Soft-part Anatomy Research Articles

In search of the glow—Three‐dimensional reconstruction of Latia neritoides with specific focus on the mantel cavity (Mollusca; Gastropoda; Hygrophila)

AbstractThe freshwater snail Latia neritoides occurs in certain streams and lakes of New Zealand's North Island. It defends itself against predators with a unique mechanism – the release of sticky, glowing mucus. Two possible origins of this defence mucus had earlier been suggested: the foot and the pneumostome area. After examining the glandular system of the foot in a previous study, in the present study we examined the general morphology of L. neritoides, focusing on the mantle cavity. With the first complete 3D model of L. neritoides now available, it is possible to evaluate previous morphological studies and to give non‐specialists a better understanding of the soft part anatomy of this fascinating gastropod. As a by‐product of this, we also compared the capabilities of μ‐CT and HREM on a methodological level. We characterized the two most common gland types in the mantel cavity (Lmcg1/Lmcg2) on the basis of their ultrastructure. They are present in large numbers and, therefore, regarded as likely candidates for being the producers of one or more components of the defence mucus. This notion was confirmed by histochemical analyses of Lmcg1 and Lmcg2 and other gland types in L. neritoides.

DNA sequence data, multispecies coalescent and morphometrics shed new light on the systematics of Iberian islamiinae springsnails (Caenogastropoda: Hydrobiidae)

ABSTRACT Multilocus phylogenies have shown that soft-part anatomy alone is insufficient for the systematics of valvatiform- and trochiform-shelled springsnails of the subfamily Islamiinae (family Hydrobiidae) due to morphological similarities between taxa that are not closely related. However, a solid knowledge of their systematics and species boundaries is crucial to conserve this highly imperilled group. Here, we inferred molecular phylogenies based on two mitochondrial and two nuclear gene fragments from representatives of three morphological species of the Iberian genus Iberhoratia and performed multispecies coalescent and shell variation analyses (geometric morphometrics) to reevaluate their taxonomic status. The resulting phylogenetic analyses, which included homologous sequences of 15 other valvatiform-shelled hydrobiid species endemic to the Iberian Peninsula, depicted the topotypical specimens of I. aurorae and I. gatoa elisai distantly related to one another and the type species I. morenoi. Considering their high genetic divergence and morphological differences from other hydrobiid taxa, we have placed the former two species in the new genera Beatrix n. gen. and Actenidia n. gen. The multispecies coalescent delimitation method DELINEATE, a novel approach to the taxonomy of the Hydrobiidae, and shell morphometric data suggested two species within the ‘I. gatoa elisai’ clade. Based on morphological and molecular evidence, we recognized this clade as Actenidia, a new genus comprising the species A. elisai n. gen., n. comb. and A. baetica n. gen., n. sp. Our results underscore the importance of using multiple lines of evidence to delimitate species of Islamiinae and interpret their systematics. We also discuss the implications of our findings for conserving I. gatoa.

‘Arm brains’ (axial nerves) of Jurassic coleoids and the evolution of coleoid neuroanatomy

Although patchy, the fossil record of coleoids bears a wealth of information on their soft part anatomy. Here, we describe remains of the axial nerve cord from both decabrachian (Acanthoteuthis, Belemnotheutis, Chondroteuthis) and octobrachian (Plesioteuthis, Proteroctopus, Vampyronassa) coleoids from the Jurassic. We discuss some hypotheses reflecting on possible evolutionary drivers behind the neuroanatomical differentiation of the coleoid arm crown. We also propose some hypotheses on potential links between habitat depth, mode of life and the evolution of the Coleoidea.

Hyperstrophic Malformation of Lunella correensis (Récluz, 1853) (Vetigastropoda: Turbinidae)

We report a rare case of hyperstrophy in the intertidal turban snail Lunella correensis (Récluz, 1853), which was recently found in the collection of Kumagusu Minakata, a Japanese naturalist and folklorist. Although the soft-part anatomy is unknown, the combination of shell morphological characters indicate that the specimen is clearly dextral and hyperstrophic. Such variations in chilarity mostly hinder normal growth, hence an abnormal hyperstrophic adult individual is extremely rare. This mutation in chilarity is the first reported case of a hyperstrophic individual in Vetigastropoda.

Two species of the genus Anchistrocheles (Bairdioidea: Ostracoda: Crustacea) from Japan and their developmental characteristics for adaptation to interstitial environments

A new species and an already known species of the genus Anchistrocheles Brady & Norman, 1889 from the Pacific coast of Japan, are described in detail using scanning electron microscopy of the carapaces and soft-part anatomy of the appendages. The new species, Anchistrocheles hayatotanakai sp. nov., is only the second to be described in the genus Anchistrocheles from Japan, and this study is also the first to describe the appendages of A. yamaguchii Yajima, 1987, previously only known as a fossil from Pleistocene strata of the Atsumi Formation in central Japan. The two species are considered to be closely related because they share many common characters in their appendages, but they are distinguishable from each other based on the male and female copulatory organs, furcal chaetotaxy, brush-shaped organs, number of lateral pore systems, and outlines of the carapaces in dorsal view. Ontogenetic changes of carapace sizes were compared between three interstitial species (Anchistrocheles hayatotanakai sp. nov., A. yamaguchii, and Neonesidea sp. I) and an epifaunal species (N. sp. S). The reduction in carapace width was found to be the primary reason for the reduction in the cross-sectional area and is probably related to the adaptation to interstitial environments. The brush-shaped organs located between the 6th pair of limbs are also shown. This study is the first to report the anatomically precise position of these organs.

Hyolithid-like hyoliths without helens from the early Cambrian of South China, and their implications for the evolution of hyoliths

BackgroundA small hyolith, with a triangular operculum and a conical-pyramidal conch with a sharp apex, originally documented as Ambrolinevitus ventricosus, is revised based on new material from the Chengjiang biota. The operculum of ‘Ambrolinevitus’ ventricosus displays strong morphological similarities with the operculum of Paramicrocornus from the Shuijingtuo Formation (Cambrian Series 2), indicating that the species should be reassigned to Paramicrocornus.ResultsBased on the unusual morphology of Paramicrocornus, we herein propose a new family Paramicrocornidae fam. nov. A cladistic analysis of Cambrian and Ordovician hyoliths clearly delineates hyolithids as a monophyletic group which evolved from the paraphyletic orthothecids in the early Cambrian and with Paramicrocornidae as its closest relative.ConclusionsThe phylogenetic analysis, together with the distribution of hyoliths from the Cambrian to the Ordovician, reveals the presumptive evolution model of both the skeleton and soft-part anatomy of hyoliths. The Family Paramicrocornidae plays an intermediate role in hyolith evolution, representing the transitional stage in the evolution from orthothecids to hyolithids.

Two new stygobiotic species of Horatia Bourguignat, 1887 (Hydrobiidae) from Croatia

In this paper we describe two new species of the freshwater snails of genus Horatia. A new stygobiotic species of Horatia Bourguignat, 1887 is described from Izvor Beguša in Croatia. It occurs in sympatry with the crenobiotic H. klecakiana Bourguignat, 1887, but is morphologically and molecularly distinct. It is characterized by the terminal part of the body whorl separated from the columella, and neither eyes nor any pigment on the soft parts. It is a stygobiont gastropod, known so far only from one living specimen and several empty shells, thus its soft part morphology and anatomy remain unknown. Another new species of stygobiotic Horatia was found inside the cave Mali Rumin, its description is based solely on numerous empty shells from the cave sediments.

Palaeontological evidence reveals convergent evolution of intervertebral joint types in amniotes

The intervertebral disc (IVD) has long been considered unique to mammals. Palaeohistological sampling of 17 mostly extinct clades across the amniote tree revealed preservation of different intervertebral soft tissue types (cartilage, probable notochord) seen in extant reptiles. The distribution of the fossilised tissues allowed us to infer the soft part anatomy of the joint. Surprisingly, we also found evidence for an IVD in fossil reptiles, including non-avian dinosaurs, ichthyosaurs, plesiosaurs, and marine crocodiles. Based on the fossil dataset, we traced the evolution of the amniote intervertebral joint through ancestral character state reconstruction. The IVD evolved at least twice, in mammals and in extinct diapsid reptiles. From this reptilian IVD, extant reptile groups and some non-avian dinosaurs independently evolved a synovial ball-and-socket joint. The unique birds dorsal intervertebral joint evolved from this dinosaur joint. The tuatara and some geckos reverted to the ancestral persisting notochord.

A revision of the poorly known Pontocaspian gastropod genus Abeskunus, and its Central Paratethyan origin

ABSTRACT Biodiversity and conservation assessments rise and fall with taxonomic accuracy. An example of a still largely unresolved taxonomy is found in the Gastropoda of the Caspian Sea. The present paper clarifies the taxonomy of the genus Abeskunus and its three species of anomalohaline gastropods endemic to the Caspian Sea. Based on material from Pleistocene, Holocene, and (sub-)recent deposits from Russia, Azerbaijan, and Kazakhstan we discuss species discriminations, synonyms, systematic position, as well as uncertainties regarding the type species. Given the apparent loss of all type material, we designate neotypes for all three species. Despite our efforts to collect and analyse new material and available material housed in museum collections, molecular data, and soft-part anatomy are unavailable precluding a firm systematic classification. Overall shell morphology and protoconch microsculpture are indicative of the family Lithoglyphidae. Comparison with Miocene and Pliocene fossils attributed to the genus Zagrabica suggests it to be a likely ancestor of Abeskunus, tracing back the lineage to the late Miocene Lake Pannon. Although the recent literature lists all three species of Abeskunus among the extant Pontocaspian fauna, two of the three species have never been found living and the third one not since the nineteenth century.

<p class="HeadingRunIn"><strong>Combined visualization of echinoderm hard and soft parts using contrast-enhanced micro-computed tomography</strong></p>

Recent studies have shown that micro-computed tomography (µCT) must be considered one of the most suitable techniques for the non-invasive, three-dimensional (3D) visualization of metazoan hard parts. In addition, µCT can also be used to visualize soft part anatomy non-destructively and in 3D. In order to achieve soft tissue contrast using µCT based on X-ray attenuation, fixed specimens must be immersed in staining solutions that include heavy metals such as silver (Ag), molybdenum (Mo), osmium (Os), lead (Pb), or tungsten (W). However, while contrast-enhancement has been successfully applied to specimens pertaining to various higher metazoan taxa, echinoderms have thus far not been analyzed using this approach. In order to demonstrate that this group of marine invertebrates is suitable for contrast-enhanced µCT as well, the present study provides results from an application of this technique to representative species from all five extant higher echinoderm taxa. To achieve soft part contrast, freshly fixed and museum specimens were immersed in an ethanol solution containing phosphotungstic acid and then scanned using a high-resolution desktop µCT system. The acquired datasets show that the combined visualization of echinoderm soft and hard parts can be readily accomplished using contrast-enhanced µCT in all extant echinoderm taxa. The results are compared with µCT data obtained using unstained specimens, with conventional histological sections, and with data previously acquired using magnetic resonance imaging, a technique known to provide excellent soft tissue contrast despite certain limitations. The suitability for 3D visualization and modeling of datasets gathered using contrast-enhanced µCT is illustrated and applications of this novel approach in echinoderm research are discussed.

Two new species of Bairdiidae (Ostracoda: Crustacea) from the western Pacific coast of Japan.

Herein, two new bairdiid ostracod species in the western Pacific Coast of Japan, namely Neonesidea kamiyai sp. nov. and Bairdoppilata japonica sp. nov. are described. They are the fourth and first species described in their respective genus in Japan within the Recent Bairdiidae. The description of the two new species is based on scanning electron microscopic investigation of carapaces and on the analysis of anatomy and chaetotaxy of appendages. Scanning electron microscopy of the carapace and soft-part anatomy of appendages of the two new species provided the complete species description. An asymmetric brush-shaped organ, with the right part considerably larger than the left part, is found in both species; this characteristic is suggested to be synapomorphic for some taxa in the family Bairdiidae.

The trilobite Redlichia from the lower Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia: systematics, ontogeny and soft-part anatomy

The trilobite Redlichia Cossmann, 1902 is an abundant element of the lower Cambrian (Series 2, Stage 4) Emu Bay Shale (EBS) Konservat-Lagerstätte on Kangaroo Island, South Australia. Well-preserved, fully articulated specimens from this deposit are known to reach lengths of up to 25 cm, representing one of the largest known Cambrian trilobites. Until now, all Redlichia specimens from the EBS have been referred to Redlichia takooensis Lu, 1950, a species originally described from South China. Previous work recognized considerable differences in exoskeletal morphology among specimens of varying sizes, which was attributed to ontogeny. However, close examination of a large collection of recently acquired specimens shows that this variation actually represents two distinct morphs, interpreted here as separate species: R. takooensis, and a large, new species, Redlichia rex sp. nov. An analysis of morphological variation in holaspides (‘adults’) of the more common R. takooensis reveals considerable ontogenetic change occurred even during this later phase of growth. Some specimens of both Redlichia species from the EBS also exhibit exceptionally preserved soft-part anatomy, particularly the antennae and biramous appendages. Here, appendages (antenniform and biramous) and digestive structures are described, and biramous appendage reconstructions of R. rex sp. nov. are presented, which show a striking resemblance to some early Cambrian trilobites from South China. In particular, R. rex has a tripartite exopodite, as well as a dorsoventrally deep protopodite with gnathobasic spines used to shred or crush food items. Based on recent phylogenetic analyses, it is possible that an exopodite with tripartite subdivisions represents the plesiomorphic condition for Artiopoda (trilobites and kin). The digestive system of R. takooensis exhibits a series of paired digestive glands in the cephalon and anterior thorax, similar to those described for a number of other Cambrian and Ordovician trilobites.http://zoobank.org/urn:lsid:zoobank.org:pub:507BEAFC-4AFA-43F4-A5C4-49E4B58C658E

Solaropsis brasiliana, anatomy, range extension and its phylogenetic position within Pleurodontidae (Mollusca, Gastropoda, Stylommatophora).

A detailed anatomical revision on Solaropsis brasiliana (Deshayes 1832) has been carried out. New characters on shell, anatomy of soft parts, and a review of the genus distribution in South America, as well as clarification on S. brasiliana distributional area are provided in the present study. Solaropsis brasiliana is diagnosed by its globose, solid, and hirsute shell, with periphery obsoletely angular, bursa copulatrix with a thick, long diverticulum, a thick, long flagellum and a penis retractor muscle forked, with the vas deferens passing through it. This compiled information was used to test the phylogenetic position of S. brasiliana within South American Pleurodontidae through a cladistics analysis. In the phylogenetic hypothesis obtained, S. brasiliana is sister group of S. gibboni (Pfeiffer 1846) and the monophyly of the genus Solaropsis Beck is also supported. Here, we sustain that the distribution of S. brasiliana is restricted to Brazil, inhabiting the States of Rio de Janeiro, Espírito Santo, Bahia and Minas Gerais.

The attachment strategies of Cambrian kutorginate brachiopods: the curious case of two pedicle openings and their phylogenetic significance

AbstractThe kutorginates are commonly the most abundant rhynchonelliform brachiopod found in the early Cambrian; they are also some of the oldest known rhynchonelliforms, first appearing in the Unnamed Series 2 (Atdabanian equivalent) and becoming extinct sometime in Cambrian Series 3 (Amgaian equivalent). Moreover, kutorginates are the first known member of the rhynchonelliforms for which we have a detailed knowledge of their soft-part anatomy, including the lophophore, digestive tract, and pedicle—all exceptionally preserved inKutorgina chengjiangensisZhang et al., 2007 from the early Cambrian Chengjiang Lagerstätte of southern China. The stout and annulated pedicle in the original report was described as protruding between the valves; however, newly collected better-preserved material now clearly shows that the pedicle actually protrudes from the apical perforation ofKutorgina chengjiangensis.This type of apical pedicle has also been described from other early Cambrian rhynchonelliforms, including the problematic chileateLongtancunella chengjiangensis(Zhang et al., 2011a). Exceptionally preserved similar pedicles are also known to emerge apically from the Silurian chileate dictyonellidEichwaldia subtrigonalisBillings, 1858, as well as from the recently described Silurian chileateTrifissura rigidaHolmer, Popov, and Bassett, 2014. However, it is clear that the only other exceptionally preserved kutorginate—a silicifiedNisusia—was provided with an adult pedicle emerging between the valves from a posterior gap; thus,Nisusiahas two pedicle openings. However, the apical foramen may represent the earliest attachment of the larvae, which subsequently became nonfunctional through ontogeny. It is suggested that both types of attachment strategies may have appeared early in the stem lineage of the Rhynchonelliformea.

Digestive and appendicular soft-parts, with behavioural implications, in a large Ordovician trilobite from the Fezouata Lagerst\xe4tte, Morocco

Trilobites were one of the most successful groups of marine arthropods during the Palaeozoic era, yet their soft-part anatomy is only known from a few exceptionally-preserved specimens found in a handful of localities from the Cambrian to the Devonian. This is because, even if the sclerotized appendages were not destroyed during early taphonomic stages, they are often overprinted by the three-dimensional, mineralised exoskeleton. Inferences about the ventral anatomy and behavioural activities of trilobites can also be derived from the ichnological record, which suggests that most Cruziana and Rusophycus trace fossils were possibly produced by the actions of trilobites. Three specimens of the asaphid trilobite Megistaspis (Ekeraspis) hammondi, have been discovered in the Lower Ordovician Fezouata Konservat-Lagerstätte of southern Morocco, preserving appendages and digestive tract. The digestive structures include a crop with digestive caeca, while the appendages display exopodal setae and slight heteropody (cephalic endopods larger and more spinose than thoracic and pygidial ones). The combination of these digestive structures and the heteropody has never been described together among trilobites, and the latter could assist in the understanding of the production of certain comb-like traces of the Cruziana rugosa group, which are extraordinarily abundant on the shallow marine shelves around Gondwana.

A hyolithid with preserved soft parts from the Ordovician Fezouata Konservat-Lagerstätte of Morocco

Hyolithids are an extinct group of early lophotrochozoans with an external skeleton consisting of a conical conch, an externally fitting operculum, and a pair of long, lateral spines named helens. Their phylogenetic position within the lophotrochozoans is unclear, but traditionally they have been regarded as molluscs. Although hyolithids occur in Konservat-Lagerstätten, their soft-part preservation had so far been restricted to the gut. The few known examples suggested that a simple U-shaped gut was characteristic of the group, but new occurrences show a diversity of gut configurations suggesting certain ecological diversity within the group. Here is reported an exceptionally preserved hyolithid specimen from the Ordovician Fezouata Konservat-Lagerstätte of Morocco with a relatively complete gut possibly including an oesophagus, a mouth and a faecal string. Uniquely for hyoliths, other soft parts, likely those associated with the inner surface of the operculum, appear to be preserved as well protruding from the aperture. The anatomy of the preserved soft parts is in accordance with inferences from skeletal anatomy suggesting that hyolithid soft parts did not extend much beyond the aperture, and that only the internal portion of the helens was associated with soft tissues. It is also compatible with lophotrochozoan affinities, but molluscan apomorphies, such as a foot or a radula are not present in the specimen. Taken together, the newly available information suggests that hyolithids may have had a relatively generalized feeding organ, which could adapt to various feeding modes in the suspension-detritus-deposit feeding spectrum. A specialized deposit feeding strategy would be at odds with what is known about hyolithid functional morphology, therefore the presence of a sediment-like infill in the posterior part of the gut of the presently described specimen is puzzling and, as it has been suggested for some Chengjiang taxa, may represent a taphonomic “artefact”.

Ostracods (Crustacea): Some problems of systematics

The initially established ostracod classification was based mainly on soft part anatomy of extant taxa. In the fossil record, ostracods are usually represented by shells alone, complicating the elaboration of a unified taxonomic system. A brief review of ostracod development in the Phanerozoic is outlined. Long-lived groups, such as Myodocopida, Podocopida, and Platycopida (Ordovician-Recent), display stable uniformity of the shell and soft part structures. The Paleozoic ostracod groups possess sharply different shell structures. The ostracod shell type is undoubtedly an important taxonomic feature. It is noteworthy that the points of view on the systematic position of extraordinary ostracod groups which became extinct in the Paleozoic (leperditicopids, beyrichicopids, kloedenellocopids) vary widely. It is proposed to assign all the ostracodomorphs and ostracods (bradoriamorphs, palaeocopids sensu lato, platycopids, podocopids) to the same high-rank taxon.

Vesicomyinae (Bivalvia: Vesicomyidae) of the Kuril–Kamchatka Trench and adjacent abyssal regions

Representatives of the subfamily Vesicomyinae (Bivalvia, Vesicomyidae) are tiny deep-sea molluscs distributed worldwide and reaching huge abundances of hundreds and thousands of specimens in trawl catches. During the German–Russian deep-sea expedition KuramBio (R/V Sonne, 2012) for the first time two vesicomyin species were collected from the abyssal plain adjacent to the Kuril–Kamchatka Trench from the depths of 4861–5787m, Vesicomya pacifica (Smith, 1885) and “Vesicomya” filatovae sp.n. Two species of vesicomyins, V. sergeeviFilatova, 1971 and V. profundiFilatova, 1971, which were previously reported from the hadal of the Kuril–Kamchatka Trench, were not collected at the abyssal depth despite of the close geographical proximity of the sampling area to their distribution ranges. Altogether nine species of vesicomyins are recorded now from the West and Indo-West Pacific; data on distribution and morpho-anatomical characters of these species are provided. Taxonomic description of V. pacifica is revised including information on its soft part anatomy, new localities and COI sequences. For the first time for a vesicomyin bivalve molecular data is given for a species with an explicit morphological description and unambiguous taxonomic affiliation. Molecular analysis of 160 published COI sequences of vesicomyids and newly obtained molecular data on V. pacifica showed that V. pacifica and two undescribed vesicomyin species forming a monophyletic clade which exhibits sister relationships with the Pliocardiinae, the group of chemosymbiotic vesicomyids. “Vesicomya” filatovae sp.n. is provisionally assigned to the genus Vesicomya (s.l.) until additional morphological and molecular data are obtained. It differs from Vesicomya s.s. by a broader hinge margin with more radiating teeth and the presence of only one pair of demibranchs.

The affinities of the cosmopolitan arthropodIsoxysand its implications for the origin of arthropods

Isoxys is a cosmopolitan bivalved arthropod genus known almost exclusively from Cambrian Konservat-Lagerstatten. Despite its wide geographical distribution in such sites of exceptional preservation, little was known of its soft-part anatomy until recently when remains of eyes and raptorial frontal appendages were discovered. This absence has precluded determination of affinities. The new discovery of soft parts led to two important hypotheses: (1) that Isoxys was related to the ‘great-appendage’ arthropods and (2) that its contained species were not congeneric. Neither has been tested using a detailed cladistics analysis. The morphology of Isoxys is re-evaluated and coded into an extensive cladistics analysis. Our results indicate that Isoxys was indeed a monophyletic genus with all representatives united by the presence of an expansive dorsal shield with prominent antero- and posterolateral cardinal spines. It also indicates that Isoxys occupies a crucial role in arthropod evolution, resolving at the base of Arthropoda. The ‘great appendages’ of Isoxys are interpreted as innovating from either the protocerebral or deutocerebral somite and are therefore not homologous to those of other ‘great-appendage’ arthropods, which are interpreted as originating from the tritocerebral somite of the head.

Polymorphic organization in a planktonic graptoloid (Hemichordata: Pterobranchia) colony of Late Ordovician age

AbstractGraptolites are common fossils in Early Palaeozoic strata, but little is known of their soft-part anatomy. However, we report a long-overlooked specimen ofDicranograptusaff.ramosusfrom Late Ordovician strata of southern Scotland that preserves a strongly polymorphic, recalcitrant, organic-walled network hitherto unseen in graptoloid graptolites. This network displays three morphologies: proximally, a strap-like pattern, likely of flattened tubes; these transform distally into isolated, hourglass-shaped structures; then, yet more distally, revert to a (simpler) strap-like pattern. The network most likely represents a stolon-like system, hitherto unknown in graptoloids, that connected individual zooids. Its alternative interpretation, as colonial xenobionts that infested a graptoloid colony and mimicked its architecture, is considered less likely on taphonomic and palaeobiological grounds. Such polymorphism is not known in non-graptolite pterobranchs, which are less diverse and morphologically more conservative: a division of labour between graptoloid zooids for such functions as feeding, breeding and rhabdosome construction may have been the key to their remarkable evolutionary success.