34 research outputs found
Between Vanuatu tides: 3D anatomical reconstruction of a new brackish water acochlidian gastropod from Espiritu Santo
No full textNeusser, Timea P., Schrödl, Michael (2009): Between Vanuatu tides: 3D anatomical reconstruction of a new brackish water acochlidian gastropod from Espiritu Santo. Zoosystema 31 (3): 453-469, DOI: 10.5252/z2009n3a4, URL: http://www.bioone.org/doi/abs/10.5252/z2009n3a
Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)
No full textSchrödl, Michael, Neusser, Timea P. (2010): Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia). Zoological Journal of the Linnean Society 158 (1): 124-154, DOI: 10.1111/j.1096-3642.2009.00544.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00544.
FIG. 4 in Between Vanuatu tides: 3D anatomical reconstruction of a new brackish water acochlidian gastropod from Espiritu Santo
No full textFIG. 4. — Radula of Pseudunela espiritusanta n. sp., SEM-micrographs: A, row of radular teeth; B, rhachidian teeth, right view; C, rhachidian tooth, anterior view; D, right lateral teeth, arrow points to blunt protrusion; E, left lateral teeth. Abbreviations: cc, central cusp; d, denticle; ltl, left lateral tooth; ltr1, first right lateral tooth; ltr2, second right lateral tooth; n, notch; 1-4, lateral denticle on rhachidian tooth. Scale bars: 10 μm.Published as part of Neusser, Timea P. & Schrödl, Michael, 2009, Between Vanuatu tides: 3D anatomical reconstruction of a new brackish water acochlidian gastropod from Espiritu Santo, pp. 453-469 in Zoosystema 31 (3) on page 459, DOI: 10.5252/z2009n3a4, http://zenodo.org/record/539026
Figure 2 in Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)
No full textFigure 2. Schematic overview of the cephalic copulatory organs of different acochlidian species. A, Tantulum elegans; B, Hedylopsis spiculifera; C, Pseudunela spp.; D, Strubellia spp. Abbreviations: bf, basal finger; bfg, gland inside basal finger; bs, basal swelling; de, ejaculatory duct; go, copulatory/male genital opening; p, penis; pd, paraprostatic duct; pg, penial gland; ppr, paraprostate; pr, prostate; ps, penial sheath; sg, external sperm groove; st, hollow stylet; th, solid thorn; vd, vas deferens; vdb, back leading vas deferens. Not drawn to scale.Published as part of Schrödl, Michael & Neusser, Timea P., 2010, Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia), pp. 124-154 in Zoological Journal of the Linnean Society 158 (1) on page 137, DOI: 10.1111/j.1096-3642.2009.00544.x, http://zenodo.org/record/544777
Figure 1 in Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia)
No full textFigure 1. External morphology of living specimens of limnic (A and B) and marine (C–J) Acochlidia. A, Strubellia sp. from Vanuatu (subadult, 2-cm long), with large lateral eyes and a broad foot; B, Acochlidium fijiense from Fiji (2-cm long), note the propodial tentacles and the heart bulb; C, Pseudunela sp. from Vanuatu (3.5-mm long), with long, free posterior foot; D, Asperspina rhopalotecta from Italy (2-mm long), note anterior mantle margin forming a permanent rim; E, Microhedyle glandulifera from Italy (2-mm long), with epidermal glands; F, Paraganitus sp. from Vanuatu (1.5-mm long), with convoluted digestive gland; G, Pontohedyle milaschewitchii from Croatia (3-mm long; ventral view), with head–foot completely retracted into visceral hump; H, P. milaschewitchii from Italy (3-mm long), with short and blunt free posterior foot; I, Hedylopsis spiculifera from Italy, (juvenile, 1-mm long); J, Hedylopsis ballantinei from Egypt (5.5-mm long), note the net-like arrangement of spicules. Abbreviations: dg, digestive gland (shining through the integument); eg, epidermal gland; ey, eye; f, foot; hb, heart bulb; k, kidney (shining through the integument); lt, labial tentacle; mm, anterior mantle margin; pt, propodial tentacle; rh, rhinophore; sp, spicule; vh, visceral hump. A, right view; B–F, I, dorsal view; G, H, ventral view; J, left view.Published as part of Schrödl, Michael & Neusser, Timea P., 2010, Towards a phylogeny and evolution of Acochlidia (Mollusca: Gastropoda: Opisthobranchia), pp. 124-154 in Zoological Journal of the Linnean Society 158 (1) on page 130, DOI: 10.1111/j.1096-3642.2009.00544.x, http://zenodo.org/record/544777
Cryptic species in tropic sands--interactive 3D anatomy, molecular phylogeny and evolution of meiofaunal Pseudunelidae (Gastropoda, Acochlidia)
No full textTowards realistic estimations of the diversity of marine animals, tiny meiofaunal species usually are underrepresented. Since the biological species concept is hardly applicable on exotic and elusive animals, it is even more important to apply a morphospecies concept on the best level of information possible, using accurate and efficient methodology such as 3D modelling from histological sections. Molecular approaches such as sequence analyses may reveal further, cryptic species. This is the first case study on meiofaunal gastropods to test diversity estimations from traditional taxonomy against results from modern microanatomical methodology and molecular systematics
Tiny but complex - interactive 3D visualization of the interstitial acochlidian gastropod <it>Pseudunela cornuta </it>(Challis, 1970)
No full textAbstract Background Mesopsammic acochlidians are small, and organ complexity may be strongly reduced (regressive evolution by progenesis), especially in microhedylacean species. The marine interstitial hedylopsacean Pseudunela cornuta (Challis, 1970), however, was suggested as having a complex reproductive system resembling that of much larger, limnic and benthic species. The present study aims to reconstruct the detailed anatomy and true complexity of P. cornuta from serial, semithin histological sections by using modern computer-based 3D visualization with Amira software, and to explain it in an evolutionary context. Results Our results demonstrate considerable discordance with the original species description, which was based solely on paraffin sections. Here, we show that the nervous system of P. cornuta has paired rhinophoral, optic and gastro-oesophageal ganglia, three distinct ganglia on the visceral nerve cord, and a putative osphradial ganglion, while anterior accessory ganglia are absent. The presence of an anal genital cloaca is clearly rejected and the anus, nephropore and gonopore open separately to the exterior; the circulatory and excretory systems are well-differentiated, including a two-chambered heart and a complex kidney with a long, looped nephroduct; the special androdiaulic reproductive system shows two allosperm receptacles, three nidamental glands, a cavity with unknown function, as well as highly complex anterior copulatory organs with two separate glandular and impregnatory systems including a penial stylet that measures approximately a third of the whole length of the preserved specimen. Conclusion In spite of its small body size, the interstitial hermaphroditic P. cornuta shows high complexity regarding all major organ systems; the excretory system is as differentiated as in species of the sister clade, the limnic and much larger Acochlidiidae, and the reproductive system is by far the most elaborated one ever observed in a mesopsammic gastropod, though functionally not yet fully understood. Such organ complexity as shown herein by interactive 3D visualization is not plesiomorphically maintained from a larger, benthic ancestor, but newly evolved within small marine hedylopsacean ancestors of P. cornuta. The common picture of general organ regression within mesopsammic acochlidians thus is valid for microhedylacean species only.</p
Really a “secondary gill under the skin”? Unveiling “dorsal vessels” in freshwater slugs (Mollusca, Panpulmonata, Acochlidimorpha)
No full textThe freshwater slugs of the genus Acochlidium (Heterobranchia, Gastropoda, and Acochlidimorpha) are peculiar, one to two centimeter sized animals found only in small coastal rivers and streams of Southeast Asian and Western Pacific islands. When first described by Bücking, the author observed a branching “net of dendritic vessels connected to the heart,” which he assumed to have replaced the original gastropod gill. In the present study, we compare the renopericardial systems of four Acochlidium species in microanatomical, histological and ultrastructural detail and identify where exactly the enigmatic, subepidermal “dorsal vessels” connect to the renopericardial system to examine if they can really function as a gill. Acochlidium have elaborate renopericardial systems compared to their ancestrally marine and also freshwater relatives. The primary site of ultrafiltration is the epicardium of the atrium with podocytes as usual for gastropods. The “dorsal vessels” in Acochlidium are extensions of the outer epithelium of the pericardial cavity and represent true vessels, that is, coelomatic channels, having an endothelium with podocytes. Hence, they considerably enlarge the site of ultrafiltration increasing the pericardial surface. “Dorsal vessels” in Acochlidium are therefore not homologous to externally similar morphological structures in Sacoglossa (marine panpulmonate slugs and snails). The multiplication of renopericardioducts in Acochlidium is a unique feature within Mollusca that enhances the negative pressure necessary for ultrafiltration in the thin, tube-like dorsal vessels and as a consequence the transport of primary urine from the pericardium to the kidney. The circulatory and excretory systems in Acochlidium are adaptations to a lifestyle in their freshwater environment in which snail bodies are hyposmotic and accrue considerable influx of surplus water into the body, which needs to be expelled
Undersized and underestimated: 3D visualization of the Mediterranean interstitial acochlidian gastropod Pontohedyle milaschewitchii (Kowalevsky, 1901)
No full textAbstractPontohedyle milaschewitchii (Kowalevsky, 1901) is one of the most common mesopsammic opisthobranchs in the Mediterranean and Black Seas and has been considered as a comparably well-described acochlidian species. However, data on its complex internal anatomy were fragmentary and little detailed due to inadequate methodology available, and contradictory between different sources. The present study redescribes all major organ systems of P. milaschewitchii in full detail by three-dimensional reconstruction from serial semithin sections using AMIRA software. The prepharyngeal central nervous system (cns) of P. milaschewitchii is highly concentrated and shows a euthyneurous and epiathroid condition. Contrary to earlier reports, the cerebral and pleural ganglia are not fused. Aggregations of precerebral accessory ganglia can be grouped into three complexes supplied by distinct cerebral nerves. Rhinophoral ganglia with thin, double cerebro-rhinophoral connectives are described for the first time in acochlidians. A Hancock's organ is present in the form of a conspicuous, curved fold in the epidermis posterior to the oral tentacles. Cerebral nervous features and sensory structures are discussed comparatively. Our study confirms P. milaschewitchii as having the male genital opening in an unusual position above the mouth. Homology of the ciliated vas deferens of the gonochoristic and aphallic P. milaschewitchii with that of hermaphroditic acochlidian species with cephalic male genitals is discussed. The radula formula of P. milaschewitchii is 41–54×1-1-1, i.e. the single lateral teeth are broad and, contrary to previous descriptions, undivided. SEM examination of the body wall of entire specimens revealed a special and constant ciliary pattern. Providing a novel additional set of characters for taxonomic and phylogenetic purposes, external SEM examination is suggested as the standard method for describing acochlidian species in the future
Re-description of a female Pontohedyle brasilensis (Rankin, 1979), a junior synonym of the Mediterranean P. milaschewitchii (Kowalewsky, 1901) (Acochlidia, Gastropoda)
No full textVolume: 55Start Page: 283End Page: 29
