Data are presented on the density of ten species of Amphipoda and two species of Isopoda from terrestrial to aquatic (freshwater through brackish water to marine) habitats, derived using a new modification of the displacement method involving batch testing of animals and subsequent Probit Analysis of data.

Surprisingly few data are available in the literature concerning the densities of marine organisms. Extensive work on this topic was published some half a century ago by A.G. Lowndes. He reported widely on crabs and lobsters (Lowndes, 1943a), echinoderms (Lowndes, 1953) and fishes (Lowndes, 1955). In his paper to the Linnean Society (Lowndes, 1938a) he included data on some of the smaller freshwater Crustacea. Gross & Raymont (1942) have published on the specific gravity of the marine copepod Calanus finmarchicus.

In espousing the displacement method for dealing with live individuals (Lowndes, 1938a,b, 1942, 1943b, 1955), he dismissed summarily earlier techniques that involved ascertaining whether killed or narcotized animals sank or floated in liquids of known density. While we recognize the limitations of the old methods, Lowndes’ displacement technique, although very accurate for individuals (he quoted figures to five decimal places), is very tedious to replicate [“elegant if somewhat exacting”, according to Hutchinson, 1967] and so reliance tends to be placed on figures obtained for very few individuals, typically only one or two. Even Lowndes himself was wary of attributing significance to the last two decimal places in his estimations, since individuals will vary in density according to sex, the contents of the gut etc. (Eyden, 1923; Lowndes, 1938b; but see Fox & Mitchell, 1953).

Enhydrosoma curvirostre is redescribed from archived and new material with particular attention to the structure of the mouthparts and other details of the fine structure not previously reported. It is shown that the species cannot be maintained in Enhydrosoma but is more closely related to Cletodes, the genus in which the original author placed it. However, it is shown that the species must be assigned to a new genus, Spinapecruris, as a result of possessing autapomorphies on the maxillule (only seven setae on the basis), thoracopods 2–4 (a large spine on the distal margin) and possibly the caudal ramus (proximal insertion of seta VII) and lacking apomorphies which may define Cletodes.

The ninhydrin-positive patterns produced by chromatography of foot tissue of Nassariics reticulatus from Plymouth and North Wales and of specimens of Nassarius from Essex were established. The similarities and differences between the two are described and the consistent differences found are considered to be indicative of genetic differences between the specimens from Essex and those from the other two areas. The only factor found to affect the otherwise remarkably reproducible pattern given by individuals from the same area was the degree of starvation; the effect was reversible. The pattern given by another marine gastropod, Littorina littorea (L.), is also described. Reference is made to the potentialities of the technique.

At the end of June, 1924, a female of Typton spongicola, dredged by the Salpa, bearing eggs, was taken from the sponge Desmacidon fruticosus in which it lives, and given to me alive. This was placed in a Plunger Jar in the Laboratory, and on July 8th most of the eggs hatched out. The larvæ did not live long, and never sloughed the skin; but several were preserved, and the following notes on these are of interest, as very little is known of the development in the Pontoniinæ to which subfamily of the Palaemonidee in the Caridea, Typton belongs (Gurney, 1925). The female continued to live for some months at the bottom of the Plunger Jar without any sponge shelter. It ate any dead plankton, and was a useful scavenger. This is interesting, as its ordinary food is the Desmacidon in which it lives (Hunt, 1923).

Reproduction in the pantropical chiton Acanthopleura gemmata was examined at One Tree Island, Great Barrier Reef, near the southern limit of its distribution, using gonad histology and gonad index (GI). Gonad growth was associated with the onset of gametogenesis in mid-spring. Fully mature gonads were present from early summer until late autumn. During these months gametes at various stages of development were present in the gonads indicating a continuous pattern of gamete development and release over the six month spawning season. Following the maximum GI (March/April) there was a sharp drop in the index marking the end of spawning. In winter, the gonads entered a rest period and remained small in size. The reproductive pattern of A. gemmata at its southern limit is similar and 6 months out of phase to that reported for populations in the Gulf of Suez, at the northern limit of its distribution. This suggests that photoperiod may be an important factor in modulating reproduction. Reproduction of A. gemmata at One Tree Island is also similar to that for populations in the northern Great Barrier Reef.

This study characterized shell occupation by two species of hermit crabs and analysed the occurrence of ectosymbionts on their shells, in a comparative way. The hermit crabs Clibanarius antillensis and Calcinus tibicen were selected for this comparative study because of their abundance and wide distributions. Specimens were collected manually during spring low tides every 2 months, from February 2011 to January 2012 in north-eastern Brazil (03°S), and in south-eastern Brazil (23°S). The populations showed different patterns of shell occupation and ectosymbiont coverage. The plasticity of these ecological traits is discussed in a broad context and possibly correlated to habitat differences.

The near-cosmopolitan genus Clytia is abundantly found in coastal waters, but difficulties of identification in this genus make nearly all species records of medusae suspect. Complex life histories, ambiguous taxonomic characters, and phenotypic plasticity pose serious problems for accurate species-level identifications and future revisions of Clytia species. In the present study, morphological investigations and molecular analyses of Clytia specimens from the coastal waters of the East China Sea revealed Clytia gulangensis sp. nov. as a new species. DNA barcoding based on the mitochondrial cytochrome oxidase I (COI) gene supported the new species as a separate species within Clytia, and phylogenetic analyses based on mitochondrial 16S rDNA and nuclear 18S rDNA further confirmed this new species to be a distinct lineage. Moreover, detailed observation of medusae and polyps of this species showed sufficient morphological differences from other Clytia species for a diagnosis. Our results indicated that life cycle and DNA-based studies should be a standard approach in future biodiversity investigations of Clytia species.

An increasing number of studies have forecast the potential responses of marine life to future climate change. This study predicts how the distributional range of temperate and tropical worm reefs (WRs) might respond to climate and environmental changes (CECs). Compared with current distributions, the tested hypotheses were: (i) under a low CO2 concentration and active atmospheric carbon capturing scenario (RCP2.6), both tropical and temperate WRs will maintain their current distributions and face only slight multi-directional biogeographic changes along the century; and (ii) under a high CO2 concentration scenario (RCP8.5) WRs will shift toward higher latitudes, with marked changes for tropical species and slight changes for temperate species, specifically at the end of the 21st century. The hypotheses were tested using species distribution modelling, and exploratory statistical analyses were performed to tune model settings. Under scenario RCP2.6, in the middle of the century, areas of suitable habitat are predicted to slightly increase for the temperate WRs and conversely contract for tropical WRs. At the end of the century, multi-directional shifts without range retraction were predicted for both species, but tropical WRs showed major changes in their distribution. Under scenario RCP8.5 and throughout the century, multi-directional shifts increased the areas of suitable habitat for temperate WRs, whereas tropical WRs experienced shifts toward high latitudes and significant retraction at low latitudes. Results indicate that biogeographic range shifts are idiosyncratic for temperate and tropical WRs depending on the CECs scenarios considered.

Rock oysters of the genus Saccostrea are the dominating group of filter-feeding communities on rocky beaches worldwide. The edible rock oyster (Saccostrea cucullata) is used as food and fish bait along the Indian coast. Morphometric analyses of S. cucullata from Baindur, Karnataka (India) were performed from June 2010 to May 2011, aiming to establish relationships between length and weight (total weight, shell weight, meat wet weight and meat dry weight). Morphometric relationships between length (L)-breadth (B) and length (L)-width (W) were B = 6.4952 + 0.4619 L and W = 3.1806 + 0.3276L, respectively. The equations of the length (L)-total weight (TW), length (L)-shell weight (SW), length (L)-meat wet weight (WW) and length (L)-meat dry weight (DW) were TW = 0.001227L2.3973, SW = 0.001165L2.3164, WW = 0.000037L2.1327 and DW = 0.000030L2.3289, respectively. The allometric growth pattern revealed changes in shell shape and weight variation throughout ontogeny in rocky habitats. The condition index and meat yield of S. cucullata exhibited seasonality, with higher values recorded during the periods post-monsoon and pre-monsoon.

Many studies have already assessed how wave action may affect morphology of intertidal species among sites that vary in wave exposure, but few attempted to look to this issue in smaller scales. Using the most common limpet of the Brazilian coast, Lottia subrugosa, and assuming position on rocky boulders as a proxy for wave action at small scale, we tested the hypothesis that waves may also influence limpet morphology at a smaller spatial scale by investigating how individual size, foot area and shell shape vary between sheltered and exposed boulder sides on three shores in the coast of Ubatuba, Brazil. Limpets consistently showed a proportionally larger foot on exposed boulder sides for all shores, indicating that stronger attachment is an important mechanism to deal with wave action dislodgement at a smaller scale. Shell shape also varied in the scale investigated here, with more conical (dissipative) shells occurring in exposed boulder sides in one exposed shore across time and in the other exposed shore in one year. Shell shape did not vary regarding boulder sides across time in the most sheltered shore. Although we did not assess large spatial scale effects of wave action in this study, variations of the effect of waves at small spatial scale observed for shell shape suggest that it may be modulated by the local wave exposure regime. Our work highlights the importance of wave action at small spatial scales, and may help to understand the ecological variability of limpets inhabiting rocky shores.

This paper presents the results of a comparative study of five osteological complexes, the infraorbital bones, branchial arches, urohyal bone, interdigitation of the median fins, and the caudal fin skeleton, of some members of the fish family Tripterygiidae. Osteological characters that may prove valuable for taxonomic purposes are described, and on the basis of the material handled, their use to separate species within the family is discussed. Several formulae were developed for the distribution of the osteological complexes of the dorsal fin, dorsal and ventral caudal procurrent ray distribution, and caudal fin in the different tripterygiid species studied.

The physical characteristics of the Bay having been set out in the preceding paper, it will not be necessary to repeat that description here, since only special local featureswill be dealt with, as occasion arises. Peculiarities of distribution had been noted for the Trochidæ and Littorinidæ, and it was with a view to obtaining further information as to the operation of local littoral conditions and their effects upon the fauna that these grouops were more particularly examined. These notes detail some of the peculiarities, and outline what are believed to the controlling causes, at any rate for the central area of the Bay. It would be of great interest to know whether similar peculiarities have been, or can be, observed for other areas of coast. The region discussed lies between Gwbert-on-Sea at the mouth of the Teifi, to the south; and a point a few miles beyond Pwllheli to the north. The portion more closely examined extends from near Llanrhstyd, some eight miles south of Aberyswyth, to Mochras, a few miles south of Harlech. Some observations were also made about Portmadoc, Borth-y-Gest, and Pwllheli in the northern part of the Bay, and about New Quay, and the mouth of the Teifi the south, the most southerly being some miles below Cemmæs Head.

The sterol biochemistry of the highly advanced molluscan class – the cephalopods – is poorly understood. Few analyses of their component sterols have been published in which GC-MS has been employed (Voogt, 1973; Idler et al. 1978; ApSimon & Burnell, 1980) and these have only involved 5 species.

From the available data the cephalopods appear to have a much simpler sterol make-up than the other less-advanced molluscs. Cholesterol appears to be easily the predominant sterol (ca. 90%) with minor amounts of up to 10 other common marine sterols. Of the species analysed, four (Sepia officinalis, Octopus vulgaris, Eledone aldrovandi and Illex illecebrosus) had a very similar major and minor sterol composition. Only the more primitive Nautilus sp. (Idler et al. 1978) had a noticeably different minor sterol composition.

Voogt (1973) reported cephalopods to be able to synthesise sterols though molluscs generally appear only to be able to carry out this biosynthesis slowly (Goad, 1978). Cephalopods are extremely active carnivores and thus would be expected to have a diverse diet. If their component sterols are of a dietary origin, a considerable variation in their minor sterol composition might be expected on the basis of the range in sterol composition reported for pelagic organisms (e.g. Morris & Culkin, 1977), many of which may be possible dietary components.

Detailed knowledge however of cephalopod diets is limited. Quite apart from the fact that healthy specimens are rarely caught in nets, those that are caught often feed voraciously on the other organisms trapped in the net prior to being brought on board for examination.

The sampler to be described takes a small unstratified sample of the sea-bed, the sample being subject to a minimum of loss while being brought up. Such samples are of use in survey work, or for studies on grade size, mineralogical composition, chemical properties, or microfauna and flora of the deposits.

Although core-samples, in which the original stratification is retained, can be taken in soft muddy sediments without difficulty, it is not at all easy to take cores of sand or gravel. On such deposits an unstratified sample may be the best that can be obtained. Coarse sediments may be sampled by a dredge fitted with canvas bag, but when a small sample is required quickly, a light instrument which can be lowered vertically from the ship on a rope or hydro-graphic wire is needed. ‘Snapper’ samplers do not always take a satisfactory sample as the jaws may be prevented from closing by a pebble or shell wedged between them, much of the sample being lost while hauling up (cf. Stetson, 1938, p. 7). Stetson describes an instrument which takes a small semicircular core of sediment, the sample being sealed in the coring tube while being brought up, so preventing any loss of material. While no doubt taking good samples, the instrument is rather heavy (57 kg) and complicated in construction.

There have been recent attempts to improve our knowledge about dinoflagellates of the order Dinophysales either in Mexican marine waters or worldwide, and although new records and even new species have reliable illustrations and descriptions, this group is so diverse that it needs to be studied in more detail. This paper is the product of the analysis of net phytoplankton material collected from coasts of the tropical Mexican Pacific (Gulf of California, Central Mexican Pacific and Gulf of Tehuantepec), and the southern Gulf of Mexico. Material was studied using light microscopy and scanning electron microscopy (SEM). Eleven taxa (10 species and one variety) of the section Hastata were fully identified, with nine species studied for the first time by electron microscopy (only Dinophysis hastata and D. schuettii had been previously studied by SEM), and including seven new records for the Mexican Pacific (Dinophysis monacantha, D. nias, D. phalacromoides, D. pusilla, D. swezyae, D. uracantha var. mediterranea, and D. uracanthoides), and one new record for the Gulf of Mexico (Dinophysis uracanthoides). Two species remain as unidentified, as only one specimen of each was found. Additionally, we studied in detail the new species, Dinophysis conjuncta sp. nov., for which a full description is provided. Descriptions, measurements, illustrations and local distribution data are provided for each species.

The sulphur compound composition of the hydrothermal vent mussel Bathymodiolus azoricus (Bivalvia: Mytilidae) was analysed in order to determine the specific biochemical characteristics of a thiotrophic mode of nutrition. In specimens collected from two contrasting vent fields on the Mid-Atlantic Ridge (Menez Gwen and Lucky Strike), substantial differences in the sulphur composition were observed between tissues and sampling sites. Total sulphur content was higher for samples from Lucky Strike than for those from Menez Gwen. The amount of elemental sulphur in the gill of B. azoricus was in the same range as values previously reported for the vesicomyid clam Calyptogena phaseoliformis and the lucinid clam Lucinoma annulata. Rings of orthorhombic sulphur or compounds such as polythionates or organopolysulphides excreted in the cytoplasm by the symbionts may account for the large amounts of elemental sulphur evidenced for the first time in an hydrothermal vent mussel. A large proportion of the tissue-sulphur was incorporated into free amino compounds such as taurine, hypotaurine, thiotaurine and cysteine, and in a lesser extent to the tripeptide glutathione. In mantles, sulphur seems to be contained mainly in organic compounds such as proteins, mucopolysaccharides and lipids. However, the occurrence of specific compounds such as thiotaurine and elemental sulphur in gills indicate that in this tissue a large proportion of the sulphur might be involved in specific pathways related to transport, storage and detoxification of sulphide. Moreover, our results suggest a greater reliance on thiotrophy of mussels from Lucky Strike as compared to specimens from Menez Gwen.

This work reports on the fine structure and histochemistry of several regions of the alimentary canal in Pholoe minuta (Fabricius, 1780). Particular emphasis is placed on the elaborate secretory cells (tryptophan-containing secretion) associated with the pharyngeal jaws. Mucus gland cells were located and described for the oesophagus (acid mucins), pharynx papillae (sulphated acid mucins), pharynx luminal lining (mixed acid mucins) and the intestine (mixed acid mucins). Enzymic gland cells (zymogen-like secretory granules) were identified in the luminal lining of the pharynx and in the intestine. Lysosome-containing cells (presumably absorptive) were described in the intestine. Glycogen reserves were observed along the coelomic peritoneum and a seasonal pattern for their deposition and utilization is briefly discussed.

The glandular epithelium of both escae and caruncles originates from a solid, branched ingrowth of epidermal cells from the distal surface of the bulb-shaped light gland primordia in the larva. The lumina within the glandular epithelium appear to originate by the breakdown of the central cells within the solid mass of epithelial cells. An epithelium-lined duct connecting the central glandular lumina with the distal surface of the bulb-shaped primordium was seen only in sections of the posterior esca. This suggests that the intraglandular lumina are formed before the duct to the surface, which then develops within an initially solid strand of cells.

The oxygen content of air-equilibrated haemolymph from three species of hyperiid amphipods, Hyperoche medusarum, Parathemisto sp. and Hyperia galba was similar to that of air-equilibrated sea-water. The concentration of haemolymph protein was low in each case. Both features, taken together with the fact that we were unable to detect the presence of copper in the haemolymph in any of the species examined, suggests that hyperiids, unlike gammaridean amphipods, do not possess the respiratory pigment haemocyanin.

All the information available on the O2-binding properties of amphipod haemolymph has been derived from members of the amphipod sub-order Gammaridea. In common with many other crustaceans (Truchot, 1992), O2 carriage in gammarid haemolymph is facilitated by the presence of the copper-containing respiratory protein, haemocyanin (Spicer, 1994). Unfortunately no comparable data exist for the other major amphipod sub-orders, the Hyperiidea, the Caprellidea and the Ingolfiellidea. Consequently we have examined haemolymph from three species of hyperiid amphipod, Hyperoche medusarum (Miiller, 1777) and Parathemisto sp., from the west coast of Vancouver Island, Canada, and Hyperia galba (Montagu, 1813) from the Clyde Sea area, Scotland.