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1.
Proc Natl Acad Sci U S A ; 118(23)2021 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-34088834

RESUMO

Engineering structures that bridge between elements with disparate mechanical properties are a significant challenge. Organisms reap synergy by creating complex shapes that are intricately graded. For instance, the wear-resistant cusp of the chiton radula tooth works in concert with progressively softer microarchitectural units as the mollusk grazes on and erodes rock. Herein, we focus on the stylus that connects the ultrahard and stiff tooth head to the flexible radula membrane. Using techniques that are especially suited to probe the rich chemistry of iron at high spatial resolution, in particular synchrotron Mössbauer and X-ray absorption spectroscopy, we find that the upper stylus of Cryptochiton stelleri is in fact a mineralized tissue. Remarkably, the inorganic phase is nano disperse santabarbaraite, an amorphous ferric hydroxyphosphate that has not been observed as a biomineral. The presence of two persistent polyamorphic phases, amorphous ferric phosphate and santabarbaraite, in close proximity, is a unique aspect that demonstrates the level of control over phase transformations in C. stelleri dentition. The stylus is a highly graded material in that its mineral content and mechanical properties vary by a factor of 3 to 8 over distances of a few hundred micrometers, seamlessly bridging between the soft radula and the hard tooth head. The use of amorphous phases that are low in iron and high in water content may be key to increasing the specific strength of the stylus. Finally, we show that we can distill these insights into design criteria for inks for additive manufacturing of highly tunable chitosan-based composites.


Assuntos
Estruturas Animais/química , Quitosana/química , Compostos Férricos/química , Poliplacóforos/química , Impressão Tridimensional , Animais
2.
Zootaxa ; 4981(2): 275300, 2021 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-34186721

RESUMO

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.


Assuntos
Poliplacóforos/anatomia & histologia , Poliplacóforos/classificação , Animais
3.
Zootaxa ; 4950(1): zootaxa.4950.1.4, 2021 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-33903320

RESUMO

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.


Assuntos
Poliplacóforos , Animais , Moluscos , Poliplacóforos/classificação , Poliplacóforos/fisiologia
4.
Biol Bull ; 240(1): 23-33, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33730533

RESUMO

AbstractChitons have a distinctive armature of eight articulating dorsal shells. In all living species, the shell valves are covered by a dense array of sensory pores called aesthetes; but in some taxa, a subset of these are elaborated into lensed eyes, which are capable of spatial vision. We collected a complete ontogenetic series of the eyed chiton Tonicia lebruni de Rochebrune, 1884 to examine the growth of this visual network and found that it expands continuously as eyes are added at the margin during shell growth. Our dataset ranged from a 2.58-mm juvenile with only 16 eyes to adults of 25-31 mm with up to 557 eyes each. This allowed us to investigate the organization (and potential constraints therein) of these sensory structures and their development. Chiton eyes are constrained to a narrowly defined region of the shell, and data from T. lebruni indicate that they are arranged roughly bilaterally symmetrically. We found deviations from symmetry of up to 10%, similar to irregularity reported in some other animals with multiplied eyes. Distances separating successive eyes indicate that, while shell growth slows during the life of an individual chiton, eyes are generated at regular time intervals. Although we could not identify a specific eye-producing tissue or organ, we propose that the generation of new eyes is controlled by a clock-like mechanism with a stable periodicity. The apparent regularity and organization of the chiton visual system are far greater than previously appreciated. This does not imply the integration of shell eyes to form composite images, but symmetry and regular organization could be equally beneficial to a highly duplicated system by ensuring even and comprehensive sampling of the total field of view.


Assuntos
Poliplacóforos , Animais , Visão Ocular
5.
J Morphol ; 282(3): 355-367, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33314288

RESUMO

The esophageal pouches of Chaetopleura angulata and Acanthochitona fascicularis were investigated using light and transmission electron microscopy. These pouches linked to the posterior region of the esophagus are known as sugar glands as they contain a fluid rich in polysaccharide digesting enzymes. They are the second largest glands in the digestive system of chitons, just after the digestive gland. In both species, the pouches contain a dense array of finger-shaped villi. The villi epithelium includes absorptive cells, basophilic secretory cells, mucus-secreting cells, and basal cells. Some absorptive cells were bordered by a dense cover of long microvilli, whereas other absorptive cells had short and sparse microvilli. Absorptive cells contain several lysosomes, mitochondria, peroxisomes, a few small Golgi stacks, some lipid droplets, and large amounts of glycogen. The basophilic secretory cells are characterized by the presence of many electron-dense vesicles, with a glycoprotein content, a large number of rough endoplasmic reticulum cisternae, and a highly developed Golgi apparatus. Mucus-secreting cells are characterized by large vesicles containing acid polysaccharides and wide Golgi stacks. Basal cells that were found at the base of the epithelium in contact with the basal lamina exhibit histological and ultrastructural features of enteroendocrine cells. We suggest that these glandular pouches are involved in extracellular and intracellular digestion, and accumulate lipid and glycogen reserves.


Assuntos
Estruturas Animais/anatomia & histologia , Esôfago/anatomia & histologia , Poliplacóforos/anatomia & histologia , Estruturas Animais/citologia , Estruturas Animais/ultraestrutura , Animais , Esôfago/citologia , Esôfago/ultraestrutura , Poliplacóforos/citologia , Poliplacóforos/ultraestrutura , Vesículas Secretórias/metabolismo , Coloração e Rotulagem
6.
Genome Biol Evol ; 13(1)2021 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-33320175

RESUMO

Molluscs biomineralize structures that vary in composition, form, and function, prompting questions about the genetic mechanisms responsible for their production and the evolution of these mechanisms. Chitons (Mollusca, Polyplacophora) are a promising system for studies of biomineralization because they build a range of calcified structures including shell plates and spine- or scale-like sclerites. Chitons also harden the calcified teeth of their rasp-like radula with a coat of iron (as magnetite). Here we present the genome of the West Indian fuzzy chiton Acanthopleura granulata, the first from any aculiferan mollusc. The A. granulata genome contains homologs of many genes associated with biomineralization in conchiferan molluscs. We expected chitons to lack genes previously identified from pathways conchiferans use to make biominerals like calcite and nacre because chitons do not use these materials in their shells. Surprisingly, the A. granulata genome has homologs of many of these genes, suggesting that the ancestral mollusc may have had a more diverse biomineralization toolkit than expected. The A. granulata genome has features that may be specialized for iron biomineralization, including a higher proportion of genes regulated directly by iron than other molluscs. A. granulata also produces two isoforms of soma-like ferritin: one is regulated by iron and similar in sequence to the soma-like ferritins of other molluscs, and the other is constitutively translated and is not found in other molluscs. The A. granulata genome is a resource for future studies of molluscan evolution and biomineralization.


Assuntos
Genoma , Ferro/metabolismo , Poliplacóforos/genética , Poliplacóforos/metabolismo , Animais , Materiais Biocompatíveis , Biomineralização/genética , Carbonato de Cálcio , Ferritinas , Proteínas Reguladoras do Ferro/genética , Masculino , Moluscos/genética , Moluscos/metabolismo , Poliplacóforos/química , Transcriptoma
7.
Zootaxa ; 4878(3): zootaxa.4878.3.3, 2020 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-33311143

RESUMO

Seventeen chiton species of the genus Leptochiton are reported from Philippine waters. Of these, nine are reported from the Philippines for the first time, including three species new to science: Leptochiton costatoacus n. sp., L. longigranum n. sp. and L. spiniferus n. sp. The majority of the Philippine leptochitons live mainly in the bathyal zone or deeper.


Assuntos
Poliplacóforos , Animais , Moluscos , Filipinas
8.
Zootaxa ; 4772(3): zootaxa.4772.3.1, 2020 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-33055600

RESUMO

This study describes the chiton fauna (Mollusca, Polyplacophora) from the marine Pleistocene coral reef deposits bordering the Red Sea coast and dating to the last interglacial epoch (Marine Isotopic Substage 5e, MIS5e). Twenty-one species were identified, of which only three were previously known from the Pleistocene of the Red Sea (Lucilina sueziensis, Acanthopleura vaillantii and Acanthochitona penicillata). Eight are recorded as fossil for the first time. Six are described as new (Lucilina confusa n. sp., L. aqabaensis n. sp., L. aegyptiaca n. sp., L. colantonii n. sp., "Onithochiton" vandingeneni" n. sp., and Acanthochitona interglacialis n. sp.) and two are assigned at generic level (Callochiton sp. and Craspedochiton sp.). Four of these new species (Lucilina confusa n. sp., L. aegyptiaca n. sp., L. colantonii n. sp. and "Onithochiton" vandingeneni n. sp.) are still living in the Red Sea, bringing to 28 the number of extant species known from the Red Sea. These Pleistocene Red Sea assemblages represent the most diverse chiton fauna yet reported from any interglacial deposit worldwide.


Assuntos
Poliplacóforos , Animais , Fósseis , Oceano Índico , Moluscos
9.
Zootaxa ; 4851(3): zootaxa.4851.3.1, 2020 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-33056716

RESUMO

Eighteen species of the chiton genus Leptochiton are present in Australian and New Zealand waters. Leptochiton beui n. sp. and L. marshalli n. sp. are introduced as new to science. Leptochiton laurae and L. cf. opiparus are here recorded for the first time from New Zealand waters. The present material allowed to obtain new information about the number of aesthetes, the girdle armature as well as about the radula morphology in several species. A considerable variability in the valve shape of Leptochiton subantarcticus was observed leading to the consideration of L. deecresswellae being a junior synonym of this species. Nine of the eighteen Leptochiton species are found around New Zealand and nine belong to the Australian region. With the possible exception of L. opiparus, both regions do not share any species.


Assuntos
Poliplacóforos , Animais , Austrália , Moluscos , Nova Zelândia
10.
Philos Trans A Math Phys Eng Sci ; 378(2181): 20190355, 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-32862815

RESUMO

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'.


Assuntos
Ecossistema , Aquecimento Global , Animais , Organismos Aquáticos/classificação , Organismos Aquáticos/crescimento & desenvolvimento , Regiões Árticas , Biomassa , Hidrozoários/classificação , Hidrozoários/crescimento & desenvolvimento , Noruega , Oceanos e Mares , Poliplacóforos/classificação , Poliplacóforos/crescimento & desenvolvimento , Alga Marinha/classificação , Alga Marinha/crescimento & desenvolvimento
11.
J Mech Behav Biomed Mater ; 111: 103991, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32823075

RESUMO

Chitons are herbivorous invertebrates that use rows of ultrahard magnetite-based teeth connected to a flexible belt (radula) to rasp away algal deposits growing on and within rocky outcrops along coastlines around the world. Each tooth is attached to the radula by an organic structure (stylus) that provides mechanical support during feeding. However, the underlying structures within the stylus, and their subsequent function within the chiton have yet to be investigated. Here, we investigate the macrostructural architecture, the regional material and elemental distribution and subsequent nano-mechanical properties of the stylus from the Northern Pacific dwelling Cryptochiton stelleri. Using a combination of µ-CT imaging, optical and electron microscopy, as well as elemental analysis, we reveal that the stylus is a highly contoured tube, mainly composed of alpha-chitin fibers, with a complex density distribution. Nanoindentation reveals regiospecific and graded mechanical properties that can be correlated with both the elemental composition and material distribution. Finite element modeling shows that the unique macroscale architecture, material distribution and elemental gradients have been optimized to preserve the structural stability of this flexible, yet robust functionally-graded fiber-reinforced composite tube, providing effective function during rasping. Understanding these complex fiber-based structures offers promising blueprints for lightweight, multifunctional and integrated materials.


Assuntos
Poliplacóforos , Dente , Animais , Óxido Ferroso-Férrico , Microscopia Eletrônica
12.
BMC Evol Biol ; 20(1): 22, 2020 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-32024460

RESUMO

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.


Assuntos
Genoma Mitocondrial , Poliplacóforos/classificação , Poliplacóforos/genética , Animais , DNA Mitocondrial/análise , DNA Mitocondrial/genética , Evolução Molecular , Fósseis , Ordem dos Genes , Genoma Mitocondrial/genética , Moluscos/classificação , Moluscos/genética , Filogenia , Análise de Sequência de DNA/métodos
13.
Proc Natl Acad Sci U S A ; 117(1): 503-512, 2020 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-31871200

RESUMO

In contrast to the Hox genes in arthropods and vertebrates, those in molluscs show diverse expression patterns with differences reported among lineages. Here, we investigate 2 phylogenetically distant molluscs, a gastropod and a polyplacophoran, and show that the Hox expression in both species can be divided into 2 categories. The Hox expression in the ventral ectoderm generally shows a canonical staggered pattern comparable to the patterns of other bilaterians and likely contributes to ventral patterning, such as neurogenesis. The other category of Hox expression on the dorsal side is strongly correlated with shell formation and exhibits lineage-specific characteristics in each class of mollusc. This generalized model of decoupled dorsoventral Hox expression is compatible with known Hox expression data from other molluscan lineages and may represent a key characteristic of molluscan Hox expression. These results support the concept of widespread staggered Hox expression in Mollusca and reveal aspects that may be related to the evolutionary diversification of molluscs. We propose that dorsoventral decoupling of Hox expression allowed lineage-specific dorsal and ventral patterning, which may have facilitated the evolution of diverse body plans in different molluscan lineages.


Assuntos
Biodiversidade , Gastrópodes/genética , Regulação da Expressão Gênica no Desenvolvimento , Genes Homeobox/genética , Poliplacóforos/genética , Animais , Evolução Biológica , Gastrópodes/crescimento & desenvolvimento , Perfilação da Expressão Gênica , Larva/genética , Larva/crescimento & desenvolvimento , Filogenia , Poliplacóforos/crescimento & desenvolvimento
14.
Zootaxa ; 4564(1): zootaxa.4564.1.1, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-31716514

RESUMO

The chiton fauna of Hainan Island and its vicinity is poorly known. In this contribution, we present the first comprehensive account of the living chitons from this area. The present compilation is based on the study of historical collections housed in Qingdao (China), Saint Petersburg (Russia), new samples from Hainan Island and data from literature. Six species (Rhyssoplax venusta, Lucilina lamellosa, L. tenuicostata, L. tilbrooki, Onithochiton stracki and Acanthochitona intermedia) are reported for the first time from this area. Three species (Acanthochitona achates, A. britayevi and A. lanae) are re-identified on the basis of descriptions, drawings and photographs in old articles. We now know a total of 30 species (belonging to 18 genera in seven families) from the vicinity of Hainan Island. While examining material of Lucilina lamellosa, we found two forms: L. lamellosa forma typica and the new form L. lamellosa forma costata. Both forms differ from each other in the structure of the tegmentum of the pleural areas.


Assuntos
Poliplacóforos , Animais , China , Ilhas , Moluscos , Federação Russa
15.
Biol Lett ; 15(10): 20190429, 2019 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-31573429

RESUMO

Many animals with external armour, such as hedgehogs, isopods and trilobites, curl into a protective ball when disturbed. However, in situations where predators would engulf an exposed animal whole, regardless of position, conglobation may provide limited added defence and the benefits were previously unclear. We show that polyplacophoran molluscs (chitons) are three times less likely to spend time curled into a ball in the presence of a predator. When the cue of a potential predator is present, animals instead spend significantly more time in active, high risk, high reward behaviours such as arching, balancing on the head and tail ends of their girdle and pushing the soft foot up into an exposed position. Arching increases vulnerability, but also can increase the likelihood of rapidly encountering new substratum that would allow the animal to right itself. In some other animals, the ability to roll into a ball is associated with rolling away from danger. Curling into a ball would improve mobility, to be rolled on to a safer position, but reattachment is the higher priority for chitons in the face of danger.


Assuntos
Poliplacóforos , Animais , Moluscos , Recompensa
16.
Proc Biol Sci ; 286(1902): 20190115, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-31064303

RESUMO

Recent molecular phylogenetic investigations strongly supported the placement of the shell-less, worm-shaped aplacophoran molluscs (Solenogastres and Caudofoveata) and chitons (Polyplacophora) in a clade called Aculifera, which is the sister taxon of all other molluscs. Thus, understanding the evolutionary history of aculiferan molluscs is important for understanding early molluscan evolution. In particular, fundamental questions about evolutionary relationships within Aplacophora have long been unanswered. Here, we supplemented the paucity of available data with transcriptomes from 25 aculiferans and conducted phylogenomic analyses on datasets with up to 525 genes and 75 914 amino acid positions. Our results indicate that aplacophoran taxonomy requires revision as several traditionally recognized groups are non-monophyletic. Most notably, Cavibelonia, the solenogaster taxon defined by hollow sclerites, is polyphyletic, suggesting parallel evolution of hollow sclerites in multiple lineages. Moreover, we describe Apodomenia enigmatica sp. nov. , a bizarre new species that appears to be a morphological intermediate between Solenogastres and Caudofoveata. This animal is not a missing link, however; molecular and morphological studies show that it is a derived solenogaster that lacks a foot, mantle cavity and radula. Taken together, these results shed light on the evolutionary history of Aplacophora and reveal a surprising degree of morphological plasticity within the group.


Assuntos
Moluscos/genética , Filogenia , Transcriptoma , Animais , Moluscos/anatomia & histologia , Poliplacóforos/anatomia & histologia , Poliplacóforos/genética
17.
Sci Rep ; 9(1): 856, 2019 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-30696920

RESUMO

Many species of chiton are known to deposit magnetite (Fe3O4) within the cusps of their heavily mineralized and ultrahard radular teeth. Recently, much attention has been paid to the ultrastructural design and superior mechanical properties of these radular teeth, providing a promising model for the development of novel abrasion resistant materials. Here, we constructed de novo assembled transcripts from the radular tissue of C. stelleri that were used for transcriptome and proteome analysis. Transcriptomic analysis revealed that the top 20 most highly expressed transcripts in the non-mineralized teeth region include the transcripts encoding ferritin, while those in the mineralized teeth region contain a high proportion of mitochondrial respiratory chain proteins. Proteomic analysis identified 22 proteins that were specifically expressed in the mineralized cusp. These specific proteins include a novel protein that we term radular teeth matrix protein1 (RTMP1), globins, peroxidasins, antioxidant enzymes and a ferroxidase protein. This study reports the first de novo transcriptome assembly from C. stelleri, providing a broad overview of radular teeth mineralization. This new transcriptomic resource and the proteomic profiles of mineralized cusp are valuable for further investigation of the molecular mechanisms of radular teeth mineralization in chitons.


Assuntos
Óxido Ferroso-Férrico/metabolismo , Poliplacóforos/fisiologia , Dente/fisiologia , Animais , Biomineralização , Calcificação Fisiológica , Ferritinas/genética , Ferritinas/metabolismo , Globinas/metabolismo , Proteômica , Calcificação de Dente , Transcriptoma
18.
Zootaxa ; 4434(2): 385-390, 2018 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30313194

RESUMO

Crabs of the family Pinnotheridae have been considered a phylogenetically heterogeneous group and taxonomically problematic (Palacios-Theil 2009, 2016; Tsang et al. 2018). The lack of knowledge of sexual dimorphism and morphological variation throughout the life history for many species have complicated its taxonomy and has resulted in errors in its classification (Campos 1989, 1993, 2016). Consequently, if the taxonomy of these symbiotic crabs had been based on juveniles and undeveloped character states, the problems get even more serious (Campos 1989, 1993). Melzer Schwabe (2008) studied three juvenile crabs living in the chiton Tonicia chilensis (Frembly, 1827) (Polyplacophora: Chitonidae) collected in Muelle Dichato, Chile, and they identified them as the putative invasive stage of a species of Orthotheres Sakai, 1969. The crabs are of the typical juvenile pinnotherid form with a masculine habitus, including a suborbicular carapace, large eyes and a slender pleon (= abdomen) with the telson well defined (Ocampo et al. 2017). Unpublished observations on juveniles and adults of several species of pinnotherid crabs by the author, for example, Juxtafabia muliniarum (Rathbun, 1918), Dissodactylus lockingtoni Glassell, 1935, D. xantusi Glassell, 1936, Calyptraeotheres granti (Glassell, 1933), Austinotheres angelicus (Lockington, 1877) and Tumidotheres margarita (Smith, 1870) have revealed that the third maxilliped exhibit little morphological variation through the post-larval stages of development (from juvenile to adult). This appendage, including the partial or total fusion of the ischium and merus (Fig. 1A-G; Fig 2A, C-G), has been considered a valuable feature for distinguishing genera in the family Pinnotheridae (Bürger 1895; Rathbun 1918; Manning 1993; Ahyong Ng 2007; Campos 2009). According to Melzer Schwabe (2008) the ischium and merus of the third maxilliped are completely fused, the carpus is larger than the propodus and the small dactylus is subterminally inserted on the propodus (Fig 1C), and as such the juveniles studied are possibly members of the genus Orthotheres Sakai, 1969. A detailed re-examination of the third maxilliped, chela of pereiopod 1 (cheliped) and pleon, however, has shown otherwise. Campos (1989) discussed the taxonomy of Orthotheres and treated all the species he recognised as belonging to this genus; characterising its members by its diagnostic third maxilliped palp structure. Ng Ho (2014) rediagnosed the genus based on the type species, O. turboe Sakai, 1969, from Japan, and restricted it for three Indo-West Pacific species; commenting that the American species as well as some Indo-West Pacific taxa will need to referred to other genera when a full revision is done. This revision is now in progress by the author, PKL Ng and ST Ahyong. Until the revision is complete, the genus is treated here in the broader sense of Campos (1989) and Geiger Martin (1999).


Assuntos
Moluscos , Poliplacóforos , Animais , Chile , Japão , Quênia , Masculino
19.
Zootaxa ; 4422(3): 301-344, 2018 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-30313489

RESUMO

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.


Assuntos
Moluscos , Poliplacóforos , Animais , Japão , Oceano Pacífico , Inquéritos e Questionários , Taiwan
20.
Zootaxa ; 4447(1): 1-62, 2018 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-30313867

RESUMO

This study describes the chiton fauna (Mollusca, Polyplacophora) from the upper Miocene Tortonian deposits of northwest France previously known as the 'Redonian'. Twenty-two species were identified (represented by 9,380 valves), of which seven were already known, one is assigned at generic level (Leptochiton sp.) and 14 are described as new (Lepidopleurus pseudobenoisti sp. nov., L. gallicus sp. nov., Leptochiton parvus sp. nov., Leptochiton lateropustulosus sp. nov., Leptochiton renauleauensis sp. nov., Hanleya sancticlementensis sp. nov., H. sossoi sp. nov., Ischnochiton nitidum sp. nov., Callochiton pouweri sp. nov., Rhyssoplax assurrectum sp. nov., Tonicella redoniensis sp. nov., Acanthochitona globosa sp. nov., A. andegavensis sp. nov. and A. chauvereauensis sp. nov.). Regarding the stratigraphic distribution of the 21 taxa identified, 15 are restricted to the Miocene, the remaining six are extant and are distributed in the Atlantic and Mediterranean (Lepidopleurus cajetanus, Leptochiton algesirensis, Hanleya hanleyi, Ischnochiton rissoi, Callochiton doriae and Rhyssoplax corallinus. The number of new species is high (14 out of 22), possibly explained in part by the fact that this is the first description of the northwestern French upper Miocene chiton fauna - true endemicity is less likely in the light of scarce sampling.


Assuntos
Moluscos , Poliplacóforos , Animais , França
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