INTRODUCTION

The preceding paper (Allen, Blaxter & Denton, 1976) describes the development of the swimbladder-inner ear-lateral line system of the herring.

In the larval stage of herring the pro-otic bullae start to develop at a body length of about 18 mm. Between 18 and 30 mm the bullae become filled with gas. At 26 mm the lateral recess membrane starts to develop, becoming silvered at about 42 mm. The lateral line develops between 19 and 45 mm. The swimbladder silvers and contains gas from about 38 mm. The adult system is complete at 50–60 mm body length, some four months after hatching.

This paper concerns the system in its intermediate stages of development. It examines the problems of how the bullae are filled with gas and how the gas spaces are maintained. It gives evidence on the possible roles of the gas-filled spaces as hydrostatic pressure receptors and as aids to buoyancy and discusses the limitations of the system before it can gain or lose gas to a gas-filled swimbladder.

After transplantation and acclimatization of populations of the barnacle Balanus balanoides from the coast of New England to the Menai Straits, differences in breeding behaviour persisted over a period of from 4 to 18 months. The two populations are believed to belong to distinct physiological races.

The New England populations fertilized 1½–3 weeks in advance of adjacent British populations.

Embryonic development in the post-cleavage stages of the New England population proceeded in vitro at about twice the rate of the development of the British population, under identical conditions.

The volume of the eggs of the New England population was 1.3–1.6 times as great as the volume of the eggs of the British specimens.

Both populations, when growing in British waters, liberated their nauplii in March at a time which coincided with the beginning of the vernal plankton increase in the locality. The embryos of the American population had therefore remained in the mantle space for a much longer period than had those of the British specimens and for a longer period than that reported for New England populations in their native habitat.

In B. balanoides the time of fertilization and rate of development may be genetically adapted in each general locality so that the embryos reach full term before the plankton increase is due. The actual time of liberation is then mediated by the hatching substance in response to prevailing food conditions.

If the B. balanoides population of the Western Atlantic area as a whole belongs to a physiological race distinct from that of the Eastern Atlantic, and responding differently to temperature levels at the breeding season, there is no reason to expect any close correlation in respect of environmental conditions between the southern limits of the species in Europe and in America.

While engaged in the examination of some vase pictures which have been stated to represent certain parts of the shores of the Bay of Pozzuoli as it existed in Roman times, I was struck by two drawings of Roman Oyster culture grounds, or ostrearia, which seem to me to be of considerable interest, not only as affording us direct information concerning the method of oyster culture employed by the Romans in the neighbourhood of Baiæ, but also because they show clearly that that method was the same as the one which still survives and is still carried on, in common with so many other Roman customs in the same locality, exactly as it was nearly two thousand years ago.

Mytilus galloprovincialis Lmk. is recorded as dominating the mussel population on the north coast of Devon and the north and south-west coasts of Cornwall from Instow to the Lizard. It was also found less frequently on the coast of South Wales from Angle to Cardiff and on the south coast of Cornwall from the Lizard to Plymouth.

The chief distinguishing features of M. galloprovincialis from Cornwall are summarized, in comparison with M. edulis L.

M. galloprovincialis is apparently intolerant of estuarine conditions, but otherwise appears to be ecologically similar to M. edulis.

M. galloprovincialis is not resistant to infection by Mytilicola intestinalis, but appears to be less affected by the parasite than is Mytilus edulis.

The synonymy of the species is briefly discussed and it is concluded that, although earlier workers tended to confuse M. ungulatus L. (recorded also as M. ungulata and M. angulata) with M. galloprovincialis Lmk., the two types are distinct. M. ungulatus is a name of doubtful validity applied by Linnaeus to a distorted form of M. edulis.

Styela mammiculata n.sp. is based on four specimens collected in the Plymouth area during the summer of 1953. The most noticeable external feature is the extensive mammillation of the test. The mammillae are much smaller than those of Phallusia mammillata and deserve to be called rather ‘mammiculae’.

Of the four specimens, two were taken from Drake's Island buoy (National Grid Reference, 20/4753)m Plymouth Sound, growing about half a metre below the water line, and two from the oyster bed of the Lynher river estuary, near Antony Ferry (National Grid Reference, 20/4257), growing about 12 m. below low-tide mark attached to oyster shells. The largest specimen was from the latter locality and measured III mm. long in the contracted, fixed condi- tion. The smallest, from Drake's Island buoy, was 54 mm. long.

Cetacean species and their habitats are under threat and effective marine management mitigation strategies require knowledge and understanding of cetacean ecology. This requires data that are challenging and expensive to obtain; incidental sightings/strandings data are potential underused resources. In this study, incidental cetacean sightings (N = 6631) and strandings (N = 1856) in coastal waters of Cornwall, south-west Britain (1991 to 2008) were analysed for evidence of spatial and temporal patterns or trends. Eighteen species were recorded sighted and/or stranded; key species were identified as bottlenose dolphin (Tursiops truncatus), harbour porpoise (Phocoena phocoena), common dolphin (Delphinus delphis), Risso's dolphin (Grampus griseus) and minke whale (Balaenoptera acutorostrata). There were significant decreases in bottlenose dolphin sightings and pod size but an increase in harbour porpoise and minke whale sightings. Cetacean strandings showed a recent decrease over time although there was a significant positive trend in harbour porpoise strandings that correlated with sightings. Incidence of sightings and strandings were both greater on the south coast than the north coast. When Marine Tour Operator data were analysed, distinct species-specific inshore and offshore habitat use was evident. With rigorous interrogation and editing, significant patterns and trends were gained from incidentally collected data, highlighting the importance of public engagement with such recording schemes and the potential of these underused resources.

Larger algae and protozoa plankton of inshore waters seem generally well known, except for a few groups of very small flagellates. The same statement cannot be made for the micro-organisms of the bottom sediment-water interfaces and intertidal sand. Many ecologists and physiologists would like to know more about what species and how many individuals can be expected in such locations as these.

The leopard-spotted goby, Gobius forsteri Corbin 1958, described from the western English Channel, is identified with the Madeiran Gobius ephippiatus Lowe 1839, the latter name becoming a senior subjective synonym for this species. From study of variation, with size of fish, in number of lateral-line sensory papillae in preopercular-mandibular row i, it is concluded that the Aegean Gobius thori De Buen 1928 may also be referred to G. ephippiatus. Examination of the syntypes of G. macrolepis Kolombatovic 1891, from the Adriatic, has shown that this name belongs to a close relative of G. ephippiatus and not to Mediterranean populations of the Atlantic Lesueurigobius friesii (Malm), as recent authors have supposed. A new genus, Thorogobius, is proposed for G. ephippiatus, the type species, and G. macrolepis, and a key provided to these two species, which differ in meristic features, development of pelvic anterior membrane and disc, head coloration, and relative number of sensory papillae. Further systematic data on material studied, synonymies, body proportions, papillae and meristic counts are also given.

As the complete list of known occurrences indicates, T. ephippiatus appears to be a warm temperate Mediterranean-Atlantic form which penetrates the eastern Atlantic boreal region around the British Isles at least as far north as the North Channel and eastwards to Lulworth Cove (western English Channel). As an inshore shelf species, T. ephippiatus occurs in or near crevices associated with vertical rock faces, from LWST to 30–40 m. Diet probably consists chiefly of crustaceans and polychaetes. Maximum total length recorded is 129 mm, and greatest age 9 years (determined from otoliths), with sexual maturity by the fifth year of life (age 4 +).

As well as being a popular sport fish, the bass (Dicentrarchus labrax L. 1758) is a valuable commercial species in England and Wales. In 1984 bass landings in England and Wales were estimated to have a first sale value of between £5–6 million (G. D. Pickett, personal communication). Concern has been expressed about the vulnerability of the stock to overfishing and to variability in recruitment, and there have been a number of studies of bass biology, distribution of the eggs and larvae, and of possible migratory movements of the fish during the adult phase, (Kennedy & Fitzmaurice, 1968, 1972; Kelley, 1979; Holden & Williams, 1974; Dando & Demir, 1985). This paper reviews the published data on eggs and larvae and presents new data on their distribution and abundance in the English Channel and southern North Sea between 1981 and 1984.

Food partitioning between species is a common strategy for avoiding resource competition which allows the coexistence of two or more species in the same place. In order to evaluate the feeding of four species of batoids regularly caught by artisanal fisheries in southern Brazil, the present study aimed to analyse and compare the diet of the four batoid species. The Chola guitarfish, Rhinobatos percellens, had a specialized diet, consisting predominantly of blue crabs Callinectes sp., followed by teleost fish. The Lesser guitarfish Zapteryx brevirostris also had a very specialized diet, consuming mainly on Polychaeta, followed by Caridea shrimp. The Cownose ray, Rhinoptera bonasus, fed mainly on Ophiuroidea, followed by Gastropoda and Bivalvia. Finally, the Rio skate Rioraja agassizi, fed on teleost fish, Gammaridae, Caridea shrimp and Dendrobranchiata shrimp. An analysis of similarity showed significant differences among species in their diet. The trophic levels of the batoids in this study are <4.0, placing them in intermediate trophic levels. The analysis of the diets indicates that feeding differs substantially among the four species, suggesting a partitioning of food resources available in the environment.

Relative spectral emission curves are available for the lights of many invertebrate animals, but none exists for fish. It seems likely that many bony fish use their photophores to signal to one another. Information about the spectral composition of fish luminescence is desirable to permit comparisons with the spectral sensitivities of fish eyes, to enable calculations to be made of luminous intensities, and to allow estimates to be made of the rate of attenuation of such lights in sea water. To further these ends, measurements were made of the spectral composition of the luminescence of the lantern-fish, Myctophum punctatum.

The timing of spawning and recruitment in the squid Loligo forbesi in Scottish waters is described on the basis of data from three sources: monthly samples of squid caught by commercial trawls (1986–1988), egg masses found by fishermen (1987–1991), and statistical data on animals caught by research trawls (1978–1987).

Spawning females were present in samples from December to June, with peak spawning occurring in March. Most records of egg masses were from these months, but eggs were also found in August and September. These results suggest that there is an extended spawning season.

Small squid (≤100 mm dorsal mantle length) were rarely present in commercial samples, but were recorded in research samples almost all year round. Thus there appears to be more or less continuous recruitment into the catchable population.

The results of the present study are consistent with published data from other parts of the geographic range in that there is a regular seasonal peak in spawning, and spawning adults disappear from the population in summer. Further interpretation of the life-cycle of this species is not justified on the basis of current knowledge, and more information is needed on migrations, geographical variation, and lifespan in Loligo forbesi.

The Raman spectrum of a cell homogenate obtained from the unfractioned blood cells of Ascidia gemmata was recorded in an effort to determine the ratio of the level of sulphate to that of vanadium in the blood cells. The ratio obtained was 1·47, which is close to 1·5, the value predicted if sulphate ions are present as the counter ions of V3+ ions. We found evidence that an aliphatic sulphonic acid is present in the blood cells, namely, the Raman spectrum of the cell homogenate included a band at 1044 cm−1, which corresponds to the symmetrical stretching vibration of the SO3− group of the anion of cysteic acid.

Off central Chile, around 33.5°S, the freshwater discharge of the River Maipo generates a small- to intermediate-size plume, which moves up to the north driven by the daily sea breeze and with localized effects on a costal zone of about 10–15 km. The influence of this river plume motion on abundance patterns of larval barnacles was studied in a ∼12 km long transect, including 2–3 stations inside the river plume, one station on the visible turbidity front, and two stations outside the plume. Shipboard campaigns were conducted in January (summer), August (winter), and October 2003 (spring). On each occasion, conductivity–temperature–depth casts, bottom track acoustic Doppler current profiler current measurements, size-fractioned chlorophyll concentration, and stratified plankton sampling were conducted. A significantly higher abundance of barnacle nauplii was found at the river plume front than at the plume or outside the plume. Abundance was highest in the upper 10 m of the water column, where most nauplius larvae were found. The river plume appeared as a surface layer of less saline water moving north of the river mouth, with a buoyant frontal structure progressing at speeds of 5 to 20 cm s−1. Although no peak in chlorophyll was observed at the buoyant front, the highest concentration of effective prey size for feeding nauplii (chlorophyl-a <5 and 5–20 μm) was generally associated with less saline plume waters. Thus, the accumulation of barnacle larvae at the front may facilitate foraging, potentially increasing larval growth and energy reserves. Our results suggest that the spatial structure and temporal dynamics of river plumes should be considered by benthic ecologists as transport mechanisms that potentially affect larval delivery and settlement of barnacles on rocky shores.

1. Eight species of Actinians (enumerated on p. 148) have been specially studied with regard to their reproductive processes.

2. Among these forms five methods of reproduction occur—longitudinal fission; laceration by tearing; laceration by constriction; production of young viviparously; deposition of ova.

3. Deposition of ova may co-exist with any other method, except perhaps in certain viviparous forms.

4. Apart from this, one method only prevails in any one of the selected species—

A. Longitudinal fission in Sagartia sphyrodeta and Diadumene luciœ.

B. Laceration by tearing in Sagartia elegans and Diadumene cincta.

C. Laceration by constriction in Sagartia lacerata.

D. Viviparity in Sagartia troglodytes and Cereus pedunculatus.

5. In Sagartia anguicoma neither viviparity nor asexual reproduction occurs.

6. The viviparous forms studied do not reproduce asexually; nor are those which reproduce asexually viviparous.

7. In the experiments and observations of the author and of W. E. Evans, no exceptions to the above statements occurred. The question of exceptions is discussed on page 161.

8. Four of the above species were selected for regeneration experiments. Pieces were cut off from the margin of the base in each (artificial laceration).

9. In Sagartia elegans (which lacerates naturally) it was found that nearly 100% of such pieces would regenerate easily; in S. lacerata the same was true in the best experiment.

10. In Sagartia troglodytes (which does not lacerate naturally) only two pieces out of 76 regenerated fully, and the regenerative ability of the species appeared to be weak. In S. anguicoma, however, the percentage of pieces which regenerated fully (and did so strongly) was very much higher, though not reaching that of S. elegans.

Artemia salina has been reared on unialgal diets of Phaeodactylum tricornutum, Monochrysis lutheri, Platymonas tetrahele and Chlamydomonas sp. In most instances the component fatty-acid distribution of the Artemia bore little resemblance to that of its food. Thus, oleic and stearic acids are relatively enriched in the shrimps, whereas hexadecatetraenoic acid is much depleted. It is suggested that the metabolic requirements of the shrimps is of at least equal importance to the composition of their food in determining the component fatty-acid distribution of their lipids.

As is well known, the species Gammarus zaddachi, established by E. W. Sexton in 1912 on material from European brackish and fresh-water localities, has caused great confusion among zoologists, as the characteristics distinguishing it from various related species, particularly Gammarus locusta, G. duebeni and G. pulex, have been very frequently disregarded. This confusion still persists to-day—that is amply shown by the material received for the present investigations from various museums.

Dogfish eggs would appear to be eminently suitable for physiological study because of their large size, easy availability (egg laying seems to be continuous throughout the year except for a break during the autumn (Craik, 1978)); their long lasting development (between 240 and 300 days from laying to hatching (Foulley & Mellinger, 1980a)); the clear separation between yolk-sac and embryo, and the fact that eggs are normally laid in pairs (opening up the possibility of keeping one of them as control whilst experimenting upon the other).

Fifteen marine strombidiid species were measured and identified after protargol staining of bottle-cast samples collected during an annual study of the ciliate microzooplankton in the Caribbean Sea. Nine of these are described herein as new species. One new species from the genus Tontonia, T. simplicidens sp. nov., is defined, based on the pattern of the girdle and ventral kinety. Six new species of Strombidium, S. bilobum sp. nov., S. eurystomum sp. nov., S. ioanum sp. nov., S. maedai sp. nov., S. pollostomum sp. nov. and S. sphaericum sp. nov. are defined, based on cell size and shape, the arrangement of the oral ciliature, and the nature of the macronucleus. One new strombidiid genus Cyrtostrombidium gen. nov., is defined by the presence of a unique oral ‘basket’ and the absence of the ventral polykinetidal zone. Two species of Cyrtostrombidium, C. longisomum sp. nov. and C. wailesi sp. nov., are distinguished, based on cell size and macronuclear structure. Assemblages of six previously-described strombidiid species, S. constrictum, S. dalum, S. epidemum, S. inclinatum, S. wulffi, and Laboea strobila are also briefly described.

The investigations in the American Tropics described in this paper were made during the summers of 1911 and 1912 under the auspices of the Carnegie Institution of Washington: the work was made possible by the invaluable help and kindness of Dr. Alfred G. Mayer, Director of the Department of Marine Biology. The investigations in Temperate waters were made from the Plymouth Laboratory of the Marine Biological Association of the United Kingdom, and my thanks are due to the Council and Director of the Association for giving me every facility for the work.