The Mediterranean proliferation of Caulerpa taxifolia provides an opportunity to examine the extent to which an introduced species can modify biodiversity. During 1992, benthic invertebrates were sampled in Roquebrune-Cap Martin area, at depths of 6 and 10 m, from a Caulerpa station and a reference station. Species richness is slightly lower at 6 m within Caulerpa while the number of specimens is much reduced at both depths. Similarity indices compare well between reference and Caulerpa stations.

Caulerpa taxifolia, distributed in tropical seas, was recorded for the first time in the Mediterranean in 1984, as a single 1 m2 patch. This surface increased to 3 ha by 1990, 30 ha in 1991, 100 to 430 ha in 1992, and 1000 to 2000 ha at the end of 1993 (Meinesz & Hesse, 1991; Boudouresque & Meinesz, 1994).

Maximum colonization is between 2 and 6 m depth, but the alga has been observed down to 99 m. Density can reach 350 m of fronds and 14,000 leaves per m2. Caulerpa taxifolia colonizes any type of substrate and invasion results in a drastic impoverishment of the algal components of the communities (Boudouresque et al., 1992; Verlaque & Fritayre, 1994). According to these authors, maximal poverty of communities coincides with the maximal development of C. taxifolia (summer-autumn) and epiflora is negligible, except during spring.

These changes may induce functional and structural modifications of the fauna that lived in the communities before infestation. Invasion, particularly of photophilic algae and Posidonia beds (Ros et al., 1985), can modify quality and intensity of physical, chemical and hydrodynamical factors, number and quality of shelters, quantity and quality of food, and exchange of individuals between communities and populations.

In September 1992 a blue runner (Caranx crysos) (37 cm) was caught off Portland Harbour, Dorset, by an angler. Initially the specimen was not recognized as a rarity and it was damaged while being prepared as bait for a lobster pot. Fortunately it was retrieved and sent to the Ministry of Agriculture Fisheries and Food (MAFF) laboratory at Lowestoft where it was identified. In August 1993, a second blue runner (29 cm), (see Figure 1) was hand-lined in St Ives Bay, Cornwall by Mr Astrinsky, of Penzance. It was also taken to a MAFF office, at Newlyn, for identification where one of the authors made a provisional identification before sending it to the British Marine Fishes Database at the Marine Biological Association for final verification. These two fishes are the first records of the blue runner C. crysos from British waters, and represent a northerly extension to its range.

Common dolphin, Delphinus delphis (bairdi), were monitored acoustically across a survey area of 2747 km2 during a three month period before, during and after an oil industry two dimensional (2D) seismic reflection survey. Over 900 h of audio survey data were collected and analysed, along with GPS positional data, to reveal trends in presence and distribution of animals. The presence of dolphins was determined from vocalization events on the survey recordings. Dolphin presence was assessed by a system of percentage acoustic contact. This was highest before and after the seismic survey, with common dolphins showing a clear south-westerly skew within the survey area and a probable south-westerly migration of animals between September and December. Acoustic contact with dolphins during the seismic survey also showed a south-westerly skew within the survey area, although percentages were lower. Monitoring during the period of seismic activity was restricted to the immediate vicinity (1–2 km) of the seismic vessel, so percentage contact most likely reflects the response of dolphins to such immediate activity. The overall result suggests an avoidance reaction by common dolphins to air gun emissions, although certain observations suggest tolerance to these sounds outside a 1 km radius of the guns.

Bopyrids are highly modified epicaridean isopod ectoparasites with the adult females showing extreme specialization of body form when compared with free-living isopods (Shiino, 1965). The smaller males are similar to free-living isopods, retaining the basic cryptoniscus larval form (Naylor, 1972), and are typically found in the brood chamber of the female or attached to the ventral surface of the female's pleon (Salazar-Vallejo & Leija-Tristán, 1989).

Whilst examining the branchial morphology of the upogebiids, Upogebia stellata (Montagu), Upogebia deltaura (Leach) and Upogebia pusilla (Petagna) as part of a wider study of the physiological ecology of thalassinidean mud-shrimps, some shrimps were observed to have a branchial gall (distended branchiostegite) containing a bopyrid parasite. In this short note we add to the previous records of two bopyrid species and briefly discuss the host/parasite relationship.

Parasitized material examined: U. stellata (three males, two females) collected subtidally using an anchor dredge from White Bay, Isle of Cumbrae, Scotland (55°48'N 4°55'W) at depths of 25–30 m. A single male specimen of U. deltaura was caught using a box corer from the Irish Sea (54°7'N 3°27'W). Upogebia pusilla (one male, one female) were collected intertidally from the Arcachon Basin, France (44°40'N l°10'W) by Professor J.P. Truchot. Prior to examination, the mud-shrimps were preserved in 10% buffered formalin, the parasites removed, rinsed with distilled water and transferred to 70% ethanol. Some preserved material was also available from the Robertson Collection housed at the University Marine Biological Station Millport.

Parasitized mud-shrimps had an enlarged branchial chamber, or branchial gall, a result of branchiostegite deformation caused by the presence of the parasite. When the parasite was removed from the branchial chamber, the gills appeared splayed and flattened but showed no other signs of disturbance or damage.

Suspected viral erythrocytic necrosis (VEN) was detected in two specimens of the intertidal fish Mauligobius maderensis (Teleostei: Gobiidae) from Madeira, Portugal. While one host was lightly infected, the other showed intraerythrocytic cytoplasmic inclusions within all mature erythrocytes examined. The inclusions were round to oval, 0·8–2·0 μm in diameter, and most were associated with dense eosinophilic granular areas of various sizes and shapes. Up to three of these granular regions accompanied each inclusion body, but they were sometimes widely separated from it. In a number of infected erythrocytes, a granular halo was observed surrounding the nucleus. The cytoplasm enclosed by the halo often had a different refringence from that outside. None of the 120 other fishes examined from Madeira, representing 43 species of intertidal, pelagic, and deep-sea origin, had detectable infections.

An important aspect of marine biodiversity studies is identification of species and subspecies complexes. Here we present a number of examples from marine algae in which allozymes, DNA sequences and RAPDs are used to identify cryptic species and explore phylogenetic-population level relationships over several biogeographic spatial and temporal scales. In addition to evidence for recent dispersal over large distances, effects of present and past climates are reflected in the phylogenetic history of many biogeographic complexes. In some cases temperature adaptations can also be detected. Phylogeographic studies on coastal seaweeds and oceanic phytoplankton which utilize molecular genetic data contain a wealth of previously unrecognized information relevant to biodiversity.

Thirty ‘rock-populations’ of the intertidal isopod, Jaera albifrons (Isopoda: Asellota), from South Wales area were found to display a significant and persistent sex ratio bias, with females outnumbering males by up to 12 to 1. This thelygeny was not mirrored in broods that were isolated in aquaria after insemination, nor in broods that developed under various temperature and light regimes. Such a discrepancy suggests that the mechanism generating sex ratio biases in natural populations is not innate, nor is influenced by cytoplasmic or environmental factors. The possible causes of thelygeny in natural populations are discussed.

The spawning period of the nudibranch mollusc Onchidoris bilamellata (L.), although generally extending from December to May, has occasionally been reported to occur also in summer and early autumn. Preliminary data are presented here on the larval development of summer and early autumn spawnings and compared to previous studies of the larval development of ‘normal’ (winter-spring) spawnings. The possible causes and consequences of the rare summer and early autumn spawnings are discussed.

The nudibranch mollusc Onchidoris bilamellata is distributed around the British Isles, the Atlantic coast of France, Iceland, Greenland, and the coasts of North America and Japan (Thompson & Brown, 1976). It exhibits an annual life cycle with a single spawning season, generally extending from December to May in which the adults spawn repeatedly. At the end of May/June the post-spawning mortality of the adults is usually complete (Todd, 1979). Summer and early autumn spawnings have been recorded in intertidal populations only occasionally (Todd, 1979 and references therein; present study). Larval development has been studied previously on larvae hatching from eggs laid during the ‘normal’ spawning season. No information is available on the larval growth and development of summer and early autumn spawnings. In the present study two key points were addressed: the occurrence of individuals and spawn masses in the field throughout the year; and the identification of any distinctive traits of the July and September offspring.

The field observations were carried out on the south-eastern coast of Scotland (56°18′N 2°39′W) from July 1993 to August 1994. The surface sea-water temperatures were recorded from January 1993 to August 1994 in St Andrews (56°20′N 2°47′W), seven miles from the location under study (Figure 1).

Static toxicity tests (20.5 ±1°C, 24 ±2% salinity) were run to assess the toxicity of copper to the embryonic development of Scrobicularia plana (Mollusca: Bivalvia); the end point of interest was the production of D-larvae after 48 h culture. While a nominal concentration of 10 μg Cu I1 was not found to be toxic, an EC90 (concentration preventing 90% of the experimental population from achieving the end point defined) can be set at ~20 μg Cu I1. For this end point, copper is indicated to be 16 times less toxic than the antifoulant tributyltin (TBT). Moreover, copper has probably little relation with the reported recent decline of S. plana throughout northern Europe.

An in vitro bioassay has been developed which shows that oogenesis in Harmothoe imbricata is controlled by a gonadotrophic hormone which promotes egg protein synthesis in developing oocytes. A similar endocrine control mechanism is found in Eulalia viridis and analysis of in vivo assays indicate that the hormone acts as a transducer between the environment and the gamete. The timing of gametogenesis is controlled by environmental cues in both species and may be affected by predicted global climate change. With the development of these sensitive hormone assays it is possible to test the impact of climate change on both species, providing a possible early warning system for global warming and potential bio-indicators of climate change. Harmothoe imbricata is likely to be the more sensitive indicator species.

Clumps of macroalgae on sheltered shores exposed at low tide provide a mosaic of micro-habitats for halacarid mites. The predominant pattern is one of zonation, with the level of high water neap tides limiting the distribution of many species of Halacaridae. Within emersed clumps of macroalgae four micro-habitats are recognized: the dry surface layer of the clump; damp fronds within the clump retaining surface moisture; lower stipes and holdfasts; the surface of the substratum between the holdfasts. Halacaridae are spatially segregated, different species being associated with different micro-habitats within clumps. This has implications for the way in which intertidal phytal meiofaunal communities are sampled. In general damp fronds from within seaweed clumps are collected. Species characteristically associated with stipes, holdfasts and the substratum beneath the clumps are probably under-represented in the majority of collections, and may, therefore, be considered rare.

There are no species of salps (Order: Salpida) indigenous to British waters. Those species that can be found, the most abundant being Salpa fusiformis Cuvier (Fraser, 1981) are carried to British and Irish waters from the open ocean of the western Atlantic. Because of this salps can be good indicators of oceanic water movements near to Britain (Fraser, 1981). The largest species of the Salpidae is Thetys vagina (Tilesius, 1802) which generally reaches ≥230 mm in total length (TL) in the solitary asexual form and ~250 mm TL in the aggregate sexual form (Metcalf, 1918; Fraser, 1981). However, a solitary form measuring 333 mm TL was caught in a trawl from the Hawaiian islands (Nakamura & Yount, 1958). The distribution of T. vagina is usually limited to warm water throughout the Atlantic, including the Mediterranean, Indian and Pacific Oceans (Berrill, 1950). Up to 1981 there have been only two records of T. vagina in British waters (Fraser, 1981). This short paper describes, to the best of my knowledge a third recording of this salp from British waters.