Boring systematics: A genome skimmed phylogeny of ctenostome bryozoans and their endolithic family Penetrantiidae with the description of one new species.

Ctenostomes are a group of gymnolaemate bryozoans with an uncalcified chitinous body wall having few external, skeletal characters. Hence, species identification is challenging and their systematics remain poorly understood, even more so when they exhibit an endolithic (boring) lifestyle. Currently, there are four Recent families of endolithic bryozoans that live inside mineralized substrates like mollusk shells. In particular, Penetrantiidae Silén, 1946 has received considerable attention and its systematic affinity to either cheilostomes or ctenostomes has been debated. Species delimitation of penetrantiids remains difficult, owing to a high degree of colonial and zooidal plasticity. Consequently, an additional molecular approach is essential to unravel the systematics of penetrantiids, their phylogenetic placement and their species diversity. We therefore sequenced the mitochondrial (mt) genomes and two nuclear markers of 27 ctenostome species including nine penetrantiids. Our phylogeny supports the Penetrantiidae as a monophyletic group placed as sister taxon to the remaining ctenostomes alongside paludicellids, arachnidioids and terebriporids. The boring family Terebriporidae d'Orbigny, 1847 were previously considered to be among vesicularioids, but our results suggest an arachnidioid affinity instead. Ctenostome paraphyly is supported by our data, as the cheilostomes nest within them. A Multiporata clade is also well supported, including the former victorelloid genus Sundanella. Altogether, this study provides new insights into ctenostome systematics, assists with species delimitation and contributes to our understanding of the bryozoan tree of life.

Rediscovering the unusual, solitary bryozoan Monobryozoon ambulans Remane, 1936: first molecular and new morphological data clarify its phylogenetic position.

BACKGROUND: One of the most peculiar groups of the mostly colonial phylum Bryozoa is the taxon Monobryozoon, whose name already implies non-colonial members of the phylum. Its peculiarity and highly unusual lifestyle as a meiobenthic clade living on sand grains has fascinated many biologists. In particular its systematic relationship to other bryozoans remains a mystery. Despite numerous searches for M. ambulans in its type locality Helgoland, a locality with a long-lasting marine station and tradition of numerous courses and workshops, it has never been reencountered until today. Here we report the first observations of this almost mythical species, Monobryozoon ambulans. RESULTS: For the first time since 1938, we present new modern, morphological analyses of this species as well as the first ever molecular data. Our detailed morphological analysis confirms most previous descriptions, but also ascertains the presence of special ambulatory polymorphic zooids. We consider these as bud anlagen that ultimately consecutively separate from the animal rendering it pseudo-colonial. The remaining morphological data show strong ties to alcyonidioidean ctenostome bryozoans. Our morphological data is in accordance with the phylogenomic analysis, which clusters it with species of Alcyonidium as a sister group to multiporate ctenostomes. Divergence time estimation and ancestral state reconstruction recover the solitary state of M. ambulans as a derived character that probably evolved in the Late Cretaceous. In this study, we also provide the entire mitogenome of M. ambulans, which-despite the momentary lack of comparable data-provides important data of a unique and rare species for comparative aspects in the future. CONCLUSIONS: We were able to provide first sequence data and modern morphological data for the unique bryozoan, M. ambulans, which are both supporting an alcyonidioidean relationship within ctenostome bryozoans.

Alcyonidium kuklinskii sp. nov., a new species of Antarctic ctenostome bryozoan with a key to all Antarctic species of the genus.

Recent surveys of Antarctic waters in the Terra Nova Bay (Ross Sea) revealed numerous bryozoan species including ctenostome bryozoans. Whereas cheilostome bryozoans are well-studied in these latitudes, ctenostomes remain highly neglected. Large ctenostomes are easily recognized by their lack of calcified skeletons, but this lack also renders them difficult and tedious to identify. As a result, histology and reconstructions of internal soft tissues are required to classify this group of bryozoans. Thanks to the availability of new specimens from Terra Nova Bay, a detailed analysis of growth form, gut morphology and tentacle number of two colonies, initially ascribed to the ctenostome bryozoan genus Alcyonidum Lamouroux, 1813, turned out to be a new species, Alcyonidium kuklinskii sp. nov., which we described in this study. These specimens were also barcoded (COI) and sequences compared to available ones. Together with the new species described here, a total of ten species of Alcyonidium is now known for the Southern Ocean, accounting for one eighth of the entire genus diversity. All Southern Ocean species appear to be endemic. In order to speed the identification of the Antarctic Alcyonidium species, we provide an identification key and a distribution map of all type species. In brief, colony morphology, zooidal size and, in particular tentacle number represent the most suitable characters for identifying species within this genus. Supplementary Information: The online version contains supplementary material available at 10.1007/s13127-023-00629-4.

Morphology of ctenostome bryozoans: 7. Hislopia, Echinella and Timwoodiellina.

Ctenostome bryozoans are a small group of gymnolaemates comprising less than 400 recent species. They are paraphyletic and ctenostome-grade ancestors gave rise to Cheilostomata, the most dominant and speciose taxon of Bryozoa in the present day. Investigations into ctenostomes are important for reconstructing character evolution among Gymnolaemata. As a continuation of studies on a morphological series of ctenostome bryozoans, we herein investigate six species of hislopiids, a small clade of three genera occurring in freshwater habitats. The general morphology of all species is similar in having primarily uniserial chains of encrusting zooids, which are mostly oval to ellipsoid and have a flattened frontobasal axis. Hislopia prolixa and Echinella placoides often have more slender zooids with a higher frontobasal axis. Apertures of hislopiids are quadrangular, lined by a thickened cuticle. Apertural spines are present in various lengths in E. placoides, Hislopia lacustris and Hislopia corderoi. The remaining cuticle is rather thin except at lateral areas, close to the pore-plates which are prominent in hislopiids because of abundant special and limiting cells. All species except H. corderoi and Timwoodiellina natans have a prominent collar obstructing the vestibulum, whereas the latter two species instead have an 'external collar' as cuticular, outer folds projecting over the aperture. Hislopiid lophophores carry eight, or more commonly 12-18 tentacles. The digestive tract is distinguished by an often highly elongated esophagus and/or cardia, with the latter always having a prominent bulbous part in the form of a proventriculus-or gizzard in E. placoides. The caecum is extensive in all species. In Hislopia the intestine is characteristically two-chambered with a proximal and distal part before entering an anal tube of various length. The latter is present in all species except T. natans and terminates in mid-lophophoral area. Oocytes in E. placoides are large and macrolecithal indicating brooding and the production of lecithotrophic larvae. Hislopia species produce small, oligolecithal ones, which suggests zygote spawning and planktotrophy. In general, the morphology is similar among the different hislopiids with characters of the gut aiding in delineating the genera Echinella and Timwoodiellina.

Deep-sea ctenostome bryozoans: revision of the family Pachyzoidae, with description of a new genus and three new species from Zealandia.

Pachyzoidae is a little-known family of deep-sea ctenostome Bryozoa that until now was monospecific for Pachyzoon atlanticum. Originally described from the Atlantic Ocean, the genus was also found off southeastern New Caledonia in deep waters of the geological continent of Zealandia. Pachyzoon atlanticum forms globular to flat round colonies, living on soft, muddy to sandy bottoms with a few rhizoidal cystid appendages extending from the basal, substrate-oriented side. In this study, we investigate additional pachyzoids, collected between 1965 and 2015 from over 40 sites around New Zealand, by means of detailed morphological and histological investigations. In total, several hundred colonies were encountered in the NIWA Invertebrate Collection, comprising two new species of the genus Pachyzoon, P. grischenkoi sp. nov. and P. pulvinaris sp. nov., and the new genus and species Jeanloupia zealandica gen. et sp. nov.. The genus Jeanloupia is characterized by small disc-shaped colonies with highly elongated peristomes and a quadrangular aperture, distinct from the round apertures of the genus Pachyzoon. Pachyzoid species differ in colony structure and shape, apertural papillae and polypide features such as tentacle number or digestive-tract details. Cystid appendages are non-kenozooidal, but may originate from laterally flanking kenozooids. Based on published images, alleged P. atlanticum from New Caledonia is re-interpreted as P. pulvinaris n. sp.. Morphological characters support alcyonidioidean relationships, as previously suggested. First observations on pachyzoid reproduction show macrolecithal oocytes and brooding of embryos, which seems to be the general pattern for this family. The occurrence of three new Zealandian species in a comparatively small geographical area far from the Atlantic indicates a high possibility of more species to discovered.

Boring bryozoans: an investigation into the endolithic bryozoan family Penetrantiidae.

An endolithic lifestyle in mineralized substrates has evolved multiple times in various phyla including Bryozoa. The family Penetrantiidae includes one genus with ten extant and two fossil species. They predominantly colonize the shells of molluscs and establish colonies by chemical dissolution of calcium carbonate. Based on several morphological characters, they were described to be either cheilostome or ctenostome bryozoans. For more than 40 years, neither the characters of species identity and systematics nor the problem of their phylogeny was approached. Consequently, the aim of this study is to reevaluate species identities and the systematic position of the genus Penetrantia by analyzing at least six different species from eight regions with the aid of modern methods such as confocal laser scanning microscopy and 3D-reconstruction techniques. This study demonstrates that the musculature associated with the operculum and brood chamber shows significant differences from the cheilostome counterparts and seems to have evolved independently. Together with the presence of other ctenostome-like features such as true polymorphic stolons and uncalcified body wall, this finding supports a ctenostome affinity. Operculum morphology reveals many new species-specific characters, which, together with information about gonozooid morphology, tentacle number, and zooid size ranges, will enhance species identification. It also revealed a probable new species in Japan as well as potential cryptic species in France and New Zealand. In addition, this study increases the known distribution range of the family and its substrate diversity. Altogether, the new information collated here provides the basis for future work on a neglected taxon. Supplementary Information: The online version contains supplementary material available at 10.1007/s13127-023-00612-z.

Genomic and transcriptomic survey of bryozoan Hox and ParaHox genes with emphasis on phylactolaemate bryozoans.

BACKGROUND: Bryozoans are mostly sessile aquatic colonial invertebrates belonging to the clade Lophotrochozoa, which unites many protostome bilaterian phyla such as molluscs, annelids and brachiopods. While Hox and ParaHox genes have been extensively studied in various lophotrochozoan lineages, investigations on Hox and ParaHox gene complements in bryozoans are scarce. RESULTS: Herein, we present the most comprehensive survey of Hox and ParaHox gene complements in bryozoans using four genomes and 35 transcriptomes representing all bryozoan clades: Cheilostomata, Ctenostomata, Cyclostomata and Phylactolaemata. Using similarity searches, phylogenetic analyses and detailed manual curation, we have identified five Hox genes in bryozoans (pb, Dfd, Lox5, Lox4 and Post2) and one ParaHox gene (Cdx). Interestingly, we observed lineage-specific duplication of certain Hox and ParaHox genes (Dfd, Lox5 and Cdx) in some bryozoan lineages. CONCLUSIONS: The bryozoan Hox cluster does not retain the ancestral lophotrochozoan condition but appears relatively simple (includes only five genes) and broken into two genomic regions, characterized by the loss and duplication of serval genes. Importantly, bryozoans share the lack of two Hox genes (Post1 and Scr) with their proposed sister-taxon, Phoronida, which suggests that those genes were missing in the most common ancestor of bryozoans and phoronids.

The unplumatellid Plumatella fruticosa found its home: Hirosella gen. nov. morphological arguments for the systematic placement of a freshwater bryozoan.

Bryozoans are colonial, suspension-feeding lophotrochozoans. The phylum consists of the large group of chiefly marine Myolaemata and the exclusively limnic Phylactolaemata. Each colony consists of individual zooids that comprise the protective cystid and the retractable polypide. Phylactolaemates are a small group of approximately 90 species in 6 families. They feature a body wall, that can either be gelatinous, as in the families Stephanellidae, Lophopodidae, Cristatellidae and Pectinatellidae, or encrusted, as in Plumatellidae and Fredericellidae. Morphological investigations of the most specious plumatellids are rare and focus on few species. Plumatella fruticosa is of particular interest in this regard, as it shows a mosaic of plumatellid and fredericellids characters. The most recent phylogeny clusters P. fruticosa with cristatellids and pectinatellids as sister groups to fredericellids. Hence, there is considerable doubt, whether P. fruticosa is truly a plumatellid. Therefore, this study aims to reinvestigate the morphology of P. fruticosa with confocal microscopy and section-based three-dimensional reconstruction. The new data show that P. fruticosa has numerous conspicuous stumps from fragmented proliferation buds, which are otherwise only known from fredericellids. Like fredericellids, P. fruticosa grows erect, but in contrast, has a horseshoe-shaped lophophore and floatoblasts. Besides the proportions of the lophophore, the tentacle sheath and digestive tract resemble a fredericellid-like situation. Myoanatomical details like the pronounced longitudinal muscles of the vestibular wall and tentacle sheath differ from plumatellids and favour the recently proposed scenario, which places P. fruticosa next to Pectinatellidae and Cristatellidae. In addition, the intertentacular membrane of P. fruticosa shows structural similarity to cristatellids as it is attached to the tentacles via lamellae. Taking all aspects into account, we erect a new family: Hirosellidae fam. nov. including the new genus Hirosella gen. nov.

Phylogenomics reveals deep relationships and diversification within phylactolaemate bryozoans.

Bryozoans are mostly sessile colonial invertebrates that inhabit all kinds of aquatic ecosystems. Extant bryozoan species fall into two clades with one of them, Phylactolaemata, being the only exclusively freshwater clade. Phylogenetic relationships within the class Phylactolaemata have long been controversial owing to their limited distinguishable characteristics that reflect evolutionary relationships. Here, we present the first phylogenomic analysis of Phylactolaemata using transcriptomic data combined with dense taxon sampling of six families to better resolve the interrelationships and to estimate divergence time. Using maximum-likelihood and Bayesian inference approaches, we recovered a robust phylogeny for Phylactolaemata in which the interfamilial relationships are fully resolved. We show Stephanellidae is the sister taxon of all other phylactolaemates and confirm that Lophopodidae represents the second offshoot within the phylactolaemate tree. Plumatella fruticosa clearly falls outside Plumatellidae as previous investigations have suggested, and instead clusters with Pectinatellidae and Cristatellidae as the sister taxon of Fredericellidae. Our results demonstrate that cryptic speciation is very likely in F. sultana and in two species of Plumatella (P. repens and P. casmiana). Divergence time estimates show that Phylactolaemata appeared at the end of the Ediacaran and started to diverge in the Silurian, although confidence intervals were large for most nodes. The radiation of most extant phylactolaemate families occurred mainly in the Palaeogene and Neogene highlighting post-extinction diversification.

Morphology of ctenostome bryozoans: 6. Amphibiobeania epiphylla.

Ctenostome bryozoans are unmineralized and mostly marine. Their lack of calcified skeletal features requires other characters to be considered for systematic and phylogenetic considerations. As a continuation of an ongoing series of studies, we herein investigate the morphology of Amphibiobeania epiphylla, a unique bryozoan inhabiting mangrove leaves that are highly exposed to tidal cycles and regular dry events according to the tidal cycle. Besides this interesting mode of life, the species was originally interpreted to be a weakly mineralized cheilostome bryozoan, whereas molecular data place it among ctenostome bryozoans. To elucidate the systematic and phylogenetic position of the genus and also find morphological adaptations to an extreme habitat, we investigated the morphology of A. epiphylla in detail. Zooids show a lophophore with eight tentacles and a simple gut with a prominent caecum, lophophoral anus and most notably a distinct gizzard in the cardiac region. Gizzard teeth are multiple, simple homogeneous cuticular structures. The cuticle of the zooid is rather uniform and shows no respective thickenings into opercular flaps or folds. Likewise, apertural muscles are represented by a single pair of muscles. There are no specific closing muscles in the apertural area like the operculum occlusors of cheilostomes. Most prominent within zooids is a spongiose tissue filling most of the body cavity. Although not properly understood, this tissue may aid in keeping animals moist and hydrated during prolonged dry times. In summary, all morphological characters support a ctenostome rather than a cheilostome affinity, possibly with Vesicularioidea or Victorelloidea. In addition, we provide new molecular data that clearly supports such a closer relationship.

Novel 3D in situ visualization of seal heartworm (Acanthocheilonema spirocauda) larvae in the seal louse (Echinophthirius horridus) by X-ray microCT.

The seal heartworm Acanthocheilonema spirocauda (Nematoda: Onchocercidae) parasitizes the heart and pulmonary arteries of various phocid seals of the Northern Hemisphere. Over many decades, potential vectors of this parasite have been discussed, and to this date, the life cycle is not fully known. The seal louse Echinophthirius horridus (Anoplura: Echinophthiriidae) is an obligatory, permanent and haematophagous ectoparasite of phocids that has been hypothesized to function as obligate intermediate host for A. spirocauda. We examined 11 adult E. horridus specimens collected from stranded harbour seals (Phoca vitulina) in rehabilitation at the Sealcentre Pieterburen by X-ray microCT imaging, aiming to illustrate larval A. spirocauda infection sites in situ. In three of these specimens, thread-like larvae were detected in insect organs. Detailed imaging of the most infected louse revealed a total of 54 A. spirocauda larvae located either in fat bodies or the haemocoel. Histological analysis of the same specimen illustrated nematode cross-sections, confirming X-ray microCT data. The current data strongly suggest that E. horridus is a natural intermediate host for A. spirocauda. Moreover, we demonstrate the potential of X-ray microCT-based imaging as a non-destructive method to analyze host-parasite interactions, especially in the neglected field of marine mammal parasitology.

Midbody-Localized Aquaporin Mediates Intercellular Lumen Expansion During Early Cleavage of an Invasive Freshwater Bivalve.

Intercellular lumen formation is a crucial aspect of animal development and physiology that involves a complex interplay between the molecular and physical properties of the constituent cells. Embryos of the invasive freshwater mussel Dreissena rostriformis are ideal models for studying this process due to the large intercellular cavities that readily form during blastomere cleavage. Using this system, we show that recruitment of the transmembrane water channel protein aquaporin exclusively to the midbody of intercellular cytokinetic bridges is critical for lumenogenesis. The positioning of aquaporin-positive midbodies thereby influences the direction of cleavage cavity expansion. Notably, disrupting cytokinetic bridge microtubules impairs not only lumenogenesis but also cellular osmoregulation. Our findings reveal a simple mechanism that provides tight spatial and temporal control over the formation of luminal structures and likely plays an important role in water homeostasis during early cleavage stages of a freshwater invertebrate species.

Morphology of ctenostome bryozoans: 5. Sundanella, with description of a new species from the Western Atlantic and the Multiporata concept.

Ctenostome bryozoans are a small group of gymnolaemates that comprise only a few hundred described species. Soft-tissue morphology remains the most important source for analysing morphological characters and inferring relationships within this clade. The current study focuses on the genus Sundanella, for which morphological data is scarce to almost absent. We studied two species of the genus, including one new to science, using histology and three-dimensional reconstruction techniques and confocal laser scanning microscopy. Sundanella generally has a thick, sometimes arborescent cuticle and multiporous interzooidal pore plates. The lophophore is bilateral with an oral rejection tract and generally has 30 or 31 tentacles in both species. The digestive tract shows a large cardia in S. floridensis sp. nov. and an extremely elongated intestine in Sundanella sibogae. Both terminate via a vestibular anus. Only parietodiaphragmatic muscles are present and four to six duplicature bands. Both species show a large broad frontal duplicature band further splitting into four individual bands. The collar is vestibular. Sundanella sibogae shows highly vacuolated cells at the diaphragm, whereas S. floridensis sp. nov. has unique glandular pouches at the diaphragmal area of the tentacle sheath. Such apertural glands have never been encountered in other ctenostomes. Both species of Sundanella are brooders that brood embryos either in the vestibular or cystid wall. Taken together, the current analysis shows numerous characteristics that refute an assignment of Sundanella to victorellid ctenostomes, which only show superficial resemblance, but differ substantially in most of their soft-body morphological traits. Instead, a close relationship with other multiporate ctenostomes is evident and the families Pherusellidae, Flustrellidrae and Sundanellidae should be summarized as clade 'Multiporata' in the future.

Comparing head muscles among Drusinae clades (Insecta: Trichoptera) reveals high congruence despite strong contrasts in head shape.

The subfamily Drusinae (Limnephilidae, Trichoptera) comprises a range of species exhibiting differently shaped head capsules in their larval stages. These correspond to evolutionary lineages pursuing different larval feeding ecologies, each of which uses a different hydraulic niche: scraping grazers and omnivorous shredders sharing rounded head capsules and filtering carnivores with indented and corrugated head capsules. In this study, we assess whether changes in head capsule morphology are reflected by changes in internal anatomy of Drusinae heads. To this end, internal and external head morphology was visualized using µCT methods and histological sections in three Drusinae species-Drusus franzi, D. discolor and D. bosnicus-representing the three evolutionary lineages. Our results indicate that Drusinae head musculature is highly conserved across the evolutionary lineages with only minute changes between taxa. Conversely, the tentorium is reduced in D. discolor, the species with the most aberrant head capsule investigated here. Integrating previous research on Drusinae head anatomy, we propose a fundamental Drusinae blueprint comprising 29 cephalic muscles and discuss significance of larval head capsule corrugation in Trichoptera.

The male reproductive system in whip spiders (Arachnida: Amblypygi).

Whip spiders (Arachnida, Amblypygi), like many other soil arthropods, transfer their spermatozoa indirectly via a stalked spermatophore. While the complex courtship behavior as well as the morphological differences of spermatophores and corresponding female genitalia between taxa have received great attention in the past, comparative research on the internal reproductive system is lacking so far. In this study, the morphology of the male whip spiders of four neoamblypygid taxa has been comparatively studied via computer tomography and subsequent 3D reconstruction. We investigated four species belonging to the Neoamblypygi, that is, the phrynichid species Damon medius (Damoninae), and Euphrynichus bacillifer (Phrynichidae), the phrynid species Phrynus hispaniolae (Phrynidae), and the charontid species Charon grayi (Charontidae). The male reproductive organs consist of paired testes and two pairs of accessory glands, the ventral and lateral glands, which project their ducts anteriorly into the ventrally located unpaired spermatophore producing organ where the respective seminal and secretory reservoirs are located. While this general organization of the male reproductive system is similar among all investigated taxa, there are some notable differences in some structures. The most surprising findings include the complete absence of ventral glands in D. medius, the presence of unique spherical ventral gland reservoirs in C. grayi as well as differences in the organization of the seminal and secretory reservoirs and their connections to the inner genital slit. In addition, the secretory products of both, ventral and lateral glands, are stored in combined secretory reservoirs in E. bacillifer and P. hispaniolae. This study is the first to show that there is some morphological variation in the male reproductive system in Neoamblypygi. These results are the basis for the reconstruction of the Bauplan for the reproductive organs of the whip spiders.

Cerotegument microstructure of whip spiders (Amblypygi: Euamblypygi Weygoldt, 1996) reveals characters for systematics from family to species level.

Like other arthropods, whip spiders of the arachnid order Amblypygi Thorell, 1883 protect themselves against external environmental influences. In this taxon, in addition to the epicuticle, the outermost layer of the exoskeleton, a cement layer (cerotegument) with superhydrophobic properties is deposited over certain body parts. Due to the high level of interspecific variation, the cerotegument structure and the morphology of its associated gland openings have been suggested to be informative for whip spider systematics. The first comparative study of the cerotegument is presented herein, based on a survey across 4 families, 16 genera, and 62 species of Euamblypygi Weygoldt, 1996, the suborder comprising all extant whip spiders except the rare monotypic family Paracharontidae Weygoldt, 1996. Results confirmed that the morphology of the colloidal particles and their assembly on cement globules differ considerably among taxa, but that the level of variation differs among lineages. Interspecific variation in cerotegument ultrastructure was highest among species of Neoamblypygi Weygoldt, 1996, making it an informative character in this clade. Evolutionary trends and intraspecific variation in the structure of the amblypygid cerotegument are briefly discussed.

Fine structure of the epicuticular secretion coat and associated glands of Pedipalpi and Palpigradi (Arachnida).

Pedipalpi Latreille, 1810 is a poorly studied clade of arachnids comprising the whip spiders (Amblypygi Thorell, 1883), short-tailed whip scorpions (Schizomida Petrunkevitch, 1945) and whip scorpions (Thelyphonida Cambridge, 1872). It has recently been shown that whip spiders coat their exoskeleton with a solid cement layer (cerotegument) that forms elaborate microstructures and turns the cuticle into a super-hydrophobic state. The amblypygid cerotegument provides taxonomic information due to its fine structural diversity, but its presence and variation in the sister groups was previously unknown. The present contribution reports the surface structure of the cuticle in species of Palpigradi, Thelyphonida, and Schizomida to determine if these taxa possess a solid epicuticular secretion coat. Scanning electron microscopy revealed that in addition to Amblypygi only species of Thelyphonida possess solid epicuticular secretion layers. Unlike in Amblypygi, in the Thelyphonida this layer does not usually form microstructures and is less rigidly attached to the underlying cuticle. A species of Typopeltis Pocock, 1894, which exhibited globular structures analogous to the amblypygid cerotegument, was an exception. Glandular structures associated with cement secretions in Amblypygi and Thelyphonida were considered homologous due to similar structure. Solid epicuticular secretion coats were absent from Schizomida, which is interpreted as a secondary loss despite the presence of slit-like glandular openings that appear to produce such epicuticular secretions. The micro-whip scorpion order Palpigradi Thorell, 1900 exhibited markedly different cuticular surface structures and lacked solid epicuticular secretions, consistent with the hypothesis that this order is not closely related to Pedipalpi. These results enhance the knowledge of the small, enigmatic orders of Arachnida.

Morphology of ctenostome bryozoans: 4. Pierrella plicata.

The genus Pierrella was originally created for a single fossil ctenostome bryozoan species from the Late Cretaceous, which is characterized by runner-like colonies, with zooids possessing a distinctive radial, folded aperture. Not long ago, a few specimens of a recent deep-sea congener, Pierrella plicata, were discovered and described from the Russian exploration area of the Clarion-Clipperton Fracture Zone, eastern Central Pacific Ocean. Owing to the lack of data on the internal morphology of this species, we investigated the soft-body morphology of P. plicata using serial sectioning and 3D-reconstruction in order to compare it to other more recently investigated ctenostome bryozoans and to infer the systematic position of the genus. The most striking peculiarity of the examined species is the radial aperture formed by multiple cuticular, pleated folds of the cystid wall. The cuticle is thickened into triangular-shaped folds in this area. An orifical sphincter underlies the folded aperture. Apertural muscles are present as a single pair of parieto-diaphragmatic muscles and four duplicature bands. The remaining polypide anatomy is mainly characterized by its miniature design: the lophophore has eight short tentacles and the digestive tract is one of the shortest and most compact ever observed in any bryozoan. A small intertentacular organ was detected at the lophophoral base. Taken together the genus Pierrella shows unique characters, such as the radial apertural folds that are closed by a series of orificial sphincter muscles, and its particularly small polypide. The general colony morphology resembles arachnidioidean ctenostomes whereas its internal morphology resembles alcyonidioidean species.

Digital dissection of the head of the frogs Calyptocephalella gayi and Leptodactylus pentadactylus with emphasis on the feeding apparatus.

Micro-computed tomography (microCT) of small animals has led to a more detailed and more accurate three-dimensional (3D) view on different anatomical structures in the last years. Here, we present the cranial anatomy of two frog species providing descriptions of bone structures and soft tissues of the feeding apparatus with comments to possible relations to habitat and feeding ecology. Calyptocephalella gayi, known for its aquatic lifestyle, is not restricted to aquatic feeding but also feeds terrestrially using lingual prehension. This called for a detailed investigation of the morphology of its feeding apparatus and a comparison to a fully terrestrial species that is known to feed by lingual prehension such as Leptodactylus pentadactylus. These two frog species are of similar size, feed on similar diet but within different main habitats. MicroCT scans of both species were conducted in order to reconstruct the complete anatomical condition of the whole feeding apparatus for the first time. Differences in this regard are evident in the tongue musculature, which in L. pentadactylus is more massively built and with a broader interdigitating area of the two main muscles, the protractor musculus genioglossus and the retractor musculus hyoglossus. In contrast, the hyoid retractor (m. sternohyoideus) is more massive in the aquatic species C. gayi. Moreover, due to the different skull morphology, the origins of two of the five musculi adductores vary between the species. This study brings new insights into the relation of the anatomy of the feeding apparatus to the preferred feeding method via 3D imaging techniques. Contrary to the terrestrially feeding L. pentadactylus, the skeletal and muscular adaptations of the aquatic species C. gayi provide a clear picture of necessities prescribed by the habitat. Nevertheless, by keeping a certain amount of flexibility of the design of its feeding apparatus, C. gayi is able to employ various methods of feeding.