A series of nineteen different biometrical characters have been measured on the scutal and tergal valves of the boreo-arctic Balanus balanoides collected from over its whole area of distribution; these values attempt to define the shape of the valves.

The life-cycle of a population of Pandalina brevirostris living off the Northumberland coast is described. Most specimens were taken over sandy gravel or sandy mud with a covering of zoophytes in depths ranging from 20 to 30 fm. A very few specimens were taken over soft mud in 50 fm.

Eggs are laid during the period from January to the beginning of September. Females may lay two or possibly three broods in each breeding season. There is a period of 12–14 weeks between the laying of the eggs and the hatching of the larvae. The ova of those females that have a brood of eggs within the first half of the breeding season mature as the eggs develop, and are ready for laying following the release of the larvae. The adult P. brevirostris reaches maturity 8–12 months after hatching as a larva and lives on to breed again in the following season. They die at the end of their second breeding season. Thus, the probable life-span of the female is 24–30 months following its release as a larva, while that of the males is about 21–27 months.

The hitherto unknown hydroid of the anthomedusa Neoturris pileata has been found abundantly in the Clyde Sea Area, and medusae from it have been reared. The hydroid and the stages of development of the medusa are described and figured. The medusa is commonly present in the plankton in this area.

When the oscular tube grows the spicules tend to separate from one another, but the separation is not uniform; local displacements of spicules occur with respect to other spicules in the vicinity. The same is found when the tube elongates while constricting, or changes shape in other ways. The spicule displacements reveal that the mesogloeal matrix is plastic. The spicules are probably anchored to the surface epithelia, the system of anchorage varying with time and from one spicule to another.

Small growing spicules may rotate through considerable angles and move relative to the fully grown spicules in their vicinity. The relative movements are most frequently towards the osculum. They are attributed to displacements of either the mesogloeal matrix or the internal epithelium, each relative to the other. They are not likely to be caused by the concerted amoeboid activity of the founder calcoblasts.

The monaxons tend to maintain their positions and orientations relative to the tri- and quadri-radiate spicules, apart from small localized displacements. Thus no significant movement of the pinacoderm relative to the rest of the wall could be deduced.

Fragments of broken spicules likewise tend to retain their relative positions and orientations in the spicule arrangement, though some moved or rotated by quite considerable amounts.

Spicules occasionally disappeared from the wall of some tubes. Monaxons were shed relatively easily, probably as a result of the spicule crowding associated with contraction of the tube. Some tri- and quadri-radiates were also shed through the pinacoderm. In some tubes spicule protrusion occurred at the oscular edge.

Pandalus bonnieri is a dioecious species and no protandrous hermaphrodites have been seen.

The breeding season and incubation period for P. bonnieri are described.

The number of eggs laid increases with the size of the female. At 16 mm. carapace length the number of eggs is c. 1000 and at 24 mm. carapace length the number of eggs is c. 4000. The number for a single mm. size group varies roughly by ±10%.

Both male and female P. bonnieri become sexually mature at about 18 months, and in the Clyde seldom live beyond 3 years of age.

The colour of the eggs in P. bonnieri is sage green, in P. borealis blue green, in P. montagui light emerald green and in P. propinquus fawn.

Juvenile P. bonnieri can be separated into males and females by the shape of the pleopods within 4–6 months of hatching.

Both the need for shelter and the need for food can be motivations that alter animal behaviour. We tested the hypothesis that the hermit crab, Pagurus samuelis, deprived of food, shells, or both will respond differently from control hermit crabs when presented with food and shells concurrently. We measured the number of contacts made with both food and shells, and time elapsed until hermit crabs either began feeding or inserted into shells. We interpreted making few contacts and initiating behaviour quickly to be an indication of short decision time and high motivation; whereas, making many contacts and having long initiation time indicated a long decision time and low motivation to acquire resources. Control (C) hermit crabs made 72% more contacts with food and 53% more contacts with shells than shell-less (S) crabs. Control hermit crabs also made 34% more contacts with food and 35% more contacts with shells than starved and shell-less (StS) hermit crabs. This suggests that S hermit crabs were more motivated to acquire shells than C crabs. In addition, StS hermit crabs chose to insert into provided shells, while hermit crabs remaining in their shells chose to feed. Results indicate that being shell-less is a stronger motivation than being starved, such that finding shelter takes priority over finding food when both are needed. In rocky intertidal environments, resources such as food and shells are likely to be ephemeral. Hermit crabs that are motivated to make appropriate decisions to acquire specific resources may have a distinct advantage over those that are distracted by numerous objects in their environment.

The recruitment of subtidal macrofouling organisms was studied in the Patagonian harbour of Comodoro Rivadavia (Argentina, 45°51′35″S 67°27′23″W). Changes in coverage and density were analysed in the central 100 cm2 of upper and lower surfaces which were replaced monthly from January to December 2004. The fouling assemblage consisted of algae, spirorbid polychaetes, compound ascidians, hydrozoans, bryozoans and egg masses spawned by the small fish Helcogrammoides cunninghami. Monthly changes in richness and diversity of taxa on upper and lower surfaces were significantly correlated with sea surface temperature. Fouling assemblage structure differed significantly between upper and lower surfaces. Filamentous algae were dominant on upper surfaces, while filter-feeding invertebrates were more abundant on the lower surfaces of the experimental panels. The density of the spirorbid Romanchella scoresbyi was two orders of magnitude higher on lower than on upper surfaces. Its recruitment began in late winter, reaching maximum values in spring.

INTRODUCTION

Between 4 May 1973 and 29 March 1975 we did not visit Duckpool. Indeed after the 1973 visit (Wilson, 1974, pp. 429–30) the intention had been to discontinue observations on colony formation and growth, for it seemed unlikely that much more data of value were obtainable, and that is still true. However, at Easter 1975 Monsieur Yves Gruet, who has done much excellent work on Sabellaria associations on the coast of France (references in Wilson, 1974), visited Plymouth with his family and wished to see Duckpool. We went there on 29 March and arising out of that visit my wife and I were again there the following October, with one main object in view as explained below, and this in turn led to a further visit in November. This paper records observations made during those visits.

The reproductive cycle of Zygochlamys patagonica was studied from October 1999 to February 2001 in a bed located in the south-western Atlantic (Reclutas bed 39°24′ S–55°56′W). Scallops were collected monthly and the sexual maturity stages were determined histologically (N = 508). Sex-ratio was 1:1 (t-test P > 0.05). The size of first sexual maturity was estimated from males of an average of 36.63 mm and females of 36.31 mm of shell height. The relative gonadal condition index (RGCI) showed an annual cycle, with higher values during winter–spring and lower values during summer–autumn; an inverse relationship for the relative muscle condition index (RMCI) was observed with maximum values in early summer. Thus, a reallocation of energy from soma to gonad appears to be inevitable to meet energy demand of gonad development. Seven histological stages of sexual maturity were established for both sexes: (1) immature; (2) early maturity; (3) advanced maturity,;(4) ripe; (5) spawning; (6) spent; and (7) recovery. Individuals in early and advanced maturity were found throughout the year; however, they were found more frequently between June and September. Spawning began in October (early spring) and extended through March (late summer–early autumn) coexisting with early and advanced maturity stages supported by the annual variation of the RGCI and the food availability into the system.

Since 1995, research cruise catches of anchovy Engraulis encrasicolus (Pisces: Engraulidae) have increased in the Irish Sea. Their distribution shows distinct seasonality with anchovy being found in the deeper waters of the western Irish Sea in the spring and spreading out into the eastern Irish Sea by summer and autumn. Their length distributions show two modes at 7–11 cm and 13–16 cm.

A tide pool population of the brittle-star Amphipholis squamata in South Devon was monitored from July 1986 to July 1987 with respect to a number of population dynamical attributes. The population had a simple life history. Most individuals recruited into the population in the period June-September, were reproductively active in the following summer and died when 13-17 months old. The population differed from others studied in temperate latitudes in pattern of recruitment, survival and in duration of reproductive activity. We speculate that these differences are a consequence of tide-pool conditions.

The work began in June, 1912, simply as a study of the life-history of some of our common amphipods. The genus Gammarus was chosen, because of the number and the wide distribution of its species in the neighbourhood. Seven of these species, all black-eyed, from marine, estuarine, brackish and fresh waters, were kept in the laboratory for investigation until the first red-eyed specimens were discovered in one of the brackish species, later described as Gammarus chevreuxi (see p. 360). Since the manner in which these red-eyed individuals occurred raised points of considerable interest, it was decided to confine investigation to G. chevreuxi, and a series of experiments was started. The different variations involving both the structure and the pigmentation of the body and of the eyes appeared from time to time, some behaving as simple mendelian characters and attributable to the presence of a single recessive gene, others with a more problematical hereditary basis. These variations have been recorded as they occurred (see bibliography). For ten years, no second mutation appeared, although frequent dredgings were made and the animals thus obtained were kept for several generations in laboratory conditions. Because of this apparent stability of character the wild Gammarus was regarded as a homogeneous population until, in 1922, it became increasingly evident that the results showing in the laboratory cultures could only be explained on the supposition that many recessive factors must be present in the natural conditions.

The evidence steadily accumulated, but direct proof was very difficult to obtain partly because (as we found in our experience with the cultures) the recessive types are often less viable than the normal, and therefore probably less able to withstand the competition in the wild, and partly perhaps because we had no criteria by which to assess the influence of the laboratory conditions (changes of temperature, food, salinity, pressure, etc.) on the constitution of the Gammarus, and so could not decide whether a variation was caused by the inherent action of the recessive genes, or by the untoward environment producing a change in the action of the normal genes.

The incidental capture of sharks in the bottom-set gill-net fishery off the south coast of Ireland was quantified by placing observers on commercial gill-netters for the duration of a fishing trip. Forty fishing trips were sampled resulting in 1,167 km and 19,760 km h of observed fishing effort. Sixty individual sharks of seven species were reported entangled in the fishing gear. Tope, porbeagle and six-gilled sharks were the most frequently caught species, with black-mouthed dogfish, blue shark, basking shark and starry smooth hound also recorded. Total fishing effort along the south coast was calculated and total capture extrapolated from observed catch rates. An estimated 6,000 sharks were caught in this fishery during the study period.

This study examined the use of replica limpets made from modelling wax to provide an index of encounter frequency between crabs and their limpet prey. Video observations at Port Erin Marine Laboratory, showed that the intertidal crabs, Carcinus maenas (L.), Necora puber (L.) and to a lesser extent Cancer pagarus L., regularly examined and tried to remove both real and replica limpets with their chelae. Replica limpets became scratched or gouged as a result of these encounters. The frequency of attack was similar for both real and replica limpets. Hence marks on the limpet models provided a reliable index of attacks on real limpets. The frequency, timing and spatial distribution of encounters between limpets and crabs were recorded by scoring the marks made on model limpets deployed amongst real limpets on the shore. During a 28-day period at Port St Mary on the Isle of Man, limpet models were marked more frequently and with longer scratches on the lower shore than on the upper shore, suggesting that larger crabs were present on the lower shore. Models, deployed at Prawle Point, Devon, showed that encounters between crabs and limpets occurred during both day and night-time high tides. The models were durable and provided an inexpensive method for recording encounters between crabs and limpets. Some replicas were also marked by the teeth of small fish and rodents. Model prey such as these could also be used to study other predator–prey encounters, particularly in conditions which preclude direct observation or video recording, or for use with animals that might be disturbed by observers or cameras.

Echinoderms are exclusively marine, osmoconformer invertebrates. Their distribution patterns are strongly influenced by salinity. Nevertheless, several species of the phylum inhabit the challenging intertidal zone, characterized by steep and fast salinity fluctuations. This study evaluated the response of coelomic fluid ionic concentrations (sodium, chloride, magnesium and potassium) of the intertidal sea cucumber Holothuria grisea to hypo- and hypersaline challenges. A stepwise protocol was performed for the whole animal exposure to both anisosmotic conditions: from 35 to 15 psu along 8 h, and from 35 to 45 psu along 6 h, to simulate intertidal conditions. Tissue water regulation by the longitudinal muscle, oesophagus and posterior intestine was also evaluated, upon hypo- and hyper-osmotic shocks of 20 and 50% of intensity with respect to the isosmotic control. Ionic gradients were observed between coelomic fluid and external water, mainly for potassium and magnesium, but also sodium, and in a greater extent under hyposaline conditions than under hypersaline exposure. Consistently, H. grisea shows retracted tube feet in 15 psu, but a more relaxed appearance and exposed tube feet in 45 psu. In addition, H. grisea showed greater capacity for tissue water maintenance during hyper- than in hyposmotic conditions. Holothuria grisea shows an avoidance behaviour in low salinity (thus sustaining ionic gradients), preventing its tissues from intense swelling. This strategy allows it to dwell in the intertidal region.

Previous methods of survey by American workers are described and the differences between the species of seaweed involved are emphasized. The small stature of the European kelps renders all methods of survey difficult and the results can only be described as the best approximations. The British survey was divided into (1) a preliminary survey in order to determine the regions with the biggest beds, and (2) a detailed survey, when some of these major beds were mapped in detail. The primary survey was a rapid affair and the results were based on information obtained from (a) use of boat and grapnel, (b) existence of cast weed, (c) lobster fishermen, (d) coastguards, fishery officers, borough surveyors, harbour-masters, (e) inspection from cliffs, (f) a study of Admiralty Charts.

In the section on the detailed survey the different types of grapnel employed and also the method of using the box sextant are described. The use of an echo-sounder to locate weed beds is discussed and the different types of record obtained over various types of bottom or weed are noted. The use of a viewbox and personal observation is also mentioned, and finally an account is given of aerial photography as a means of survey. The most suitable conditions for success are noted and also the technique of interpretation for both oblique and vertical photographs. The plotting of these two types of photograph is described in some detail.

This paper presents data on the diet of the musky octopus, Eledone moschata, caught with bottom-trawl nets in the northern Adriatic Sea from October 2001 to June 2003. A total of 1226 stomachs were examined, out of which 34.8% were empty. Several indices were used to describe the diet of the species. Crustaceans were found to be the most important prey category and their remains occurred in 65.0% of stomachs with food. Fish and cephalopods were present in 37.8% and 21.8% of stomachs, respectively. Differences in food composition between smaller and larger individuals were observed. In specimens with mantle lengths up to 80 mm crustaceans dominated, occurring in 79.4% of examined stomachs. Important prey categories of the larger specimens (>80 mm) were crustaceans, fish and cephalopods. No significant differences in the diet between males and females were found. Cannibalism occurred only occasionally and at larger sizes. Seasonal changes in the diet were observed, but seasonality did not seem to be a limiting factor in the feeding intensity of the species. Results indicate that the observed differences in the diet composition and feeding dynamics of the musky octopus are primarily due to the animals' changes in size.

Patterns in larval supply and recruitment of the invasive European green crab, Carcinus maenas, were examined at two sites in Nova Scotia, Canada: a typical Atlantic coastal site with high salinity (∼33) and strong tidal signal (Terence Bay); and a microtidal site in the Bras d'Or Lakes, where surface salinity fluctuated from 0 to 23 (Benacadie Pond). Abundance of all life history stages (zoeae, megalopae, juveniles and ovigerous females) was sampled approximately biweekly at each site from June 2001 to June 2002. The reproductive season, based on the presence of ovigerous females, is ∼5 months (June to October) at both sites. Zoeae-I were collected from June to July 2001 and in June 2002 at Terence Bay, and from June to August 2001 at Benacadie Pond. We did not collect later zoeal stages at either site. Megalopae were collected from September to October 2001 at Terence Bay, and from August to September 2001 at Benacadie Pond. Juveniles 1–6 mm carapace width (CW) were present throughout the summer at Terence Bay, and only in autumn at Benacadie. Juveniles 6–12 and 12–27 mm CW were present throughout the summer and autumn at both sites. At Terence Bay, densities of 1–6 and 12–27 mm CW juveniles did not vary among intertidal zones. In contrast, the 6–12 mm CW size-class appeared to move higher in the intertidal through the season, possibly due to effects of predation.

A new sponge genus and species, Astrotylus astrotylus, is described from the Antarctic abyssal zone. Its peculiar microscleres, herein referred to as astrotylostyles, combine the features of asterose spicules and tylostyles. Similar spicules are observed in Hymeraphia and Discorhabdella (order Poecilosclerida). But this similarity is convergent as far as a radial choanosomal skeleton composed by principal tylostyles and a cortical palisade of small tylostyles in Astrotylus undoubtedly confirm its allocation to the order Hadromerida and most likely to the family Polymastiidae. Atergia, Acanthopolymastia and Tylexocladus have the closest affinities with Astrotylus that calls for the phylogenetic analysis of their relations. Meanwhile astrotylostyles of Astrotylus, cladotylostyles of Tylexocladus and grapnel-like exotyles of Proteleia may be the remnants of non-monaxonic ancestral spicule type in Polymastiidae that calls for reconsideration of the relations between hadromerid families.

This first description of behavioural interactions between benthic pyjama sharks Poroderma africanum (Chondrichthyes: Scyliorhinidae) and spawning squids Loligo vulgaris reynaudii (Cephalopoda: Loliginidae) was made from underwater video recordings. The behaviours are described and illustrated to show that the sharks searched for squids in egg beds, then rested there partially hidden and immobile. The pyjama sharks at-tempted to ambush the squids when they approached to lay their eggs after they had apparently habituated to the predators. Although normally nocturnal, the pyjama sharks had emerged by day from caves and cracks in the rocky reef to attack the spawning squids, thereby benefiting from an occasionally available resource.