bluuebunny/crossref_metadata_2025 huggingface dataset:
Sperm structure of Rhopalura littoralis (Orthonectida)
Authors: Slyusarev George S. , Ferraguti Marco
Published: August 2010

Abstract. We present here a description of the spermatozoon of Rhopalura littoralis, the first fine‐structural study of an orthonectid sperm. The spermatozoon contains a slightly elongate nucleus and two centrioles orientated along the longitudinal axis of the sperm. The proximal centriole bears one rootlet. A single mitochondrion is present in the mid‐piece region. An acrosome is absent. The sperm tail is a simple flagellum with 9+2 structure. We consider the orthonectan spermatozoon to be closer in structure to those of Porifera, Cnidaria, and Annelida, than to Aschelminthes and Platyhelminthes, to which orthonectids have previously been allied.
Morphology of stomatopod chemosensory sensilla facilitates fluid sampling
Authors: Mead Kristina S. , Weatherby Tina M.
Published: August 2010

Abstract. Stomatopods, like many marine crustaceans, rely on their sense of smell to detect prey and to find mates (Ache 1982; Zimmer‐Faust 1989; Atema & Voigt 1995). In lobsters, crabs, crayfishes, prawns, leptostracans, anaspidans, mysids, amphipods, tanaids, isopods, ostracodes, phyllopods, and cumaceans (Heimann 1984; Hallberg et al. 1992), this detection of odors from distant sources involves specialized chemosensory setae called aesthetascs located on the antennules. The external structure of stomatopod sensilla appears to follow the typical crustacean aesthetasc pattern, but their internal structure has not been previously examined. In this study, we use serial reconstruction from transmission electron microscopy to show that the stomatopod sensilla are aesthetascs. For chemoreception to occur, chemical‐containing fluid must be very close to the surface of the aesthetascs, such that odor molecules can diffuse to chemoreceptors on the olfactory receptor neurons inside the aesthetasc. Flicking of stomatopod antennules maximizes fluid penetration near the parts of the sensilla where the cuticle is thinnest, and where the outer dendritic segments are most fully branched with the greatest surface area. Thus, the external and the internal structure of the stomatopod aesthetasc are “matched” to maximize the efficiency of odor arrival at the surface of the olfactory receptor neurons.
Fusion between incompatible colonies of a viviparous ascidian, Botrylloides lentus
Authors: Okuyama Makiko , Saito Yasunori , Hirose Euichi
Published: August 2010

Abstract. The mode of allo‐recognition among colonies was investigated in a viviparous ascidian, Botrylloides lentus. Each embryo is enveloped by a pouch of epithelial cells (brood pouch), and is brooded in the vascular lumen of the parental colony. That is, the parental colony tolerates the presence of semi‐allogeneic conspecifics (embryos) in the vascular system. A rejection reaction occurs when incompatible colonies are brought into contact at their growing edges. The inflammatory rejection reaction is limited to a small area where the tunic of two colonies has partially fused. On the contrary, incompatible colonies fuse and their blood vessels become interconnected with one another, when they are brought into contact at artificially cut surfaces. This mode is the same as those of other viviparous species of Botrylloides, B. fuscus and B. violaceus. A relationship between viviparity and the loss of allo‐recognition in the vascular system is suggested.
Aspects of the larval biology of the sea anemonesAnthopleura elegantissimaandA. artemisia
Authors: Weis Virginia M. , Verde E. Alan , Pribyl Alena , Schwarz Jodi A.
Published: August 2010

Abstract.We investigated several aspects of the larval biology of the anemoneAnthopleura elegantissima, which harbors algal symbionts from two different taxa, and the non‐symbioticA. artemisia. From a 7‐year study, we report variable spawning and fertilization success ofA. elegantissimain the laboratory. We examined the dynamics of symbiosis onset in larvae ofA. elegantissima. Zoochlorellae, freshly isolated from an adult host, were taken up and retained during the larval feeding process, as has been described previously for zooxanthellae. In addition, larvae infected with zooxanthellae remained more highly infected in high‐light conditions, compared to larvae with zoochlorellae, which remained more highly infected in low‐light conditions. These results parallel the differential distribution of the algal types observed in adult anemones in the field and their differential tolerances to light and temperature. We report on numerous failed attempts to induce settlement and metamorphosis of larvae ofA. elegantissima, using a variety of substrates and chemical inducers. We also describe a novel change in morphology of some older planulae, in which large bulges, resembling tentacles, develop around the mouth. Finally, we provide the first description of planulae ofA. artemisiaand report on attempts to infect this non‐symbiotic species with zooxanthellae and zoochlorellae.
A systematic revision of Edwardsiidae (Cnidaria, Anthozoa)
Authors: Daly Marymegan
Published: August 2010

Abstract. Difficulties in addressing relationships among sea anemones are explored in the context of a revision of the family Edwardsiidae. This family has been important in discussions of relationships within Zoantharia (Cnidaria, Anthozoa), but has been poorly characterized. Genera within Edwardsiidae are characterized by a mosaic distribution of a few key characters whose actual distribution is not well understood; generalized and idealized morphology, rather than the actual distribution of characters, has been previously used to delimit genera. Microanatomy of muscles and the body wall, qualitative and quantitative information about muscle shape, and nematocyst size are combined with 18S rDNA sequences in a cladistic analysis. The results demonstrate that some traditional diagnostic features support groups different from those previously recognized. Character support is identified for several previously proposed taxa or clades, including the genus Edwardsiella and a clade containing Nematostella and Drillactis. Edwardsiidae and several of its genera are monophyletic; however, groups within the subfamily Edwardsiinae require revision and recircumscription. The genus Edwardsia is paraphyletic, and these data do not resolve Edwardsia species into monophyletic groups.
Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra
Authors: Dillon Robert T. , Wethington Amy R. , Rhett J. Matthew , Smith Thomas P.
Published: August 2010

Abstract. It has long been speculated that Physa acuta, a pulmonate snail widespread and invasive in fresh waters of the old world, may have originated in North America. But the identification of a new‐world cognate has been complicated by the confused systematics and taxonomy of the Physidae in America. More than 40 species of physids are currently recognized in the United States, many with variable and overlapping morphology. We have previously established that premating reproductive isolation is negligible among physid snails. Here we report the results from no‐choice crosses each involving 2 populations of the widespread American species Physa heterostropha and Physa integra, both with each other and with P. acuta, designed to compare measures of reproductive success between species and between populations within species. Samples of P. acuta were collected from France and Ireland, P. heterostropha from eastern Pennsylvania and South Carolina, and P. integra from southern Indiana and northern Michigan. The 6 intrapopulation controls varied quite significantly in their survival, age at first reproduction, parental fecundity, F1 viability, and F1 fertility under our culture conditions. Measures of survival and reproduction in the 6 interpopulation crosses were generally intermediate, but in no case significantly worse than the more poorly performing control. Thus we were unable to detect evidence of reproductive isolation among our 6 populations of snails from 2 continents. All should be referred to the oldest available nomen, P. acuta.
Crayfish induce a defensive shell shape in a freshwater snail
Authors: Krist Amy C.
Published: August 2010

Abstract. This study was undertaken to determine whether intraspecific variation in shell morphology of the freshwater snail Elimia (=Goniobasis) livescens is caused by predator‐induced morphological changes. Juvenile snails from 3 populations were grown in the presence of effluent from predatory crayfish feeding on conspecific snails or in effluent from conspecific snails only. Snails from one population, Clear Creek, exhibited a predator‐induced morphology; they grew a narrow body whorl when exposed to the effluent from crayfish. Experimental feeding trials with crayfish and snails from Clear Creek were conducted to determine whether a narrow body whorl reduced predation in the presence of the crayfish Orconectes propinquus. In the feeding trials, snails with a narrow body whorl were eaten less frequently than snails with wider shells. However, there was no difference in overall size (length) between snails that were eaten and those that were not. Thus, juvenile snails from Clear Creek exposed to the presence of crayfish were induced to develop relatively narrow shells, which reduce the risk of successful attack by these crayfish. Hence the induced shell morphology is probably a defense against predation by crayfish.
Laboratory spawning, larval development, and metamorphosis of the limpets Lottia digitalis and Lottia asmi (Patellogastropoda, Lottiidae)
Authors: Kay Matthew C. , Emlet Richard B.
Published: August 2010

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.
Do life history traits account for diversity of polychaete annelids?
Authors: McHugh Damhnait , Fong Peter P.
Published: August 2010

Abstract. Within many phylogenetic assemblages, a pattern of domination has been observed: one or a few clades have had many more speciation events or fewer extinctions than other clades in a particular assemblage. We investigated this phenomenon in the polychaete annelids. Polychaetes comprise ∼9000 described species classified in over 70 families and exhibit a great variety of life history strategies. Our goal was to test whether diverse polychaete families are characterized by species with short generation times, high reproductive output, small body size, or with planktotrophic larval development. Each of these factors has been advanced as cause for high diversity in other taxonomic assemblages. Here, we establish that the diversification pattern of polychaete families is non‐random, but the data collected show no significant correlations between familial diversity and several life history traits including age at first reproduction, life span, body size, fecundity, and egg size. Pairwise comparisons of sister families do not reveal any trends between familial diversity and any of the life history traits. The great variability of life history traits within polychaete families may explain the lack of significant results; perhaps no trends are seen because polychaete life history traits cannot be generalized at the family level.
Sperm ultrastructure and spermiogenesis in two Exogone species (Polychaeta, Syllidae, Exogoninae)
Authors: Giangrande Adriana , Sciscioli Margherita , Lepore Elena , Mastrodonato Maria , Lupetti Pietro , Dallai Romano
Published: August 2010

Abstract. The spermatozoa of Exogone naidina and E. dispar are characterized by a prominent bell‐shaped acrosome, a spheroidal nucleus, and a conventional flagellum. During spermiogenesis, the acrosomal vesicle undergoes conspicuous modifications leading to its final bell shape with a posterior opening. The subacrosomal material initially shows radiating filaments but in mature sperms it appears as a meshwork of electron‐opaque material. The acrosomal axis is oblique with respect to the main longitudinal sperm axis. The chromatin is arranged in electron‐opaque strands in the early spermatids, then becomes amorphous, and is finally organized in filaments in mature sperms. Centrioles are orthogonally arranged beneath the nucleus and fibers radiate from the distal centriole to contact the plasma membrane and the single mitochondrion. The latter is located eccentrically on the side of the nucleus opposite the acrosome. A disk‐shaped structure is evident beneath the distal centriole. The flagellar axoneme has a 9+2 microtubule pattern. A conspicuous glycocalyx surrounds the flagellar plasma membrane, and an electron‐lucent space is present between these two structures at the distal tip of the flagellum. We compare the sperm morphology of these two species of Exogone with that described in other members of the subfamily Exogoninae. The fine structure of these two species supports the occurrence of an ent‐aquasperm type within Exogoninae, in accordance with the brood strategy present within this subfamily. The mode of reproduction is of taxonomic importance for defining subfamilies within Syllidae, and is likely also of phylogenetic significance. Because epitoky is probably plesiomorphic, the ent‐aquasperm type found in Exogoninae can be considered a derived feature within Syllidae.
Comments on the mechanism of attachment in species of the monogenean genus Gyrodactylus
Authors: Shinn Andrew P. , Bron James E. , Sommerville Christina , Gibson David I.
Published: August 2010

Abstract. In species of the monogenean helminth Gyrodactylus, the opisthaptor is the main organ of attachment to the host. The opisthaptor comprises two large centrally positioned hooks or hamuli and sixteen peripherally distributed marginal hooks. This paper describes the functional morphology and the mechanism and sequence of attachment in this species. Information on the attachment process was gathered from observations of live gyrodactylids, from transmission electron microscopy, from scanning electron microscopy of skeletal elements, and by histochemical and X‐ray elemental analysis of hook chemical composition. The marginal hooks provide the principal force of attachment whilst the hamuli are not actively employed in the process of attachment. Instead, the hamuli provide a system preventing accidental dislodgement and assist the action of the marginal hooks. Attachment is achieved by the alternating action of two systems of muscles attached respectively to the hamuli and to the marginal hooks. Relaxation or contraction of the muscles connected to the hamuli manoeuvres the hamuli over the extremities of the accessory ventral bar and allows them to pivot around their longitudinal axis, effectively raising or lowering the opisthaptoral dome. Under reduced opisthaptoral tension, the independent gaffing activity of the marginal hooks ensures a secure attachment to the host's epidermis. Repositioning of the hamuli then raises the opisthaptoral dome to tension the peripheral marginal hooks. The sequence of attachment is complete when all the muscles associated with the hooks are in a state of relaxation but are held securely and under tension by the surrounding, stretched, opisthaptoral dome.
Reproductive modes and genetic polymorphism in the tardigrade Richtersius coronifer (Eutardigrada, Macrobiotidae)
Authors: Rebecchi Lorena , Rossi Valeria , Altiero Tiziana , Bertolani Roberto , Menozzi Paolo
Published: August 2010

Abstract. Allozymes were assessed by starch gel electrophoresis in 3 populations of a eutardigrade, Richtersius coronifer, with different reproductive modes. One population from Italy (with 2 sub‐populations) was amphimictic and 2 populations (1 from Italy and 1 from Sweden) were parthenogenetic. All populations, irrespective of their reproductive mode, were diploid with the same chromosome number (2n=12) and had bivalents in the oocytes. Of the 14 loci analyzed, only 3 were polymorphic. The amphimictic population had a higher degree of genetic variability (mean heterozygosity >0.25) than the parthenogenetic populations (mean heterozygosity of the 2 populations <0.01). In all female populations, allele frequencies at all 3 loci deviated from Hardy‐Weinberg equilibria due to heterozygote deficiency. These results support a hypothesis of automictic parthenogenesis in R. coronifer.
Development of asymmetry in the caenogastropods Amphissa columbiana and Euspira lewisii
Authors: Bondar Carin A. , Page Louise R.
Published: August 2010

Abstract. The asymmetry displayed by the body plan of gastropods has been directly or indirectly attributed to an evolutionary process called torsion. Torsion is defined as a rotation of 180° between the cephalopodium (head and foot) and visceropallium (visceral organs, mantle, mantle cavity, and shell). During development, the displacement of anatomical components occurs during a process called “ontogenetic torsion.” Although ontogenetic torsion is central to theories of gastropod evolution, surprisingly few studies have documented actual tissue movements during the development of asymmetry in gastropods. We investigated the development of the mantle cavity and pleurovisceral nerve connective (visceral nerve loop) in the caenogastropods Amphissa columbiana and Euspira lewisii, because displacements of both of these structures are interpreted as major consequences of torsion. Scanning electron micrographs, histological sections, and immunofluorescence images showed that the developing vis‐ceropallium twists by 90° relative to the cephalopodium, the mantle cavity initially forms on the right side, and displacements of the visceral nerve loop become evident on the left side before the right side. A developmental stage in which the mantle cavity is confined to the right side has also been reported in members of the Vetigastropoda and Heterobranchia. We suggest that further comparative studies should test the hypothesis that early development throughout the Gastropoda converges on an embryonic organization in which the mantle cavity and anus are located laterally, despite clade‐specific differences in developmental patterns both before and after this stage.
The natural history, thermal physiology, and ecological impacts of intertidal mesopredators, Oedoparena spp. (Diptera: Dryomyzidae)
Authors: Harley Christopher D.G. , Lopez James P.
Published: August 2010

Abstract. The ecological roles of small (1–1000 mg) predators in benthic marine systems are poorly understood. We investigated the natural history and predatory impact of one group of such mesopredators—larvae of dipteran flies in the genus Oedoparena—which prey on intertidal barnacles. We 1) quantified patterns of larval Oedoparena distribution and abundance in the Northwest Straits of Washington State, USA, 2) determined larval physiological tolerance limits in the laboratory, and 3) conducted a manipulative field experiment to assess the role of microhabitat temperature on predation rates in Oedoparena. Members of Oedoparena in Washington are univoltine, with peak larval abundance in late spring and early summer. Infestation frequencies in the barnacles Balanus glandula and Chthamalus dalli were as high as 22% and 35%, respectively. In laboratory studies, larvae of O. glauca were able to tolerate temperatures up to 37°C; however, this temperature is often exceeded in high intertidal habitats. In a field manipulation using experimental shades, we demonstrate that the alleviation of physiological stress greatly increased the abundance of larvae of Oedoparena spp. As a result of increased larval densities under shades, adult B. glandula mortality increased from 5% to nearly 30%, and C. dalli mortality increased from less than 20% to over 60%. Because high intertidal barnacles serve as food and habitat for a diverse array of species, Oedoparena spp. have the potential to play a major role in structuring high intertidal communities, particularly in cooler microhabitats.
Colonization of fine particulate organic matter by invertebrates in a Central Florida stream
Authors: Brady Laura , Cowell Bruce C.
Published: August 2010

Abstract. Our study was conducted to determine whether small invertebrates of the shredder and collector feeding guilds would preferentially colonize fine particulate organic matter (FPOM) from fast‐decaying species of leaves in central Florida streams. Bags of FPOM (0.2–1 mm) generated from maple, elm, sweetgum, and water oak leaves, as well as artificial Sty‐rofoam, were suspended at two sites in Poley Creek, a 1st‐order sand‐bottomed stream. Three replicate bags of each type were collected from each site after 7, 14, and 28 d, and bacteria and invertebrates present were counted. Bacteria colonized maple and elm in significantly higher numbers than sweetgum, oak and Styrofoam. The amphipod Gammarus tigrinis accounted for 97% of all shredders in FPOM bags, and 63% of total invertebrates. Deposit‐feeding chi‐ronomids comprised 87% of collectors and 28% of total invertebrates. No other taxon comprised >2% of total invertebrates. Large numbers of invertebrates colonized in the first 7 d, but densities did not increase after Day 7. Both shredders and total invertebrates occurred in significantly greater densities on maple and elm than on sweetgum and oak. Amounts of FPOM remaining in bags after 28 d were significantly smaller for maple and elm (P<.05), suggesting that shredders were eating the FPOM. Collectors occurred in similar densities in all natural FPOM bags. Only a few individuals of either functional feeding group colonized Styrofoam bags, suggesting that FPOM was being colonized for its nutritional value rather than as a refuge from predation.
Biology and taxonomy of encrusting alcyoniid soft corals in the northeastern Pacific Ocean with descriptions of two new genera (Cnidaria, Anthozoa, Octocorallia)
Authors: McFadden Catherine S. , Hochberg F.G.
Published: August 2010

Abstract. In this paper we summarize current knowledge of the distribution, ecology, and reproductive biology of 4 encrusting species in the soft coral family Alcyoniidae, with descriptions of 2 new genera and 2 new species. The new genus Discophyton is erected for Alcyonium rudyi, a species common in the lower intertidal of exposed rocky headlands from Vancouver Island, British Columbia, Canada south to Point Lobos, California, USA. Discophyton rudyi n. gen. & n. comb. propagates extensively by clonal fission, giving rise to characteristic aggregations of small, regularly spaced, disc‐shaped colonies. We describe 2 new species and place them in a new genus, Thrombophyton. Thrombophyton coronatum n. gen. & n. sp. forms irregularly shaped, membranous colonies on rock surfaces; it occurs subtidally along the southern California coast from the Palos Verdes Peninsula to San Diego and on the California Islands. Thrombophyton trachydermum n. gen. & n. sp. has a similar, membranous growth form; it occurs both intertidally and subtidally on Vancouver Island, British Columbia, Canada, and in the San Juan Archipelago, Washington, and intertidally in central California, USA. Alcyonium pacificum, reported for the first time from North American waters, occurs in subtidal kelp beds around the Aleutian islands of Attu and Adak; its mushroom‐shaped colonies are raised above the substrate on a short stalk. D. rudyi, T. trachydermum, and A. pacificum are all gonochores that reproduce in late summer; in contrast, T. coronatum appears to reproduce in the spring. D. rudyi and T. coronatum brood larvae internally to a late planula stage. A key to species is presented for all shallow‐water soft corals known to occur in the northeastern Pacific Ocean.
Effects of variable water motion on regeneration of Hemipholis elongata (Echinodermata, Ophiuroidea)
Authors: McAlister Justin S. , Stancyk Stephen E.
Published: August 2010

Abstract. To determine whether increased water motion affects patterns of regeneration in the subtidal burrowing brittlestar Hemipholis elongata (phylum Echinodermata), individuals were subjected to laboratory‐controlled turbulence conditions. Half of each replicate aquarium experienced oscillatory (wave‐like) turbulence while the other half had no turbulence. Individual brittlestars from which arm‐tips had been removed were allowed to burrow and to regenerate. Regenerated arm‐tip length and weight were tested for differences between organisms in calm and turbulent conditions. Regenerated arm‐tip length differed significantly between control and treatment, but arm‐tip dry weight and skeleton/tissue ratio of regenerated arm‐tips did not. To quantify plasticity in the skeleton, 15 morphological measurements made on the proximal face of vertebral ossicles (using scanning electron microscopy) were integrated as an index of overall ossicle size. We found a significant difference in the overall size index of the vertebral ossicles between treatments, but could not determine which of the measurements contributed most to the difference. The results indicate that regeneration in H. elongata is a complex process that can be modified by environmental conditions.
Peptidergic and serotonergic immunoreactivity in the metamorphosing ophiopluteus of Ophiactis resiliens (Echinodermata, Ophiuroidea)
Authors: Cisternas Paula A. , Byrne Maria
Published: August 2010

Abstract. Antibodies against the echinoderm‐specific neuropeptide S1 and against 5HT were used to examine the fate of the larval nervous system during metamorphosis in the ophiuroid Ophiactis resiliens. In contrast to most echinoderms, the onset of peptidergic and serotonergic expression was delayed to the advanced ophiopluteus stage, in particular for 5HT. In advanced ophioplutei, peptidergic immunoreactivity was located in simple fibres associated with the ciliated bands, a stomach nerve ring, and cells along the antero‐lateral arms. 5HT immunoreactivity was concentrated in 2 oral ganglia in the adoral projections, located at the posterior rim of the mouth. Clusters of 5HT‐positive cells were also found along the antero‐lateral arms. The ophiopluteus lacked a serotonergic (or peptidergic) anterior ganglion. In echinoids, holothuroids, and crinoids, anterior ganglia are thought to have a sensory role in settlement and metamorphosis. Given that ophioplutei metamorphose in the plankton and that larval structures degenerate before settlement, the absence of apical ganglia correlates with the lack of a functional role for larval structures in substrate selection and settlement. Although most of the larval nervous system degenerated during metamorphosis, the adoral projections and associated oral ganglia appeared to be incorporated into the juvenile mouth, suggesting a potential role for larval neurons in contributing to oral neuronal structures in the adult. S1‐positive neurons and fibres in the rudiment developed de novo and in parallel with development of the epineural canal. This structure gives rise to the primordia of the adult circumoral nerve ring and radial nerves, indicating that differentiation of the adult nervous system begins in the early stages of metamorphosis.
The aboral ring and the development of early gonads in the echinoid Paracentrotus lividus (Echinodermata, Echinoidea)
Authors: Gosselin Pol , Spirlet Christine , Jangoux Michel
Published: August 2010

Abstract. The development of the genital apparatus is described for the echinoid Paracentrotus lividus. This apparatus derives from the aboral ring, an annular structure that includes an inconspicuous coelom and, in juveniles, the germinal rachis. The germinal epithelium grows out from the germinal rachis, and the gonadal wall and coelom in early (tubular) gonads share similarities with their equivalents in the aboral ring. The original germinal rachis regresses to form a genital cord one cell wide in late juveniles. A genital cord was observed in a few field‐collected adult individuals (>40 mm test diameter).
Ultrastructural reinvestigation of the trophosome in adults of Riftia pachyptila (Annelida, Siboglinidae)
Authors: Bright Monika , Sorgo Angelika
Published: August 2010

Abstract. The trophosome of adults of Riftia pachyptila (Vestimentifera) was reinvestigated using 3‐dimensional ultrastructural reconstruction and quantitative morphological analysis. The symbionts make up 24.1%, the symbiont‐containing cells (bacteriocytes) are 70.5% of the trophosome's volume. The trophosome is composed of lobules that have a central axial blood vessel surrounded by a myoepithelium containing bacteriocytes, in turn surrounded by an apolar tissue of bacteriocytes. Part of the splanchnic peritoneum lining the trunk coelom encases the bacteriocytes and forms a ramifying network of peripheral blood vessels. Based on the morphology and ultrastructure of the adult, we hypothesize a mesodermal rather than endodermal origin of trophosome and its constitute bacteriocytes. Some of the central bacteriocytes are part of the myoepithelium surrounding the axial blood vessel and act as stem cells for a proliferating tissue produced in the center and ultimately degraded at the periphery of each lobule. Similarly, the rod‐shaped symbionts in the center act as stem cells and exhibit a simple cell cycle. Differentiation into cocci takes place in the median and peripheral zone. Lysis of cocci occurs in the degenerative zone.
Robust support for tardigrade clades and their ages from three protein‐coding nuclear genes
Authors: Regier Jerome C. , Shultz Jeffrey W. , Kambic Robert E. , Nelson Diane R.
Published: August 2010

Abstract. Coding sequences (5,334 nt total) from elongation factor‐1α, elongation factor‐2, and the largest subunit of RNA polymerase II were determined for 6 species of Tardigrada, 2 of Arthropoda, and 2 of Onychophora. Parsimony and likelihood analyses of nucleotides and amino acids yielded strong support for Tardigrada and all internal nodes (i.e., 100% bootstrap support for Tardigrada, Eutardigrada, Parachela, Hypsibiidae, and Macrobiotidae). Results are in agreement with morphology and an earlier molecular study based on analysis of 18S ribosomal sequences. Divergence times have been estimated from amino acid sequence data using an empirical Bayesian statistical approach, which does not assume a strict molecular clock. Divergence time estimates are pre‐Vendian for Tardigrada/Arthropoda, Vendian or earlier for Eutardigrada/Heterotardigrada, Silurian to Ordovician for Parachela/Apochela, Permian to Carboniferous for Hypsibiidae and Macrobiotidae, and Mesozoic for Isohypsibius/Thulinia (both within Hypsibiidae) and Macrobiotus/Richtersius (both within Macrobiotidae).
From embryos to juveniles: morphogenesis in the spionid Boccardia proboscidea (Polychaeta)
Authors: Gibson Glenys D. , Smith Heidi L.
Published: August 2010

Abstract. The polychaete Boccardia proboscidea has poecilogonous development that includes the production of both planktotrophic and adelphophagic young. In this study, we use scanning electron microscopy to analyse external morphogenesis of planktotrophic offspring with emphasis on early embryos, morphogenesis during metamorphosis, and the dynamic nature of larval structures during early ontogeny. Larval growth involves addition of terminal chaetigers and formation of segment‐specific structures such as cilia and chaetae. Our observations reveal that most ciliary bands are reduced or incomplete relative to those found in larvae of other polychaete families. We describe a small metatroch (consisting of only a few trochoblasts) in early embryos, which has not previously been reported in the Spionidae. The presence of the metatroch does not imply a function in opposed‐band feeding, as a food groove intermediate between the prototroch and metatroch is lacking. A neurotroch, inconsistently reported in the Spionidae, is also present and terminates in a ciliated pit. Many larval structures (e.g., presumptive sensory organs) are short‐lived, implying a shift towards early functionality of adult traits in larvae. Metamorphosis is gradual and occurs over the latter half of the larval life. The reduction of larval structures, and early development of adult traits, suggests an overall shift in morphology facilitating settlement and juvenile development.
Spermatophores of thalassoid gastropods (Paludomidae) in Lake Tanganyika, East Africa, with a survey of their occurrence in Cerithioidea: functional and phylogenetic implications
Authors: Glaubrecht Matthias , Strong Ellen E.
Published: August 2010

Abstract. With few exceptions, spermatozoa‐encapsulating packages in molluscs are known mostly from cephalopods and pulmonate gastropods. Among non‐stylommatophoran gastropods, the marine Cerithioidea are second only to the Neritimorpha in the number of species that posess a spermatophore, but they have only rarely been found in freshwater taxa of this superfamily. We describe and compare here the sperm packages of 11 paludomid cerithioideans as part of an ongoing study on the evolution and systematics of the thalassoid (i.e., “marine‐like”) endemic species flock from Lake Tanganyika. Stereomicroscopic and SEM examination revealed unexpected complexity in shape and structure of spermatophores within paludomids. In addition, we present a survey of other Cerithioidea, which revealed that spermatophores are in general structurally simple and confirmed their presence in 12 marine species (five families) and 15 limnic species (four families), including those of 10 thalassoid species for which spermatophores are described herein. Based on histological sections of the male genital tract, we hypothesize that spermatophores are formed anteriorly, wholly or in part, by the so‐called spermatophore‐forming organ, and which is considered a synapomorphy of the Paludomidae. In addition, we briefly discuss functional aspects inferred from morphological study of the spermatophore‐forming organ, with possible implications for spermatozoan transfer and fertilization. Finally, we place the features of the spermatophores and the spermatophore‐forming organ in a phylogenetic framework of cerithioidean and paludomid systematics, which suggests that the spermatophore‐forming organ is a synapomorphy of Paludomidae, that a bifurcate spermatophore structure is plesiomorphic, and that the evolution of structurally complex, spiny spermatophores has occurred independently in disparate lineages within the thalassoid species flock.
Seasonal variation in the regulation of testosterone levels in the eastern mud snail (Ilyanassa obsoleta)
Authors: Gooding Meredith P. , LeBlanc Gerald A.
Published: August 2010

Abstract. Some gastropods appear to utilize a strategy for regulating testosterone levels that is atypical of such processes thus far identified in other metazoans. While most animals convert testosterone largely to polar derivatives that are readily eliminated from the organism, the mud snail Ilyanassa obsoleta converts testosterone to apolar testosterone‐fatty acid esters that are retained by the organism. In the present study, we tested the hypothesis that fatty acid esteri‐fication serves to store testosterone and that stored testosterone‐fatty acid ester pools vary through the reproductive cycle of the snail. This hypothesis was tested by 1) modulating total testosterone levels in individual snails and measuring the amount of the hormone stored as the fatty acid ester relative to the amount retained as free steroid and 2) measuring changes in esterified testosterone in a field population of snails during their reproductive cycle. Adult snails were experimentally manipulated to contain from ∼36–300% the level of total testosterone measured in unmanipulated individuals. The amount of testosterone‐fatty acid ester present in these organisms increased in direct proportion to the level of total testosterone, while, free testosterone levels remained relatively constant. These observations suggest that free testosterone levels are regulated in the snail by fatty acid esterification/de‐esterification processes. Among field sampled snails, testosterone existed predominantly in the free, non‐esterified form at the onset and end of the egg laying period. At other times, the majority of testosterone was sequestered as fatty acid esters. This study provides compelling evidence that free testosterone levels in the mud snail are regulated through fatty acid esterification/de‐esterification processes and this regulatory function contributes to seasonal fluctuations in free testosterone levels.
Biology and functional morphology of Kendrickiana gen. nov. veitchi (Bivalvia: Anomalodesmata: Clavagelloidea) from southern Australia
Authors: Morton Brian
Published: August 2010

Abstract. The largest extant species of the adventitious tube‐building Clavagelloidea has hitherto been placed in the genus Foegia (itself formerly a subgenus of Brechites), the type species of which is the Western Australian F. novaezelandiae (Bruguiére 1792). Following examinations of and comparison with F. novaezelandiae and the southern Australian F. veitchi, the latter is herein placed in its own new genus Kendrickiana.

Individuals of both F. novaezelandiae and K. veitchi are essentially amyarian in terms of adductor and pedal retractor muscles, but in the latter species the connection to the adventitious tube is located dorsally by an unique horseshoe‐shaped array of muscular papillae, which are inserted into holes in the tube. K. veitchi is different from other clavagelloids too in that the siphons are capable of only limited retraction into the tube. Their extension in K. veitchi is almost exclusively by hydraulic means because the complex internal siphonal muscles seen in other species of the Clavagelloidea, and which act antagonistically with extensive blood‐filled haemocoels, are vestigial. Kendrickiana can also be separated from Foegia in other anatomical respects. For example, members of the former have paired anterior suspensory muscles, and vestigial posterior pedal retractor muscles with pericardial proprioreceptors associated with them (as in Humphreyia and Dianadema), whereas the latter does not. Similarly, in Foegia there is a muscularized pedal disc, not found in Kendrickiana. Members of F. novaezelandiae are inhabitants of intertidal hypoxic muds, whereas those of K. veitchi apparently live exclusively in subtidal sea grass beds.
Feeding and anhydrobiosis in bdelloid rotifers: a preparatory study for an experiment aboard the International Space Station
Authors: Ricci Claudia , Caprioli Manuela , Santo Nadia
Published: August 2010

Abstract. Here we report the effect of food concentration on the recovery from anhydrobiosis of a bdelloid rotifer, Macrotrachela quadricornifera. Cohorts were either starved, or fed high or low concentrations of food, before being dried and their subsequent recovery rates determined. The rotifers starved for 3 d before anhydrobiosis recovered in significantly higher proportion, and those fed lower food concentration recovered better than those fed higher food concentration. In addition, starvation did not decrease the recovery of other bdelloid species (Philodina roseola and Adineta sp. 1) which were either fed or starved before anhydrobiosis. These results suggest that a successful recovery from anhydrobiosis is not dependent on prior resource level supplied to the bdelloids. However, the lack of resources might not be the only factor in a successful recovery from anhydrobiosis. Observations using scanning electron microscopy of fed individuals of M. quadricornifera entering anhydrobiosis showed that some food remained in the digestive tract. Thus, we propose that the negative effect of rich food may be due to a purely mechanical effect and may be interfering with a proper folding of the rotifer body at the onset of anhydrobiosis. This contribution results from studies carried out in preparation for biological experiments scheduled on the International Space Station (ISS).
Reproduction and development in a vermetid gastropod, Vermetus triquetrus
Authors: Calvo Marta , Templado José
Published: August 2010

Abstract. We report on a study of reproduction and development in the Mediterranean vermetid gastropod Vermetus triquetrus from the SE coast of Spain. It is a gonochoristic species. The egg capsules are attached to the inside of the shell, and females brood up to 22 capsules simultaneously (more often 4–10). The capsules hold 10–61 eggs or embryos; the uncleaved eggs are yolk‐rich, with a mean diameter of 377.3 μm. A distinct polar lobe occurs during the first cleavage, and blastomere D has discernible qualities after the 4‐cell stage. The formation of the mesentoblast 4d occurs at the transition from the 24‐cell stage to the 25‐cell stage. Gastrulation begins after the 36‐cell stage. Internal yolk is the major source of nutrition for the encapsulated embryos, but some nurse eggs (∼ 12%) and some sibling larvae are also ingested by the developing embryos. Hatching occurs during the swimming/crawling pediveliger stage, and metamorphosis is completed outside the capsules soon after hatching. Hence, larval development in Vermetus triquetrus is lecithotrophic intracapsular, with a short free‐swimming/crawling phase.
Primary homology assessment of structures in the female atrial system among species of the Polycystididae (Rhabditophora, Eukalyptorhynchia)
Authors: Artois Tom J. , Schockaert Ernest R.
Published: August 2010

Abstract. The female atrial system of members of the Polycystididae has been studied at the light microscopical level and compared among the constituent taxa. Based on the criteria of position and conjunction, hypotheses of homology are put forward and compared with the assessments of homology found in earlier literature. Contradictory terminology is synonymized and adapted to fit new findings that recognize homology among structures in different taxa. Based on differences in position and structure, 2 types of female duct are recognized: female duct type I and female duct type II. The term “female bursa” is restricted to a sperm resorbing organ at the proximal end of the female duct type I and/or at the end of a common oviduct. Some species have bundles of glands at the place where the oviduct(s) enter the female duct type I, which are considered homologous among these species. Different types of seminal receptacles are recognized. The term “insemination duct” is restricted to the ducts which in some species, in addition to the oviducts, connect the ovaries with the female duct type I. A single muscular duct, the common oviduct, connects the joined oviducts with the female duct type I in species of Duplacrorhynchus and is considered homologous with the similar duct present in some other species. A uterus is always present, entering the common genital atrium through its frontal wall, or entering a female duct type II. This morphological review of the female atrial system reveals a mosaic distribution of characters if applied to previous phylogenies that are based primarily on the male reproductive system.
First record of Polymerurus (Gastrotricha, Chaetonotida) from Australia with the description of a new species from Queensland and of cuticular ultrastructure in P. nodicaudus
Authors: Hochberg Rick
Published: August 2010

Abstract. Identification of specimens in the genus Polymerurus (Gastrotricha, Chaetonotida) is reported for the first time from Australia. The genus includes 3 species from a freshwater lake in southern Queensland. Two species, Polymerurus rhomboides and P. nodicaudus, are well‐known cosmopolitans: P. rhomboides is now known from every continent except Antarctica, and P. nodicaudus from all continents except Africa and Antarctica. An ultrastructural description of the cuticle in P. nodicaudus is provided and confirms earlier observations on the structure of spined scales in other species of Chaetonotida, suborder Paucitubulatina. The utility of cuticle ultrastructure is discussed in reference to the search for characters defining higher‐level taxa in the Paucitubulatina. A new species, P. andreae, also cohabits the Queensland lake and is distinguished by the following combination of characters: wide mouth ring; pharynx with terminal bulb; simple spineless scales on the dorsal, lateral, and ventrolateral body surfaces; and a column of ventral interciliary scales in rectangular, ovoid, and intermediate shapes.
Potential for paired vestibules in plutei (Echinodermata, Echinoidea)
Authors: Eaves Alexandra A.
Published: August 2010

Abstract. Echinoids are generally thought to develop only a single ectodermal invagination (V1), which expands into a vestibule and contributes to the formation of the juvenile rudiment on the left side of the larval body. However, in 2 echinoid species, Strongylocentrotus purpuratus and Dendraster excentricus, a second invagination (V2) was observed to form on the right side of the larval body exactly opposite V1. Formation of the invaginations was followed and characterized using light microscopy and antibodies directed against the S2amide echinoderm neuropeptide as a morphological tag. V2 consistently formed later than V1, and appeared capable of contributing to the formation of a second rudiment when it received the appropriate mesodermal influence from contact with a hydrocoel. Otherwise, in both species, V2 formed a skeletal element that has not been previously described in this location. Because of the location, shape, and timing of its formation, V2, like V1, appears to have the innate ability of the larval ectoderm to contribute to juvenile rudiment formation.
Gonadotropin‐releasing hormone‐like immunoreactivity in the planarian Bdelloura candida (Platyhelminthes, Tricladida)
Authors: Anctil Michel , Tekaya Saïda
Published: August 2010

Abstract. Although peptides similar to gonadotropin‐releasing hormone (GnRH) peptides have been reported in various taxa of invertebrates, no such evidence has yet been identified for platyhelminths. Antibodies raised against mammalian GnRH were used to investigate the distribution of GnRH immunoreactivity in specimens of the triclad turbellarian Bdelloura candida (Maricola, Bdellouridae). While no GnRH immunoreactivity was detected in the brain and nerve cords, both the putative subepidermal and submuscular nerve plexuses appeared to be immunoreactive. GnRH immunoreactivity was also present in epidermal mucous cells, in parenchymal cells, including cells surrounding the branches of the intestine, in putative neuroendocrine cells associated with the testes, and in the vitellogenic gland cells associated with the oviduct. These observations suggest that the GnRH‐like material found in specimens of B. candida may be involved in a variety of functions, including a possible pheromone‐like role for mucous cells and the control of specific reproductive activities.