Penis Sheath Research Articles

Three new tubificine species (Annelida: Clitellata: Naididae) from Japan

Three new species of Tubificinae (Oligochaeta: Naididae), Aulodrilus penicillatus sp. nov., Haber subnivalis sp. nov. and Varichaetadrilus salinus sp. nov. are described from Japanese inland waters. Aulodrilus penicillatus is unique in the genus in having tufts of fine bristles in the position of upper teeth on the chaetae. Haber subnivalis resembles the Baikalian H. vetus (Semernoy) in sharing long and hispid hairs and pectinate chaetae in dorsal bundles. However, H. subnivalis is different from H. vetus in retaining pectinate chaetae throughout the segments, and in the absence of a thick basal membrane around the penes. Varichaetadrilus salinus resembles V. psammophilus (Loden), V. fulleri Brinkhurst & Kathman and V. angustipenis (Brinkhurst & Cook) in having only bifid chaetae in dorsal bundles, but is distinguished from these congeners by having fewer number of chaetae in dorsal bundles, short upper teeth in the dorsal chaetae, and finger cot-shaped penial sheaths. In addition, V. salinus is unique among congeners in the absence of spermathecae.

New camaenid genus and species from Zhejiang, East China (Eupulmonata, Helicoidea).

We report a new land snail species representing a new genus from the mountainous area of Zhejiang, China. The snail has a depressed shell with granules all over the surface. The soft part of the new taxon is characterized by the presence of a mantle lobe whose form is reviewed herein across a wide range of helicoid snails, the presence of a developed epiphallic papilla, and the absence of a penial sheath, a dart sac apparatus and a flagellum. As indicated by a molecular-based phylogeny (16S + ITS2), the new taxon is deeply nested in the eastern Asian camaenid genera and shows a close relationship with the camaenids distributed in Central China.

Phylogenetic insights into the terrestrial snails Helicoidei (Gastropoda: Stylommatophora) with special emphasis on the Camaenidae

Abstract The superfamily Helicoidei are a widely distributed and diverse infraorder of land snails and slugs. Here, we constructed a phylogenetic tree based on sequences of the large subunit ribosomal RNA gene to investigate the relationships within the Helicoidei. Based on our phylogenetic tree, the family Camaenidae, as currently recognized, is not monophyletic, with the Polygyridae falling within the group. Likewise, the family Hygromiidae as currently defined is not monophyletic and incorporates the Geomitridae. The family Xanthoncyhidae form a monophyletic group that is sister to the Pleurodontidae. Likewise, the family Helicidae form a monophyletic group; it is sister to the branch incorporating Hygromiidae, Geomitridae, Pleurodontidae, Helicodontidae, and Xanthonychidae. The Solaropsidae are the sister group to a clade comprising other Sagdoidea. Our findings suggest that the Hygromiidae s.l. families should be restored to their previous name, Hygromiidae. A new genus of Bradybaeninae, Jiaoliaous Zhang gen. nov., is described here, with a simple genital system, single dart sac with multi-branched mucous glands, and a penis with a penial sheath.

Species catalogue of Drymaeus (Mesembrinus) Alberts, 1850 (Gastropoda: Bulimulidae) from Brazil and new data on morphology and distribution of Drymaeus (Mesembrinus) interpunctus (Martens, 1887).

Herein, we attempted to obtain detailed data on the distribution of the species of Drymaeus (Mesembrinus) in Brazil, using biodiversity databases, malacological collections and literature as sources of occurrence records. We provided a catalogue of species, along with distribution maps. We also estimated the suitable distribution of Drymaeus (Mesembrinus) interpunctus using the maximum entropy approach. A detailed description of the anatomy of the soft parts of this species was provided, with new data on the pallial system. For each species we provided information on the compiled data associated with museum collections and the literature. Distribution maps including geographic boundaries, Brazilian biomes and altitude were made with QGIS software 3.16.10 Hannover. For niche modelling, nineteen bioclimatic variables and a topographic variable were used as predictors. The models were performed with MaxEnt version 3.3.3k. Most of the species are represented by scarce material in malacological collections; for some species, these records correspond to type material, indicating that they have not been recollected. Most of the species were represented by shells making anatomical comparison and DNA analysis difficult, limiting our ability to provide new criteria for species delimitation. Our results allowed us to expand the known distribution area for three species, Drymaeus dutaillyi, D. gereti and D. oreades, with new occurrence records in Brazil. The MaxEnt model showed a thin area of high suitability to D. (M.) interpunctus in the Southeastern Brazil, corresponding to the Atlantic Forest. Minimum temperature of the coldest month and mean temperature of coldest quarter were the variables that most influenced the development of the model. Drymaeus interpunctus was described based on specimens collected in Brazil without mention to the exact localities. Herein the new records from databases allowed to expand the known geographic distribution for this species and to infer its potential distribution. Although the type locality of D. interpunctus is in Brazil, the anatomy of the soft parts of specimens from this country was not previously described. The anatomy of the reproductive system of the specimens analyzed herein mostly corresponds to a previous description for specimens from Paraguay, except for the absence of penial sheath and the relative length of the bursa copulatrix duct. The results of niche modeling showed a thin area of high suitability for D. interpunctus and a vast area of moderate suitability, indicating that this species present a niche breadth that favors its occurrence in a range of different biomes, including less suitable areas. The small number of records obtained for most of the species and their restricted ranges associated with habitat destruction may indicate that they are of conservation concern.

Integrative taxonomy and revision of the Neotropical Biomphalaria tenagophila (Mollusca: Planorbidae) complex taxa

ABSTRACT Morphological and molecular studies of the taxa of the Biomphalaria tenagophila complex were conducted on specimens from Argentina, Brazil, Paraguay, Peru, Uruguay and Venezuela. The morphological analysis included aspects of the shell, mantle, excretory organs and reproductive system. DNA barcode, ABGD and mPTP were used to group specimens into Operational Taxonomic Units (OTUs) and in attempt to solve species boundary delimitation problems within the Biomphalaria tenagophila complex. Population analyzes were also performed based on the cytochrome C oxidase I (COI) and 16S genes. The seminal vesicle, extension of the oviduct in relation to the distal ovispermioduct, vaginal pouch, aspect of the penial complex, aspect of the prepuce diaphragm, diaphragm papilla, extension of the penial sheath in relation to the prepuce and prepuce dimensions are essential for the determination of the taxa of the Biomphalaria tenagophila complex. An updated molecular phylogeny for Biomphalaria based on COI, 16S and ITS2 genes is presented and recover Biomphalaria tenagophila complex as monophyletic. The morphological, population and phylogenetic data observed in an integrated way define taxonomic questions, such as the proposition of a new status for B. guaibensis, which integrates into the Biomphalaria tenagophila complex. http://www.zoobank.org/urn:lsid:zoobank.org:pub:478145E5-D4A5-4128-AA80-DB6A69164E1E

A new species of slender flatworm in the genus Eucestoplana and a record of E. cf. cuneata (Platyhelminthes, Polycladida) from the Okinawa Islands, Japan, with an inference of their phylogenetic positions within Cestoplanidae

In this study, we describe a new species of elongated marine flatworm, Eucestoplana ittanmomensp. nov., collected from the intertidal zone of the Okinawa Islands, Japan. Eucestoplana ittanmomensp. nov. is distinguished from other congeners based on the following characteristics: i) its translucent body lacking coloration, ii) its dome-shaped penis sheath, iii) the absence of cilia on the inner wall of the male atrium except outside the penis sheath, and iv) the presence of an adhesive organ at the posterior end of the body. Additionally, we report the occurrence of E. cf. cuneata (Sopott-Ehlers & Schmidt, 1975) in Japan; E. cuneata has previously been documented in the Galapagos and Fiji Islands. We conducted phylogenetic analyses to infer the positions of the two Eucestoplana species within Cestoplanidae using a concatenated dataset comprising partial 18S and 28S rDNA sequences from E. cf. cuneata and E. ittanmomensp. nov. from Japan, as well as four known Cestoplana species with sequences available in public databases. Our phylogenetic analyses revealed that Cestoplana and Eucestoplana were reciprocally monophyletic. Furthermore, the genetic distance of the 16S rDNA sequences supported the genetic independence of the two sister species, E. cf. cuneata and E. ittanmomensp. nov.

Description of two new species of apple snail (Ampullariidae: Pomacea) from Peruvian Amazonia

Two new species of apple snails are described, Pomacea penai sp. nov. and Pomacea reevei sp. nov. that are used as food resources in Peruvian Amazonia. We used anatomical and conchological features to diagnose these two species. Pomacea penai sp. nov. is characterized by a highly variable shell morphology, spire that is prominent to immersed, apical penis sheath gland covering 1/3 penis sheath and elongated basal gland, prostate broad proximally, reduced stomach septum, green eggs, and commonly inhabits temporary flooded areas, creeks, and oxbow lakes. Pomacea reevei sp. nov. possesses a large shell, ranging from 81-137 mm, grey broad penis sheath, small apical penis sheath gland and the basal gland covering 1/3 penis sheath, tall stomach septum, white eggs, and found in deep lentic water bodies.

Muscle system of the penial complex in three species of Hygrophila (Gastropoda: Pulmonata)

The Hygrophila, a group comprising freshwater lung-bearing gastropods, have a complex copulatory apparatus, whose musculature has recently been shown to provide a number of phylogenetically informative characters that appear to concur with the results of molecular phylogenetic analyses. The number of hygrophilan species for which the male copulatory musculature is known, however, is still relatively small. We examined the muscle arrangement in the penial complex (penis and penis sheath) of three species of Hygrophila: Aplexa hypnorum (Linnaeus, 1758) (fam. Physidae), Kolhymorbis bogatovi Zatravkin et Moskvicheva, 1985 (fam. Planorbidae, tribe Segmentinini), and Planorbarius corneus (Linnaeus, 1758) (fam. Planorbidae, tribe Helisomatini) to explore whether the organization of the male copulatory musculature in these species is consistent with the previously proposed phylogenetic hypotheses. In A. hypnorum, the primarily glandular penis sheath has a three-layered musculature with outer and inner circular and intermediate longitudinal layers. The tubular penis also has a three-layered musculature, with the same sequence of muscle fibers as in the penis sheath. In K. bogatovi, the sequence of muscle layers in the penis sheath is essentially the same as in A. hypnorum. Penial musculature is also arranged in three layers, but the intermediate layer consists of small radial, rather than longitudinal fibers and the inner and outer layers are circular. In P. corneus, the boundaries between muscle layers in both penis and penis sheath are somewhat indistinct, but the circular muscles tend to lie close to their outer and inner walls, while the longitudinal fibers are concentrated in the interior. The comparison with other hygrophilan species, in which the copulatory musculature has been previously studied, shows that the male copulatory musculature of K. bogatovi is consistent in arrangement with that of other representatives of Segmentinini and that the phylogenetic lineage leading to P. corneus has probably diverged before the clade Planorbini + Segmentinini. The musculature of the penial complex of A. hypnorum is generally similar to that of another physid, Physella acuta (Draparnaud, 1805), but the penis sheath of P. acuta lacks an outer layer of circular muscle fibers, which may be explained by reduction.

Evaluation of female masculinization in Pomacea canaliculata (Caenogastropoda, Ampullariidae) induced by tributyltin, heavy metals, and uranium in culture water.

All female Pomacea canaliculata develop a small, male-like copulatory apparatus a few days after birth, which growths slowly until sexual maturity, and even further in older age. Previous studies have found trace elements like mercury (Hg), arsenic (As) and uranium (U) in tap water used for snail culture, and that these elements were accumulated in snail tissues. Here, we test whether the presence of these metals at maximum allowed concentrations (Environmental Protection Agency - EPA) in aquarium water could affect the development of the copulatory apparatus in mature females. Females of different ages were used as controls, grown in reconstituted metal-free water with or without the addition of Hg, As and U, as well as tributyltin (TBT), a compound used as masculinizing agent. Six and seven months old females cultured in tap water showed a longer penis and penile sheath, and a greater overall development of the copulatory apparatus, measured by an index (DI), as compared with same-age females cultured in reconstituted water. Moreover, when females were exposed to Hg, As or U at the maximum contaminant levels for human consumption allowed by EPA regulations, there was no further development of the copulatory apparatus, while there was a clearly positive effect in TBT-exposed females. This study confirms the masculinizing effect of organotin compounds on female copulatory apparatus and discusses the usefulness of the development of these organs as a bioindicator of environmental pollution.

Morphological and Genetic Variability in Radix auricularia (Mollusca: Gastropoda: Lymnaeidae) of Lake Baikal, Siberia: The Story of an Unfinished Invasion into the Ancient Deepest Lake

This article aims to reconstruct the invasion of the ear-shaped pond snail, Radix auricularia (Linnaeus, 1758), to Lake Baikal, East Siberia. This species is widely distributed in the Palaearctic and Northern America, and since the early 20th century has formed abundant and sustained populations in Lake Baikal. The data provided on the morphological and genetic variability of R. auricularia help to better describe and delineate the species. With an integrative approach involving morphological and molecular data, we improved the knowledge of the intraspecific variability of R. auricularia in the most important characteristics used for its determination. Molecular sequences of nuclear spacer fragment ITS-2 and mitochondrial gene fragment cyt–b were obtained from 32 individuals of Radix (including seven outgroup Radix species) collected from various parts of Lake Baikal and adjacent waterbodies and compared with sequences of 32 individuals of R. auricularia from different regions of the Palaearctic as well as with individuals determinated as R. intercisa from Lake Baikal, R. iturupica from the Kurile Islands, R. ussuriensis from the Khabarovsk region, R. narzykulovi from Tajikistan, and R. schubinae from the Amur region. Molecular genetic analyses revealed that all specimens collected from Lake Baikal belong to R. auricularia. There are no genetically distinct groups of snails that would correspond to two morphospecies previously recorded in Lake Baikal (e.g., R. auricularia s. str. and R. intercisa). Variability of the characteristics that are commonly used for species identification (shell morphology, mantle pigmentation, shape and position of the bursa copulatrix, length and position of the bursa duct, length ratio of preputium to penial sheath) were found in individuals analysed with molecular genetics to be broader than recognised in the current literature. Some shells of R. auricularia collected from Lake Baikal resemble shells of another lymnaeid species, R. balthica, and without molecular assessment can be confused with the latter. Geometric morphometric analysis of more than 250 shells revealed no observed hiatus between Baikalian and non-Baikalian R. auricularia. The probable stages and pathways of R. auricularia invasion to Lake Baikal’s ecosystem are outlined and discussed. Factors such as global climate warming and human activity stimulated and facilitated the ongoing dispersal of ear pond snails within Lake Baikal.

A new species of Haploptychius Möllendorff, 1906 (Stylommatophora: Streptaxidae) from the Western Ghats, India

ABSTRACT We here describe a new species of the streptaxid snail genus Haploptychius from the northern Western Ghats of Maharashtra, which is the third member of the genus from India. Haploptychius sahyadriensis n. sp. is distinguished from the other Indian and South-East Asian Haploptychius sp. in having suboblique-heliciform shell, low spire and presence of one strong parietal lamella. The new species has unique genital anatomy in having a long penis with a penial sheath, the presence of penial appendix, penial hooks, atrium and vagina with longitudinal ridges and irregular transverse ridges respectively, but without any hooks. It bears a shiny muscle near the junction of the vagina, gametolytic duct and the free oviduct. Based on the shell morphology and genital characters, the new species is placed in the genus Haploptychius. Our study reveals that other unexplored areas in the northern Western Ghats may potentially harbour more undescribed land snail species which could be endemic.

Tasserkidriluscf.americanus (Clitellata, Naididae) - A new record from Slovakia confirms the dissimilarity between the European and North American populations.

The main objective of this study is to present a new record of Tasserkidriluscf.americanus found in a channel near the Tešmak swamp in Slovakia (Central Europe) and to compare its morphological features and habitat requirements with those of populations occurring in North America and Europe. The new specimens are similar to those found in The Netherlands and Belgium, but dissimilar to previously reported North American material of T.americanus, reopening the question of whether the European form is a separate species. The European form has the penis sheaths approximately twice as long as and wider than the North American form and may inhabit slow-flowing or standing waters of a eutrophic character, which is in conflict with the current knowledge on the morphology and ecology of North American populations. Further investigation is necessary to solve the questions about the origin and taxonomic relationship of the European population to other populations.

Systematic revision of the limestone karst-restricted land snail genus Aenigmatoconcha (Eupulmonata: Helicarionidae), with description of a new species

Thai limestone karsts are known to contain a rich biodiversity of animals, especially terrestrial snails, but still require further intensive exploration to evaluate their biodiversity. To date, only a few studies on the limestone karst-inhabiting land snail genera have been published. The present work focuses on the species diversity and phylogenetic relationships of the limestone karst-restricted land snail genus Aenigmatoconcha from Thailand, based on comparative morphology and molecular evidence. The results yielded three known species (A. clivicola Tumpeesuwan & Tumpeesuwan, 2017, A. sumonthai Tumpeesuwan & Tumpeesuwan, 2018, and A. mitis (Pfeiffer, 1863) comb. nov.), plus a new species (A. eunetis Pholyotha & Panha sp. nov). The phylogenetic analyses of partial fragments of the mitochondrial cytochrome oxidase c subunit I (COI) gene confirmed the monophyly of all recognized species and congruence with the traditional morphology-based species designations. Average uncorrected p-distances of COI sequences between species were 9.7–12.0% and within species were 0.2–4.2%. This study also provides the re-description of penial sculpture, penial sheath, flagellum, penial caecum, and mantle lobe morphology that were neglected from the type species description. The present discovery of a new species increases the known diversity of Thai land snails and will support the conservation planning to protect karst biodiversity.

THE FIRST RECORD OF ALIEN SPECIES <i>LIMNODRILUS MAUMEENSIS </i>BRINKHURST ET COOK, 1966 (OLIGOCHAETA, TUBIFICIDAE) FROM RUSSIA

Nearctic species Limnodrilus maumeensis Brinkhurst et Cook, 1966 (Oligochaeta, Tubificidae) recorded from Russia for the first time from the Don River near Rostov-on-Don. Variations of penis sheath of sexually mature specimens are measured and illustrated by photographs. Data on macrozoobenthos community in the sampling site are provided, including species composition, number and biomass of the species.

Morphological and Molecular Identification of Limnodrilus Claparede,1862 Species(clitellata: naiDIDAE) IN Tigris River, Baghdad/Iraq

Sludge worm samples were collected from the Tigers River sediment during the period from November 2018 to June 2019 in Al Sarafiya District/ Baghdad- Iraq. Biometric morphological measurements focusing on the form of penis sheath and chaetal morphology were used for species identification, in addition to molecular analysis by amplification of conserved 18s rRNA encoding gene using ITS1 and ITS4 universal primers.According to the morphological measurement records, the results revealed the existence of Limnodrilus hoffmeisteri Claparede 1862, L. claparedeianus Ratzel, 1868 and L. cervix Brinkhurst 1963. Other two groups of specimens, with short penis sheath, were identified by molecular technology as L. hoffmeisteri complex, and L. claparedeianus.-cervix. Both species were considered as new record for Iraqi fauna, and had been registered in NCBI under the accession number LC497073 and LC497074 respectively According to the morphological measurements records, the results revealed the existence of Limnodrilus hoffmeisteri Claparede 1862, L. claparedeianus Ratzel, 1868 and L. cervix Brinkhurst 1963, which identified by molecular analysis using 18S rRNA gene and DNA sequencing recorded L. hoffmeisteri complex, This species is a new record in Iraq, and has been registered in NCBI under the accession number LC497073. There was also specimen identified by molecular analysis using 18S rRNA gene and DNA sequencing recorded L. Claparedeianus –cervix. Also, this species is a new record in Iraq, and has been registered in NCBI under the accession number LC497074. ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ Keyword: Limnodrilus hoffmeisteri complex, Iraq, LC497073, NCBI, Limnodrilus hoffmeisteri, L. Claparedeianus, L. cervix, L. Claparedeianus –cervix, LC 497073. *Part of M.Sc. Thesis of Research Sludge worms samples were collected from the Tigers River sediment in Al Sarafiya district, / Baghdad- Iraq. Biometric morphological measurement focusing on the form of penis sheath and chaetal morphology, in addition to molecular analysis using 18s rRNA gene, were used for species identification. According to the morphological measurements records, the results revealed the existence of two groups of Limnodrilus hoffmeisteri Claparède 1862 Individuals have long penis sheath with distal end with symmetrical or asymmetrical hood, while other individuals with short penis sheath with circular plate- like hood, which identified by molecular analysis as L. hoffmeisteri complex, and the isolate 18S rRNA recorded with the accession number LC497073 Two groups of very long penis sheath identified as L. claparedeianus Ratzel, 1868, and L. cervix Brinkhurst 1963, with dorsal and ventral projections. There are also a group of specimens with short penis sheath, which identified by molecular techniques as L. Claparedeianus –cervix 18S rRNA encoding genomic sequence was resented to the NCBI, recorded with the accession number LC497074. Limnodrilus hoffmeisteri complex and L. claparedeianus – cervix were considered as new records for Iraq.

Nagyelma n. gen. for Ennea aliena Bavay and Dautzenberg, 1912 (Gastropoda: Eupulmonata: Streptaxidae)

Nagyelma n. gen. is erected for the northern Vietnamese Ennea aliena Bavay and Dautzenberg, 1912. The most closely related genus is probably Elma H. Adams, 1866, which also has a high-spired shell but differs from the new genus in the absence of a parietal tooth, the pointed-ovoid shell shape, and the penial sheath, which covers only half of the penis.

<p class="HeadingRunIn"><strong>New species and new records of Japanese Lumbriculidae (Annelida, Clitellata)</strong></p>

Most Japanese records and descriptions of the family Lumbriculidae are from the work of H. Yamaguchi, who described 6 endemic species and one genus, in addition to reporting the cosmopolitan Lumbriculus variegatus (Müller, 1774). Yamaguchi's work focused largely on the northern island of Hokkaido; since then, only one new Japanese lumbriculid genus and species has been described, also from Hokkaido. Recent collections from Honshu Island include several species not recorded in earlier literature, and here we report 4 new species of Lumbriculidae, plus a range extension of the Korean Lamprortus orientalis Rodriguez, 1994. Of the new species, only Styloscolex (Styloscolex) tazawaensis can be confidently assigned to an accepted genus using current morphological diagnoses. Styloscolex (Neoscolex) tatsukoae n. sp. is provisionally assigned to that Asian genus and subgenus based on the prosoporous male duct, spermathecae in the preatrial segment, and penial sheath—despite differing from congeners in having a single, median atrium in X, and single spermatheca in IX. Two additional species are here attributed to a new genus, Honshudrilus, which is distinguished by a combination of characters: spermathecae 2 or more segments anterior to the male pores, non-functional anterior male ducts (with loss of anterior testes), elongate-petiolate atria, penes formed by extruding the atrial duct lining, and spermathecal ducts with vestibules.

Finding of Systrophia (S.) argentina n. comb. in the Argentine Precordillera a century and a half after its description (Mollusca: Gastropoda: Scolodontoidea)

Systrophia (Systrophia) argentina (Strobel, 1874) n. comb. is here re-described 150 years after its discovery. The specimens were found in the Argentine Precordillera (Quebrada San Isidro, Mendoza province, Argentina), at 2.000 m, near the typical locality of the species, here restricted to the Angostura or garganta (gullet) of Villa Vicencio and Casa de Piedra. This snail has a shell of medium size, planispiral, with six whorls; radula with central plate tricuspid, and latero-marginal teeth aculeate, formula: 13 – C – 13; genital tracts very long; vagina short, spermathecal duct reaching the distal extreme of the vagina, near the atrium; penial sheath long, with some circumvolutions, penis occupying most of the penial sheath, deferent duct penetrating laterally at the base of the penis, epiphallus with a retractor muscle adhered to its extreme, large and quadrangular gland attached to the penial sheath; atrium very short. S. (S.) argentina is the only species of the genus Systrophia L. Pfeiffer, 1855 so far found in Argentina.

Jawless land snail Sinorachis, a new bradybaenine genus from China (Eupulmonata, Camaenidae).

A new land snail species that represents a new genus is reported from Hubei, China. The snail has a conical shell with pits and/or granules on embryonic whorls and a smooth teleoconch with straight peristome. The head of the animal has a developed wart. The mantle lobe is only developed on the left side. At the front of the buccal mass there is no chitinous jaw that is without exception seen in Chinese camaenids. Its radular teeth are usually slender and tongue-shaped, not typical in bradybaenine snails. The genital system is typical of Bradybaeninae and is characterized by the absence of a membranous sac surrounding the terminal genitalia, penial caecum or flagellum; a well-developed penis sheath; a symmetrical dart sac apparatus; and one distally branched mucous gland. The new species Sinorachis baihu Wu & Chen, gen. and sp. nov., is assigned to the type species of the new genus, in which all the known Chinese Rachis species are included. Thereby, the new genus is composed of three species, namely Sinorachis onychinus (Heude), comb. nov., Sinorachis aureus (Heude), comb. nov. and the new species.

Nerves innervating copulatory organs show common FMRFamide, FVRIamide, MIP and serotonin immunoreactivity patterns across Dinophilidae (Annelida) indicating their conserved role in copulatory behaviour

BackgroundMales of the microscopic annelid family Dinophilidae use their prominent glandomuscular copulatory organ (penis) to enzymatically dissolve the female’s epidermis and thereafter inject sperm. In order to test for putative conserved copulatory structures and neural orchestration across three dinophilid species, we reconstructed the reproductive myo- and neuroanatomy and mapped immunoreactivity patterns against two specific neurotransmitter markers with reported roles in invertebrate male mating behaviour (FVRIamide, MIP) and three general neural markers (acetylated α-tubulin, serotonin, FMRFamide).ResultsSeminal vesicles (one or two pairs), surrounded by a thin layer of longitudinal and circular muscles and innervated by neurites, are found between testes and copulatory organ in the larger males of Dinophilus vorticoides and Trilobodrilus axi, but are missing in the only 0.05 mm long D. gyrociliatus dwarf males. The midventral copulatory organ is in all species composed of an outer muscular penis sheath and an inner penis cone. Neurites encircle the organ equatorially, either as a ring-shaped circumpenial fibre mass or as dorsal and ventral commissures, which are connected to the ventrolateral nerve cords. All three examined dinophilids show similar immunoreactivity patterns against serotonin, FMRFamide, and FVRIamide in the neurons surrounding the penis, supporting the hypotheses about the general involvement of these neurotransmitters in copulatory behaviour in dinophilids. Immunoreactivity against MIP is restricted to the circumpenial fibre mass in D. gyrociliatus and commissures around the penis in T. axi (but not found in D. vorticoides), indicating its role in controlling the copulatory organ.ConclusionsThe overall myo- and neuroanatomy of the reproductive organs is rather similar in the three studied species, suggesting a common ancestry of the unpaired glandomuscular copulatory organ and its innervation in Dinophilidae. This is furthermore supported by the similar immunoreactivity patterns against the tested neurotransmitters around the penis. Smaller differences in the immunoreactivity patterns around the seminal vesicles and spermioducts might account for additional, individual traits. We thus show morphological support for the putatively conserved role of FMRFamide, FVRIamide, MIP and serotonin in dinophilid copulatory behaviour.