Ultrastructure of the ovary and oogenesis in six species of patellid limpets (Gastropoda: Patellogastropoda) from South Africa

Abstract. The ultrastructural features of the ovary and oogenesis have been described in 6 species of patellid limpets from South Africa. The ovary is a complex organ that is divided radially into numerous compartments or lacunae by plate-like, blind-ended, hollow trabeculae that extend from the outer wall of the ovary to its central lumen. Trabeculae are composed of outer epithelial cells, intermittent smooth muscle bands, and extensive connective tissue. Oocytes arise within the walls of the trabeculae and progressively bulge outward into the ovarian lumen during growth while partially surrounded by squamous follicle cells. During early vitellogenesis, the follicle cells lift from the surface of the underlying oocytes and microvilli appear in the perivitelline space. Follicle cells restrict their contact with the oocytes to digitate foot processes that form desmosomes with the oolamina. When vitellogenesis is initiated, the trabecular epithelial cells hypertrophy and become proteosynthetically active. Yolk synthesis involves the direct incorporation of extraoocytic precursors from the lumen of the trabeculae (hemocoel) into yolk granules via receptor-mediated endocytosis. Lipid droplets arise de novo and Golgi complexes synthesize cortical granules that form a thin band beneath the oolamina. A fibrous jelly coat forms between the vitelline envelope and the overlying follicle cells in all species.     

Morphology of the anterior digestive system of tonnoideans (Gastropoda: Caenogastropoda) with an emphasis on the foregut glands

ABSTRACT

Tonnoideans are marine carnivorous caenogastropods that prey on different invertebrates, namely polychaetes, sipunculids, bivalve and gastropod molluscs, and echinoderms. The morphology of the digestive system of 20 species from five families of the Tonnoidea was examined (for most of these species for the first time), and the salivary glands of six of them were studied using serial histological sections. Most of the studied families are rather similar anatomically, except Personidae (Distorsio), which differs both in proboscis morphology and the structure of the salivary glands. In most tonnoideans the salivary glands are split morphologically and functionally into anterior and posterior lobes, the latter synthesising strong sulfuric acid. The ducts of the posterior lobes are lined with non-ciliated epithelium and receive usually paired ciliated ducts from the anterior lobes to form a non-ciliated common duct, opening into the buccal cavity. In Personidae, the salivary glands are not separated into lobes, but are instead composed of ramifying tubules that are histologically different in the proximal and distal parts. Radulae of Tonnoidea are rather variable, with different patterns of interlocking teeth, both in the transverse and longitudinal rows, which may be related to particular feeding mechanisms. Due to the peculiarities of Personidae, the close relationship between that family and the rest of the Tonnoidea is questioned.     

A comparative analysis of the feeding apparatus in pomacanthids, with special emphasis of oesophageal papillae in Genicanthus personatus

Of the pomacanthids examined in the present study (22 species; seven genera), only Genicanthus (eight species) had unique oesophageal papillae. The papillae of the masked angelfish, Genicanthus personatus are arranged in a radial fashion, finger-like or polypoid in shape, very abundant, fill the lumen, and vary considerably in length (0·38–2.40 mm) and width (0·12–1·18 mm). The surface pores (2.8–45.2 μm in diameter) of each papilla are part of the gastric or mucus-secreting oesophageal glands as determined by histological examination. Preliminary stomach content analyses revealed that G personatus consumes a variety of animal and plant material, including algae, copepods, diatoms, and eggs, but dominated in volume by plant material. The oesophageal papillae may constitute a morphological specialization of the digestive tract at the genus level. This may enable Genicanthus spp. to utilize and process a food source not readily available to other pomacanthid species. Additional studies are necessary to determine other ecological, behavioural, social, and morphological variables that separate this large and diverse group of fishes ecologically.     

An integrative taxonomic approach to infer the systematic position of Chalepotaxis Ancey, 1887 (Gastropoda: Stylommatophora: Helicarionidae)

In the absence of knowledge about its anatomy, the systematic position of the genus Chalepotaxis, which inhabits a large part of South East Asia, has been historically dubious. The genitalia, sole of the foot and the caudal region of the type species, Chalepotaxis infantilis (Gredler, V. 1881. Zur Conchylien-Fauna von China. III. Stück. Jahrbücher der Deutschen Malakozoologischen Gesellschaft 8, 110–128), are described, which place this genus into the Helicarionidae family. DNA markers (cytochrome oxidase subunit I [COI] and 28S rRNA genes) corroborate this assignment and unequivocally remove the species from the Camaenidae (=Bradybaenidae) and Ariophantidae, where it had previously been placed. Radular morphology of the type species is also re-described and illustrated.     

Morphology of the jaw apparatus in 8 species of Patellogastropoda (Mollusca, Gastropoda) with special reference to Testudinalia tesulata (Lottiidae)

The fine structure of the jaw apparatus was studied by scanning electron microscopy in eight species of Patellogastropoda. The jaw apparatus is an unpaired two-layered dorsolateral structure with anterior and posterior wings attached to the odontophore by muscles. The jaw of Testudinalia tesulata (O.F. Müller, 1776) is a derivative of the cuticle typical for the foregut. The tissue forming the jaw is a specialized foregut epithelium (gnathoepithelium), consisting of a special type of cells called gnathoblasts. The jaw grows in areas of the epithelium characterized by high concentration of electron-dense vesicles, ER and long microvilli that penetrate deep into the jaw plate. This indicates that the gnathoblasts take an active part in jaw growth. In most cases, these areas of the gnathoepithelium are highly folded. The main differences between the species studied are form and thickness of the frontal edge of the jaw. These differences do not correlate with the systematic position of the species studied but likely depend more on the feeding mode. The transmission electron microscopy studies yielded new morphological criteria for comparison between various gastropod species and other members of Trochozoa, in particular, Annelida. The jaws of Annelida are cuticular structures formed on the surface of specialized epithelial cells, often also called gnathoblasts. The jaw of Patellogastropoda can be attributed to the first type of annelid jaw formation characterized by an epithelium with long microvilli and continuous growth.     

Further studies on the morphology of the Triviidae (Gastropoda: Prosobranchia) with emphasis on species from southern Africa

Aspects of the morphology of II species of Triviidae are described, including the living animal, shell, radula, mantle complex, central nervous system and reproductive system. Interspecific differences in radular morphology are important in distinguishing closely allied species. Trivia aperta, T. costata and T. verhoeft are protandric hermaphrodites while T. caluariola, T. neglccta, T. pellucidula, T. rubra, T. solandri and T. suavis are gonochoric. The elaboration of the receptaculum seminis varies between species. In T. aperta, T. calvariola, T. neglecta and T. who& the receptaculum is undivided while in T. costafa, T. pellucidula, T. solandri and T. suavis there are two or more lobes of the receptaculum.     

Neurogenesis in the mossy chiton,Mopalia muscosa (Gould) (Polyplacophora): evidence against molluscan metamerism

Neurogenesis in the chiton Mopalia muscosa (Gould, 1846) was investigated by applying differential interference contrast microscopy, semithin serial sectioning combined with reconstruction techniques, as well as confocal laser scanning microscopy for the detection of fluorescence-conjugated antibodies against serotonin and FMRFamide. The ontogeny of serotonergic nervous structures starts with cells of the apical organ followed by those of the cerebral commissure, whereas the serotonergic prototroch innervation, pedal system, and the lateral cords develop later. In addition, there are eight symmetrically arranged serotonergic sensory cells in the dorsal pretrochal area of the larva. FMRFamide-positive neural elements include the cerebral commissure, specific "ampullary" sensory cells in the pretrochal region, as well as the larval lateral and pedal system. In the early juvenile the cerebral system no longer stains with either of the two antibodies and the pedal system lacks anti-FMRFamide immunoreactivity. Outgroup comparison with all other molluscan classes and related phyla suggests that the cord-like, nonganglionized cerebral system in the Polyplacophora is a reduced condition rather than a primitive molluscan condition. The immunosensitivity of the pedal commissures develops from posterior to anterior, suggesting independent serial repetition rather than annelid-like conditions and there is no trace of true segmentation during nervous system development. Polyplacophoran neurogenesis and all other available data on the subject contradict the idea of a segmented molluscan stem species.     

Patellogastropoda and Vetigastropoda (Mollusca,Gastropoda) from the marine Jurassic of Patagonia,Argentina

Gastropod faunas from the Early Jurassic (Late Pliensbachian–Early Toarcian) marine deposits of Chubut Province, Argentina, are described from Lomas Occidentales, Cerro La Trampa and Puesto Currumil localities, representing eight species, three of them new. These are Scurriopsis? sp., Chartronella gradata sp. nov., Calliotropis? sp., Pleurotomaria sp., Leptomaria sp., Hamusina? wahnishae sp. nov., Colpomphalus musacchioi sp. nov. and Jurassiphorus? cf. triadicus Haas. The gastropod assemblage reported here testifies paleobiogeographical connections with other coeval gastropod associations from the western Tethys. However, Chartronella, Hamusina and Jurassiphorus may represent survivors of Triassic associations, considering the ancient seaway from Peru as the most plausible hypothesis for biotic exchange of these faunas during the Late Triassic–Early Jurassic boundary. An abundant and diverse invertebrate fauna such as corals, echinoderms, cephalopods, brachiopods, bivalves and other gastropods found in association with the gastropods described here characterises a shallow marine environment for the gastropod-bearing rocks.http://www.zoobank.org/urn:lsid:zoobank.org:pub:7B8EAFC0-3AC0-4F91-97A5-22AAC6A19909     

A new species of the genus Pectinodonta Dall, 1882 (Gastropoda: Pectinodontidae) from the East China Sea

A new pectinodontid species collected from sunken wood in the East China Sea off Zhejiang Province, China, is described and assigned to the genus Pectinodonta Dall, 1882. This new species, Pectinodonta mazuae n. sp., has a medium sized shell with a fine sculpture; shell width about 72%–75% of shell length, height about 61%–66% of length, and each lateral tooth has 16 or 17 cusps. These features may be used to distinguish the new species from its congeners.

http://zoobank.org/urn:lsid:zoobank.org:act:4B3D491F-868D-4F9A-8CC9-005829BF691E     

Effects of environmental calcium deprivation on the egg masses of Physa marmorata Guilding (Gastropoda: Physidae) and Biomphalaria glabrata Say (Gastropoda: Planorbidae)

Eggs of the basommatophoran snails Physa marmorata and Biomphalaria glabrata were cultured in low concentrations of calcium to determine effects on growth and development. In both species there was some development in media with 0.12 mg/l Ca²⁺ but embryos were unable to hatch. 61.04% of embryos of P. marmorata could develop to hatching in 0.22 mg/l Ca²⁺ but those of B. glabrata required a level of 0.42 mg/l Ca²⁺, to attain even a 31.07% hatch. Marked effects on growth rate, embryo size and on time taken to achieve hatching were noted in both species at very low calcium levels. The possibility of cation-controlling mechanisms in the egg membrane is discussed.     

Comparative investigation of the genital systems in the Opisthobranchia (Mollusca, Gastropoda) with special emphasis on the nidamental glandular system

The reproductive systems and especially the nidamental glands of 20 species of Opisthobranchia belonging to the ”Cephalaspidea s. l.”, Anaspidea, Sacoglossa, Tylodinoidea and Pleurobranchoidea, have been investigated histologically and ultrastructurally. The nidamental glandular system is responsible for the formation of the egg masses. In all investigated species it is divided into three distinct parts. The most proximal part can be an albumen gland (some ”Cephalaspidea s. l.”, Anaspidea and Sacoglossa) or can exhibit a capsule gland (some ”Cephalaspidea s. l.”, Tylodinoidea and Pleurobranchoidea). All species additionally possess a membrane gland and a distally lying mucous gland. In some species the most distal part of the oviduct was also found to be glandular. The structure of the nidamental glands is described and compared within the Opisthobranchia. Albumen and capsule glands are found to be homologous glandular parts of the system. It can be concluded that the albumen gland has undergone a structural and functional change within the evolution of the Opisthobranchia. Accepted: 26 December 2000     

Interactive 3D anatomy and affinities of Bathysciadiidae (Gastropoda,Cocculinoidea): deep‐sea limpets feeding on decaying cephalopod beaks

The anatomy of five bathysciadiid limpets, the type species Bathysciadium costulatum (Locard, 1898 ), Bathysciadium sp. B (off New Zealand), Bathypelta pacifica (Dall, 1908 ), Bathypelta sp. A (off New Zealand), and Bathyaltum wareni n.g., n.sp. (deep East Atlantic Ocean Basins), which all feed on decaying cephalopod beaks, has been investigated by means of semithin serial sectioning and interactive, computer‐aided 3D reconstructions. Bathyaltum wareni is described as a species new to science based on additional SEM photos of shell and radula. Differences between species are found in conditions of shell, protoconch, mantle papilla, copulatory organ, receptaculum openings, oral lappets, and rectal histology. The Bathysciadiidae share several synapomorphies with the Cocculinidae (s. str.), namely the pseudoplicatid gill, a single, left kidney, the hermaphroditic gonad with the single, glandular gonoduct, and the statocysts with single statoliths. Therefore, these families are united in a clade Cocculinoidea, which is considered to be highly modified offshoot of early gastropods independent of the likewise “cocculiniform” Lepetelloidea, which should be classified among the Vetigastropoda. J. Morphol. 272:259–279, 2011. © 2010 Wiley‐Liss, Inc.     

Redescription of the western Balkan species Xerocampylaea waldemari and its phylogenetic relationships to other Urticicolini (Gastropoda: Hygromiidae)

The proper identification of species has significant implications for conservation and general knowledge of ecosystem variety. It is especially important for biodiversity hotspots and former Pleistocene refugia, such as the Balkans. In this paper, we evaluate the taxonomic status of the endemic Balkan species Fruticicola waldemari A. J. Wagner, 1912, using both recently collected material and museum specimens. Phylogenetic analyses based on two mitochondrial markers, 16S rRNA and cytochrome c oxidase subunit I, show that this species is closely related to the representatives of Xerocampylaea, including a conchologically similar and partly sympatric species, X. erjaveci. Analyses of shell and genital morphology as well as mitochondrial DNA sequences indicate that X. waldemari and X. erjaveci are separate but closely related species. These species differ in shell morphology (size, umbilicus diameter, microsculpture) as well as genital morphology. Nevertheless, a further study with more comprehensive sampling of both taxa is required to fully understand the complex pattern of genetic and morphological variation observed.     

Short-term climate change and the extinction of the snail Rhachistia aldabrae (Gastropoda: Pulmonata)

The only known population of the Aldabra banded snail Rhachistia aldabrae declined through the late twentieth century, leading to its extinction in the late 1990s. This occurred within a stable habitat and its extinction is attributable to decreasing rainfall on Aldabra atoll, associated with regional changes in rainfall patterns in the late twentieth and early twenty-first century. It is proposed that the extinction of this species is a direct result of decreasing rainfall leading to increased mortality of juvenile snails.     

Laboratory spawning, larval development, and metamorphosis of the limpets Lottia digitalis and Lottia asmi (Patellogastropoda, Lottiidae)

Abstract. This study describes and compares laboratory spawning, larval development, and metamorphosis in the patellogastropod limpets Lottia digitalis and Lottia asmi. Both species were dioecious and freely spawned their gametes, which were fertilized externally. Eggs from L. digitalis and L. asmi averaged 155 and 134 μm in diameter, respectively. Early cleavage patterns were typical of other patellogastropods. Swimming trochophore larvae had developed ∼ 15 hours after fertilization, and ultimately developed into lecithotrophic veliger larvae that reached metamorphic competence at 5.25–5.5 days after fertilization (13°C). Food particles were frequently visible in the gut of newly metamorphosed individuals one day after settlement, and adult shell growth was typically initiated within 2–4 days of settlement. Small egg size in L. asmi , relative to other eastern Pacific lottiids, may be directly related to the need for high fecundity in this small-bodied species; however, developmental information is available for relatively few lottiid species. Because broadcasting lottiids do not secure egg masses in safe microhabitats for development, this reproductive mode may have been conducive to their ecological radiation into novel habitats.     

Biology of Latia neritoides Gray 1850 (Gastropoda,Pulmonata, Basommatophora): the Only Light-producing Freshwater Snail in the World

This report on the freshwater pulmonate basommatophoran Latia neritoides of the North Island of New Zealand is based on field and laboratory studies. It deals with aspects of the habitat, describes biological adaptations of organs and organ systems in Latia, reviews the chemical basis of bioluminescence in this species, discusses the possible roles of light production in Latia, and addresses zoogeographic and phylogenetic questions.     

Characterization of 15 microsatellite loci in the pulmonate snail Pseudosuccinea columella (Mollusca, Gastropoda)

We characterized 15 new variable microsatellites in the freshwater snail Pseudosuccinea (Lymnaea) columella, as well as conditions for multiplexing and simultaneously genotyping sets of loci. Two to six alleles were detected per locus over the six populations studied. Gene diversity ranged from 0.000 to 0.498, but essentially no heterozygous individuals were observed. This resulted in extremely high F(IS) estimates, and therefore high selfing rates. The F(ST) estimates ranged from 0.18 to 1 among populations, but was generally high. These markers will constitute efficient tools for investigating the population structure of this invasive species. Cross-species amplification was on the whole unsuccessful.     

Development of 10 microsatellite loci in the pulmonate snail Biomphalaria kuhniana (Mollusca, Gastropoda)

We characterized 10 variable microsatellite loci in the freshwater snail Biomphalaria kuhniana, as well as conditions for multiplexing and co-loading sets of loci. Two to five alleles were detected per locus over the two studied populations in Venezuela. High inbreeding coefficients suggest high selfing rates. Cross-species amplification provided some variability at eight and three loci in the other species belonging to the Biomphalaria straminea complex (B. straminea and B. intermedia), but was unsuccessful in more divergent species.     

Ovoviviparity and the structure of the brood pouch in Melanoides tuberculata (Gastropoda: Prosobranchia: Thiaridae)

The freshwater gastropod Melanoides tuberculata broods its young in a pouch located in the anterodorsal region of the head-foot. The wall of the brood pouch is composed of smooth muscle surrounded by connective tissue. The lumen of the brood pouch is incompletely partitioned by trabeculae, formed by extensions or folds in the chamber wall that are composed of smooth muscle, connective tissue, nonciliated squamous epithelial cells, and some storage cells containing lipid and glycogen. The lumen of the chamber also contains a few cells with storage products. The general absence of secretory cells suggests that embryos derive little nutrition from the mother, and therefore embryonic development is probably ovoviviparous. Embryos in various stages of development were found within brood pouches, with later stage embryos varying in size. There was a negative relationship between embryo size and number of embryos in the brood pouch.