Ventrolateral Position Research Articles

Meristoderes zmaj sp. n., a new species of Kinorhyncha (Cyclorhagida: Echinoderidae) from the Adriatic Sea

Abstract A new species of the cyclorhagid genus Meristoderes is described. Meristoderes zmaj sp. n. is distinguished from its congeners by its unique arrangement of spines and tubes. It possesses acicular spines on segments 4, 6 and 8 in middorsal position and on segments 6–9 in lateroventral position; and tubes on segment 2 in subdorsal, midlateral and ventrolateral position, on segment 5 in lateroventral position and on segment 10 in laterodorsal position. With the formal description of M. zmaj sp. n., the number of species within the genus is increased to 10. In addition, the appearance of a new species and its accompanying fauna within the North-Eastern Adriatic Sea fauna, extensively studied by Kinorhyncha taxonomists, is discussed.

A new coccid family, Adocimycolidae fam. nov. (Hemiptera: Coccomorpha), with extended hamulohalteres in Burmese (Myanmar) amber

The present paper describes a male coccid (Hemiptera: Coccoidea) in mid-Cretaceous Burmese amber with the largest known hamulohalteres on any extant or extinct coccid. Aside from this character, the specimen has an unusual assortment of features, including a prolonged head with three cylindrical dorsal simple eyes in three rows joining laterally, a single ocellus dorsally placed at apex of a prolonged head, compound eyes in a ventro-lateral position and a 10-segmented antennae longer than body length. These features prohibit it from being assigned to any known extant or extinct family. Whether the large hamulohalteres on Adocimycolus aarondavisii gen. et sp. nov. are evidence of a plesiomorphic state of a lineage of Mesozoic Coccoidea that had fully developed metathoracic wings or could be a genetic mutation, is addressed.

Mixtophyes toothlessi sp. n., a new Kinorhyncha species (Anomoirhaga: Neocentrophyidae) from the Clarion-Clipperton Zone, with a revision of terminology and taxonomic features of the family.

A new species of Mixtophyes Sánchez et al. 2014 is described from the Clarion-Clipperton Fracture Zone (north-eastern Pacific Ocean). The new species is characterised by the presence of spinose processes on segments 1-11 in middorsal position and on segments 1-10 in midlateral position, paired paradorsal setae on segments 2, 4-6 and 8-9, and unpaired ones on segments 3 and 7, paired setae in paralateral and ventrolateral positions on segments 2-9. In addition, some morphological characteristics of the family Neocentrophyidae and the genus Mixtophyes are discussed, and the diagnoses of both taxa are updated. Lastly, the taxonomic nomenclature of Neocentrophyidae and the sexual characters of the genus are accordingly emended.

Dracophyes cepedai gen. et sp. nov., a new Dracoderidae genus and species (Kinorhyncha: Allomalorhagida) from the Peru Basin

A new Dracoderidae genus, Dracophyes gen. nov., and a new species Dracophyes cepedai sp. nov. from the Peru Basin are described. The new genus is characterized by the presence of acicular spines showing conspicuous intracuticular structures on segments 1–9 (either anchor for the dorsal or groove-like for the lateral series), alternating laterally displaced dorsal spines, becoming more lateral towards the posterior segments, males with two pairs of minute, poorly sclerotized penile spines, and its conspicuous obovate trunk shape. The new genus accommodates three species: Dracophyes toyoshioae comb. nov., Dracophyes chaac comb. nov. and D. cepedai sp. nov. The latter was collected in abyssal depths in the Peru Basin (East Pacific Ocean) and is recognised by having dorsal acicular spines on segments 1 to 9, alternating laterally displaced from the middorsal line, ventral acicular spines in ventrolateral position on segment 1, lateroventral position on segments 2–4 and 6–9, and in lateral accessory position on segment 5, tubes in lateroventral position on segment 5 and in lateral accessory position on segments 2 and 8, type 2 glandular cell outlets in lateroventral position on segment 10 and extremely long lateral terminal spines. Moreover, with the erection of the new genus, emended diagnoses for the family Dracoderidae and the former single genus within the family, Dracoderes, are proposed.

Echinoderes beringiensis sp. nov. - The first Kinorhyncha from deep-sea methane seepages in the north Pacific

A new species of echinoderid kinorhynch, Echinoderes beringiensis sp. nov., collected from bacterial mats at the deep-sea cold methane seepages area on the Chukchi slope (Bering Sea, NW Pacific), is described using light and scanning electron microscopy. This new representative of the most diverse kinorhynch genus is characterized by its unique arrangement of spines, tubes and glandular cell outlets and cuticular plates composition on trunk segment 11, thus being distinguished from other congeners. Modified glandular cell outlets type 2 are present in subdorsal, laterodorsal, sublateral and ventrolateral positions on trunk segment 2; in midlateral position on trunk segment 5; in sublateral position on trunk segment 8 in males, and in midlateral and sublateral position in female. Acicular spines are present in middorsal position on trunk segments 4–8, and in lateroventral position on trunk segments 6–9. Tubes are present in lateral accessory position on trunk segment 5. Trunk segment 11 has two tergal and two sternal cuticular plates. Echinoderes beringiensis sp. nov. constitutes the first kinorhynch species described from extreme, deep-sea environments of cold methane seepages in the Pacific Ocean, and the second representative of the Kinorhyncha known from the Bering Sea.

A new species of Echinoderes (Kinorhyncha: Cyclorhagida: Echinoderidae) from the Argentinean continental shelf with notes on its postembryonic development and on subcuticular morphological characters unreported for Kinorhyncha

Echinoderes goku sp. nov. is described from adult and juvenile specimens in samples collected from the Argentinean continental shelf in March 2019 during the campaign of the Motorsailer Bernardo Houssay, based on light and scanning electron microscopy studies. Echinoderes goku sp. nov. is differentiated from other species by its unique spine and tube pattern: (1) middorsal spine on segments 4, 6, and 8, (2) spine in lateroventral position on segments 69, (3) tube present in subdorsal position on segment 2, sublateral to midlateral position on segments 7 and 9, lateral accessory position on segment 8, lateroventral position on segment 5 and ventrolateral position on segment 2. Additionally, this species (4) lacks type-2 gland cell outlets and female-specific papillae or subcuticular funnel-like structures. (5) The male possesses a sublateral tube on segment 10 with a basal cylindrical reinforcement structure and three penile spines on segment 11, whereas the female lacks penile spines but reveals a lateral terminal accessory spine on segment 11 and on segment 10 lacks a subdorsal tube but possesses instead a sublateral fringe on the surface connected with a subcuticular conical structure and a basal cylindrical reinforcement structure. Among several juvenile specimens, one was captured in the process of moulting from the last juvenile stage to the female. Whereas the last juvenile stage revealed a sublateral tube on segment 10, the moulting female lacked this tube and showed a conical subcuticular structure with a basal cylindrical reinforcement structure instead. A cylindrical reinforcement structure at the base of a tube and a subcuticular conical structure have not been reported before for Kinorhyncha, and 14 selected species of Echinoderidae available for study were screened for these characters in order to get a first idea of their possible taxonomic importance. This article reports about the second species of Echinoderes from Argentinean waters.

Echinoderes xiphophorus sp. nov. – the first deep-water representative of Echinoderidae in the Sea of Japan (Kinorhyncha: Cyclorhagida)

A new species of echinoderid kinorhynchs, Echinoderes xiphophorus sp. nov. collected from oxidized brown silt at the deepest depression in the Sea of Japan, North-West Pacific, is described and illustrated using light and electron microscopy. This new representative of the most speciose kinorhynch genus is characterized by the unique set of spines and tubes and can easily be distinguished from most of its congeners. The second trunk segment bears three pairs of tubes in subdorsal, midlateral and ventrolateral position in both sexes; one pair of tubes on trunk segment 5 in lateroventral position and on trunk segment 8 in sublateral position; aciculate lateroventral spines on trunk segments 6–9; aciculate middorsal spines on trunk segments 4, 6, 8. This species is well recognized by very long tergal extensions of the posteriormost segment, some of the longest within the family Echinoderidae. Males of Echinoderes xiphophorus sp. nov. are well distinguished from all the congeners by extremely long sword-like appendages dorsally to three pairs of penile spines. The species constitutes the first deep-sea representative of the Echinoderidae in the Sea of Japan and the deepest representative of the Kinorhyncha in this sea.

Our experience with the management of penile fracture: a single institutional prospective observational study in eighteen patients over a two-year period

Background: Penile fracture is a not an unusual encounter in urological emergency. The condition results from disruption of the tunica albuginea which envelops the corpora cavernosa as a result of any condition which leads to the sudden rise of intra-cavernosal pressure. The study was designed to analyse the clinical spectrum and complication of penile fracture.Methods: This is a prospective observational study undertaken from April, 2019 to March, 2021on 18 patients. The demographic profile of all the patients, aetiology of penile fracture, management strategies and pre-operative sexual functions were documented. Erectile function was evaluated using international index of erectile function (IIEF).Results: Seventeen out of 18 patients (94.44%) gave a history of injury during sexual intercourse. Out of the seventeen patients with history of injury following sexual intercourse, only 9 (52.94%) were married. 15 (93.75%) had disruption of the tunica albuginea in the ventrolateral position with 10 patients (66.66%) on the right side. Patients were followed up in the OPD after 2 weeks and then at 6 month and 1-year intervals. At 12 months postop, none of the patients complained of sexual inactivity. Average time to return to sexual activity was 3.2 months. Two patients complained of penile curvature >20 degree. Six patients complained of penile nodule at the site of repair.Conclusions: Penile fracture is a urological emergency which is primarily diagnosed clinically. Prompt diagnosis and surgical exploration gives good outcome in terms of preservation of sexual function.

A new species of driftwood catfish emCentromochlus/em Kner, 1858 (Siluriformes, Auchenipteridae, Centromochlinae) from Tocantins-Araguaia River drainage.

The genus Centromochlus includes eight catfish species in the Amazon and Orinoco river systems: C. schultzi from Xingu and Tocantins-Araguaia rivers; C. melanoleucus from Tapajós and Teles Pires rivers; C. macracanthus from Negro River; C. orca from Nhamundá River; C. heckelii and C. existimatus from Amazon and additionally at the Essequibo rivers; C. carolae and C. musaica from Orinoco River system. Recent field expeditions and collection examination revealed an undescribed species of Centromochlinae that has compatible features with Centromochlus. We herein describe a new species of Centromochlus from the Tocantins-Araguaia River drainage, diagnosed among most Centromochlinae by having a vermiculated color pattern on the dorsum and included in Centromochlus by sharing the derived features: ventrolateral position of eye socket; sphenotic notched for the exit of infraorbital canal; and posterior serrations along pectoral-fin spine numerous. The new species is diagnosed from congeners by having the pectoral-fin spine with dark bars, alternating with light bars (vs. pectoral-fin spine with light and uniform color in all Centromochlus); and it is further distinguished from its congeners (except C. carolae) by the ventral surface of head moderate to largely pigmented (vs. ventral surface of head unpigmented in C. heckelii, C. existimatus, C. orca, C. musaicus, C. schultzi, with few scattered dark chromatophores in C. macracanthus and C. melanoleucus; see diagnosis). A discussion about the systematics of the genus, plus the conservation status of the new species, and an identification key to species of Centromochlus, are also provided.

Chiloscyphus parapilistipulus (Lophocoleaceae), a new species of liverwort from New Caledonia, with the typification of Lophocolea pilistipula

Thouvenot, L. & M.J. Price (2020). Chiloscyphus parapilistipulus (Lophocoleaceae), a new species of liverwort from New Caledonia, with the typification of Lophocolea pilistipula. Candollea 75: 285–289. In English, English abstract.During a review of Lophocoleaceae types housed in G in the context of research on the liverworts of New Caledonia, a set of three specimens collected by Louise Le Rat in 1909 that were filed as types of Lophocolea pilistipula Steph. (≡ Chiloscyphus pilistipulus (Steph.) J.J. Engel & R.M. Schust.) turned out to be heterogeneous: the one originating from Île des Pins is fertile and corresponds to the protologue as well as Stephani's illustration of this taxon. This original material is designated here as lectotype of Lophocolea pilistipula. The two other specimens in G collected on Mount Dogny are sterile and exhibit some morphological differences from the designated lectotype material, namely the plants are large, with wider stems that have larger and broader leaves with smooth rather than crenulate margins, and that lack trigones. A new fertile collection from Mount Dogny was identified as belonging to Chiloscyphus Corda and is conspecific with the material collected from Mount Dogny over a century earlier. A new species, Chiloscyphus parapilistipulus Thouvenot, is described. It closely resembles Lophocolea pilistipula but differs from it by its larger size, smooth leaf margins, the dioicous sexuality and the ventro-lateral position of the gynoecia at the apex of short leafless branches.Received: June 15, 2020; Accepted: August 31, 2020; First published online: October 29, 2020

Effects of injectable dexmedetomidine-ketamine-midazolam and isoflurane inhalation anesthetic protocols on ocular variables in captive black-tailed prairie dogs (Cynomys ludovicianus).

To evaluate the effects of injectable dexmedetomidine-ketamine-midazolam (DKM) and isoflurane inhalation (ISO) anesthetic protocols on selected ocular variables in captive black-tailed prairie dogs (Cynomys ludovicianus; BTPDs). 9 zoo-kept BTPDs. The BTPDs received dexmedetomidine hydrochloride (0.25 mg/kg, IM), ketamine hydrochloride (40 mg/kg, IM), and midazolam hydrochloride (1.5 mg/kg, IM) or inhalation of isoflurane and oxygen in a randomized complete crossover design (2-day interval between anesthetic episodes). Pupil size, globe position, tear production, and intraocular pressure measurements were recorded at 5, 30, and 45 minutes after induction of anesthesia. For each BTPD, a phenol red thread test was performed in one randomly selected eye and a modified Schirmer tear test I was performed in the other eye. Intraocular pressure was measured by rebound tonometry. Compared with findings for the DKM protocol, pupil size was smaller at all time points when the BTPDs underwent the ISO protocol. Globe position remained central during anesthesia with the DKM protocol, whereas it varied among central, ventromedial, and ventrolateral positions during anesthesia with the ISO protocol. Tear production and intraocular pressure decreased significantly over time when the BTPDs underwent either protocol. Results indicated that ophthalmic examination findings for anesthetized BTPDs can be influenced by the anesthetic protocol used. The DKM protocol may result in more consistent pupil size and globe position, compared with that achieved by use of the ISO protocol. Tear production and intraocular pressure measurements should be conducted promptly after induction of anesthesia to avoid the effect of anesthetic episode duration on these variables.

Investigation of echinoderid kinorhynchs described 90 years ago: redescription of Echinoderes capitatus (Zelinka, 1928) and Echinoderes ferrugineus Zelinka, 1928

The two kinorhynch species Echinoderes capitatus (Zelinka, 1928) and Echinoderes ferrugineus Zelinka, 1928 are redescribed herein, based on specimens collected at different Mediterranean locations. Echinoderes capitatus is characterized by the presence of middorsal acicular spine on segment 4 and lateroventral acicular spines on segments 6–9; at least three pairs of tubes on segment 2 (subdorsal, midlateral, and ventrolateral); subdorsal tubes on segment 8; laterodorsal tubes on segment 10; lateral accessory tubes on segments 5 and 8; subdorsal sensory spots on segments 1 and 3–11; and ventromedial sensory spots on segments 2 and 5–7, often additionally on segment 8; occurrence of subdorsal tubes on segments 6 and 7, laterodorsal tubes on segment 2, midlateral tubes on segments 7 and 8, and ventromedial tubes on segment 8 showing intraspecific variation; and the absence of the type-2 gland cell outlets. The pattern of the additional tubes is relatively well-preserved within a population but differs among populations. Echinoderes ferrugineus is characterized by the presence of middorsal acicular spines on segment 4–8; lateroventral acicular spines on segments 6–9; lateral accessory tubes on segment 5; type-2 gland cell outlets in subdorsal, laterodorsal, sublateral, and ventrolateral position on segment 2, subdorsal and midlateral position on segment 4, midlateral position on segment 5, and midlateral position on segment 8; long lateral terminal spines (ca. 140–180 μm, 45–63% of trunk length). Comments are provided on the intraspecific variation in tube pattern in E. capitatus, and its potential importance in a speciation and evolutionary context.

Four new species of Kinorhyncha from the Gulf of California, eastern Pacific Ocean

Several meiofaunal samples from the central and lower Gulf of California were studied. Four new species of kinorhynchs, Cristaphyes fortis sp. nov., Higginsium mazatlanensis sp. nov., Cephalorhyncha teresae sp. nov. and Echinoderes xalkutaat sp. nov., are described herein. C. fortis sp. nov. may be distinguished from its most similar congeners by its more strongly developed pachycycli and ball-and-socket joints and the presence of unpaired paradorsal setae on segments 2, 4 and 6, two pairs of ventrolateral setae on segment 5, one pair of ventrolateral setae on segments 2–4, 6–7 and 10, and one pair of ventromedial setae on segments 8–9. H. mazatlanensis sp. nov. is easily distinguished from its congeners by the combined presence of subdorsal setae only on segment 1 and lateroventral setae only on even segments. C. teresae sp. nov. is unique within the genus by the presence of acicular spines in middorsal position on segments 4, 6 and 8, in sublateral position on segment 7 and in lateroventral position on segments 8 and 9, as well as tubes in subdorsal position on segment 2, and in lateroventral position on segment 5. Moreover, this species has primary pectinate fringes of segments 2–7 bearing a tuft of elongated spinous projections in middorsal position, which is unique among its congeners. E. xalkutaat sp. nov. belongs to a group of Echinoderes characterized by possessing type 2 glandular cell outlets in subdorsal, laterodorsal, sublateral and ventrolateral positions on segment 2, together with middorsal spines on segments 4–8, lateroventral spines on segments 6–9 and lateroventral tubes on segment 5, but the arrangement of the remaining type 2 glandular cell outlets (in midlateral position on segment 5, in sublateral position on segment 8 and in laterodorsal position on segment 10) and the cuticular composition of segment 11 (one tergal and two sternal plates) allow its morphological differentiation.

First report of the family Zelinkaderidae (Kinorhyncha: Cyclorhagida) for the Caribbean Sea, with the description of a new species of Triodontoderes Sørensen & Rho, 2009 and an identification key for the family

A new species of Kinorhyncha, Triodontoderes lagahoo sp. nov., is described from Tobago Island, Caribbean Sea (western Atlantic Ocean) from a coastal, sandy habitat using both light and scanning electron microscopy. The species is characterized by the presence of middorsal acicular spines on segments 1–11 (that on segment 10 crenulated in males), laterodorsal crenulated spines on segment 10 only in males, lateroventral acicular spines on segments 3–4 and 6–8 (lateroventral spines also on segment 10 in females), lateroventral cuspidate spines on segments 5 and 9, lateral accessory acicular spines on segments 5 and 9, lateral accessory cuspidate spines on segment 8, ventrolateral acicular spines on segment 2 and ventrolateral cuspidate spines on segment 2. Females furthermore possess short papillae in ventrolateral position on segment 8 and ventromedial position on segment 9. The absence of cuspidate spines in lateral accessory position on segment 6 easily distinguishes T. lagahoo sp. nov. from the single known congener, Triodontoderes anulap. Moreover, also the arrangement of female papillae and sensory spots differ between the species. The finding of a new species of Triodontoderes in the Caribbean Sea is the first report of the genus for American waters and the Atlantic Ocean since its original description. Additionally, a dichotomous key for identification of the family Zelinkaderidae to species level, as well as systematic remarks on some morphological characters of the new species are included herein.

Redescription of Echinoderes levanderi Karling, 1954 (Kinorhyncha: Cyclorhagida) – a kinorhynch tolerant to very low salinities

The kinorhynch species Echinoderes levanderi Karling, 1954 is redescribed. The species can now be recognized by the presence of spines in middorsal positions on segments 4–8, and in lateroventral positions on segments 6–9, with lateroventral spines on segment 9 showing sexual dimorphism; tubes in subdorsal and ventrolateral positions on segment 2, in sublateral positions on segments 4 and 8, in lateroventral positions on segment 5, and in laterodorsal positions on segment 10. Furthermore, the enlarged sieve plates on segment 9 make the species highly characteristic. New records of the species extend its distributional range into the Bothnian Bay where the bottom water salinity drops below 5 ppt, which is the lowest salinity recorded for a habitat with kinorhynchs.

Diversity and distribution of Arctic Echinoderes species (Kinorhyncha: Cyclorhagida), with the description of one new species and a redescription of E. arlis Higgins, 1966

The kinorhynch fauna from Svalbard and the Arctic Ocean north of Svalbard was explored, and a total of nine species of Echinoderes was identified. Two species were new to science, and one, Echinoderes balerioni sp. nov., is described. Echinoderes balerioni sp. nov. is characterized by the presence of short middorsal spines on segments 4, 6, and 8, and in lateroventral positions on segments 6 to 9. Tubes are present in laterodorsal, sublateral, and ventrolateral positions on segment 2, lateroventral positions on segment 5, and lateral accessory positions on segment 8, and tergal extensions conspicuously long and spiniform. The collected material also offered the first chance to examine specimens of Echinoderes arlis with scanning electron microscopy, which prompted a redescription of the species. The recorded species are compared with all other known records of Echinoderes in the Arctic region, and the summarized data suggests that at least some species show a circumpolar distribution.

New species of Echinoderes (Kinorhyncha: Cyclorhagida) from Mediterranean seamounts and from the deep-sea floor in the Northeast Atlantic Ocean, including notes on two undescribed species.

Two new species of Echinoderes from the Eratosthenes Seamount and a deep-sea station near the Sedlo Seamount are described. Echinoderes multiporus sp. nov. from the Eratosthenes Seamount is characterized by a combination of the presence of middorsal acicular spines on segments 4, 6, and 8, ventrolateral tubes on segment 2, lateroventral tubes on segment 5, lateroventral acicular spines on segments 6-9, midlateral tubes on segment 10, and type-2 glandular cell outlets in subdorsal position on segment 2 and in laterodorsal position on segments 4-9. Echinoderes unispinosus sp. nov. from the deep-sea station differs from its congeners by the combination of middorsal acicular spine on segment 4, lateroventral acicular spines on segments 6 and 7, type-2 glandular cell outlets present in midlateral position on segment 1, in subdorsal, laterodorsal, sublateral, and ventrolateral position on segment 2, in lateral accessory position on segment 5, and in sublateral position on segment 8, and densely aligned pectinate fringe teeth of the primary pectinate fringes similar in width on segments 1-10. In addition, the morphological data of two undescribed species from the Anaximenes Seamount and a deep-sea station near the Sedlo Seamount are given. An undescribed species from the Anaximenes Seamount is morphologically similar to Echinoderes unispinosus sp. nov., but differs in the smaller trunk length, the presence of broader pectinate fringe teeth of the primary pectinate fringe on segment 1, and the absence of ventromedial sensory spots on segment 8. Another undescribed species from the deep-sea station differs from its congeners in the pattern of spines, tubes, and type-2 glandular cell outlets and length of middorsal and lateral terminal spines. New names are not given to both undescribed species in this study, because only one specimen is available for each species, and both of the specimens were damaged during the preparation.

Consequences of intraoperative spinal cord manipulation in dogs with thoracolumbar intervertebral disc extrusion

ABSTRACT The objective of the present study was to evaluate if extradural contact during hemilaminectomy would cause neurological deterioration in the early and/or late postoperative period in dogs with intervertebral disc extrusion. Nineteen dogs with thoracolumbar intervertebral disc extrusion underwent hemilaminectomy for spinal cord decompression and removal of extruded disc material. Meningeal contacts during surgery were quantified. Paraplegia (with nociception) and paraparesis were observed in 11/19 and 8/19 of dogs, respectively, before surgery. At the end of our study, only two (2/19) had paraplegia and one (1/19), paraparesis. There were more extradural contacts when extruded intervertebral disc material was at a ventrolateral position. Extradural contacts during surgery had no influence on neurological progression nor on time to recovery of motor function. Immediately (24 and 48 hours) after surgery, 13/19 dogs had the same neurological stage before surgery. At 7 and 90 days, 13/19 and 17/19 dogs, respectively, showed neurological improvement, compared with their preoperative stage. There was no influence of the number of extradural contacts on neurological recovery. These findings indicate that a careful inspection of the vertebral canal for removal of as much extruded disc material as possible does not cause neurologic deterioration.

New species of Semnoderidae (Kinorhyncha: Cyclorhagida: Kentrorhagata) from the Gulf of Mexico

Two new species of Semnoderidae from the Gulf of Mexico are described, and the presence of Antygomonas cf. gwenae and a yet undescribed species of Antygomonas is reported. Sphenoderes aspidochelone nov. sp. is recognized by the presence of a first segment forming a closed ring with deep middorsal and midventral incisions, stout, middorsal acicular spines on segments 1 to 11, lateroventral acicular spines on segments 3 to 9, sexually dimorphic laterodorsal spines on segment 10 and minute cuspidate spines in lateroventral positions on segment 5. Semnoderes lusca nov. sp. is characterized by its first segment forming a closed ring with deep, wedge-shaped middorsal and midventral incisions, acicular middorsal spines on segments 1 to 9 and 11, acicular lateroventral spines on segments 2 to 9, crenulated middorsal and midlateral spines on segment 10 and well-developed cuspidate spines on segments 2 (more lateral than acicular spines), 5 (more ventral than acicular spines), 8 (lateral accessory positions) and 9 (ventrolateral positions). A discussion of the diagnostic characteristics of Antygomonas, Sphenoderes and Semnoderes is included. A comparison of these three genera with the specimens recorded in the present study indicates that Antygomonas should be considered as closely related with Sphenoderes and Semnoderes, but it also suggest that A. gwenae could represent a separate lineage within Semnoderidae, and that the species should be reassigned to a new genus.

Cell Proliferation Pattern and Twist Expression in an Aplacophoran Mollusk Argue Against Segmented Ancestry of Mollusca.

ABSTRACTThe study of aplacophoran mollusks (i.e., Solenogastres or Neomeniomorpha and Caudofoveata or Chaetodermomorpha) has traditionally been regarded as crucial for reconstructing the morphology of the last common ancestor of the Mollusca. Since their proposed close relatives, the Polyplacophora, show a distinct seriality in certain organ systems, the aplacophorans are also in the focus of attention with regard to the question of a potential segmented ancestry of mollusks. To contribute to this question, we investigated cell proliferation patterns and the expression of the twist ortholog during larval development in solenogasters. In advanced to late larvae, during the outgrowth of the trunk, a pair of longitudinal bands of proliferating cells is found subepithelially in a lateral to ventrolateral position. These bands elongate during subsequent development as the trunk grows longer. Likewise, expression of twist occurs in two laterally positioned, subepithelial longitudinal stripes in advanced larvae. Both, the pattern of proliferating cells and the expression domain of twist demonstrate the existence of extensive and long‐lived mesodermal bands in a worm‐shaped aculiferan, a situation which is similar to annelids but in stark contrast to conchiferans, where the mesodermal bands are usually rudimentary and ephemeral. Yet, in contrast to annelids, neither the bands of proliferating cells nor the twist expression domain show a separation into distinct serial subunits, which clearly argues against a segmented ancestry of mollusks. Furthermore, the lack of twist expression during the development of the ventromedian muscle argues against homology of a ventromedian longitudinal muscle in protostomes with the notochord of chordates.