From April 3rd to May 17th of this year I occupied a table at the Plymouth Laboratory, to study the embryology of Teleosteans. As some of the fish in the flat-fish tank were known to be spawning, a net was fitted to the overflow channel into the adjoining tank. By the kind permission of the Director I examined this net daily, and, as a rule, a number of times a day, so that I obtained a pretty complete record of the spawning of the fish in this tank during the period mentioned.

Sea water originally at pH8·2 became as alkaline as pH9·4 by the photosynthetic action of Ulva in removing carbonic acid. This degree of alkalinity did not prove injurious to Ulva, but exposure to it for two and a half hours at 27° C. sufficed to increase the permeability of the superficial cells of Ceramium rubrum irreversibly and fatally. Similar though less rapid changes brought about the death of numerous Vorticellæ epiphytic on Ceramium. The criteria for living cells were permeability to neutral red and impermeability to brom cresol purple. Dead cells do not retain neutral red specifically and are permeable to brom cresol purple.

It is suggested that the above facts have a bearing upon the distribution of these and similar algæ upon the shore.

The population dynamics of the stout reef octopus, Octopus insularis fished with longlines of pots in mid-shelf waters of north-eastern Brazil was studied based on fishermen's logbooks and onboard monthly fishing trips from September 2009 to August 2010. Specimens marked with oxytetracycline kept in tanks for up to 21 days provided evidence of the daily deposition of growth increments in the lateral wall of the upper beaks. Sampled specimens weighed 50–1280 g and had 43–172 daily growth increments. Compared with congeneric species from higher latitudes, O. insularis grows faster and has a shorter longevity in the north-eastern Brazil tropical environment. Total catches and catch-per-unit effort were substantially higher in the dry season, with less wind and cooler temperatures. The presence of larger specimens was seasonal, correlated with the chlorophyll-a levels recorded six months earlier. The year-round presence of mature females and males, spawned females, and egg masses attached to the pots, were considered evidence of migration of small and young specimens from coastal areas towards the 20–40 m depth range for reproduction. Annual landings attained ~200 tonnes (2005–2010). Although recent landing statistics are missing, fishermen interviewed in 2021 claimed that the fishery was still profitable. It is suggested that, despite the lack of management, the fast growth, year-round reproduction and limited market for this relatively small octopus, prevented the fishery from collapse and reinforces the current view of the high resilience of cephalopod fisheries.

Distichopora robusta, the first shallow-water stylasterid coral from the tropical eastern Pacific, is described from the west coast of Panama. The new species is distinguished from all species of Distichopora described thus far by having robust branches and poorly defined pore rows.

Studies of mysid diets by gut contents analysis have generally revealed a broadly omnivorous feeding habit, but there are also tendencies towards carnivory, herbivory and/or detritivory (e.g. Nath & Pillai, 1973; Siegfried & Kopache, 1980; Mauchline, 1980; Zagursky & Feller, 1985; Wooldridge & Bailey, 1982; Webb & Wooldridge, 1989). Examination of feeding structures is also necessary to support inferences about feeding ecology (e.g. Webb & Wooldridge, 1989). However, there have been few studies relating to the functional morphology of mysid foreguts (Gelderd, 1909; Haffer, 1965; Nath & Pillai, 1973; Mauchline, 1980; Friesen et al., 1986; Webb & Wooldridge, 1989; Storch, 1989). With the exception of the latter two studies, qualitative descriptions and characterization of the different internal foregut structures have been primarily based on light microscopy. These studies may misinterpret the internal arrangement, topography, and three-dimensional orientation of the internal armature of the foregut, mainly due to problems with depth of field (Grice & Lawson, 1971). Oshel & Steele (1988), from SEM observations, briefly described some foregut features of Gnathophausia ingens. In a comparative study, Storch (1989), using the techniques of transmission and scanning electron microscopy, described in detail the different food chambers and channels, cuticular ridges, and ultrastructure of the epithelial and cuticular linings of the mysid foregut. Webb & Wooldridge (1989) noted the strong relationship between mouthparts, foregut morphology, and the feeding habits of two co-occurring mysids.

The number and size of colonies found in bacterial counts of sea water collected from the Menai Straits varies with the concentration of peptone in the medium. The optimum concentration of peptone was found to be 0.3%. Neither yeast extract, beef extract or added iron increased the count when added to media made from Menai Straits water. The effect of various temperatures on the count, and the relative merits of pour plates and surface growth techniques were examined. Vigorous shaking, or passage through a Sharpies centrifuge, was found to increase the count.

The survey, the results of which are described in this paper, was primarily intended to investigate the zonation of Littorina littorea, but notes have also been included of the zonation of such other gastropod species as occurred with it. The material was collected from the following localities: Torpoint. 2. ×. 36. Just west of the ballast dock at Torpoint, Cornwall. The shore consists of stones, many of them bedded in mud, and thickly overgrown with fucoids. There is little wave-action, but at times a considerable drop in salinity (Hartley & Spooner, 1938; Mime, 1938).

The host-response of the polynoid Polynoë scolopendrina Savigny, commensal with the terebellid Polymnia nebulosa (Montagu), is relatively specific within the family Terebellidae.

Evidence is presented that an unstable or closely bound attractant is present on the outside of the host and perhaps in tube material, but apparently absent in the mucus secreted by the host. Efforts to demonstrate its presence in ground-up whole host resulted in failure.

The polynoid Lepidasthenia argus Hodgson demonstrates a similar specificity of response to its host Amphitrite edwardsi Quatrefages.

The polynoid Harmothoë spinifera Ehlers, commensal with Amphitrite gracilis Grube, responds to the alternate host Polycirrus caliendrum Claparede as strongly as to its own host, and more strongly than to other species of Amphitrite. Likewise, Polynoë scolopendrina, commensal with Polymnia, responds with greater intensity to the alternate host, the eunicid Lysidice ninetta Audouin and Milne-Edwards, than to any non-host terebellid. This behaviour may be i terpreted as evidence that the specificity of at least some single commensal species for hosts which are not closely related to each other may depend upon the production of similar attractants by these hosts.

The responses of three commensal populations of Harmothoe lunulata (Delle Chiaje), commensal respectively with the ophiuroid Acrocnida brachiata (Montagu), the holothurian Leptosynapta inhaerens (O. F. Miiller), and the terebellid Amphitrite johnstoni Malmgren were tested against seven alternate hosts. Each gave maximum response to its own host. However, the population from Acrocnida responded as strongly to Leptosynapta as to its own host, while giving no responses at all to any of the other five.

Light adaptive strategies were studied in a comparative analysis of the congeneric seagrass species Zostera muelleri and Zostera marina at two case study areas in New Zealand and Germany. Surveys in intertidal seagrass meadows were conducted from pre-dawn until sunset on days when either low or high tide coincided with noon. The results show marked fluctuations of photophysiology (optimum and effective quantum yield, non-photochemical quenching, cycling of xanthophyll cycle (XC) pigments) over daily and tidal cycles. At both locations, we observed a near complete conversion (de-epoxidation) of violaxanthin to zeaxanthin at times with high irradiance and a rapid and complete re-epoxidation under subsequent lower light conditions. At the New Zealand site we also observed significantly larger XC-pigment pool sizes in seagrass leaves sampled in a week when low tide coincided with noon (larger daily fluence and higher maximum irradiance), compared with leaves sampled in a week when high tide was at noon. This dynamic adjustment of xanthophyll pool size has not been previously reported for intertidal seagrasses. It adds to our understanding of an important adaptive feature in a highly dynamic light environment and to the general ecology and adaptability of seagrasses.

The population structure of the common shrimp Crangon crangon (L.) in British waters is investigated. Samples were collected from 31 sites along the coasts of England, Wales, Holland, Belgium and France. Using a morphometric analysis it is concluded that English and Welsh waters hold six distinct populations. Animals belonging to the same population are found on the opposing English and continental coasts in the southern North Sea and English Channel which indicates that the avoidance of offshore waters is not isolating the shrimps. The boundaries between the populations are found to correspond with the boundaries between major plankton assemblages. It is suggested that the populations are isolated by the reduced dispersal of the planktonic larvae across fronts where bodies of water with different physical properties meet but incompletely mix.

The ophiuroid, Ophiocomina nigra, is noted for its variability of colour, a phenomenon most pronounced where the species also has its greatest distribution in depth. Observations have been made on two geographically distinct populations, from the vicinities of Millport and Plymouth. The body colour of the observed animals ranges in a continuously graded series from black to orange-yellow. While both populations exhibit analogous variations, there is a distinct difference in the range and tone of coloration which each displays. It is suggested that this geographical difference is correlated in some degree with differences in colour tone of the substratum. It was observed that the incidence of light-coloured phases in each population increased with increasing depths, and some statistical evidence supports this conclusion. Thus, at least two factors, depth and substratum, may affect the distribution of colour variations in O. nigra

In addition to the variations in general body colour, there are two distinct colour patterns found on the disk. These are probably truly polymorphic and may be of cryptic value.

A scheme of colour classification is described which facilitates observations in the field and in the laboratory.

A new contribution on spatial and seasonal variability of physico-chemical parameters of the Golfo San Jorge benthic system from autumn 2001 through summer to 2002 is presented. Temperature, salinity, density, oxygen content and chlorophyll-a in bottom water as well as concentration of total organic matter, total organic carbon, total nitrogen, total phosphorus, chlorophyll-a and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The results reflect the existence of: (1) a typical temperate water seasonal cycle; (2) a bimodal cycle in the phytoplanktonic production; and (3) seasonal variations in the chemical variables and in organic matter origin in sediments.

Three sectors which geographically correspond with those identified in previous studies were defined: (1) the inner area of the gulf; (2) the areas next to the north and south extremes; and (3) the coastal and south-east part.

Powers, working on some marine fishes, arrived at the important conclusion that the ability of fishes to absorb oxygen at low pressures is more or less dependent upon the hydrogen ion concentration of the water. His method of research was briefly as follows: a fish was placed in a two-quart jar filled with water, which was closed airtight with a rubber stopper. The pH and the oxygen determinations were made immediately after all the movements of the fish had ceased. The amount of oxygen left at death represented, according to Powers, the pressure below which the fish at the particular pH could not extract any more oxygen from water. Powers did not control the amount of oxygen at the beginning of an experiment; he says, “it was always sufficiently high so that the fish did not at first suffer from oxygen want.”

During biological sampling of hydrothermal vents on the East Pacific Rise, the manned submersible ‘Nautile’ caught the first female of the endemic cephalopod Vulcanoctopus hydrothermalis. The specimen caught at the vent site Gromit (21°33 66′S, 114°17 98′W at 2832 m depth) is described here in detail and an amended diagnosis of the species proposed. The external morphology, measurements and internal structure resemble that of males of this species. One of the most remarkable characters is the lack of spermathecae and the absence of apical filaments in the oocytes to provide a site for sperm storage. It is suggested that some species of the genera Benthoctopus and Bathypolypus would be the most suitable octopod ancestor of V. hydrothermalis.

From an analysis of previous records of E. nordmanni, considered in conjunction with those furnished by the present investigation, the following points of interest emerge.

1. E. nordmanni, while being generally distributed in the North Sea and adjacent waters throughout the summer months, has been shown to breed freely in inshore waters in early summer and again in autumn when maximum numbers of individuals are obtained.

2. These two periods of maximal abundance are produced as the result of successive parthenogenetic broods and alternate with periods of depression. This is indicated not only by the sexually-produced winter-egg, but also by a reduction in the number of embryos contained in the brood chamber and consequent change in body-shape. This serves to show that the supposedly distinct races, described as being characteristic of the North Sea and the Baltic, have no doubt been founded on material taken at different periods of the agamic phase.

Thirty-five specimens of the articulate brachiopod Neorhynchia strebeli were collected from a site at 814 m in the Weddell Sea. This was only the second species of the order Rhynchonellida to be found in Antarctica. Formerly N. strebeli was known solely from abyssal Pacific Ocean localities. A circumantarctic distribution is suggested in addition to the known deep-sea Pacific range. The specimens of this collection showed considerable commissure variation, suggesting that the previously proposed erection of two subspecies on the basis of this character is erroneous, and emphasises the phenotypic plasticity of some articulate brachiopods. The valve lengths and the number of alpha growth rings in the sample showed a normal distribution and a von Bertalanffy growth function was fitted to the data: Lt = 23 (1-exp[-0·228t]). If the alpha growth rings were of annual periodicity, the ages attained by the Antarctic N. strebeli of 11 y would be substantially lower than those reported for other Weddell Sea brachiopods. The epibiotic communities occurring on the valves of N. strebeli were impoverished, which is characteristic of deep water Antarctic brachiopods. The few specimens collected with their substratum were attached to small pebbles, but the typical attachment substrata may be different.

Methods for assessing the occurrence and recency of mating are important for the management and conservation of exploited brachyuran crabs. Using multiparous females of the snow crab Chionoecetes opilio, we evaluated by experiment the efficacy of three indicators of recent mating: a white deposit in the spermathecae, extended mate-guarding, and fresh grasping marks on the female pereiopods. This was done by contrasting sperm counts between the left and the right spermatheca of females that were exposed to males with the right gonopod ablated, at treatment sex ratios of 20[female]:3[male ] or 50[female]:3[male ]. We expected that sperm reserves would be balanced between the two spermathecae of non-mated females and larger in the right than in the left spermatheca of mated females. Although no mating indicator was infallible, the presence of a white deposit was the most accurate because it maximized the median difference of sperm counts between the two spermathecae for the group of presumably mated females and minimized it for the group of presumably non-mated females. The use of grasping marks overestimated the mating frequency and resulted in the misclassification of a large proportion of females. Extended mate-guarding was a slightly better mating indicator than grasping marks, but it is not practical for field studies. Classification errors associated with each indicator can be explained mostly by female and male behaviours and may vary in magnitude with sociosexual context.

A single-season mark-recapture experiment was carried out on queen scallops, Aequipecten opercularis (L.) (Bivalvia: Pectinidae) to assess the suitability of the technique for estimating population sizes and mortality rates of exploited populations. Tag-loss and tagging-induced mortality were 7.7% and 11.9% respectively. Non-reporting was negligible.

In a single fishing season (June-December 1989) 25.4% of releases were recaptured alive. Mean density of commercial-sized queens was estimated as 0.47 m−2 over the fishing ground. Instantaneous rates of total (Z), fishing (F) and-natural (M) mortality, calculated from the monthly decline of recaptures during the fishing season, were 0.;41,0.21 and 0.20 per month respectively. The calculated M is very high but includes non-yield or indirect fishing mortality. Analysis of the age-frequency distribution of queens from an adjacent, largely unexploited, area indicated an M of only 0.036 per month (0.43 y−1). There was some indication of an increase in M in older year classes, associated with senescence.

The mark-recapture methodology used here is suitable for this species, but single-release experiments place too much reliance on commercial catch-statistics.

Egg masses, juveniles and adults of the gastropod Palio dubia were found in shallow rocky habitats of eastern Canada dominated by the bryozoan Eucratea loricata. Multiple-choice experiments and direct field observations revealed that P. dubia prefers to feed on E. loricata. Courtship, copulation and egg-laying as well as hatching of P. dubia were closely related to the lunar cycle. Reproduction was preceded by increased pairing and aggregative behaviour. The duration of embryonic development in the capsules was 10–15 d. After hatching, most veligers were retained within the bryozoan branches during their pelagic phase (1–3 d). In multiple-choice experiments, settlement occurred preferentially on the bryozoan E. loricata. In the absence of the preferred substratum, the larvae continued to swim and died after a period that never exceeded 8 d. Juveniles remained associated with the bryozoans on which they settled and reached the adult size in ~3 months.

Stable isotope compositions were studied in particulate organic matter (POM), zooplankton and different trophic groups of teleosts to compare food chains based on plankton at two sites (lagoon and outer slope) in a New Caledonian coral reef. For each trophic compartment, δ13C values were always lower in the outer slope than in the lagoon. This result may be explained by potential differences in POM composition between the two environments, suggesting that the two food chains are based on different primary sources of carbon. In contrast, δ15N values did not vary between the lagoon and the outer slope, indicating that these two food chains presented similar length and trophic levels, despite being distinguishable.