Four species of gymnamoebae isolated from a sandy shore were subjected to hydrodynamic disturbance within microcosms. Increasing the level of disturbance increased the generation times of all four isolates. Generation times of a small Platyamoeba sp. and a limax amoeba were least affected by increasing disturbance. The greatest increase in generation times was observed in populations of two large (>15 μm) Mayorella sp. and Vannella sp. This study shows that hydrodynamic disturbance may be an important community structuring force within natural marine amoebae communities.

It may be useful to put on record the following notes of renewed attempts to solve the difficult problem of rearing fish larvæ.

Many morphological, chemical, and behavioural characteristics of echinoderms have been implicated as defences against ultraviolet light, though no studies have investigated whether adult echinoderms are damaged by this form of radiation. This study tests whether the brittlestar Ophioderma brevispinum (Ophiuroidea: Echinodermata) is damaged by solar ultraviolet radiation. Specimens of O. brevispinum were exposed to sunlight at a field station on the North Carolina coast. After 4 d of exposure, 12 out of 13 animals were dead and the remaining animal was moderately damaged. The animals in the control treatment, protected by a UV-opaque filter, suffered almost no damage.

Characteristics of the second gnathopod are traditionally used to distinguish between species of caprellid amphipods. However, these distinctions are often subjective and can be variable within a species. Geometric morphometrics were used to quantitatively assess shape variation of the second gnathopod propodus of three species of caprellids in North America, including the non-native Caprella mutica. Gnathopod shapes of C. mutica specimens from different latitudes revealed distinct morphologies; the factors responsible for the shape variations are unknown. Allometric change of propodus shape was observed in C. mutica. Larger individuals showed a wide array of possible propodus morphologies. Despite this variability, there were clear differences between large specimens of C. mutica and two species native to North America: C. alaskana and C. kennerlyi. The use of geometric morphometrics and the thin-plate spline method can serve to both complement descriptions using traditional keys and aid in identification of non-native species in novel geographical regions.

Population structure of the short-finned squid Illex illecebrosus (Ommastrephidae) was studied on the Nova Scotian shelf between July–September 1984. It was characterized by a prevalence of winter-hatched squid in summer–early autumn, their short (three months of the summer) occurrence on the shelf, and a predominance of females in sex ratios during the feeding period. Ages of squid were estimated by statolith increment counts and ranged from 128 to 201 d. Growth in length was described by linear model with daily growth rates of 0.99 mm/d−1. Adding the length-at-age data from juveniles caught in 1979 to the 1984 data set enabled to construct an ontogenetic growth curve for the winter-hatched squid which was best approximated by the Gompertz growth function.

Typically, adult digenetic trematodes are found as parasites of vertebrates, but Freeman & Llewellyn (1958) described sexually mature, unencysted digeneans from the kidney region of the mud-dwelling lamellibranch Scrobicularia plana (da Costa) collected from Chalkwell, near Southend-on-Sea, in the Thames estuary. The trematodes were identified as belonging to the genus Proctoeces (Odhner, 1911) and of the family Fellodistomatidae, subfamily Haplocladinae (Odhner, 1911). Freeman and Llewellyn considered that the features exhibited by the specimens were consistent with the description for Proctoeces subtenuis (Linton, 1907) Hanson, 1950, a species which had been recorded up until that date only as a parasite of the hind gut of marine teleosts belonging to the families Labridae and Sparidae from the Red Sea, New Zealand and the eastern seaboard of America.

The armoured planktonic dinoflagellates present at a site adjacent to a floating fish-farm in Loch Eriboll, North Scotland, were studied by surface net-sampling, mainly at two-weekly intervals, over a period of four years 1990–1993. A total of 62 species was recorded. Some dinoflagellates were present at all times of the year but they reached their lowest numbers in May, during the spring diatom bloom, and their highest numbers in mid-summer. There was usually a seasonal pattern in which the most abundant dinoflagellate during the early summer was the heterotrophic species Protoperidinium ovatum, and this was followed in the later summer by the autotroph Ceratium fusus. In 1993 the pattern was rather different, with Gonyaulax species abundant in June and, later in the year, both Protoperidinium cerasus and P. excentricum having periods of abundance. Potential toxin-producing dinoflagellates, Alexandrium tamarense (PSP) and Dinophysis acuminata (DSP), were found in small numbers.

The pearl oyster, Pinctada radiata, shows great variation in shell morphology throughout its distribution. This variation can be related to phenotypic plasticity, genetic variability or a combination of both. Using geometric morphometric and microsatellite DNA analyses, two morphologically distinct populations of the pearl oyster were studied in the northern Persian Gulf, i.e. from the Lavan and Hendourabi Islands. Ten landmarks were selected to define the shape of the left shell. In addition, concentration of Zn, Mg, Fe, Cu, Pb, Cd, Mn and Cr of the soft tissues were measured using atomic absorption spectrometry. Six microsatellite loci were used to assess the population genetic structure of the pearl oyster. There were morphometric differences between the populations suggesting the existence of two morphotypes. There was a significant difference between the two populations in concentrations of Fe, Mg, Zn, Cd, Mn and Cr indicating that the specimens from the Lavan Island experience a more stressful environment than those from the Hendourabi Island. Analysis of molecular variance (AMOVA) indicated that the proportion of the genetic variation attributed to differences among populations of the pearl oyster was highly significant for both FST and RST (FST = 0.066, RST = 0.265, P < 0.001). Our findings showed that stressful conditions resulting from heavy metals may have a direct influence on the separation of the populations in Lavan and Hendourabi despite the lack of a physical barrier.

The family Entoniscidae (Isopoda-Epicaridea) is included in the superfamily Bopyrina, which comprises the families Bopyridae, Dajidae and Entoniscidae. The Bopyridae are parasitic in the branchial cavity or on the abdomen of decapods, mainly Macrura and Anomura. The Dajidae occur in the incubatory chamber or on the dorsal surface of mysids and euphausiids, and rarely on Brachyura. The Entoniscidae are found in the visceral cavity of Anomura and Brachyura (an exception is Synalpheion, in a macruran, Coutière 1908), surrounded by a membrane of host origin, and communicating with the branchial cavity of the host by a pore. Together with this internal habitat the family has extreme morphological specialization. Females of the Bopyridae have distinct thoracic segmentation and well-developed peraeopods; in the Dajidae the peraeopods are distinct, but segmentation is less evident; in adult females of the Entoniscidae, however, the peraeopods consist of only the enlarged oostegites, with rudimentary endopodites in some species, and the thorax has only traces of segmentation.

The present paper is a continuation of the work already published under the above general title and should be considered in relation to the results previously recorded. The method of performing the measurements remained unchanged; xylenol blue was used to check the determinations made with cresol red in the more alkaline regions—namely, around pH 8.24. The water was tested immediately after being drawn, or within a few hours, unless otherwise stated in the tables.

Information on the ontogeny of complement system might help us better understand the anti-infection mechanism in the early fish life. The ontogenic expression of the representative complement genes and their response to lipopolysaccharides (LPS) challenge in zebrafish larvae are reported here. The expression of C1r/s, C3, C4, C6 and MBL steadily increased before 21 days post-fertilization (dpf) and a decrease was detected thereafter. MASP expression elevated and peaked on 14 dpf and a decline followed. Bf expression fluctuated during the experimental period. Moreover, Bf (involved in alternative pathway, AP) expressed at higher levels than C1r/s (involved in classical pathway, CP), MASP (involved in lectin pathway, LP) and C4 (involved in both CP and LP) in the normal adult fish and larvae, suggesting the more significance of AP than CP and LP during the development of zebrafish. LPS challenge induced up-regulation of all the genes at 12 h in the adult fish. For the larvae, Bf, C3 (key complement component) and C6 (involved in lytic pathway) responded to LPS challenge at earlier stages than the other complement genes, with the up-regulation detected since 14, 14 and 7 dpf, respectively. In the larvae at 28 dpf, all the above three genes responded to LPS challenge by up-regulating their expression in a fashion similar to that of the adult fish, hinting that complement operating via AP develops earlier and plays a key role in protecting the larvae; it showed effective responses to LPS challenge from 14 dpf and might mature before 28 dpf.

Introduction

The morphology of the Cardiidae is extremely variable and their taxonomy is uncertain because of the difficulty in recognizing the differences that are genetic and the variations that are due to environmental conditions. This is the reason why Cerastoderma glaucum (Bruguière) (Fig. 1) and C. edule have been for a long time considered as ecotypes of one species or two taxons belonging to a super-species C. edule (Lubet, 1976).

The reproductive activity of a population of barnacle-dwelling littorinids at Peak Steel, on the north-east coast of England, was investigated. Variation in the number of mature males and females, expressed as a percentage of the whole population, showed a marked difference among the barnacle-dwelling littorinids. Littorina neglecta displayed a distinct seasonal component to its reproductive activity, with a peak in early summer. Littorina arcana B also displayed a distinct seasonal component, with a lull in the summer months. However, L. saxatilis B maintained its reproductive activity all year, but with an increase in output in the summer. The reproductive activity of both L. arcana B and L. saxatilis B follow similar patterns of reproductive activity as their typical non barnacle-dwelling forms, suggesting that these are true barnacle-dwelling ecotypes. The controversy surrounding the specific status of L. neglecta is also discussed.

The results of a survey of the distribution of phosphates in the south-western area in April 1938 show that there were three regions exceptionally rich in phosphate. These regions appeared to be associated respectively with the outflow of the Bristol Channel, with the flow of more oceanic water across the entrance of the English Channel, and with upwelling of deeper water at the edge of the Continental Shelf.

The surface water was poorer in phosphate than the deeper water, and regions poorer in phosphate were in some cases associated with a crop of phytoplankton.

The Laboratory which ia now in the course of erection at Plymouth for the Marine Biological Association, is situated between the south wall of the “Citadel” and the Sound, at a height of 95 feet above the level of the sea. The site, which has been granted to the Association by the War Office, occupies the whole length of King Charles's Curtain, 265 feet, and extends southwards from the Citadel wall 240 ft., giving a surface of, say, 63,600 feet.

The population dynamics of shrimp Pleoticus muelleri was used as a model to verify if the trend of continuous reproduction periodicity, shorter body size and longevity, and early sexual maturity found in tropical regions is corroborated in upwelling regions. Shrimps were sampled in a region under the influence of upwelling (northern coast of Rio de Janeiro State, Brazil). Characteristics of bottom water were registered, and shrimps were measured (carapace length – CL) and classified by sex and gonadal development stages. Reproduction was seasonal, from September to December, and favoured by water mass intrusions of low temperatures and high chlorophyll concentrations. The greatest number of reproductive females preceded periods with the highest chlorophyll concentrations in the water column (cross-correlation; P < 0.05, lag (month) = −3, r = 0.50), suggesting greater developmental success of larval stage due to increase of food availability. Von Bertalanffy growth models resulted in asymptotic carapace length estimates of CL∞ = 40.21 mm and CL∞ = 36.78 mm for females and males, respectively. The reproductive and growth characteristics of the P. muelleri population studied herein were similar to that of populations from higher latitudes, demonstrating that the latitudinal pattern rule cannot be applied in regions influenced by an upwelling phenomenon.

Life cycle, population dynamics and productivity of the larviparous mudsnail species Ventrosia maritima were investigated at low salinities (0·3–6 psu) in differentiated parts of a Mediterranean lagoon (Monolimni Lagoon). Monthly samples were collected during the period from February 1998 to February 1999 in both parts of the lagoon. Ventrosia maritima displayed an annual life cycle. Recruitment occurred in summer and autumn at the outer part of the lagoon and additionally in late winter at the innermost part. A positive correlation was found between the percentages of small individuals and salinity or sediment organic matter at the outer part. Growth practically ceased in winter. The mudsnail displayed remarkable densities and an increase in growth in spring at <1 psu indicating that it is highly tolerant to extremely low salinities. Population density showed a significant seasonal variation; it increased from early summer to autumn (30,000–40,000 individuals m−2) following the summer and autumn recruitment. No significant correlation between the density of V. maritima and several examined physicochemical variables was found; a negative correlation was observed between the density of the mudsnail and that of the co-occurring polychaete Streblospio shrubsolii. Secondary production calculated by the size–frequency method gave a mean annual density (N) of 9740 ind m−2, a mean biomass (B) of 1·66 g ash-free dry weight (AFDW) m−2 y−1, a production (P) of 4·51 g m−2 y−1 and a P:B ratio of 2·72 at the outer part of the lagoon and a N of 14,570 ind m−2, a B of 3·2 g AFDW m−2 y−1, a P of 9·9 g m−2 y−1 and a P:B ratio of 3·09 at the innermost part. At the innermost part of the lagoon, where the seawater renewal rate and hydro-dynamism were lower and the sediment finer and organically richer, V. maritima displayed more recruitment pulses, a larger body size and a denser and more productive population than the one at the outer part. Our findings are compared to published data for the direct-developing congeners V. ventrosa and V. truncata.

Seasonal and spatial variations in the distribution and abundance of Ophiothrix fragilis larvae (2-arm to 8-arm stages) were determined from a series of plankton net tows in the Dover Strait in 1995 and 1996. Ophioplutei appeared in the plankton between June and September. Larval population was constituted by ophioplutei from different spatio–temporal origins. A major fraction of the ophioplutei observed in the Dover Strait might come from a population localized southward.

The use of a mixture of copper soap, 5 or 10 per cent, with 1 per cent mineral oil, dissolved in petrol or benzol, increases the life of silk plankton nets by about four or five hundred per cent, and roughly doubles that of a hemp net for a single treatment. The beneficial effects last far longer than does the green colour. Re-treatment at suitable intervals is recommended.

The use of 5 or 10 per cent of resin * with an equal percentage of the soap improves its adherence to the fabric, as does also the addition of tar or anti-fouling paint. For silk nets, to avoid clogging, only one-half per cent of resin should be used with 5 per cent of soap.

A liquid soap mixture, which may be used with paraffin oil, can be obtained by adding one pound of resin to one pound of melted copper soap, and then dissolving in one and a half pounds of carbon tetrachloride. When wanted, this is used to make up a paraffin oil soap solution of the desired concentration, but adherence is less than with petrol.