A pedunculate barnacle, Leucolepas longa, occurs in densities over 1000 individuals m−2 on the summit of a small seamount near New Ireland, Papua New Guinea. Most of the population grows on vesicomyid clams projecting from sulphide-rich sediments, or on their dead shells, but the barnacle also settles on rock and on tubes of a vestimentiferan. Collections of several hundred barnacles allowed comparison of population and reproductive characteristics. The barnacle is a suspension feeder with a lightly-armoured stalk that can grow to 40 cm above the bottom. Growth appears to be rapid and both reproduction and recruitment are continuous. The barnacles brood egg masses within the capitular chamber and 46% of one sample was brooding. Lecithotrophic nauplii released upon retrieval to the surface were cultivated for 45 days. Metamorphosis to Stage IV yielded an actively swimming larva about 1 mm long overall, which still contained lipid reserves, indicating capacity for wide dispersal.

The ctenostome bryozoan Alcyonidium disciforme is the only known free-living Arctic bryozoan. Alcyonidium disciforme has a strictly Arctic circumpolar distribution. The material studied was collected during 1995–2002 in West Spitsbergen, Svalbard. Densities of the bryozoan in Van Veen grab and SCUBA diving samples are presented together with environmental data. Alcyonidium disciforme is restricted to the inner part of Kongsfjorden—main area of study. The activity of the tidal glacier situated in the inner part of the fjord results in strong environmental gradients, meltwater outflows causing salinity and temperature fluctuations together with high concentrations and rates of mineral material sedimentation. The wide bathymetric range of the species (8 to 240 m) suggests that depth is not its limiting factor within the fjord. High densities of A. disciforme recorded in shallow glacial bay waters indicate that it is highly tolerant of fluctuations in salinity. It also tolerates high mineral sedimentation rates; this is unusual for a suspension-feeding animal. The species has a very regular disc-like shape. Colonies develop a central hole when they reach approximately 3 mm in diameter. There are significant positive correlations between wet mass vs colony diameter, wet mass vs central hole diameter, and diameter of the whole colony vs central hole diameter. Alcyonidium disciforme is adapted, through its colony shape and zooids filled with sand particles acting as a ballast to survive in a dynamic sedimentary environment.

The Monaco shrimp Lysmata seticaudata is a warm temperate species with strong potential for the marine aquarium industry and knowledge on embryo production and brood loss during incubation is essential for the establishment of proper maturation techniques. Average (±SD) brood size of small (total length (TL) 40–44 mm), medium (TL 48–52 mm) and large (TL 58–62 mm) simultaneous hermaphroditic (SH) phase were 753 (±215), 1351 (±163) and 1810 (±264) newly extruded embryos, respectively, in early reproductive season (ERS); and 745 (±258), 1314 (±191) and 1813 (±219), respectively, in late reproductive season (LRS). Senescence does not seem to occur in the Monaco shrimp, since during both ERS and LRS larger SH shrimp always presented a higher number of embryos and negative allometry was not recorded. No significant differences in brood size were recorded among broods at different embryonic stages of shrimp in the same size-class in both ERS and LRS. Brood losses recorded from embryonic Stage 1 to Stage 4 for small, medium and large shrimp were 14.3%, 11.3% and 8.9%, respectively, for ERS and 10.9%, 14.4% and 12.2%, respectively, for LRS. The mean embryo volume in the same development stage was not significantly different among the small, medium and large shrimp, and between ERS and LRS for shrimp of same size-class. For all shrimp size-classes during both ERS and LRS, mean embryo volume significantly increased from 108.5% to 127.9%, from first to last embryonic stage. The occurrence of sex change does not affect egg production since small females in ERS (before the major period of sex change) and LRS (after the major period of sex change) had similar brood sizes.

Uric acid is an excellent nitrogen source for the growth of cultures of Platymonas convolutae, the symbiotic alga from Convoluta roscoffensis, and related Platymonas and Tetraselmis species. Nitrate-grown cells of P. convolutae and T. tetrathele have two uptake systems for uric acid, which conform to Michaelis–Menten kinetics; a high-affinity system operating in the concentration range 0·2–4·5 μM a nd a low-affinity system operating at higher concentrations of uric acid. Uric acid uptake by P. convolutae is abolished by uncouplers of phosphorylation. In darkness, intact cells of P. convolutae metabolize [2-14C]uric acid to [14C]carbon dioxide. These results are consistent with the proposal that the algal symbionts of C. roscoffensis utilize uric acid, received from the host, as a nitrogen source.

Aposymbiotic juvenile and symbiotic adult C. roscoffensis under standard culture conditions contain uric acid. The solid uric acid content of juveniles declines on establishment of symbiosis with P. convolutae and the endogenous uric acid is utilized in the adult symbiosis under conditions of nitrogen demand. However, adult C. roscoffensis do not utilize exogenous uric acid. The growth of adult but not juvenile C. roscoffensis is dependent on nitrogen enrichment of the medium, and it is proposed that uric acid utilization is of significance to the growth of the developing symbiosis in a nitrogen-poor environment.

Simple community parameters, such as number of species caught and the species diversity of a planktonic group (in this case Ostracoda), have been found to be stable enough in time and space to detect shifts in these parameters likely to be generated by interannual and decadal variation, especially if sampling is conducted at mesopelagic depths. At this time scale, changes in spatial variability will be expressed most clearly as shifts in zoogeographical boundaries. The clearest boundary to be detected in the North-east Atlantic occurs in the vicinity of 40°N, across which is a rapid equatorwards reduction in the total available nutrient as a result of a reduction in the depth of the mixed layer in winter. The boundary at 40°N is marked in satellite images by a sharp reduction in seasonality of surface chlorophyll concentrations. In the planktonic ostracods there is a sharp decline in both species numbers and diversity on the poleward side to a depth of at least 2000 m. If these changes are related to the degree of seasonality in the production cycle, then they can be expected to be climatically controlled. Monitoring this boundary will give an unambiguous signal of any future climate change, natural or anthropogenic, having a significant biological impact on the oceanic ecosystem and on fluxes of material within the water column.

Some features of the digestive and reproductive systems, as well as the habits and swimming of the pteropod Clione limacina have been studied from specimens of the dwarf ‘southern’ race, which occurs at Plymouth. The animal swims rapidly by the sculling action of its two short rounded ‘wings’ or parapodia. Its buccal mass is characterized by specialized prehensile organs, consisting—as well as the radula—of adhesive tentacles (cephaloconi) and a pair of hook sacs. The rest of the gut is simple, consisting chiefly of a ‘stomach’ formed by two spacious digestive diverticula, that have replaced the true stomach. The lining includes absorbing-digestive cells and excretory cells. C. limacina is a protandrous hermaphrodite. The size distribution of a sample of 338 is shown. The youngest specimens are all males; in older groups developing oocytes are found, and in the largest are eggs not yet ready for shedding (September), as well as sperms. The genital tract is of the primitive opisthobranch form, with a sperm-storing hermaphrodite duct, albumen gland and mucus gland. An external seminal groove leads forward to the penial sheath in the head. The structure of the penis and prostate is described, and some previous views on the nature and functioning of these parts are criticized. Finally, the relationships of the gymnosomatous and thecosomatous pteropods are briefly reviewed, and the use of separate orders is recommended in place of the recently revived single group Pteropoda.

Protozooplankton growth was measured by incubation in a walk-in cooling room at 5°C of filtered seawater from six stations on a south–north transect from open water through drift ice and into fast ice in the central Barents Sea (72°30′N–76°32′N). Eight species of naked ciliates, two species of tintinnids, seven species of athecate dinoflagellates and nine species of thecate dinoflagellates grew in the 24 and 48 h bottle incubations. Maximum potential mean specific growth rates of 0.84, 0.59, 0.39 and 0.39 d−1, respectively, indicated a hierarchy in growth rates determined by taxonomic differences where growth of naked ciliates > tintinnids > athecate dinoflagellates > thecate dinoflagellates. The mean±SD in situ temperature (4 to −1.8°C) corrected growth rates (Q10=2.8) for the six stations (0.74±0.31, 0.74±0.16, 0.25±0.16, 0.23±0.27 d−1) also suggested a higher growth for ciliates in comparison to dinoflagellates. Additionally, it revealed that the naked ciliates responded to the increased food availability, whereas this was not the case for all other groups of protozooplankton.

When observed from a submersible, the mesopelagic paralepidid Notolepis rissoi (Pisces: Paralepididae) will hover head up with the body at about 45°. The fish's swimming motion is restricted to the extreme caudal region with most of the body rigid. The trunk lateral-line canal ends at about the position that caudal motion becomes noticeable and there is a great decrease in neuromast size near the posterior end of the canal. The size of the neuromasts is also inversely related to the percentage of red muscle at the same body level. The eyes have an aphakic space oriented dorso-anteriorly at about 45° to the body axis so that during hovering the aphakic space is oriented vertically. Retinal anatomy indicates that photoreceptors opposite the aphakic space appear to enhance resolution at the cost of sensitivity, whilst lateral photoreceptors enhance sensitivity at the expense of resolution. We interpret the swimming attitude and mechanics as adaptations to minimize self-induced oscillations which would be deleterious to visual and lateral-line function.

The trematode Parorchis acanthus is widely distributed and exhibits a broad host spectrum, with larval stages occurring in marine gastropods and adult flukes parasitizing on various seabird species. Unlike the majority of digeneans, its cercariae do not invade a second intermediate host but encyst on a substrate in the open. In a series of laboratory experiments, we investigated factors influencing cercarial emergence and settlement of P. acanthus. Emergence of cercariae from the gastropod intermediate host Nucella lapillus increased with increasing temperature, whereas cercarial encystment success decreased. Numbers of emerged cercariae were highest in the presence of light and water. However, although in much lower numbers, cercariae were also released from N. lapillus and successfully encysted under relatively dry conditions. Cercariae were found to settle predominantly on filtering blue mussels Mytilus edulis, suggesting that cercarial concentration on the valves is largely facilitated by the bivalve's inhalation current. After being inhaled, cercariae actively emerged from the mussels using their suckers and subsequently encysted on the shells, preferably along the rim of the valves. Barnacle epibionts Semibalanus balanoides were observed to impair cercarial settlement on mussels, by disturbing or preying on cercariae. Whilst settlement success of cercariae on M. edulis increased with increasing mussel density, intensity of encysted metacercariae decreased. Furthermore, cercariae settled more efficiently on small than on large mussels. Our findings suggest that the transmission of P. acanthus cercariae is regulated by a range of abiotic and biotic factors, with filtering activity of mussels playing a key role by enhancing accumulation of cercariae on a substrate suitable for transmission to the bird final host.

The species composition, abundance and spatial distribution of macroplanktonic cnidarians in the eastern part of the Weddell Gyre are described from a series of nekton samples collected over three depth ranges between 0 and 2000 m. On average, cnidarians contributed 52·6% to the biovolume of these samples, although the range was high (5·0–93·1%). In total 23 species of siphonophores and 20 species of medusae were identified; a number that is very high in comparison with previous studies. There was a high diversity at bathypelagic depths, with 38 species being collected below 1000 m. The most abundant siphonophores were Dimophyes arctica (up to 45 nectophores per 104 m3) and Heteropyramis crystallina (up to 22 nectophores per 104 m3). The most abundant medusa was Pantachogon haeckeli (up to 30 specimens per 104 m3). Medusae were most abundant at mesopelagic depths, reaching 46 specimens per 104 m3 in the 500–1000 m depth range. Smaller calycophoran siphonophores were concentrated in the top 500 m of the water column, with total numbers averaging 107 per 104 m3. The number of larger calycophorans in-creased with depth, being most abundant in the 1000–2000 m depth range. Although many species had a widespread geographical distribution within the sampling area, the hydrographical conditions appeared to be affecting the distribution of some.

Amphinomida is an ‘isolated’ clade within the polychaete group Aciculata and traditionally includes the families Amphinomidae, Archinomidae and Euphrosinidae. Archinomidae were erected for a single species, the hydrothermal vent polychaete Archinome rosacea. Originally, A. rosacea was assigned to Euphrosinidae although it shares more morphological similarities with Amphinomidae. In this study we assess the position of Archinome, Euphrosinidae and Amphinomidae by using molecular data from nuclear 18S rDNA and 28S rDNA. Parsimony, maximum likelihood and Bayesian analyses are performed on the nucleotide datasets covering in total 19 terminals from Amphinomidae, Euphrosinidae, Archinomidae and outgroups. Our results conclusively show that Euphrosinidae and Amphinomidae are sister taxa and that Archinome is sister to Chloeia within Amphinomidae. Based on these results the family name Archinomidae is treated as a junior synonym of Amphinomidae.

Diving observations and more wide-spread coverage by Asdic show that the late Holocene basal neritic deposits of the broad bay between The Lizard and Start Point are represented by three main facies whose character depends on the two bed-transport paths converging there. The sheet sands laid at the end of the path with a good supply show a progressive geographical change in texture. On the other path, where sand is in short supply, there are elongated patches of somewhat coarser, well-sorted sand with ‘silt’ balls, alternating with shell-rich gravel patches. While the sand patches are laid out along the path of the strongest tidal currents, the ripple marks of the gravel can only be constructed by long waves from the Atlantic.

In experiments in Cornwall and Yorkshire 214 marked lobsters (Homarus vulgaris M. Edw.) were returned after moulting. Of these a number had moulted more than once, and the separation into once-, twice- and three-times-moulted lobsters was achieved using probability paper.

There was no significant difference in growth of lobsters from the two areas. It is concluded that the best method of plotting growth in lobsters is to plot carapace length before moulting against carapace length after moulting.

It is concluded that male lobsters show arithmetic growth over the size range 68–123 mm carapace length, adding a constant mean increment of 9.8 mm carapace length at each moult.

It is concluded that arithmetic growth, with a mean increment of 8.4 mm, adequately describes the growth of female lobsters over a small size range centred on a mean size of about 85 mm, but would lead to inaccuracies over a wider size range.

The concept of arithmetic growth in relation to the general growth pattern is briefly discussed.

Introduction

In a population study a knowledge of the growth rate is essential. In crustaceans estimation of the growth rate is complicated by two factors: first, it is usually not possible to age the animals, and second, the growth rate is made up of two components, the increase in size at moulting and the frequency with which moults occur.

The present paper presents data on the growth of lobsters at a moult, obtained from field experiments conducted in Cornwall in 1957–59, and in Yorkshire in 1958 and 1960.

1. Putrefaction in sea-water sets free compounds toxic to Calanus. A portion of these compounds withstands oxidation to non-toxic forms in air saturated water for considerable periods.

2. “Deep water” from the English Channel contains a catalyst, probably an iron compound, which increases the rate of oxidation of a number of easily oxidisable organic compounds. Its action is inhibited in surface and inshore waters by dissolved organic matter.

3. Hydrogen peroxide decomposes relatively quickly in “deep water” from the English Channel, at a velocity corresponding to that of a monomolecular reaction. A catalyst, probably an iron compound, active towards hydrogen peroxide, occurs in sea-water. The action of the catalyst is inhibited by dissolved organic substances in surface and inshore water, until such substances are oxidised by the hydrogen peroxide.

the embryonic and larval development of epinephelus malabaricus are described and illustrated for the first time. fertilized eggs, with a mean diameter of 0.90±0.02 mm and a range from 0.87 to 0.93 mm, were spherical, transparent, buoyant and unpigmented. embryonic development lasted 26 h 30 min at 25.5°c. newly hatched larvae were 1.93±0.04 mm in total length (tl) with 26 (11+15) myomeres and had an oil globule in the ventroposterior area of the yolk sac. three days after hatching (2.76 mm tl), the mouth opened. early larvae had two clusters of well-developed melanophores appearing on the alimentary canal and at the caudal region of the body, and the appearance of xanthophores on the dorsal finfold. nine days after hatching (4.04 mm tl), the buds of the second dorsal and pelvic fin spines had appeared. at 5.41 mm tl, the notochord was slightly flexed, and the hypural bones and caudal fin rays had begun to develop. at 7.39 mm tl, the ratios of the second dorsal and pelvic-fin spine lengths to tl attained their maximums, 52.68% and 48.62%, respectively. at 20.19 mm tl, all fins had the adult complement of rays and spines. by 30.18 mm tl, the body had become red, with five irregular, oblique, dark brown bars visible on the body. the larval habitat shifted from the surface and middle layers to the tank bottom.

Sperm whales (Physeter macrocephalus) typically produce sharp onset, broadband pulse sounds at varying repetition rates. Acoustic recordings of different social units of sperm whales in the Mediterranean Sea included apparent non-click sounds of tonal quality, termed ‘squeals’. Quantitative analysis of the spectral signal and waveform indicate that although squeals are perceived as tonal and appear spectrally as narrowband frequency-modulated structures with harmonics, they actually consist of pulses at high repetition rates exceeding 1600 clicks/s. Squeals contained energy at between 400 Hz and 22 kHz, with mean peak energy at the relatively low frequency of 700 Hz. Five spectral forms of squeal could be recognized, with the dominant form (45%) of squeals showing a decrease in frequency along the squeal contour. Mean click repetition rate ranged between 713 and 1385 clicks/s for individual squeals, and also varied within squeals at rates of between 64 and 444 clicks/s. Variation in click repetition rate was reflected in the frequency spacing of the spectral sidebands, in a statistically significant inverse relationship. Squeals were recorded only during bouts of sperm whale social behaviour, consistent with their having a communicative social function. Sperm whale squeals are structurally and audibly similar to the burst-pulse sounds produced by many smaller odontocete species, and might fall on the continuum between distinct click trains and pure-tone whistles.

The population biology and reproduction of the hermit crab Clibanarius longitarsus were studied with emphasis on size structure, sex ratio, breeding season and fecundity. Specimens were sampled monthly over a period of one year (January–December 2003) at Costa do Sol mangrove, Maputo Bay, southern Mozambique. A total of 597 individuals was obtained of which 202 were males, 192 non-ovigerous females and 203 ovigerous females. Annual size–frequency distributions were polymodal for males and bimodal for non-ovigerous and ovigerous females, respectively. Sexual dimorphism was recorded by the larger average size attained by males in relation to females. Sex ratio was female-biased during most months of the study. Clibanarius longitarsus showed a higher reproductive activity with two major peaks (March and October). Juvenile recruitment was continuous throughout the study period. Clutch size was positively associated with female size. The high number of ovigerous females as obtained in the present population may evidence a higher reproductive activity displayed by C. longitarsus at Costa do Sol mangrove.

The shallow water sea anemone Phymanthus crucifer exhibits three distinct morphotypes, characterized by the presence or absence of protuberances on the marginal tentacles, as well as intermediate forms. The taxonomic status of the different morphotypes and the diagnostic value of protuberances on the tentacles have been debated for this species and the family Phymanthidae. We analysed the external and internal anatomy, cnidae and three mitochondrial molecular markers for representatives of each of the three morphotypes. In addition, we address the putative monophyly of the family Phymanthidae based on molecular data. With the exception of the protuberances, our morphological and molecular results show no differences among the three morphotypes; thus, we consider this feature to be intraspecific variability within P. crucifer. Furthermore, molecular data reveal that the family Phymanthidae is not monophyletic. In addition, we discuss several diagnostic morphological features of the family Phymanthidae.

The demographic structure of a population of Paracentrotus lividus living in a coastal Mediterranean lagoon was studied in 1990. Analysis of this structure revealed that the population examined was made up of four distinct cohorts which represented individuals 2, 3, 4 and over 4 y of age. The variability in demographic structure as a function of biotope revealed that sea urchin migration occurred from the pebble area (recruitment area, high sea urchin density and overgrazing facies) towards areas made up of Cymodocea nodosa sea grass beds (growth areas, low density and abundant prefered food). These migrations seem to have been caused by food limitation in the former biotope coupled with a shift in diet in young individuals.

The saithe, Pollachius virens (L.), makes substantial diel vertical migrations like many other teleost fish. Adulst saithe offshore are known to ascent at dusk from 100 to 10 m (Schmidt, 1955) during which they experience a pressure decrease from 11 to 2 atm. If the swimbladders of these fish were fully adapted to the daytime depth, the gas of the swimbladder (which ‘obeys’ Boyle's Law) would expand 4½ times and rupture the swimbladder wall (Tytler & Blaxter, 1973). Even if not fullly adapted it is likely that some increase in volume would be experienced, giving not only the danger of the swimbladder bursting, but also a serious equilibrium problem as the fish become more positively buyant during the ascent. Jones (1952) for example suggested that the physoclistous perch adapted to a particular pressure could only cope with a 33% decrease in pressure without rising to the surface out of control.