A morphological basis for path-dependent evolution of visual systems.

Path dependence influences macroevolutionary predictability by constraining potential outcomes after critical evolutionary junctions. Although it has been demonstrated in laboratory experiments, path dependence is difficult to demonstrate in natural systems because of a lack of independent replicates. Here, we show that two types of distributed visual systems recently evolved twice within chitons, demonstrating rapid and path-dependent evolution of a complex trait. The type of visual system that a chiton lineage can evolve is constrained by the number of openings for sensory nerves in its shell plates. Lineages with more openings evolve visual systems with thousands of eyespots, whereas those with fewer openings evolve visual systems with hundreds of shell eyes. These macroevolutionary outcomes shaped by path dependence are both deterministic and stochastic because possibilities are restricted yet not entirely predictable.

HES and Mox genes are expressed during early mesoderm formation in a mollusk with putative ancestral features.

The mesoderm is considered the youngest of the three germ layers. Although its morphogenesis has been studied in some metazoans, the molecular components underlying this process remain obscure for numerous phyla including the highly diverse Mollusca. Here, expression of Hairy and enhancer of split (HES), Mox, and myosin heavy chain (MHC) was investigated in Acanthochitona fascicularis, a representative of Polyplacophora with putative ancestral molluscan features. While AfaMHC is expressed throughout myogenesis, AfaMox1 is only expressed during early stages of mesodermal band formation and in the ventrolateral muscle, an autapomorphy of the polyplacophoran trochophore. Comparing our findings to previously published data across Metazoa reveals Mox expression in the mesoderm in numerous bilaterians including gastropods, polychaetes, and brachiopods. It is also involved in myogenesis in molluscs, annelids, tunicates, and craniates, suggesting a dual role of Mox in mesoderm and muscle formation in the last common bilaterian ancestor. AfaHESC2 is expressed in the ectoderm of the polyplacophoran gastrula and later in the mesodermal bands and in putative neural tissue, whereas AfaHESC7 is expressed in the trochoblasts of the gastrula and during foregut formation. This confirms the high developmental variability of HES gene expression and demonstrates that Mox and HES genes are pleiotropic.

Composition of the genus Loricella (Mollusca: Polyplacophora: Loricidae) and the description of two new species.

The genus chiton Loricella is revised. It comprises nine species. Two of these species, L. neoguinensis n. sp. and L. solomonensis n. sp., are described as new. Based on the analysis of morphological features studied using a scanning electron microscope, a revised diagnosis of the genus is provided. The characters diagnostic for this that distinguish it from the related genus Squamophora are as follows: a tubular hollow inside the dorsal scales, bristles on the dorsal side of the girdle, a wide ventral mouth region, a narrow mantle fold covered with simple longitudinally ribbed scales, smooth ventral scales, pits arranged in longitudinal rows in the central area of the tegmentum, and a bicuspid head of the major lateral teeth of the radula.

Composition of the genus emConnexochiton/em Kaas, 1979 (Mollusca: Polyplacophora: Ischnochitonidae).

The species composition of the genus Connexochiton is revised. So far, six Recent species of the genus Connexochiton have been known: C. platynomenus, C. kaasi, C. crassus, C. bromleyi, C. moreirai and C. discernibilis After the present revision, the genus consists of Connexochiton platynomenus, C. kaasi, C. crassus, as well as three new species, C. costatus n. sp. from the Philippines, C. kermadeci n. sp. from New Zealand and C. solomonicus n. sp. from the Solomon Islands. Connexochiton discernibilis was assigned to the ischnochitonid genus Stenosemus (now Stenosemus discernibilis). Connexochiton bromleyi and C. moreirai are transferred back to the genus Ischnochiton. Principle features of the genus Connexochiton include: a distinctive shape of the valves with the hind edge of the intermediate valves noticeably turned down, which makes the lateral areas narrow and appearing strongly raised; tegmentum delicately sculptured by quincuncially arranged triangular granules that form an alveolate pattern; each granule has 9 to 11 aesthete pores; apophyses are connected medially by a short jugal plate, dorsal scales of the girdle are strongly bent, with short longitudinal ribs or spherules or both; head of the major lateral teeth of radula is unicuspid and sickle-shaped. An identification key for the species of the genus Connexochiton is provided.

Arctic coastal benthos long-term responses to perturbations under climate warming.

Climate warming influences structure and function of Arctic benthic ecosystems. Assessing the response of these systems to perturbations requires long-term studies addressing key ecological processes related to recolonization and succession of species. Based on unique time-series (1980-2017), this study addresses successional patterns of hard-bottom benthos in two fjords in NW Svalbard after a pulse perturbation in 1980 and during a period of rapid climate warming. Analysis of seafloor photographs revealed different return rates of taxa, and variability in species densities, through time. It took 13 and 24 years for the community compositions of cleared and control transects to converge in the two fjords. Nearly two decades after the study initiation, an increase in filamentous and foliose macroalgae was observed with a subsequent reorganization in the invertebrate community. Trait analyses showed a decrease in body size and longevity of taxa in response to the pulse perturbation and a shift towards small/medium size and intermediate longevity following the macroalgae takeover. The observed slow recovery rates and abrupt shifts in community structure document the vulnerability of Arctic coastal ecosystems to perturbations and continued effects of climate warming. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.

A mitogenomic phylogeny of chitons (Mollusca: Polyplacophora).

BACKGROUND: Polyplacophora, or chitons, have long fascinated malacologists for their distinct and rather conserved morphology and lifestyle compared to other mollusk classes. However, key aspects of their phylogeny and evolution remain unclear due to the few morphological, molecular, or combined phylogenetic analyses, particularly those addressing the relationships among the major chiton lineages. RESULTS: Here, we present a mitogenomic phylogeny of chitons based on 13 newly sequenced mitochondrial genomes along with eight available ones and RNAseq-derived mitochondrial sequences from four additional species. Reconstructed phylogenies largely agreed with the latest advances in chiton systematics and integrative taxonomy but we identified some conflicts that call for taxonomic revisions. Despite an overall conserved gene order in chiton mitogenomes, we described three new rearrangements that might have taxonomic utility and reconstructed the most likely scenario of gene order change in this group. Our phylogeny was time-calibrated using various fossils and relaxed molecular clocks, and the robustness of these analyses was assessed with several sensitivity analyses. The inferred ages largely agreed with previous molecular clock estimates and the fossil record, but we also noted that the ambiguities inherent to the chiton fossil record might confound molecular clock analyses. CONCLUSIONS: In light of the reconstructed time-calibrated framework, we discuss the evolution of key morphological features and call for a continued effort towards clarifying the phylogeny and evolution of chitons.

Phylogenetic Relationships Among Japanese Species of the Genus Ischnochiton (Polyplacophora: Ischnochitonidae), Including a New Species.

Seven (including one new) species of the polyplacophoran genus Ischnochiton (Ischnochitonidae) from the Pacific coast of Japan, namely, I. boninensis, I. comptus, I. manazuruensis, I. hakodadensis, I. hayamii sp. nov., I. paululus, and I. poppei, were investigated on the basis of DNA sequence analyses of COI, 16S rRNA, 18S rRNA, and 28S rRNA gene regions. For the latter four species, SEM observations were simultaneously carried out. A molecular phylogenetic tree based on the four gene regions for 18 chiton species indicated that the seven Japanese Ischnochiton species are polyphyletic and originated from two different clades. A haplotype network based on the COI gene region for the six Japanese Ischnochiton species, except I. hakodadensis, showed that the genetic distances among them were large. The SEM observations revealed that the denticles of the major lateral teeth in the seven Japanese Ischnochiton species were bicuspid, and an accessory process was only observed in the minor lateral teeth of I. hakodadensis. Ischnochiton hayamii sp. nov. cooccurs with I. boninensis, I. comptus, and I. manazuruensis at the two investigated localities, and was difficult to distinguish from other, similar species by naked eyes. However, these can be discriminated based on a combination of adult body size, girdle scales, and valve sculpturing in the lateral and central areas.

Mitochondrial gene order evolution in Mollusca: Inference of the ancestral state from the mtDNA of Chaetopleura apiculata (Polyplacophora, Chaetopleuridae).

The mitochondrial genome architecture of polyplacophorans has been usually regarded as being very ancient in comparison to all mollusks. However, even if some complete chiton mtDNAs have been recently sequenced, thorough studies of their evolution are lacking. To further expand the set of complete chiton mtDNAs and perform such analysis, we sequenced the mitochondrial genome of the Eastern beaded chiton Chaetopleura apiculata (Chaetopleuridae) using next-generation sequencing. With mitochondrial sequences from all available chiton mtDNAs, we also built a phylogeny on which we reconstructed the evolution of gene arrangement in this class. The arrangement of C. apiculata proved to be the most primitive known so far for polyplacophorans. Comparing this gene order to those of other molluscan classes, we found that it most probably is the original gene order of the last common ancestor to all extant Mollusca. The ancient mitochondrial genome organization of C. apiculata is an important information that may help reconstructing the phylogeny of Mollusca and their relationship with other lophotrochozoans.

Update of the genus Leptochiton (Mollusca: Polyplacophora) in Chilean deep waters: three new reports and description of two new species.

We update the list of the bathyal chitons of the genus Leptochiton inhabiting Chilean waters. We report new records of Leptochiton belknapi and L. laurae, the first record of L. sigwartae for the area and the new species L. ibanezi sp. nov. and L. ferreirai sp. nov. With 12 species, including those described herein as new, the highest species richness of Leptochiton is found in Chilean deep waters. Taking into consideration the potential late Paleozoic origin of the genus Leptochiton, we propose that Leptochiton originated in the old Pacific Ocean and migrated to the young Atlantic Ocean. However, the genus has also been considered non-monophyletic.

Shallow and deep-sea chitons of the genus Leptochiton Gray, 1847 (Mollusca: Polyplacophora: Lepidopleurida) from Peruvian and Chilean waters.

The Southeast region off Chile and Peru has yielded a very rich diverse fauna of basal chitons of the genus Leptochiton. The present contribution is based on the study of 1055 specimens of chitons. Thirteen leptochitonid species are reported of which seven species are new, namely Leptochiton lascrusesi n. sp., L. linseae n. sp., L. longibranchiae n. sp., L. peruvianus n. sp., L. macleani n. sp., L. sigwartae n. sp., and L. mutschkeae n. sp. Five species were found on the shelf, but only one of those is limited to this zone. The other eight species live in bathyal or abyssal depths. Thus, 12 of 13 species were found deeper than 200 m. The genus Leptochiton originated in the late Palaeozoic in shallow waters. It probably shifted to deep-waters because of competition by more advanced genera of chitons. The leptochitonid fauna of the Peru-Chile Trench turned out to be rich. Five species were studied from this trench system. Two of them-L. longibranchiae n. sp. and L. peruvianus n. sp.-are characterized by an unusually high number of gills and an accordingly wider distribution in the mantle cavity, reaching in an anterior direction to valves V and III. This morphological peculiarity is unusual for Lepidopleurida and resembles the conditions found in the order Chitonida.

A new name for the deep-sea chiton Leptochiton clarki Sigwart & Sirenko non Berry (Lepidopleurida: Leptochitonidae).

Recently we described several new species of chitons living in deep water deposits of sunken wood in the southwest Pacific (Sigwart & Sirenko 2012). Among these, one species, Leptochiton clarki Sigwart & Sirenko, 2012, is homonymous with a fossil taxon of the same genus: Leptochiton clarki Berry, 1922. Herein, we replace this homonym with a new name according to International Code of Zoological Nomenclature (ICZN 1999: Art. 57.2).

The continuing debate on deep molluscan phylogeny: evidence for Serialia (Mollusca, Monoplacophora + Polyplacophora).

Molluscs are a diverse animal phylum with a formidable fossil record. Although there is little doubt about the monophyly of the eight extant classes, relationships between these groups are controversial. We analysed a comprehensive multilocus molecular data set for molluscs, the first to include multiple species from all classes, including five monoplacophorans in both extant families. Our analyses of five markers resolve two major clades: the first includes gastropods and bivalves sister to Serialia (monoplacophorans and chitons), and the second comprises scaphopods sister to aplacophorans and cephalopods. Traditional groupings such as Testaria, Aculifera, and Conchifera are rejected by our data with significant Approximately Unbiased (AU) test values. A new molecular clock indicates that molluscs had a terminal Precambrian origin with rapid divergence of all eight extant classes in the Cambrian. The recovery of Serialia as a derived, Late Cambrian clade is potentially in line with the stratigraphic chronology of morphologically heterogeneous early mollusc fossils. Serialia is in conflict with traditional molluscan classifications and recent phylogenomic data. Yet our hypothesis, as others from molecular data, implies frequent molluscan shell and body transformations by heterochronic shifts in development and multiple convergent adaptations, leading to the variable shells and body plans in extant lineages.

Emergence, development, and maturity of the gonad of two species of chitons "sea cockroach" (Mollusca: Polyplacophora) through the early life stages.

This study describes and recognises, using histological and microscopical examinations on a morphometrical basis, several gonad traits through the early life stages of Chiton articulatus and C. albolineatus. Gonadal ontogenesis, gonad development stages, sexual differentiation, onset of the first sexual maturity, and growth sequences or "early life stages" were determined. In addition, allometry between lengths and body weight pooled for both sexes per each chiton were calculated using equation Y = aX(b) . A total of 125 chitons (4≤TL≤40 mm, in total length "TL") were used. All allometric relations showed a strong positive correlation (r), close to 1, with b-values above three, indicating an isometric growth. Gonadal ontogenesis and gonad development stages were categorised into three periods ("Pw" without gonad, "Pe" gonad emergence, and "Pf" gonadal sac formed) and four stages ("S0" gametocytogenesis, "S1" gametogenesis, "S2" mature, and "S3" spawning), respectively. Compound digital images were attained for each process. Periods and stages are overlapped among them and between species, with the following overall confidence intervals in TL: Pw 6.13-14.32 mm, Pe 10.32-16.93 mm, Pf 12.99-25.01 mm, S0 16.08-24.34 mm (females) and 19.51-26.60 mm (males), S1 27.15-35.63 mm (females) and 23.45-32.27 mm (males), S2 24.48-40.24 mm (females) and 25.45-32.87 mm (males). Sexual differentiation (in S0) of both chitons occurs first as a female then as a male; although, males reach the onset of the first sexual maturity earlier than females, thus for C. articulatus males at 17 mm and females at 32 mm, and for C. albolineatus males at 23.5 mm and females at 28 mm, all in TL. Four early life stages (i.e., subjuvenile, juvenile, subadult, and adult) are described and proposed to distinguish growth sequences. Our results may be useful to diverse disciplines, from developmental biology to fisheries management.

A tale of two chitons: is habitat specialisation linked to distinct associated bacterial communities?

Although most chitons (Mollusca: Polyplacophora) are shallow-water molluscs, diverse species also occur in deep-sea habitats. We investigated the feeding strategies of two species, Leptochiton boucheti and Nierstraszella lineata, recovered on sunken wood sampled in the western Pacific, close to the Vanuatu Islands. The two species display distinctly different associations with bacterial partners. Leptochiton boucheti harbours Mollicutes in regions of its gut epithelium and has no abundant bacterium associated with its gill. Nierstraszella lineata displays no dense gut-associated bacteria, but harbours bacterial filaments attached to its gill epithelium, related to the Deltaproteobacteria symbionts found in gills of the wood-eating limpet Pectinodonta sp. Stable carbon and nitrogen isotope signatures and an absence of cellulolytic activity give evidence against a direct wood-feeding diet; both species are secondary consumers within the wood food web. We suggest that the distinct associations with bacterial partners are linked to niche specialisations of the two species. Nierstraszella lineata is in a taxonomic family restricted to sunken wood and is possibly adapted to more anoxic conditions thanks to its gill-associated bacteria. Leptochiton boucheti is phylogenetically more proximate to an ancestral form not specialised on wood and may itself be more of a generalist; this observation is congruent with its association with Mollicutes, a bacterial clade comprising gut-associated bacteria occurring in several metazoan phyla.

A Silurian armoured aplacophoran and implications for molluscan phylogeny.

The Mollusca is one of the most diverse, important and well-studied invertebrate phyla; however, relationships among major molluscan taxa have long been a subject of controversy. In particular, the position of the shell-less vermiform Aplacophora and its relationship to the better-known Polyplacophora (chitons) have been problematic: Aplacophora has been treated as a paraphyletic or monophyletic group at the base of the Mollusca, proximate to other derived clades such as Cephalopoda, or as sister group to the Polyplacophora, forming the clade Aculifera. Resolution of this debate is required to allow the evolutionary origins of Mollusca to be reconstructed with confidence. Recent fossil finds support the Aculifera hypothesis, demonstrating that the Palaeozoic-era palaeoloricate 'chitons' included taxa combining certain polyplacophoran and aplacophoran characteristics. However, fossils combining an unambiguously aplacophoran-like body with chiton-like valves have remained elusive. Here we describe such a fossil, Kulindroplax perissokomos gen. et sp. nov., from the Herefordshire Lagerstätte (about 425 million years bp), a Silurian deposit preserving a marine biota in unusual three-dimensional detail. The specimen is reconstructed three-dimensionally through physical-optical tomography. Phylogenetic analysis indicates that this and many other palaeoloricate chitons are crown-group aplacophorans.

[Lepidochitona bullocki, a new species of chiton (Polyplacophora: Ischnochitonidae) from the Colombian Caribbean]. / Lepidochitona bullocki, una nueva especie de quitón (Polyplacophora: Ischnochitonidae) del Caribe colombiano.

The genus Lepidochitona is one of the most diverse in the Southern Caribbean. In order to describe this new species, twenty specimens of L. bullocki sp. nov. were collected by hand on the rocky coast, from 0.25 to 1.5m depth, and a shore distance of 1 to 5m, between the Northern section of Rodadero beach and Puerto Luz, in Santa Marta, Colombia. The specimens were small, with maximum observed size of 7.3mm. This is the fourth species of the genus Lepidochitona described for the Caribbean. The previously known species were L. liozonis (Dall & Simpson 1901), L. rosea (Kaas 1972) and L. rufoi (Garcia-Ríos 2010). L. bullocki differs from L. liozonis and L. rosea in having a rough tegmentum and color. It differs from L. rufoi in having longer and numerous hyaline spicules, bigger size and broader central radula tooth. Lepidochitona bullocki is the only Caribbean species of the genus frequently located on the illuminated side of rocks in the shallow sublitoral zone.

Lepidochitona bullocki, una nueva especie de quitón (Polyplacophora: Ischnochitonidae) del Caribe colombiano

Lepidochitona bullocki, a new species of chiton (Polyplacophora: Ischnochitonidae) from the Colombian Caribbean. The genus Lepidochitona is one of the most diverse in the Southern Caribbean. In order to describe this new species, twenty specimens of L. bullocki sp. nov. were collected by hand on the rocky coast, from 0.25 to 1.5m depth, and a shore distance of 1 to 5m, between the Northern section of Rodadero beach and Puerto Luz, in Santa Marta, Colombia. The specimens were small, with maximum observed size of 7.3mm. This is the fourth species of the genus Lepidochitona described for the Caribbean. The previously known species were L. liozonis (Dall & Simpson 1901), L. rosea (Kaas 1972) and L. rufoi (García-Ríos 2010). L. bullocki differs from L. liozonis and L. rosea in having a rough tegmentum and color. It differs from L. rufoi in having longer and numerous hyaline spicules, bigger size and broader central radula tooth. Lepidochitona bullocki is the only Caribbean species of the genus frequently located on the illuminated side of rocks in the shallow sublitoral zone. Rev. Biol. Trop. 59 (3): 1105-1114. Epub 2011 September 01.

El género Lepidochitona (Gray 1821) se encuentra representado en el Caribe por tres especies: L. liozonis (Dall & Simpson 1901), L. rosea (Kaas 1972) y L. rufoi. Veinte ejemplares de L. bullocki sp. nov. Fueron recolectados en un recorrido a lo largo del litoral rocoso, entre el norte de la playa del Rodadero y Puerto Luz, en Santa Marta, Colombia. Los ejemplares son pequeños, hasta 7.3mm, fueron recolectados a mano, entre 0.25 y 1.5m de profundidad, a distancias entre 1 y 5m de la orilla. Esta es la cuarta especie del género que se describe para el Caribe. Las tres especies previamente descritas son L. liozonis (Dall & Simpson, 1901), L. rosea Kaas, 1972 y L. rufoi García-Ríos, 2010. L. bullocki se diferencia de L. liozonis y L. rosea por tener la superficie del tegumento irregular y de otros colores. La misma se distingue de L. rufoi por tener muchas espículas hialinas largas, mayor tamaño, dientes centrales de la rádula anchos. Es la única especie del género en el Caribe que se localiza con mayor frecuencia en la superficie iluminada de las rocas, en el sublitoral somero.

Larval transport modeling of deep-sea invertebrates can aid the search for undiscovered populations.

BACKGROUND: Many deep-sea benthic animals occur in patchy distributions separated by thousands of kilometres, yet because deep-sea habitats are remote, little is known about their larval dispersal. Our novel method simulates dispersal by combining data from the Argo array of autonomous oceanographic probes, deep-sea ecological surveys, and comparative invertebrate physiology. The predicted particle tracks allow quantitative, testable predictions about the dispersal of benthic invertebrate larvae in the south-west Pacific. PRINCIPAL FINDINGS: In a test case presented here, using non-feeding, non-swimming (lecithotrophic trochophore) larvae of polyplacophoran molluscs (chitons), we show that the likely dispersal pathways in a single generation are significantly shorter than the distances between the three known population centres in our study region. The large-scale density of chiton populations throughout our study region is potentially much greater than present survey data suggest, with intermediate 'stepping stone' populations yet to be discovered. CONCLUSIONS/SIGNIFICANCE: We present a new method that is broadly applicable to studies of the dispersal of deep-sea organisms. This test case demonstrates the power and potential applications of our new method, in generating quantitative, testable hypotheses at multiple levels to solve the mismatch between observed and expected distributions: probabilistic predictions of locations of intermediate populations, potential alternative dispersal mechanisms, and expected population genetic structure. The global Argo data have never previously been used to address benthic biology, and our method can be applied to any non-swimming larvae of the deep-sea, giving information upon dispersal corridors and population densities in habitats that remain intrinsically difficult to assess.

[Diversity and microstructure of quitons (Mollusca: Polyplacophora) from the Caribbean of Costa Rica]. / Diversidad y microestructura de quitones (Mollusca: Polyplacophora) del Caribe de Costa Rica.

Diversity and microstructure of quitons (Mollusca: Polyplacophora) from the Caribbean of Costa Rica. The polyplacophorans of the coral reef on the Caribbean coast of Costa Rica have been insufficiently studied. The examination of coral rubble accumulated in the shallow sublitoral waters on four collection stations in Provincia Limón revealed a higher diversity of chitons than was documented. From the country eight species were previously known: Ischnochiton erythronotus (C.B. Adams 1845); Ischnoplax pectinata (Sowerby 1840); Stenoplax boogii (Haddon 1886); S. purpurascens (C.B. Adams 1845); Acanthopleura granulata (Gmelin 1791); Chiton marmoratus Gmelin 1791; C. tuberculatus Linnaeus 1758 and Acanthochitona rhodea (Pilsbry 1893). This study added five more species that are reported here for the first time: Callistochiton portobelensis Ferreira 1976; Ischnochiton kaasi Ferreira 1987; I. pseudovirgatus Kaas 1972; Acanthochitona balesae Abbott 1954 and Cryptoconchus floridanus (Dall 1889).

Diversidad y microestructura de quitones (Mollusca: Polyplacophora) del Caribe de Costa Rica

Diversity and microstructure of quitons (Mollusca: Polyplacophora) from the Caribbean of Costa Rica. The polyplacophorans of the coral reef on the Caribbean coast of Costa Rica have been insufficiently studied. The examination of coral rubble accumulated in the shallow sublitoral waters on four collection stations in Provincia Limón revealed a higher diversity of chitons than was documented. From the country eight species were previously known: Ischnochiton erythronotus (C.B. Adams 1845); Ischnoplax pectinata (Sowerby 1840); Stenoplax boogii (Haddon 1886); S. purpurascens (C.B. Adams 1845); Acanthopleura granulate (Gmelin 1791); Chiton marmoratus Gmelin 1791; C. tuberculatus Linnaeus 1758 and Acanthochitona rhodea (Pilsbry 1893). This study added five more species that are reported here for the first time: Callistochiton portobelensis Ferreira 1976; Ischnochiton kaasi Ferreira 1987; I. pseudovirgatus Kaas 1972; Acanthochitona balesae Abbott 1954 and Cryptoconchus floridanus (Dall 1889). Rev. Biol. Trop. 59 (1): 129-136. Epub 2011 March 01.

Los poliplacóforos asociados a los arrecifes de coral en la costa caribeña de Costa Rica han sido poco estudiados. El examen del cascajo de coral acumulado en el sublitoral somero, en cuatro estaciones de colección, localizadas en la Provincia de Limón reveló una diversidad de quitones mayor a la documentada. Anteriormente se habían registrado ocho especies para el Caribe costaricense: Ischnochiton erythronotus (C.B. Adams, 1845); Ischnoplax pectinata (Sowerby 1840); Stenoplax boogii (Haddon, 1886); S. purpurascens (C.B. Adams, 1845); Acanthopleura granulata (Gmelin, 1791); Chiton marmoratus Gmelin, 1791; C. tuberculatus Linnaeus, 1758; Acanthochitona rhodea (Pilsbry, 1893). Otras cinco se registran aquí por primera vez: Callistochiton portobelensis Ferreira 1976; Ischnochiton kaasi Ferreira 1987; I. pseudovirgatus Kaas 1972; Acanthochitona balesae Abbott 1954; Cryptoconchus floridanus (Dall 1889).