Terrestrial nemerteans thirty years on

The present paper records changes in the reported distribution and abundance of terrestrial nemerteans during the last 30 years. New records are reported from the Isles of Scilly, Bermuda and New Zealand of species previously only known elsewhere. Human activity, especially the increased importation and exportation of plants between countries, has probably led to terrestrial nemerteans, as well as other organisms, becoming introduced into many new localities. However, the conservation outlook is not hopeful because of a global loss of appropriate habitat, particularly forests. Today three species (Geonemertes rodericana Gulliver, 1879, Pantinonemertes agricola Willemoes-Suhm, 1874 and Antiponemertes allisonae Moore, 1973) are feared to be extinct, and none of the extant species seem to be as abundant as they once were. Behavioural changes in Antiponemertes pantini (Southgate, 1954) under arid conditions may be associated with heavy gregarine infestations.     

Biochemical sex dimorphism in Lineus lacteus

Egg-specific and sperm-specific proteins fromLineus lacteus females and males were investigated byanalytical electrophoreses. These major sex-specificproteins define the sexual dimorphism of biochemicalmetabolism and are useful for studying vitellogenesisand spermatogenesis. The major yolk proteins in theeggs of the nemertean, Lineus lacteus, wereidentified by gradient gel electrophoresis. The 2vitellin proteins were designated vitellin V1 (460 kDa) andvitellin V2 (260 kDa). The vitellins wereidentified as lipoglycoproteins by selective staining.Three major vitellin subunits (75, 41 and 40 kDa) werefound in oocytes of L. lacteus byelectrophoresis under denaturing conditions(SDS-PAGE). Polyclonal antibodies were raised to eachvitellin subunit. The binding of these rabbitantibodies to vitellins V1 and V2 showed that vitellinV1 contained a single major 75 kDa polypeptide, whilevitellin V2 had two major polypeptides (41 and 40 kDa).Five male-specific proteins (52, 50, 41, 35 and 32 kDa) wereidentified in the sperm of Lineuslacteus by gradient gel electrophoresis. Four lowmolecular weight proteins (18–13 kDa) can also be usedas molecular markers of male sexual maturation. Theseproteins were nucleosomal core histones. The chromatinof L. lacteus sperm contained onlyhistones as no protamines or protamine-like proteinswere detected. But the sperm nucleosomal protein maynot be entirely somatic-histones, as a sperm-specifichistone (Sp H) was also found.     

Muscle fibers in the central nervous system of nemerteans: Spatial organization and functional role

The system of muscle fibers associated with the brain and lateral nerve cords is present in all major groups of enoplan nemerteans. Unfortunately, very little is known about the functional role and spatial arrangement of these muscles of the central nervous system. This article examines the architecture of the musculature of the central nervous system in two species of monostiliferous nemerteans (Emplectonema gracile and Tetrastemma cf. candidum) using phalloidin staining and confocal microscopy. The article also briefly discusses the body‐wall musculature and the muscles of the cephalic region. In both species, the lateral nerve cords possess two pairs of cardinal muscles that run the length of the nerve cords and pass through the ventral cerebral ganglia. A system of peripheral muscles forms a meshwork around the lateral nerve cords in E. gracile. The actin‐rich processes that ramify within the nerve cords in E. gracile (transverse fibers) might represent a separate population of glia‐like cells or sarcoplasmic projections of the peripheral muscles of the central nervous system. The lateral nerve cords in T. cf. candidum lack peripheral muscles but have muscles similar in their position and orientation to the transverse fibers. The musculature of the central nervous system is hypothesized to function as a support system for the lateral nerve cords and brain, preventing rupturing and herniation of the nervous tissue during locomotion. The occurrence of muscles of the central nervous system in nemerteans and other groups and their possible relevance in taxonomy are discussed. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Nemerteans of the genus <Emphasis Type="Italic">Ototyphlonemertes</Emphasis> (Enopla: Ototyphlonemertidae) from Van Phong Bay (South Vietnam)

Two species of the interstitial nemerteans from the intertidal zone of Van Phong Bay (southern Vietnam) are described. By the structure of the proboscis and statocysts, the nemertean Ototyphlonemertes ani sp. n. can be referred to the species group “Lactea” (sensu Envall, Norenburg, 2001), but it differs from other species of this group by the presence of cerebral organs and caudal cirri. The second species new for the region is very similar to O. martynovi, but differs from it in having 2 to 3 cephalic cirri in group C (instead of 4 to 6 cirri found in O. martynovi).     

Nemerteans of the Great Barrier Reef 4. Anopla Heteronemertea (Valenciniidae)

A new valenciniid heteronemertean, Valencinina albula , gen. et sp. nov. from the Great Barrier Reef province of Australia, is described and illustrated. This is the first record of a valenciniid from Australasian waters.     

Heavy metals in marine nemerteans

Accumulation of lead, cadmium and zinc by two species of eulittoral nemerteans, Lineus ruber (Heteronemertea) and Amphiporus lactifloreus (Hoplonemertea) varies both seasonally and interspecifically.The proportion of surface mucus-adsorbed metals can be quantified by immersion of experimental animals in iminodiacetic acid (IDA) coupled to Epoxy-activated Sepharose 6B (40–100 µm diameter). In this way surface associated adsorbed metals can be differentiated from absorbed metals present in the body tissues.Applications of the above technique and proposed future work on heavy metals in nemerteans are discussed.     

Notes on gamete production in Lanice conchilega (Annelida,Polychaeta, Terebellidae)

Summary

Male and female gametogenesis in Lanice conchilega are described and illustrated as seen by light microscopy. There is no evidence for size-selectivity in the uptake of male gametes by the hypertrophied reproductive nephromixia, since undissociated motile sperm platelets as well as spermatozoa appear to be taken up by the genital funnels, and such funnels show no sexual dimorphism. Maturation of the coelomic oocytes is marked by a change in shape and the appearance of a surface reticulum of ridges.     

Ultrastructure of larval epidermis of the nemertean <Emphasis Type="Italic">Quasitetrastemma stimpsoni</Emphasis> (Chernyshev, 1992) (Hoplonemertea)

The ultrastructure of the epidermis of free-swimming larvae of the nemertean Quasitetrastemma stimpsoni was examined. At about 24 hours after hatching, the provisional epithelium of larva is 28–35 μm thick and consists of two layers of cells—peripheral and basal. The peripheral layer consists of multiciliated cells and two kinds of gland cells. The “basal cup” zone is formed from the vacuoles of basal cells. At about 50 hours after hatching, the definitive epithelium is 14–17 μm thick and exhibits a typical hoplonemertean structure. However, it has numerous yolk vesicles, few processes of granular basal cells, and a weakly developed dermis. Thus, the replacement of the provisional epithelium by the definitive one occurs in Q. stimpsoni at an earlier stage, compared to the hidden larva of Tetrastemma candidum.     

Classification of the family Plectonemertidae (Nemertea): a phenetic comparison

A phenetic classification based on overall morphological similarity between the species in the family Plectonemertidae (genera Plectonemertes, Campbellonemertes, Potamonemertes, Leptonemertes, Katechonemertes, Argonemertes, Anliponemertes, and Acteonemertes) was undertaken and the result compared with a cladistic and an evolutionary classification. Similarity between species was computed by Gower's general coefficient of similarity and various techniques were used to find patterns in the similarity matrix: single-linkage, average-linkage, and complete-linkage clustering, together with principal coordinate analysis. Although the explicit aim of phenetics is not to estimate the phylogeny, the classification based on overall similarity still portrays phylogeny better than an intuitive assessment of morphological similarity, as judged by the cladistic analysis. The classification does not support the previously proposed hypothesis that the two freshwater genera Campbellonemertes and Potamonemertes have descended from a terrestrial ancestor.     

Effects on the ecological integrity of a soft-bottom habitat from a trawling disturbance

The effects of trawling disturbance on a soft-sediment system were investigated with a manipulative field experiment in an area that had been closed to shrimp trawling activities for 20 years. The area was also chosen for its weak natural physical agents i.e. no scouring of sediments by storm events or tidal flow, allowing a quantitative assessment of the effects of trawling on the benthic fauna and geochemical properties of the soft substrate.The study examined the ambient spatial and temporal patterns of sedimentological variables and benthic species abundances over a time interval of 16 months for both the reference and the trawl stations before dragging the trawling gear over the predetermined trawl sites. Shifts in the patterns of the benthic infauna and geochemical variables were identified by the post-trawl samples that were collected at both the reference and trawl stations over the next 6 months. Post-trawl changes in the bottom topography did not translate into changes in the vertical profile of the sedimentological variables. Chlorophyll a content of the trawled surface sediments was significantly elevated immediately after the trawling event in comparison to the reference concentrations.Immediately after the trawling disturbance, numbers of species, species abundance and diversity decreased in the trawled area in comparison to the reference area. Sensitive species were found to be the bivalves; Ennucula annulata, Hampson, Thyasira flexuosa (Montagu), and Yoldia sapotilla (Gould), and polychaetes; Chaetozonecf.setosa Malmgren, Anobothrus gracilis(Malmgren), Euchone incolor Hartman, and Terebellides atlantis Williams. In contrast, the carnivorous nemertea, Cerebratulus lacteus Verrill, was the resistant species to field manipulations on account of its predatory behavior; highly effective in seeking out freshly dead (dying) organisms and its active migration. Multivariate analysis confirmed the changes in the trawled community structure immediately following the trawling event and differences in the recovery patterns 6 months thereafter. Although the trawling disturbance was one of low frequency and intensity compared to commercial operations, the biological variables studied indicated that successional processes in this soft-bottom community were altered, at least for a short period, in response to the trawling disturbance.