Aplacophoran traits in the late Ordovician septemchitonid polyplacophorans.

A sample of phosphatized, originally calcareous, mollusk shells from the Katian age uppermost Mójcza Limestone at its type locality yielded a few hundred polyplacophoran plates. The chelodids are very rare among them. Three septemchitonid species dominate. They represent a gradation from underived steep roof-like plates to almost cylindrical ones, leaving only a narrow ventral slit for the foot. Apparently, this represents the first step toward the extremely derived 'segmented clam' Bauplan of the Silurian Carnicoleus, with plates completely closed at the venter except for the mouth and anal openings. To enable growth, the plates became thinner and more flexible (or perhaps resorbed) along the dorsum. The tendency toward reduction of the ventral gap of the plates in the early Paleozoic septemchitonid polyplacophorans implies their lack of ability to cling to the substrate with a muscular foot. In compensation, their plates changed toward a more efficient protective function, covering the animal body sides more and more completely. This may explain the origin of the ventral furrow of extant solenogasters hiding the rudimentary foot. An opposite route was chosen by the coeval Acaenoplax lineage, in which the plates did not contact each other, exposing much of the soft body on the dorsum. In both cases the animals appeared to be worm-like, perhaps representing different ways of evolution from the Paleozoic chitons to the extant aplacophorans.

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.

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.

Functional morphology of the glandular esophageal pouches of chitons (Mollusca, Polyplacophora).

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.

Phylogenomics of Aplacophora (Mollusca, Aculifera) and a solenogaster without a foot.

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.

Evidence for spatial vision in Chiton tuberculatus, a chiton with eyespots.

To better understand relationships between the structures and functions of the distributed visual systems of chitons, we compare how morphological differences between the light-sensing structures of these animals relate to their visually guided behaviors. All chitons have sensory organs - termed aesthetes - embedded within their protective shell plates. In some species, the aesthetes are interspersed with small, image-forming eyes. In other species, the aesthetes are paired with pigmented eyespots. Previously, we compared the visually influenced behaviors of chitons with aesthetes to those of chitons with both aesthetes and eyes. Here, we characterize the visually influenced behaviors of chitons with aesthetes and eyespots. We find that chitons with eyespots engage in behaviors consistent with spatial vision, but appear to use spatial vision for different tasks than chitons with eyes. Unlike chitons with eyes, Chiton tuberculatus and C. marmoratus fail to distinguish between sudden appearances of overhead objects and equivalent, uniform changes in light levels. We also find that C. tuberculatus orients to static objects with angular sizes as small as 10 deg. Thus, C. tuberculatus demonstrates spatial resolution that is at least as fine as that demonstrated by chitons with eyes. The eyespots of Chiton are smaller and more numerous than the eyes found in other chitons and they are separated by angles of <0.5 deg, suggesting that the light-influenced behaviors of Chiton may be more accurately predicted by the network properties of their distributed visual system than by the structural properties of their individual light-detecting organs.

Do chitons have a brain? New evidence for diversity and complexity in the polyplacophoran central nervous system.

Molluscs demonstrate astonishing morphological diversity, and the relationships among clades have been debated for more than a century. Molluscan nervous systems range from simple 'ladder-like' cords to the complex brains of cephalopods. Chitons (Polyplacophora) are assumed to retain many molluscan plesiomorphies, lacking neural condensation and ganglionic structure, and therefore a brain. We reconstructed three-dimensional anatomical models of the nervous system in eight species of chitons in an attempt to clarify chiton neuroarchitecture and its variability. We combined new data with digitised historic slide material originally used by malacologist Johannes Thiele (1860-1935). Reconstructions of whole nervous systems in Acanthochitona fascicularis, Callochiton septemvalvis, Chiton olivaceus, Hemiarthrum setulosum, Lepidochitona cinerea, Lepidopleurus cajetanus and Leptochiton asellus, and the anterior nervous system of Schizoplax brandtii, demonstrated consistent and substantial anterior neural concentration in the circumoesophageal nerve ring. This is further organised into three concentric tracts, corresponding to the lateral, ventral and cerebral nerve cords. These represent homologues to the three main pairs of ganglia in other molluscs. Their relative size, shape and organisation are highly variable among the examined taxa, but consistent with previous studies of select species, and we formulated a set of neuroanatomical characters for chitons. These support anatomical transitions at the ordinal and subordinal levels; the identification of robust homologies in neural architecture will be central to future comparisons across Mollusca and, more broadly, Lophotrochozoa. Contrary to almost all previous descriptions, the size and structure of the chiton anterior nerve ring unambiguously qualify it as a true brain with cordal substructure.

Valve microstructure and phylomineralogy of New Zealand chitons.

The microstructure and mineralogy of chiton valves has been largely ignored in the literature and only described in 29 species to date. Eight species: Acanthochitona zelandica, Notoplax violacea (Family Acanthochitonidae, Suborder Acanthochitonina, Order Chitonida), Chiton glaucus, Onithochiton neglectus, Sypharochiton spelliserpentis, Sypharochiton sinclairi (Family Chitonidae, Suborder, Chitonina, Order Chitonida), Ischnochiton maorianus (Family Ischnochitonidae, Suborder Chitonina, Order Chitonida), and Leptochiton inquinatus (Family Leptochitonidae, Suborder Lepidopleurina, Order Lepidopleurida) were collected from the Otago Peninsula, South Island, New Zealand. The valves of these chitons were analysed with X-ray diffractometry, Raman spectrometry, and Scanning Electron Micrography (SEM) to determine their mineralogy and microstructure. Both the XRD and Raman data show that the valves consisted solely of aragonite. The observed microstructures of the valves were complex, typically composed of four to seven sublayers, and varied among species. The dorsal layer, the tegmentum, of each species was granular and the ventral layer, the articulamentum, was predominately composed of a spherulitic sublayer, a crossed lamellar sublayer, and an acicular sublayer. The chitonids Sypharochiton pelliserpentis and S. sinclairi had the most complex microstructure layering with three crossed lamellar, two spherulitic sublayers, and a ventral acicular sublayer while the acanthochitonids Acanthochitona zelandica and Notoplax violacea as well as the ischnochitonid Ischnochiton maorianus had the simplest structure with one spherulitic, one crossed lamellar sublayer, and a ventral acicular sublayer. Terminal valves were less complex than intermediate valves and tended to be dominated by the crossed lamellar structure. The leptochitonid Leptochiton inquinatus generated a unique crossed lamellar sublayer different from the other analysed chitonids. Acanthochitona zelandica is the only analysed chitonid that utilizes two different crossed lamellar structures. Clearly, many of these properties do not reflect the currently recognized polyplacophoran phylogeny.

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.

Is the Schwabe Organ a Retained Larval Eye? Anatomical and Behavioural Studies of a Novel Sense Organ in Adult Leptochiton asellus (Mollusca, Polyplacophora) Indicate Links to Larval Photoreceptors.

The discovery of a sensory organ, the Schwabe organ, was recently reported as a unifying feature of chitons in the order Lepidopleurida. It is a patch of pigmented tissue located on the roof of the pallial cavity, beneath the velum on either side of the mouth. The epithelium is densely innervated and contains two types of potential sensory cells. As the function of the Schwabe organ remains unknown, we have taken a cross-disciplinary approach, using anatomical, histological and behavioural techniques to understand it. In general, the pigmentation that characterises this sensory structure gradually fades after death; however, one particular concentrated pigment dot persists. This dot is positionally homologous to the larval eye in chiton trochophores, found in the same neuroanatomical location, and furthermore the metamorphic migration of the larval eye is ventral in species known to possess Schwabe organs. Here we report the presence of a discrete subsurface epithelial structure in the region of the Schwabe organ in Leptochiton asellus that histologically resembles the chiton larval eye. Behavioural experiments demonstrate that Leptochiton asellus with intact Schwabe organs actively avoid an upwelling light source, while Leptochiton asellus with surgically ablated Schwabe organs and a control species lacking the organ (members of the other extant order, Chitonida) do not (Kruskal-Wallis, H = 24.82, df = 3, p < 0.0001). We propose that the Schwabe organ represents the adult expression of the chiton larval eye, being retained and elaborated in adult lepidopleurans.

Lepidochitona pseudoliozonis, una nueva especie de quitón (Polyplacophora: Ischnochitonidae) del norte del Caribe / Lepidochitona pseudoliozonis, a new species of chiton (Polyplacophora: Ischnochitonidae) from the North of the Caribbean

The genus Lepidochitona (Gray 1821) contains relatively small chitons with a distinctive girdle, dorsally clothed with non-overlapping calcareous corpuscles. In the Caribbean, it is represented by four species: L. liozonis (Dall, & Simpson, 1901), L. rosea Kaas, 1972, L. rufoi García-Ríos, 2010 and L. bullocki García-Ríos, 2011. A rutinary morphological inspection of 10 specimens of a Lepidochitona species from the Florida Keys was concordant with L. liozonis (the only species of the genus informed for Florida). They did not show many morphological differences that could justify its separation from the specimens from Puerto Rico (the type locality). However, the comparison of sequences of the mitochondrial gene coding for cytochrome oxidase I (COI) of L. liozonis from Puerto Rico and the Florida specimens showed a divergence of 14%. This divergence is incompatible with a reproductively connected species. In addition to their genetic differences, the new species differs from L. liozonis in having bigger size, longer marginal spicules and a postmucronal slope very concave. Rev. Biol. Trop. 63 (2): 369-384. Epub 2015 June 01.

El género Lepidochitona (Gray, 1821) agrupa a quitones relativamente pequeños con un cinturón distintivo, por estar cubierto dorsalmente por corpúsculos calcáreos no solapados. Esta representado en el Caribe por cuatro especies: L. liozonis (Dall, & Simpson, 1901), L. rosea Kaas, 1972, L. rufoi García-Ríos, 2010 y L. bullocki García-Ríos, 2011. La inspección de una muestra de ejemplares de los cayos de la Florida permite distinguir ejemplares de lepidoquitones que podrían clasificarse como L. liozonis (la única especie del género informada para la Florida) por no presentar grandes diferencias morfológicas que justifiquen su separación de los de Puerto Rico (localidad del tipo). Sin embargo, la comparación de secuencias del gen mitocondrial que codifica para el citocromo oxidasa I (COI) de los ejemplares de la Florida con ejemplares de L. liozonis de Puerto Rico evidencia una divergencia de 14%. Esta divergencia es incompatible con especies reproductivamente conectadas. Además de sus diferencias genéticas, la nueva especie se puede distinguir de su especie gemela por ser de mayor tamaño, tener espículas marginales más largas y una pendiente posmucronal muy cóncava.

Grazing under experimental hypercapnia and elevated temperature does not affect the radula of a chiton (Mollusca, Polyplacophora, Lepidopleurida).

Chitons (class Polyplacophora) are benthic grazing molluscs with an eight-part aragonitic shell armature. The radula, a serial tooth ribbon that extends internally more than half the length of the body, is mineralised on the active feeding teeth with iron magnetite apparently as an adaptation to constant grazing on rocky substrates. As the anterior feeding teeth are eroded they are shed and replaced with a new row. The efficient mineralisation and function of the radula could hypothetically be affected by changing oceans in two ways: changes in seawater chemistry (pH and pCO2) may impact the biomineralisation pathway, potentially leading to a weaker or altered density of the feeding teeth; rising temperatures could increase activity levels in these ectothermic animals, and higher feeding rates could increase wear on the feeding teeth beyond the animals' ability to synthesise, mineralise, and replace radular rows. We therefore examined the effects of pH and temperature on growth and integrity in the radula of the chiton Leptochiton asellus. Our experiment implemented three temperature (∼10, 15, 20 °C) and two pCO2 treatments (∼400 µatm, pH 8.0; ∼2000 µatm, pH 7.5) for six treatment groups. Animals (n = 50) were acclimated to the treatment conditions for a period of 4 weeks. This is sufficient time for growth of ca. 7-9 new tooth rows or 20% turnover of the mineralised portion. There was no significant difference in the number of new (non-mineralised) teeth or total tooth row count in any treatment. Examination of the radulae via SEM revealed no differences in microwear or breakage on the feeding cusps correlating to treatment groups. The shell valves also showed no signs of dissolution. As a lineage, chitons have survived repeated shifts in Earth's climate through geological time, and at least their radulae may be robust to future perturbations.

Histological description of oogenesis in chiton virgulatus (Mollusca: Polyplacophora) / Descripción histológica de la ovogénesis de chiton virgulatus (Mollusca: Polyplacophora)

This paper describes the oogenesis of Chiton virgulatus, based on histological observations under transmission and scanning electron microscopy. Three oocyte types were identified: i) previtellogenic oocytes with a mean diameter of 50±20.5 µm, surrounded by elongated follicular cells of approximately 5 µm, ii) immature vitellogenic oocytes with a mean diameter of 113±15.3 µm and small cytoplasmic projections denoting the onset of the oocyte hull development; adjacent to each projection are pores approximately 0.7 µm in diameter, and iii) mature vitellogenic oocytes with a mean diameter of 146±24.8 µm; the oocyte cytoplasmic projections grow and its apical zone becomes trident-shaped; follicular cells adopt a bulbous shape due to the growth of the elongation and can reach up to 20 µm in length. The morphology and ultrastructure of the projections of the mature vitellogenic oocyte, as well as the size of pores at their base, are specific to C. virgulatus; therefore, these features could be used in taxonomic or fertilization studies.

En el presente trabajo se describe la ovogénesis de Chiton virgulatus, utilizando histología y las técnicas de microscopía electrónica de barrido y de transmisión. Se identificaron tres tipos de ovocitos: i) ovocitos previtelogénicos con un diámetro promedio de 50±20,5 µm, rodeados por células foliculares de forma alargada y un tamaño de aproximadamente 5 µm, ii) ovocitos vitelogénicos inmaduros con un diámetro promedio de 113±15,3 µm, este tipo de ovocitos presentan pequeñas proyecciones citoplasmáticas, que indican el inicio del desarrollo del casco del ovocito. Adyacentes a cada prolongación se presentan poros con un diámetro aproximado de 0,7 µm y iii) ovocitos vitelogénicos maduros con un diámetro promedio de 146±24,8 µm, las proyecciones citoplasmáticas del casco del ovocito crecen y en su parte apical adquieren la forma de un tridente, las células foliculares, dado el crecimiento de la prolongación toman el aspecto bulboso y llegan a medir hasta 20 µm de longitud. La morfología y la ultraestructura de las proyecciones del casco del ovocito vitelogénico maduro, así como el tamaño del poro en la base de las proyecciones son particulares para C. virgulatus, dichas características podrían ser utilizadas en trabajos de taxonomía y fertilización.

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.

Three-dimensional structure of the shell plate assembly of the chiton Tonicella marmorea and its biomechanical consequences.

This study investigates the three-dimensional structure of the eight plate exoskeletal (shell) assembly of the chiton Tonicella marmorea. X-ray micro-computed tomography and 3D printing elucidate the mechanism of conformational change from a passive (slightly curved, attached to surface) to a defensive (rolled, detached from surface) state of the plate assembly. The passive and defensive conformations exhibited differences in longitudinal curvature index (0.43 vs. 0.70), average plate-to-plate overlap (∼62% vs. ∼48%), cross-sectional overlap heterogeneity (60-82.5% vs. 0-90%, fourth plate), and plate-to-plate separation distance (100% increase in normalized separation distance between plates 4 and 5), respectively. The plate-to-plate interconnections consist of two rigid plates joined by a compliant, actuating muscle, analogous to a geometrically structured shear lap joint. This work provides an understanding of how T. marmorea achieves the balance between mobility and protection. In the passive state, the morphometry of the plates and plate-to-plate interconnections results in an approximately continuous curvature and constant armor thickness, resulting in limited mobility but maximum protection. In the defensive state, the underlying soft tissues gain protection and the chiton gains mobility through tidal flow, but regions of vulnerability open dorsally, due to the increase in plate-to-plate separation and decrease in plate-to-plate overlap. Lastly, experiments using optical and scanning electron microscopy, mercury porosimetry, and Fourier-transform infrared spectroscopy explore the microstructure and spatial distribution of the six layers within the intermediate plates, the role of multilayering in resisting predatory attacks, and the detection of chitin as a major component of the intra-plate organic matrix and girdle.

[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.

Nanoscale chemical tomography of buried organic-inorganic interfaces in the chiton tooth.

Biological organisms possess an unparalleled ability to control the structure and properties of mineralized tissues. They are able, for example, to guide the formation of smoothly curving single crystals or tough, lightweight, self-repairing skeletal elements. In many biominerals, an organic matrix interacts with the mineral as it forms, controls its morphology and polymorph, and is occluded during mineralization. The remarkable functional properties of the resulting composites-such as outstanding fracture toughness and wear resistance-can be attributed to buried organic-inorganic interfaces at multiple hierarchical levels. Analysing and controlling such interfaces at the nanometre length scale is critical also in emerging organic electronic and photovoltaic hybrid materials. However, elucidating the structural and chemical complexity of buried organic-inorganic interfaces presents a challenge to state-of-the-art imaging techniques. Here we show that pulsed-laser atom-probe tomography reveals three-dimensional chemical maps of organic fibres with a diameter of 5-10 nm in the surrounding nano-crystalline magnetite (Fe(3)O(4)) mineral in the tooth of a marine mollusc, the chiton Chaetopleura apiculata. Remarkably, most fibres co-localize with either sodium or magnesium. Furthermore, clustering of these cations in the fibre indicates a structural level of hierarchy previously undetected. Our results demonstrate that in the chiton tooth, individual organic fibres have different chemical compositions, and therefore probably different functional roles in controlling fibre formation and matrix-mineral interactions. Atom-probe tomography is able to detect this chemical/structural heterogeneity by virtue of its high three-dimensional spatial resolution and sensitivity across the periodic table. We anticipate that the quantitative analysis and visualization of nanometre-scale interfaces by laser-pulsed atom-probe tomography will contribute greatly to our understanding not only of biominerals (such as bone, dentine and enamel), but also of synthetic organic-inorganic composites.