A single maturity classification key applied to five common chaetognath species of the eastern Mediterranean is presented. The efficiency of the key was tested using biometrical data: body length (BL), ovary length (OL) and seminal vesicle width (SVW). For each species the key proved easy to use and efficient in the distinction of the maturity stages providing a satisfactory size separation between them.

Density and spatial distributions on an intermediate scale of two flatfishes—marbled flounder Pleuronectes yokohamae, and the brown sole Pleuronectes herzensteini (Pisces: Pleuronectiformes) within large (10,000–100,000 m2 patches of homogenous substratum (sand and silted sand)) were studied. Both species dominated in the demersal fish community. Densities of brown sole, were significantly higher in both types of habitat. Flatfish distribution was highly patchy and the mean fish densities in groups were as much as ten times higher than the mean fish densities in the area. More than 85% of all recorded flatfish were found within groups. Mixed groups with both species were most prevalent. The number of flatfish in one group ranged from 2 to 20. Brown sole was more abundant in the area and dominated in mixed groups. Levels of contacts between group members and densities within groups were inversely related to visibility condition. It is suggested that flatfish form a group and stay in the group, attracted by foraging movements of other flatfish and by plumes of upset particles caused by their bottom digging movements.

Two species of large extension feeding barnacles are abundant on exposed tropical rocky shores of northern Australia. The cirri of many specimens carry varying numbers of a commensal diatom in some cases with as many as 2000 individuals on a single cirrus. The araphid diatom resembles the genus, Lichmophora within the family Fragilariaceae although no description has yet been published. Species of Lichmophora are common benthic diatoms in these waters as an epiphyte on macroalgae and common primary fouling diatoms on test panels. The diatom reported here has not been found on any substratum other than the barnacles Tetraclita squamosa and Australobalanus imperator, very rarely on Balanus amphitrite. Analysis of the diatom distribution on the cirri shows significantly higher numbers on the posterior captorial cirri. The effect of commensal diatoms on the feeding efficiency of the barnacles is discussed.

Boring sponges are an important component of bioeroder assemblages in tropical coral reefs. They are considered as a potential threat for coral reef health, and the increase of dead corals is expected to promote their abundance. The relationship between the availability of dead coral substrata and the development of boring sponge assemblages was evaluated during El Niño 2015–16 at five reefs from Zihuatanejo, Guerrero, Mexico. Environment and substrate quality were assessed. Overall, environment conditions remained normal in relation to previous studies in the area. Only water temperature showed unusually high records at all sites and coincided with bleaching and mortality of corals, possibly caused by the effects of the El Niño event. Abundance of boring sponges in dead corals and coral rubble was lower than during previous studies. Although sponge abundance was not directly related to cover of both dead corals and coral rubble, cover of dead corals showed a high correlation with the variation in the structure of sponge assemblages across sites. Cliona vermifera dominated sponge assemblages at all sites, and its abundance was high under conditions of high cover of live corals and low cover of bleached corals. Since overall sponge abundance responded in a similar way, these results suggest that boring sponge assemblages dominated by C. vermifera are enhanced by conditions favourable for corals. Our results imply that El Niño events in the Mexican Pacific are not likely to cause immediate population outbreaks of boring sponges.

Studies on the settlement and the subsequent recruitment of intertidal organisms are crucial steps in understanding their population structure in a particular bioregion. However, studying the recruitment of intertidal organisms such as barnacles, with two-phase life cycle, and understanding the determinants of recruitment is a complex problem. Many processes which operate during the pelagic pre-settlement phase and benthic post-settlement phase at different spatial and temporal scales can determine the fate of barnacle populations. In this study, observations were carried out on settlement and recruitment of the intertidal barnacle Balanus amphitrite from a tropical environment influenced by monsoons at spatial and temporal scales. Settlement and recruitment both showed significant temporal variations. In general, settlement and recruitment was lower during the monsoon season except during monsoon breaks. Consistency in settlement and recruitment was mostly observed during the pre-monsoon season, and it coincided with peaks in larval abundance observed during the same season. In general, settlement remained more or less similar on different types of substrata, whereas recruitment differed significantly. Temporal variations observed in settlement and recruitment of barnacles could be due to the influence of monsoons in this region, which leads to seasonal fluctuations in physical factors such as local hydrodynamics, that influence the retention and dispersal of larvae in the adult habitats, and could also be due to variations in the availability of food for the larvae and the settled populations.

One juvenile specimen of the vadigo Campogramma glaycos was caught on 5 December 2000 in Piran Bay (northern Adriatic). This represents a northernmost extension in the known range of this species in the Adriatic Sea (and Mediterranean), and first record of a juvenile specimen in the Adriatic Sea.

The digestive system of sea spiders (Pycnogonida) presents peculiarities that have not been discussed in the context of their ecology or feeding behaviour. We investigated the digestive system of two Mediterranean species, a carnivorous species Ammothella longipes and a detritivorous Endeis spinosa, with special focus on its correlation with behavioural feeding habits. The midgut and hindgut sections did not present significant differences between the two species, but major differences were observed in the foregut, reflecting concordance to their diet and their feeding behaviour. Jaws, setose lips, the structure of the pharyngeal filter and musculature of the proboscis are the main differential elements when comparing feeding habits of A. longipes and E. spinosa. These elements are responsible for the reduction of the food pulp down to subcellular size. The digestion process observed in the species studied agrees with that observed in other pycnogonid lineages, but differs from most marine arthropods mainly because of the absence of midgut gland cells and the presence of a unique multifunctional type of midgut epithelial cell. Epithelial digestive cells are present in a small ‘resting’ form during starvation periods. During digestion, secretion granules possibly containing zymogen move to their apical border to be secreted to the midgut lumen, secondary lysosomes are formed and intracellular digestion occurs within them. Residual bodies are formed within the epithelial cell and released to the midgut lumen to be transported towards the hindgut. The characteristics of the digestive process of the pycnogonids studied seem to reflect a plesiomorphic state in arthropods.

In the family Alepocephalidae there are ca. 19 valid genera (Markle, personal communication). Whilst luminescence has never been observed, there are four genera, Xenodermichthys, Photostylus, Rouleina and Microphotolepis, which contain species bearing structures that have been interpreted anatomically as photophores (Herring & Morin, 1978). Among these four there is a remarkable diversity of photophore structure. The photophores of Xenodermichthys and Photostylus are similar in having well developed central cores (reddish violet in Xenodermichthys) and reflector layers, yet those of Xenodermichthys are sessile whilst those of Photostylus are borne on stalks (e.g. von Lendenfeld, 1887; Best & Bone, 1976). Not all species of Rouleina have light organs but where they are present they are sessile. Photophore structure of Rouleina has been examined only in R. maderensis Maul and was found there to be rather degenerate in adults (Markle, 1978). The light organs of Microphotolepis multipunctata Sazanov and Parin differ yet again in being scale covered, which contrasts with the naked photophores in the other three genera (Sazanov & Parin, 1977). The abundance and distribution of photophores in adults also varies with genus and species. Thus in Microphotolepis and Xenodermichthys they are extremely numerous and regularly arranged but in Photostylus they are few and less ordered (Günther, 1887; Beebe, 1933; Sazanov & Parin, 1977). In different species of Rouleina photophores may be relatively abundant and regularly arranged or few in number without such regular pattern (Maul, 1948; Uyeno & Kishida, 1977; Markle, 1978).

The faunas of volcanic islands must necessarily be introduced, and more recent introductions can be recognized by the patterns of their distributions. This is obvious in the Canary Islands, where we have spent 30 days studying distributions of Spirorbidae. We now regard these as a distinct family following Pillai (1970). We sampled all the major islands, by shore collecting and diving to about 10 m, and on almost all we found nine Mediterranean species, namely Protolaeospira striata (Quiévreux, 1963) and the eight opercular incubators (species of Pileolaria and Janua) that have been recorded from both Marseilles (Zibrowius, 1968) and Chios (Bailey, 1969).

This investigation aimed to study the relative growth, morphological sexual maturity and fecundity of the swimming crab Achelous spinicarpus in a tropical region, on the south-eastern continental shelf of Brazil (25°S). Biometry of all specimens was conducted, including measurements of the cephalothorax, cheliped, abdomen and gonopods. Relative growth was described based on the equation for allometry (y = axb), and size at sexual maturity was determined from inflections in relations involving the cheliped, gonopods (males), and abdomen (females), as dependent variables, related to the cephalothorax width (independent variable). Fecundity was estimated by the gravimetric method. The relations of the length of the chelar propodus and carpal spine to the carapace width without the lateral spines (CW) showed positive allometry in both sexes, with a significant variation in the constant ‘b’ for males between the developmental stages (juvenile and adult) and the size at maturity estimated at 37 mm CW. In females, the abdomen was most appropriate for the estimate of morphological maturity, which occurred at a smaller size (32 mm CW), with a change in the growth pattern between the stages, passing from isometric (juveniles) to positive allometric (adults). The gonopods also showed different growth rates between developmental stages, in synchrony with the variables of the cheliped. Mean fecundity for the species was 53,984 eggs, with a positive correlation between the number of eggs exteriorized and the size of the female; the equations allowed interconversion between these variables, due to the adjustment of the power function (r2 ≥ 86%).

The annual gametogenic cycle in the blue mussel, Mytilus edulis L. was investigated from May 2010 to May 2011 in two locations in north-western Iceland. Food availability (chlorophyll-a) was high in early spring at both sites, with a summer maximum in July in Steingrimsfjördur but an autumn maximum in September in Patreksfjördur. Gonad development started in November at both sites, with ripe gametes still visible in the follicles, and continued throughout the year, except for a very short time prior to spawning in Steingrimsfjördur. Gametes developed mostly between November and May. Spawning was protracted, lasting from July to early winter at both sites. The main spawning events occurred from August (11.7°C) to October (9.4°C) in Patreksfjördur, but from July (9.8°C) to October (8.6°C) in Steingrimsfjördur

Five of 26 flathead mullet (Mugil cephalus) captured in the Seekoei River estuary in South Africa showed haemogregarine infections. Both trophozoites and gamonts were observed, and image analysis technology was used in parasite morphometric description. Gamonts were compared with those of Desseria mugili from Brazil and found to be different. The parasite mostly closely matched a haemogregarine previously illustrated, but not described from South Africa, and apparent lack of merogony suggested that it was a species of Desseria.

Distribution of fur seals Arctocephalus australis has been studied in October 2007 on the western, southern and eastern Falkland shelves during the survey of spawning grounds of the red cod, Salilota australis. Fur seals presence/absence, numbers and sex were recorded at every oceanographic station. Animals were found foraging on the shelf edge south-west of the islands, in a productive zone with quasi-stationary eddies at a periphery of upwelling. It was also the zone of maximum abundance of lobster-krill, Munida spp.—an important food source of fur seals and aggregations of both red cod and blue whiting, Micromesistius australis. No fur seals were found in waters of the relative cold and saline Falkland Current as well as in the relatively warm, fresh and oxygen-rich waters of Argentine Drift. It allows supposing that position and extension of the foraging grounds are caused by oceanographic features determining distribution of prey species.

The effect of aerial drying of biofilmed surfaces to simulate a tidal emersion upon the settlement preferences of spirorbid and bryozoan larvae was investigated using choice experiments with still water conditions carried out in the laboratory. Aerial drying of biofilmed slates and pieces of Fucus serratus for 1 h at 20°C negated their usual settlement-inducing properties to larvae of Spirorbis spirorbis, S. tridentatus and Flustrellidra hispida. Such larval settlement preference may contribute to observed variations in the natural distribution of these species in the intertidal.

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.

The numbers of young fish, excluding clupeids, taken in a 2 m ring trawl in the plankton off Plymouth were as high in the year 1966 as they were during the 1920s and early 1930s. There is thus evidence that the period of decreased abundance which began after 1934 and has apparently persisted since then may have ended. The year 1966 was a very early year for spring spawners and this can be correlated with the high water temperatures prevailing in the early months of that year.

The vertical distribution of the hydromedusa Aequorea ?forskalea was investigated using observations from the research submersible ‘Jago’ collected during 36 dives off the west coast of southern Africa during November 1997 and April 1999. The mean population depth of Aequorea ?forskalea deepened with increasing sea surface temperature. We suggest that this behaviour enables individuals to avoid offshore advection, to minimize spatial overlap with other large medusae and to maintain their position over the middle of the shelf.

This study analysed the regime shift of tope shark and the overlapping taxa Raja spp. in the Alboran Sea. Tope shark and Raja spp. landings are both significantly correlated with the North Atlantic Oscillation (NAO). A significant negative correlation was found between Raja spp. landings and tope shark landings. This finding suggests that climatic oscillations affect regime shifts between these taxa in the Alboran Sea. Studies are scarce on the dependence of deep-sea communities on biological and physical processes occurring in near-shore pelagic environments mediated by large-scale atmospheric phenomena. Similar to previous studies on the Mediterranean Sea, a close association was found between landings of deep-water animals and the NAO. The main conclusion is that the regime shift of tope shark and the overlapping taxa Raja spp. is mediated by a negative NAO and accumulated snow.

The hypothesis is proposed that inorganic ammonia may be adsorbed on particulate matter in the sea. The random distribution of such particulate ammonia would account for the frequent ‘contamination’ reported in ammonia analyses and for the finding of nitrifying bacteria associated only with particulate matter, but never with sea water itself.

During the two years which I spent at Plymouth I collected a number of notes on the occurrence and distribution of the Hydroidea of the district, with the intention of giving a full account of the representatives of the group in the Plymouth area. My unexpected departure has prevented my carrying out this intention, but it has seemed to me worth while to publish my notes, fragmentary as they are, in the hope that they may be useful to my successors, and particularly because the list of the Hydroidea given in Part ii of the first series of this Journal is very imperfect. The list of species now given is incomplete, and had I had the time to search more closely for the inconspicuous and deep-water forms I should have been able to add largely to it. One species, which I only succeeded in obtaining twice, appears to be new to science.