It has been suggested by Pettibone (1953) and Lwebuga-Musaka (1970) that the elytra of scaleworms may function in respiration, not as the sites of gaseous exchange, but rather the means by which respiratory water currents were created over the dorsum. A role in sensory perception was also postulated (Pettibone, 1953). However, no detailed morphological study accompanied this work. To date the scales of only a few polychaete species have been examined ultrastructurally, and these studies have focused mostly on cuticular features (Anton-Erxleben, 1977, 1981a, b). Considerable attention has been focused on the bioluminescent properties of the elytra of the scaleworm, Harmothoe lunulata (Delle Chiaje) (see Bassot, 1979; Nicholas et al. 1981, 1982). Other morphological features of Pholoe minuta studied at the ultrastructural level include gametogenic (Heffernan & Keegan, 1988a) and larval (Heffernan & Keegan, 1988b) stages as well as the digestive tract (Heffernan, 1988). There are several reports on the ultrastructure of polychaete gills (Storch & Welsch, 1972; Spies, 1973; Storch & Alberti, 1978; Menendez et al., 1984; Storch & Gaill, 1986). These works have recently been reviewed by Gardiner (1988). This study describes the fine structure of the scales of Pholoe minuta and the features illustrated here are in agreement with a role in respiration and sensory perception.

Moonshine worms are a popular bait species used for fishing. The taxon was not detected during surveys of the macrobenthos conducted in Knysna in the 1940s and 1990s, and was first reported as a harvested bait species in the mid-2000s, suggesting that it appeared for the first time in the estuary in the last three decades. A previous molecular analysis identified the worms as Diopatra aciculata, a species first described from Australia. This study provides an updated detailed morphological description of D. aciculata in South Africa to facilitate future identifications and also investigates the species' distribution and population size in the Knysna Estuary. Specimens were examined by scanning electron, stereo- and compound microscopes. Diopatra aciculata has tubes that protrude from the sediment in sandy areas, often decorated with algae and shell fragments; a large body size, up to 600 mm long and 11.5 mm wide. It has 10–18 rings on ceratophores; 5–10 teeth on pectinate chaetae; uni- and bidentate pseudo-compound falcigers and dorsal cirri approximately as long as branchiae. Diopatra aciculata was detected up to 12 km from the mouth of the Knysna Estuary with densities measured at 18 sampled sites. Statistical analysis retrieved high and low density groups that were significantly different from one another (Kruskal-Wallis H(14, 800) = 376.55; P = 0.01), but distribution of high density sites was patchy. We estimate that the population comprises 20–24 million individuals. Given the size of individual worms and the population estimate, this species can be expected to have significant ecological impacts in the estuary.

INTRODUCTION

Wild-caught squids have seldom survived for very long in laboratory aquaria. Tardent (1962) maintained Loligo vulgaris Lamarck, 1789 for a maximum of 60 days. Choe & Oshima (1963), Choe (1966) and LaRoe (1971) reared squids of the genus Sepioteuthis from eggs to adult size. Between 1975 and 1982 several successful attempts to maintain Loliginidae (e.g. Matsumoto, 1976; Hanlon, Hixon & Hulet, 1978, 1983; Yang et al. 1980, 1983) and Ommastrephidae (Flores et al. 1976; Flores, Igarashi & Mikami, 1977; O'Dor, Durward & Balch, 1977) were made. But to date only ten squid species have been maintained for more than forty days (review: Yang et al. 1980; Boletzky & Hanlon, 1983). Loligo opalescens Berry, 1911 holds the record for longevity in captivity at 233 days from egg to adult (Yang et al., 1983).

The escal light glands of some deep sea anglerfishes of the genus Melanocetus were examined by light and electron microscopy. Sections of a larval Melanocetus sp. showed that the gland originates from a solid, branched ingrowth of epidermal cells from the distal surface of the bulb-shaped esca.

The light gland of metamorphosed specimens of M. murrayi and M. johnsoni was found to be constructed in the same way as that of most other ceratioids, i.e. as a branched tubular gland enclosed by a cup-shaped reflector; the radial tubules of the gland open into a central escal cavity, from which a duct leads to an epithelium-lined space, the vestibule, lying above the gland. A duct from the vestibule opens on the upper-caudal surface of the esca.

In the smaller of two specimens of M. murrayi, the epithelium lining the escal cavity and the glandular tubules is of a uniform thickness and structure, consisting of flattened basal cells, cells extending to the lumen, and goblet cells. No bacteria were found anywhere within the esca. The reflector enclosing the gland contains only a few scattered crystals.

In the larger specimen of M. murrayi the distal (terminal) portions of the glandular tubules have tall epithelial cells, while their wide proximal parts and the central escal cavity are lined with a flattened epithelium; goblet cells are absent. Many glandular cells have processes projecting into the lumina. All glandular lumina and the central escal cavity contain numerous rod-shaped bacteria and apparently isolated anucleate cytoplasmic profiles. The reflector is thick and well-developed; each cell contains several staggered layers of crystals.

The chronometric mechanism of compensation for the apparent movement of the sun was investigated in adult individuals of Talitrus saltator (Amphipoda: Talitridae) from Mediterranean latitudes. The individuals were subjected to alteration of the duration of illumination, while its phase remained the same as in nature. A close relation between photoperiod length and the chronometric mechanism of the sun compass was observed, which could explain the seasonal adaptation of the sun compass. We propose an alternative to the classic hypothesis of daily differential compensation for the apparent movement of the sun.

Despite Holothuria scabra's wide distribution and status as one of the best candidates for sustaining the development of tropical sea cucumber aquaculture, very few data are available regarding the organic fraction it assimilates in practice. In this paper we report experimental results where H. scabra's diet was supplemented with various 15N-labelled organic fractions of sediment. We used juveniles weighing between 38 and 88 mg at the beginning of the experiment (~2 cm long and 30 days old). Their growth was measured over a four-week period and their 15N composition recorded. The results showed that H. scabra juveniles assimilated all added organic components from both dissolved and particulate fractions of the sediment. Bacteria seem to be an important food source for juveniles, even more so than microphytobenthos (diatoms).

In a previous paper in this Journal (Vol. XIV, p. 967) a theory of the control of sex in the oyster by rhythmical changes in the general metabolism has been outlined and discussed briefly with the information at present available. As the connexion between metabolism and sex has long been regarded as important, and by some, e.g. Geoffrey Smith (1913), as all-important, this relation may be considered briefly with regard to modern views on the physiology of sex.

Using laboratory experiments, this study examines the nature of the grazing relationship between the amphipod Hyale hirtipalma (Dana) and the red algae Iridaea spp., and the potential effects of grazing on the release and dispersal of algal spores. The results indicate that Hyale hirtipalma has a significant food preference for the cystocarpic stage of Iridaea laminarioides Bory when compared with consumption of Ulva rigida C. Ag. Hyale hirtipalma also shows a significantly greater food preference for cystocarpic tissues of Iridaea laminarioides and I. ciliata Kützing than for other karyological stages of these algae. By consuming the cystocarpic tissues, H. hirtipalma significantly increases the number of carpospores which are released and which settle at all measured distances from the mature cystocarpic I. laminarioides frond where measurements were taken. This evidence, together with information previously published, indicates that several Hyale species show similar food preferences towards the cystocarpic stage of Iridaea spp., and probably have the same ecological role as spore releasers and dispersal agents.

The lateral-line system of water-living lower vertebrates is provided with mechanoreceptors enabling the animals to detect water displacements, either caused by moving objects such as prey, predators or neighbours in a school or by deformations of pressure waves from the swimming animal caused by other objects. Cyclostomes, some fish and water–living amphibians have their lateral-line organs situated superficially in the epidermis as free neuromasts, while most fish besides these neuromasts possess a canal system in the dermis. Ordinarily the lateral line canal system consists of a few canals on the sides of the head and a trunk canal. In herring, however, the canal system is confined to the head and opercule. It forms a very richly branched system with numerous pores which connect the canal fluid with the surrounding sea water.

Plymouth scad (horse-mackerel) Trachurus trachurus (L.) are known to harbour three species of monogenean trematode gill parasites, of which two belong to the Gastrocotylidae and one to the Microcotylidae. The oncomiracidia (= newly hatched larvae) of these parasites have already been described (Llewellyn, 1957a), but nothing is known of the developmental stages intervening between the oncomiracidia and the adults. Bychowsky (1957) has stated that some information is available about the larval development of 13 monogenean families, leaving 15 families, including the Gastrocotylidae, about whose larval development nothing is known. The ontogenetic development of the Gastrocotylidae is of especial interest since the oncomiracidia are bilaterally symmetrical, but the adults invariably show an extreme degree of asymmetry.

The New Zealand cockle Austrovenus stutchburyi is often found stranded on the sediment surface due to infections by echinostome trematodes. High densities of heavily-infected cockles on the sediment surface affect near-seabed hydrodynamics and sedimentation and, in turn, benthic animal community structure and diversity. In a six-month field experiment on an intertidal sandflat we manipulated the density of cockle mimics on the sediment surface, and here we show that their presence had two significant impacts on community functioning. First, the benthic primary production (in terms of chlorophyll-a content) was reduced by 8–22%. Second, their presence significantly boosted (up to 5-fold) the secondary production (in terms of biomass) of Coelenterata, Nemertea, small polychaetes, small bivalves and the gastropod Diloma subrostrata. The results hence provide a field experimental example of a parasite-mediated link between diversity and productivity.

A new species of Polygordiidae, Polygordius jouinae sp. nov., along with its distribution, habitat, and reproduction is described. Polygordius jouinae sp. nov., the first North American Polygordius, is a dominant member of macrofaunal communities on the inner continental shelf, and in bays and harbours from Massachusetts to southern New Jersey. It is distinguished from most other Polygordius species by its non-inflated, heavily ciliated pygidium, absence of pygidial glands, and a conical (rather than rounded) prostomium. The 18S SSU rDNA from P. jouinae sp. nov. was sequenced and represents the first named Polygordius species with a DNA reference in GenBank. Spearman rank correlation of sediment grain size with density of P. jouinae sp. nov. at a New Jersey site showed that density was significantly (P<0.05; N=92) positively correlated with the proportion of medium to very coarse sand and negatively correlated with the fine sand fractions. Ecologically, P. jouinae sp. nov. is an important macrofaunal species given its widespread distribution and its fidelity for coarse sand habitats. Thus, its relative abundance may be useful as an indicator of changing sedimentary conditions.

Although the anatomy of the coelacanth muscles has been examined very thoroughly, their protein composition has, until recently, not been investigated. Thanks, however, to the 1972 British–French–American expedition to the Comores, frozen material has been made available and some results on myoglobin and four glycolytic enzymes have already been published. We have carried out a comparison of the sarcoplasmic proteins of red and white muscle by starch-gel electrophoresis. The ninhydrin-positive dialysable constituents and the myofibrillar proteins of white muscle have also been examined.

A few puzzling results obtained with the white muscle extracts have been related to the occurrence of o.1 M ammonia, due presumably to the splitting of urea by a bacterial urease, and to an alteration of the active thiol groups of GAPDH and PK. If due account is taken of these unusual post-mortem changes, the extractability of the proteins and their properties are strikingly similar to those of teleosteans. The comparison of the sarcoplasmic proteins of white and red muscle by starch-gel electrophoresis revealed also that the differentiation observed in the coelacanth was similar to that occurring in the carp. A study of the low-molecular-weight proteins, or parvalbumins, of white muscle and of the myofibrillar proteins also shows the expected differences between the two muscle types.

The only abnormal features observed in this study were the high concentration of parvalbumins, 1.5–2 times that found in other species examined, and the occurrence of an unusual globulin fraction which was easily extracted at ionic strength 0.5 and insoluble at ionic strength 0.35 and neutral pH.

From observations in the aquarium and by a morphological study of the feeding tentacles it is concluded that Leptopentacta elongata is not, as is commonly supposed, a mucus suspension feeder, but feeds on deposited material by mechanical entrapment with the aid of sticky papillae on the tentacle buds.

The Eupsammiidé are one of the most interesting families of the Madjeporaria. They have an exceptionally wide range of distribution, being found alike in temperate and tropical seas. In the latter they were probably originally confined to deep water, where the majority of them still occur, but they have extended their vertical range (Yonge, 1930) and various species are now found on many of the coral reefs in the Indo-Pacific region. Thus Dendrophyllia ramea occurs in moderately deep water in the Mediterranean and has also been found in the English Channel off RoscofE (Lacaze-Duthiers, 1897), while other species of this genus are common near the surface on many of the Pacific coral reefs, the bright orange-coloured polyps of Dendrophyllia manni being, for example, very conspicuous on the fringing reefs at Kaneohe Bay on the Island of Oahu, Hawaii (Edmondson, 1929; Yonge, 1930).

Simnia patula (Pennant)=0vula is common feeding on Ahyoniwm digitatum and on Eunicella verrucosa, trawled in Plymouth waters. Mr. E. A. Todd records in the 1904 Plymouth Fauna List (Plymouth Marine Invertebrate Fauna, Journal of the Marine Biological Association, VII, 1904), which is quoted in the new fauna list (1931, Marine Biological Association), that “spawn probably belonging to this species has been found in April, June-July.” This spawn is also well known to other members of the staff of the Laboratory and it is often found with the Simnia itself. It is now quite certain that it is the spawn of this mollusc, for it has been deposited in a plunger-jar on the glass and on Alcyonium (Jan. 19/20, 1932), and hatched out Feb. 21/22, 1932; it has been hatched out in the Laboratory, the larvae distinguished in the plankton and reared until the crawling stage in a plunger-jar; and young stages which bridge the gulf from larva to adult have also been found. The adults will live for months in a plunger-jar feeding voraciously on Alcyonium. The life-history is described here for the first time. It is very interesting because it is quite unlike that of Trivia euro-pea recently described (Lebour, 1931b), although the two are placed in the same family. Trivia bites holes in compound ascidians and lays its eggs in vase-shaped capsules embedded up to the neck in the ascidian, and these hatch out into larvae having accessory shells rather like those of Lamellaria but with distinct differences. Simnia lays its eggs in a single layer of capsules, spreading over the Alcyonium for an inch or more in an irregular roundish mass (Text-figure 1).

This is the first comprehensive research study on the parasites of Mytilus galloprovincialis collected from the Sinop coasts of the Black Sea and their relationships with several environmental and biotic factors. A total of 1740 mussels were collected monthly at three sampling localities representing different ecosystems in the period between August 2012 and July 2013 and examined for parasites. Identified parasites were Nematopsis legeri, Peniculistoma mytili, Urastoma cyprinae, Parvatrema duboisi and Polydora ciliata. Infection prevalence (%), mean intensity and mean abundance values of each parasite species were calculated according to season, sampling localities and length classes of mussel. Nematopsis legeri was the most prevalent species (32.5%), followed by Pe. mytili (6.70%), U. cyprinae (6.30%), Pa. duboisi (4.50%) and Po. ciliata (2.20%). Nematopsis legeri and Parvatrema duboisi had their highest infection prevalence and intensity values in sampling locality III where secondary hosts present to complete their life cycle and larger sized mussels had higher parasite loads. Statistically significant differences were determined in the prevalence of infection and intensity values among seasons, length classes of mussel and sampling localities of each parasite species. The present study provided valuable information on mussel parasites and their relationships with host length, seasons and ecology.

The salp Thalia rhomboides is distributed in the shallow depths during the day, and is thus at increased risk of predation by visual predators and from the damaging effects of ultraviolet (UV) radiation compared with species distributed in deeper layers in the daytime. The integument (tunic) of T. rhomboides may have adaptive optical properties, but the absorption spectra of the unfixed tunic demonstrate that the tunic transmits UV as well as visible light, indicating that the tunic is not an effective barrier against UV radiation. Ultrastructural observation revealed that the surface of the tunic cuticle is covered in a nipple array consisting of hemispherical protuberances approximately 40 and 30 nm in diameter in solitary and aggregate zooids, respectively. Simulation of light reflection of a nipple array using rigorous coupled wave analysis (RCWA) indicated that the reflection is slightly lower for the nipple array than for a flat surface at high angles of incidence (θ > 80°). This result supports the idea that the nipple array serves to make the salp less visible. The simulation also indicated that the height and distribution of the salp nipple array do not have an optimal structure for causing an antireflection effect. A mechanical restriction might exist on the structures, and the nipple array could also serve another function. The size and distribution of nipples may be controlled by the need to meet the complex requirements of multiple essential functions.

Although in vivo and in vitro approaches appear to be very different, they are related and complementary techniques and both are essential for the investigation of diverse biological topics. The employment of both techniques was considered particularly appropriate to investigate the role of 17β-oestradiol and testosterone in echinoid reproductive biology. The relationship between sex-steroids and echinoid reproduction has not been clearly determined yet, due to the highly variable and sometimes contrasting results obtained from steroid administration experiments. These might be due to the activation of protective metabolic mechanisms that can prevent the exogenous molecules from exerting their biological functions, as observed in our previous research. To clarify these aspects, in the present study we explored sex-steroid involvement in the reproduction of the sea urchin Paracentrotus lividus, employing both in vivo and in vitro approaches: (1) an experiment involving hormone dietary administration was performed and different reproductive parameters were deeply analysed; (2) ovarian cells were cultured in the presence of the same steroids and morphological and biochemical analyses were carried out. According to our results, sex-steroids appear not to be involved in sea urchin gonad development and gamete maturation, as neither in vivo administration nor in vitro exposure influenced gonad and gamete growth. In addition, in vitro hormonal treatment did not affect sea urchin Major Yolk Protein content. Overall, the present work complements our previous research providing information on sex-steroid involvement in echinoid reproduction and illustrates new methodological approaches that will be useful for future research on invertebrate biology and physiology.

The Molpadiida is an order of sea cucumbers identified by their stout body, the posterior region narrowing to simulate a tail and the absence of tubefeet. Typically they inhabit muddy environments from shallow water to abyssal depths. In the past the great variability in the taxonomic characters of this order has led to the formation of many genera and species (Heding, 1931, 1935), but more recently it has become apparent that many diagnostic characters change markedly during the life history of these holothurians and as a result fewer species are now recognised (Deichmann, 1940; Pawson, 1977). In a revision of the Atlantic molpadiids Deichmann (1940) recorded just three species from the north-east Atlantic (Molpadia blakei, M. musculus and Hedingia albicans) with a further three species from the Arctic Ocean and Norwegian Sea (M. arctica, M. borealis and Eupyrgus scaber). To these Sibuet (1974) added the new genus and species Cherbonniera utriculus found in the Bay of Biscay.