and a higher diversity of algae, resulting in the highest chiton diversity in these areas.

A cold-shock technique was used to determine radula production rates for the chitonsAcanthopleura hirtosaandPlaxiphora albida, and for the limpetPatelloida alticostata, which replaced their radular teeth at rates of 0.40, 0.36 and 0.51 rows d−1, respectively. These rates are far slower than those determined previously for non-iron-mineralizing molluscs, suggesting that the improved working life of the teeth afforded by iron-mineralization acts to significantly reduce replacement rates. In addition, inductively coupled plasma-atomic emission spectroscopy has been used to determine the quantity of iron and other elements comprising the radula of each species. These data, used in conjunction with the radula production rates, reveal thatA. hirtosa,Plaxiphora albidaandPatelloida alticostatahave daily radula mineralization requirements for iron of 3.06, 4.12 and 0.55 μg, respectively. Such information is vital for continuing studies related to the cellular delivery of ions and subsequent biomineralization of the tooth cusps in chitons and limpets.

The bioerosive potential of the intertidal chiton Acanthopleura gemmata on One Tree Reef was determined by quantification of CaCO3 in daily faecal pellet production of individuals transplanted into mesocosms after nocturnal-feeding forays. Mean bioerosive potential was estimated at 0.16 kg CaCO3 chiton-1 yr-1. Bioerosion rates were estimated for populations on two distinct chiton habitats, reef margin (0.013 kg CaCO3 m-2 yr-1) and beachrock platform (0.25 kg CaCO3 m-2 yr-1). Chiton density on the platform was orders of magnitude greater than on the reef margin. The surface-lowering rate (0.16 mm m-2 yr) due to bioerosion by the beachrock population is a substantial contribution to the total surface-lowering rate of 2 mm m-2 yr-1 previously reported for One Tree Reef across all erosive agents. At high densities, the contribution of A. gemmata to coral reef bioerosion budgets may be comparable to other important bioeroders such as echinoids and fish. © 2008 Springer-Verlag.

Molluscan grazers can have important effects on the abundance, colonization rates, and successional pathways of algal assemblages and the entire intertidal community. In general, early successional algae are more readily consumed than corticated algae and kelps, which usually get established later in the community succession. To generalize, however, the effect of different grazers on algal assemblages must be examined on different coasts and under different scenarios. This information could help us understand the mechanisms of ecosystem processes and situations in which general models do not apply. Along the coast of Chile, humans harvest large keyhole limpets, which seem to be the only invertebrate grazers capable of controlling the dominant corticated alga Mazzaella laminarioides, a canopy-forming species that can cover extensive areas of the mid intertidal zone. In this scenario, where large limpets are harvested, the overall effects of the diverse molluscan assemblage of limpets, chitons and snails on algal succession and on corticated algae in particular are not clear. We conducted a 26-month-long experiment to evaluate the effects of molluscan grazers on mid-intertidal algal succession and to isolate the effects of Chiton granosus, the most conspicuous member of the assemblage at these tidal elevations. At sites heavily impacted by humans the molluscan grazer assemblage had strong negative effects on colonization and abundance of green algae such as ulvoids and Blidingia minima. In doing so, the grazer assemblage had a strong negative indirect effect on the establishments of chironomid fly larvae, which were only observed on green algal mats and rarely on bare rock. No significant effects were detected on epilithic microalgae, and effects on sessile invertebrates were highly variable over space and time. C. granosus also had significant negative effects on green algae but did not account for the total grazing pressure exerted by the guild. Limited foraging excursions (ca. 35 cm) from refuges and moderate site (crevice) fidelity in this species may contribute to the patchiness in green algal distribution observed in the field. Nearly 13 months after rock surface were experimentally cleared, M. laminarioides appeared in all experimental plots, but increased over three times faster in enclosures containing C. granosus than in exclosures plots or controls, suggesting that moderate levels of herbivory could actually facilitate the establishment of this alga in the succession and that the green algal cover found in the absence of grazers may delay its establishment.