Feeding ecology of Liocarcinus depurator (Decapoda: Portunidae) in the Ria de Arousa (Galicia,north-west Spain): effects of habitat,season and life history

The diet of the portunid crab Liocarcinus depurator (L.) in soft-bottom areas of the Ría de Arousa (Galicia, north-west Spain) was studied by analysis of stomach contents, and by comparison of habitats of contrasting abundance, composition and diversity of prey communities. Monthly samples were taken from July 1989 to June 1990 (N=3747) in mussel (Mytilus galloprovincialis) raft-culture areas and central channel zones. Ninety-two food items were identified: crustaceans, molluscs, polychaetes, ophiuroids and fishes were the dominant prey. The raft epifauna and the mussels constituted the dominant group of prey in the raft areas and inner channel station (the epifaunal crab Pisidia longicornis comprised 30 to 52% of the diet), whereas the benthic macroinfauna was the dominant food component in the mid-outer channel (polychaetes constituted 32% of the diet). In the epifaunal community, diet selection for P. longicornis was positive and for amphipods was negative, whereas within the infauna diet selection for bivalves and ophiuroids was positive and for polychaetes negative or neutral. The seasonal importance of P. longicornis and M. galloprovincialis varied in the diet of L. depurator parallel to seasonal activities connected with mussel culture (seeding, thinning, harvesting) that determine the availability of prey from the rafts. Major changes in the composition of the diet related to the life history of L. depurator occurred during ontogeny. In the raft zones, consumption of mussels and fishes increased with increasing body size, while the consumption of Natantia, non-decapod crustaceans, gastropods, polychaetes Pectinariidae and plants decreased with increasing crab size. Maximum consumption of P. longicornis was by L. depurator individuals of intermediate size (15 to 44 mm carapace width). Stomach fullness (measured as dry weight of food) increased with increasing body size, but with negative allometry. During the late pre-moult and early post-moult periods L. depurator did not consume any food; maximum stomach fullness was recorded for the late post-moult and intermoult stages. Female food consumption decreased during egg incubation. Food consumption was greater in autumn and winter than at other seasons; this appears to be related to seasonal changes in reproduction and moulting.     

Man-made structures on marine sediments: Effects on adjacent benthic communities

This study (1975–1977) examines the effect of man-made structures on natural sand bottom communities in shallow water in San Diego County, southern California, USA. While there were shallow scour effects to 15 m around some artificial reefs, the reefs had no measurable effect on sand ripple patterns, grain size, organic carbon or infauna beyond the scoured areas. Foraging by reef-associated fishes produced profound alterations in the epifauna populations of the sea pen Stylatula elongata. The sea pen densities were 4 to 10 m^-2 before the reefs were established, but within 5 mo were eliminated from distances greater than 200 m around the reefs. On the other hand, densities of the tube-building polychaetes Diopatra spp. seemed to be enhanced in the immediate vicinity of the artificial reef. Oil platforms and bridge pilings seem to have much more profound effects on the nearby sand communities than do the relatively small artificial reefs. In addition to the elimination of sea pens, Diopatra spp. densities increased from <1.0 m^-2 in control areas to as many as 73 m^-2 in the vicinity of oil platforms. Grain size and infauna were strongly affected by the oil platform.     

Ecological overlap between macrourids in the western mediterranean sea

Stomachs from over 323 specimens of Hymenocephalus italicus, 168 Nezumia aequalis, 160 Coelorhynchus coelorhynchus and 1670 Trachyrhynchus trachyrhynchus were collected from September 1976 to September 1978 from the West Mediterranean continental slope at depths between 200 and 800 m. Copepods, amphipods and other pelagic crustanceans form the main fraction of the diet of H. italicus. The diets of N. aequalis and C. coelorhynchus consist largely of polychaetes, isopods, amphipods, mysids and decapod crustaceans. T. trachyrhynchus feed heavily on decapods. Decreasing fractions of small crustaceans are found in diets of all species as fish size increases. The mean size of prey increases with the body size of the fish. A positive size-depth correlation has been observed in macrourids. Juveniles and intermediates of N. aequalis, C. coelorhynchus and T. trachyrhynchus were found in shallow-water zones (<400 m), while adults were more common in deeper areas. Niche breadth and niche overlap were calculated between size groups. Niches are relatively broader with respect to habitat and narrower for prey size and prey type. The food overlaps between N. aequalis C. coelorhynchus and between C. coelorhynchus and T. trachyrhynchus are notably the greatest. Overlap in relation to habitat is high, while the correlation between niche parameters is very poor, indicating a certain degree of independence between these factors. Alpha matrices were estimated using both multiplicative ( product) and additive ( summation) multidimensional estimates for niche overlaps. Rates of competitive exclusion are low.     

Locomotor activity patterns and feeding habits in the prawn Palaemon xiphias (Crustacea: Decapoda: Palaemonidae) in Alfacs Bay,Ebro Delta (northwest Mediterranean)

Diel activity rhythms of the prawn Palaemon xiphias Risso, 1818 from Alfacs Bay, Ebro Delta, were studied by time-lapse videorecordings. Activity displayed an endogenous circadian rhythm, with maximum activity at night. Feeding habits were studied by frequency of occurrence and by the points method. The food of P. xiphias consisted mainly of crustaceans; the remains of amphipods, isopods, mysids, copepods, decapods and ostracods were identified. The remaining items consisted of molluscs, polychaetes, ophiuroids, plant material, sand, and unidentified organic debris. The results indicate that P. xiphias is a predator of benthic invertebrates rather than a scavenger or detritus feeder. Diet composition changes with increasing size of the prawn.     

Detrital pathways in a coral reef lagoon

Coral reef lagoons are generally regarded as zones of net heterotrophy reliant on organic detritus generated in more productive parts of the reef system, such as the seaward reef flat. The abundance and biomass of sediment infauna were measured seasonally for one year (1986) within the lagoon of Davies Reef, central Great Barrier Reef, to test the hypothesis that macrofaunal biomass and production of coral reef lagoons would decrease with distance from the reef flat and would change seasonally. In general, there were no simple relationships between infaunal standing stock or production and distance from the reef flat or season. Bioturbation by callianassid shrimps negatively affected the abundance of smaller infauna, suggesting a community limited by biogenic disturbance rather than by supply of organic material. Polychaetes and crustaceans were dominant amongst the smaller infauna (0.5 to 2mm) while larger animals (> 2 mm) were mostly polychaetes and molluscs. Mean biomass of infauna at both sites and all seasons was 3 181 mg C m^?2. The smaller animals (0.5 to 2 mm) contributed about 40% of total macrofaunal respiration and production although they represented only 15% of the total macrofaunal biomass. The biomass of macrofauna was about equal to that of the bacteria and meiofauna, while respiration represented 10 to 20% of total community respiration. Consumption by macrofauna accounts for only 3 to 11% of total organic inputs to sediment, with a further 14 to 17% being lost by macrofaunal respiration.     

Feeding habits of the Madeira rockfish <Emphasis Type="Italic">Scorpaena maderensis</Emphasis> from central Mediterranean Sea

In order to assess diet composition and niche breadth of this species, we analysed the stomach content of 182 specimens collected monthly along the eastern coast of Sicily (Central Mediterranean Sea). Overall, 50 prey taxa belonging to five major groups (algae, gastropods, crustaceans, polychaetes, fishes) were identified in 102 full stomachs. Benthic or epibenthic crustaceans, such as decapods, amphipods and isopods were the most important prey, whereas algae, gastropods, polychaetes and fishes were only occasionally ingested. In terms of composition by species, the diet of Scorpaena maderensis was characterized by a variety of rare or unimportant prey, which was consumed by few individuals only, although sometimes in large amount. As a result, S. maderensis can be considered a generalized and opportunistic feeder. The feeding intensity followed roughly a seasonal trend, with a minimum food intake in summer. The individual fish size was the most important factor affecting diet. According to the observed ontogenetic shift, small-sized individuals fed primarily on small crustaceans (i.e. amphipods and isopods), whereas large-sized specimens consumed preferably bigger and more vagile prey, such as walking and swimming decapods. No significant differences in diet were observed in relation to sex of predator and sampling season.     

Comparison of mussel bed community between two intertidal mytilids Septifier virgatus and Hormomya mutabilis

Mussel bed community structure of two intertidal mytilids, Septifer virgatus (Wiegmann) and Hormomya mutabilis (Gould), whose beds were contiguous vertically on a rocky intertidal shore (Wakayama Prefecture, Japan), was compared between 1982 and 1983. In the upper S. virgatus bed, crustaceans and bivalves were dominant in terms of both number of individuals and biomass. There were three barnacle species representative of the epizoans, two isopods and one amphipod as mobile fauna, and two bivalves as infauna. The lower H. mutabilis bed supported virtually no epizoans or mobile fauna. Infaunal free-ranging polychaetes and sipunculids were dominant in terms of both number of individuals and biomass. The H. mutabilis bed contained a much greater amount of sediment than did the S. virgatus bed, and the interstices among individual H. mutabilis and among their byssal threads were filled with sediment. The biomass of six of nine species dominant in the S. virgatus bed was negatively correlated with the amount of sediment. Recruitment of these faunal assemblages into artificial mussel clumps was examined in mussel enclosure experiments, and a negative sediment effect in H. mutabilis clumps was detected for one isopod and one limpet species. Factors causing the differences between two mussel bed communities are discussed, focusing on the effects of sediment.     

Biology of the conger eel Conger oceanicus in the Mid-Atlantic Bight

In the Mid-Atlantic Bight, conger eels (Conger oceanicus) occur from the coastal portions of estuaries to the edge of the continental shelf. In deeper waters they occupy burrows of the tilefish (Lopholatilus chamaeleonticeps). Between 1972 and 1974 we examined the stomachs and intestines of conger eels from inshore New Jersey (USA) waters (n=35, with a total length: TL of 21 to 49 cm) and between 1980 and 1983 offshore (n=295, 50 to 125 cm TL)_collections. Eels from both areas fed primarily on decapod crustaceans and fish. The specific identity of prey items within these groups generally differed from inshore to offshore areas, probably reflecting the differences in prey availability. Foods of specimens collected offshore varied with size: smaller eels (<80 cm TL) fed most heavily on decapod crustaceans, whereas larger eels (>80 cm) consumed more fishes. The presence of some nocturnally active prey items in the gut, primarily the eel Lepophidium cervinum, suggests that conger eels are nocturnal feeders. This is supported by in situ observations that conger eels are present in some tilefish burrows during the day and are presumably out of burrows and foraging at night.     

Benthic foraminiferal distribution on the southeastern Brazilian shelf and upper slope

Foraminiferal data were obtained from 66 samples of box cores on the southeastern Brazilian upper margin (between 23.8°–25.9°S and 42.8°–46.13°W) to evaluate the benthic foraminiferal fauna distribution and its relation to some selected abiotic parameters. We focused on areas with different primary production regimes on the southern Brazilian margin, which is generally considered as an oligotrophic region. The total density (D), richness (R), mean diversity ([`(H^￠ )] \overline{{H^{\prime } }} ), average living depth (ALD _X ) and percentages of specimens of different microhabitats (epifauna, shallow infauna, intermediate infauna and deep infauna) were analyzed. The dominant species identified were Uvigerina spp., Globocassidulina subglobosa, Bulimina marginata, Adercotryma wrighti, Islandiella norcrossi, Rhizammina spp. and Brizalina sp.. We also established a set of mathematical functions for analyzing the vertical foraminiferal distribution patterns, providing a quantitative tool that allows correlating the microfaunal density distributions with abiotic factors. In general, the cores that fit with pure exponential decaying functions were related to the oligotrophic conditions prevalent on the Brazilian margin and to the flow of the Brazilian Current (BC). Different foraminiferal responses were identified in cores located in higher productivity zones, such as the northern and the southern region of the study area, where high percentages of infauna were encountered in these cores, and the functions used to fit these profiles differ appreciably from a pure exponential function, as a response of the significant living fauna in deeper layers of the sediment. One of the main factors supporting the different foraminiferal assemblage responses may be related to the differences in primary productivity of the water column and, consequently, in the estimated carbon flux to the sea floor. Nevertheless, also bottom water velocities, substrate type and water depth need to be considered.     

Effects of ocean acidification on invertebrate settlement at volcanic CO2 vents

We present the first study of the effects of ocean acidification on settlement of benthic invertebrates and microfauna. Artificial collectors were placed for 1 month along pH gradients at CO₂ vents off Ischia (Tyrrhenian Sea, Italy). Seventy-nine taxa were identified from six main taxonomic groups (foraminiferans, nematodes, polychaetes, molluscs, crustaceans and chaetognaths). Calcareous foraminiferans, serpulid polychaetes, gastropods and bivalves showed highly significant reductions in recruitment to the collectors as pCO₂ rose from normal (336–341 ppm, pH 8.09–8.15) to high levels (886–5,148 ppm) causing acidified conditions near the vents (pH 7.08–7.79). Only the syllid polychaete Syllis prolifera had higher abundances at the most acidified station, although a wide range of polychaetes and small crustaceans was able to settle and survive under these conditions. A few taxa (Amphiglena mediterranea, Leptochelia dubia, Caprella acanthifera) were particularly abundant at stations acidified by intermediate amounts of CO₂ (pH 7.41–7.99). These results show that increased levels of CO₂ can profoundly affect the settlement of a wide range of benthic organisms.     

Growth parameters of deep-water decapod crustaceans in the Northwestern Mediterranean Sea: a comparative approach

 Relative and absolute growth were studied in 17 species of deep-water decapod crustaceans, spanning nine families of six different infra-orders, in the Northwestern Mediterranean Sea. The overall maximum abundance of these species lay between 200 m and 750 m (i.e. upper- and mid-slope species). Relative and absolute growth rates were compared by contrasting the slopes of the size–weight relationships for the different species and calculating the von Bertalanffy growth-equation parameters asymptotic length (L _∞ ) and growth rate (k). The size–weight relationships differed significantly as function of the species' life habits. The results revealed a significant decrease in weight relative to size in mesopelagic species (which carry out diel vertical migrations), an almost isometric relationship between size and weight in the less mobile nektobenthic species, and a significant increase in weight relative to size in strictly benthic species. The mean allometric coefficient for each group increased significantly from mesopelagic to benthic species. However, no general trend was observed in the growth-performance index, Φ (an index used to compare absolute growth rates between species, as a function of habit and depth of maximum abundance for all species combined), suggesting that the deep-water decapod crustaceans studied have similar absolute growth rates. Nevertheless, comparison of growth-parameter and growth-performance index values within families did reveal differences. Mesopelagic species of the families Sergestoidae and Pasiphaeidae showed slightly increased growth rates with increasing depth of distribution. Nektobenthic species of the genus Plesionika followed a trend opposite to that shown by mesopelagic species, with a higher growth rate for the shallowest-dwelling species (P. heterocarpus) than the deepest-dwelling species (P. acanthonotus). Taking growth as one of the major components of an organism's energy budget, the growth rates for the decapod crustacean species in this study were significantly lower than those reported in the literature for shallow-water penaeid crustacean species (which are distributed in higher-temperature habitats than deep-water Mediterranean crustaceans) and higher than those reported for mesopelagic myctophid fish species. Hence, the well-defined growth trends shown by deep-water decapod crustacean species in the Northwestern Mediterranean Sea, compared to the less well-defined trends in the other taxa, is discussed in the framework of the overall dynamics of their ecosystem. Received: 25 May 1998 / Accepted: 27 September 1999     

Population structure and historical demography of the thorny skate (<Emphasis Type="Italic">Amblyraja radiata</Emphasis>, Rajidae) in the North Atlantic

Population genetic structure of the thorny skate (Amblyraja radiata) was surveyed in >300 individuals sampled from Newfoundland, Iceland, Norway, the Kattegat and the central North Sea. A 290-bp fragment of the mt cytochrome-b gene was first screened by SSCP. Sequences of SSCP haplotypes revealed 34 haplotypes, 14 of which were unique to Iceland, 3 to Newfoundland, 1 to Norway and 3 to the Kattegat. The global F _ST was weak but significant. Removal of the two Kattegat locations, which were the most differentiated, resulted in no significant genetic differentiation. Haplotype diversity was high and evenly distributed across the entire Atlantic (h = 0.8) with the exception of the North Sea (h = 0.48). Statistical parsimony revealed a star-like genealogy with a central widespread haplotype. A subsequent nested clade analysis led to the inference of contiguous expansion with evidence for long distance dispersal between Newfoundland and Iceland. Historical demographic analysis showed that thorny skates have undergone exponential population expansion that started between 1.1 million and 690,000 years ago; and that the Last Glacial Maximum apparently had little effect. These results strongly differ from those of a parallel study of the thornback ray (Raja clavata) in which clear structure and former refugial areas could be identified. Although both species have similar life history traits and overlapping ranges, the continental shelf edge apparently does not present a barrier to migration in A. radiata, as it does for R. clavata.     

Spatio-temporal variations of biomass and abundance in bathyal non-crustacean megafauna in the Catalan Sea (North-western Mediterranean)

The spatio-temporal variations in diversity, biomass and abundance of bathyal invertebrates (excluding decapod crustaceans, which have been analysed elsewhere) from the North-western Mediterranean margin are described. The upper canyon (∼450 m), middle slope (∼650 m) and lower slope (∼1,200 m) habitats were investigated throughout the year. The first two sites are visited daily by a specialised commercial fisheries’ fleet, while the deeper site has not been impacted by fishing activities. A total of 140 species from 12 phyla were collected from the 3 study areas. Of these, the Mollusca, Echinodermata, Polychaeta and Cnidaria were the most speciose groups. The patterns of species diversity (H′) and evenness (E) were similar in time and space. The upper canyon and middle-slope sites were dominated by echinoderms and molluscs, while the lower-slope site was dominated by cnidarians and sponges. Multifactorial ANOVA showed significant spatio-temporal differences in the biomass and/or abundance only in echinoderms, molluscs, cnidarians and polychaetes. The faunal differences observed were explained by habitat type, but not by season. The role of submarine canyons and commercial fishing on shaping the diversity and biomass of bathyal Mediterranean invertebrates is discussed. Luis Dantart: Deceased March 2005     

Effect of MS-222 on response to light and rate of metabolism of the little skate Raja erinacea

The effect of tricaine methanesulfonate (MS-222) on the standard (SMR) and routine (RMR) metabolic rates of Raja erinacea was estimated from oxygen-consumption measurements. Data were gathered from a computerized, flow-through respirometry system. Individual trials were run for 96 h at 10 °C on anesthetized and untreated fish. The resulting rates, SMR = 20.1 ± 1.99 SE and RMR = 48.3± 2.5 SE mg O₂ kg⁻¹ h⁻¹, for an unanesthetized skate of 0.5 kg standardized weight, are the lowest reported for any elasmobranch. Periodogram analysis revealed a significant light-response component to the oxygen consumption of these fish, indicating a pattern of nocturnal and crepuscular activity. This activity pattern was disrupted in skates subjected to anesthesia. The use of low-dosage MS-222 in conjunction with the respirometry trials provides positive preliminary evidence that this technique may be useful in giving quick, accurate estimates of SMR in the more intractable elasmobranch fishes. Received: 15 January 1997 / Accepted: 6 February 1997     

Vertical distributions of decapod crustacean larvae and pelagic post-larvae over Great Sole Bank (Celtic Sea) in June 1983

Variations in the vertical distributions of pelagic stages of decapod crustaceans are described from five hauls taken over the Great Sole Bank in June 1983. Analyses of the results discriminated between the distributions mainly according to the time of day at which the hauls were taken, suggesting that diel variations were their most significant feature. Substantial ontogenetic variations were observed in the distributions of Processa canaliculata.     

Diets of four decapod crustaceans (Linuparus trigonus,Metanephrops andamanicus,M. australiensis and M. boschmai) from the continental shelf around Australia

Linuparus trigonus (Palinuridae) was collected from northeast Australia at depths of 220 to 300 m in the austral summer of 1985–1986 and its diet was analysed for diel feeding-periodicity and composition. The sex and size of the lobsters and the depth at which they were caught were recorded. About 35% of the foreguts were less than 10% full. L. trigonus appears to be a predator of slow-moving or nearsessile benthic invertebrates; its diet is mainly bivalves, gastropods, ophiuroids, crustaceans, polychaetes, and foraminiferans. Most dietary items differed significantly between the size classes of lobster. The frequency of crustacean remains increased with depth and more gastropods were consumed by lobsters caught at 260 m than at other depths. No significant periodicity in feeding was found for L. trigonus. The foreguts of three Metanephrops spp. (Nephropidae) collected from north-west Australia in August 1983 (M. andamanicus) and January/February 1984 (M. australiensis and M. boschmai) were nearly empty, and nearly half were less than 10% full. Fish, crustaceans and squids were the most common food items eaten. The main food items varied between the species: M. andamanicus ate nearly equal amounts of fish and crustaceans; M. australiensis ate chiefly crustaceans; M. boschmai mainly ate fish and seldom fed on squid. Metanephrops spp. appear to feed by attacking mobile animals and tearing off appendages or by scavenging.     

Spatio-temporal variation of hydroids and polychaetes associated with Cystoseira amentacea (Fucales: Phaeophyceae)

The temporal and spatial distribution of hydroids (sessile fauna) and polychaetes (vagile) on the brown alga Cystoseira amentacea (Fucales: Phaeophyceae) have been studied in the mid-littoral zone of the Apulian coast (Italy). Samplings were carried out in February and July 1997, at 1.5 m depth, at three sites (Gargano, Costa Merlata and Otranto), about 200 km apart from each other. Three replicates per site were collected for polychaetes, and another three, for hydroids. Samples yielded 142,426 polyps belonging to 20 hydroid species and 3,088 polychaete specimens belonging to 58 species. Seasonal variations in abundance and number of species were evident in hydroids. The only species probably exclusive of Cystoseira (the hydroid Clytia viridicans) was present only in the summer. Polychaetes showed marked seasonal differences only at the Gargano site. Multivariate techniques were used to compare, in both periods, assemblages within and among sites. Analysis of similarity testing revealed that, for both polychaetes and hydroids, assemblage structures significantly differed among sites and between seasons. Thus, the null hypothesis that the distribution in time and space of the epifauna on the same algal species is homogeneous over a wide geographical scale has been rejected, in spite of the homogeneity of the substrate. In both groups, quantitative differences of a few species seemed to be more important than qualitative ones in determining the spatial separation of sites, the species pool remaining rather consistent. A small-scale variability among replicates was also detected, especially at Gargano, for hydroids. Since the epifauna can allow better comparisons among sites than the actual distribution of the algal species, both sessile and vagile epiphytes of Cystoseira can be considered valid tools for evaluating environmental changes on coastal hard-bottom communities.     

Some aspects of the ecology of the echiuran worm Bonellia viridis and associated infauna

In inshore waters around Malta, Bonellia viridis inhabit burrows with multiple exits in calcareous rocks, and are most abundant in areas bordering Posidonia oceanica meadows. The associated epiflora and fauna are typical of the Mediterranean hard-substrate infralittoral zone. The larger infaunal species associated with B. viridis include a poriferan, Cliona sp.; an unidentified nemertean worm; various polychaetes; the sipunculans Phascolosoma granulatum and Aspidosiphon muelleri; two species of molluscs-Lithophaga lithophaga and Lepidopleurus cajetanus; 8 species of decapod crustaceans; and the teleost Gobius geniporus. Four types of burrows are found in rocks containing B. viridis. The larger burrows (referred to herein as UBA burrows) contain 3 main species-the decapods Upogebia deltaura and Alpheus dentipes and B. viridis itself. Experimental evidence suggests that U. deltaura excavates the UBA burrows mechanically, although B. viridis may secondarily modify them by secretion of an acidic mucus and gentle mechanical action. There is a definite community of organisms living as commensals in the burrow of U. deltaura. The assemblage of organisms bears a striking parallelism to the assemblages inhabiting the burrows of species of Upogebia, Callianassa and the echiuran Urechis caupo of the Pacific coast of N. America. A food web for the UBA burrow community is suggested.     

The phytal animals on the thalli of Sargassum serratifolium in the Sargassum region,with reference to their seasonal fluctuations

In the Sargassum region on the coast of Mukaishima, in the Inland Sea of Japan, the phytal animals living on Sargassum serratifolium, and the alga itself as a habitat for phytal animals, were studied from August, 1966 to August, 1968. The standing crop of Sargassum/m² bottom was 4.93 kg/m² (March, 1967) and 3.53 kg/m² (February, 1968) in the most luxuriant season, and 0.4 to 0.5 kg/m² (July, 1967 and 1968) in the off-season. The individual number of phytal animals per mean plant, without sessile fauna, reached a maximum in late winter and early spring (about 130,000 in 1967, 266,000 in 1968) when Sargassum was luxuriant, and a minimum in summer (about 15,000 in both years) when Sargassum was declining. Among the phytal animals, benthonic copepods (Harpacticoida) were very abundant in most seasons. Their dominance decreased in spring, whilst nematode dominance increased. It appears that such seasonal changes are closely related to the standing crop of S. serratifolium. Fluctuations in numbers of most groups of the meiofauna of phytal animals, such as foraminiferans, ostracods, isopods, amphipods, copepods, tanaids and nematodes, are connected with changes in the standing Sargassum crop. Seasonal fluctuations of some groups, such as echinoderms, actinians, mysids and decapod crustaceans (macrofauna), were, however, independent of Sargassum crop variations. The individual number of phytal animals/m² bottom in the Sargassum region were compared with findings of previous studies in other habitats, such as naked sandy and mud bottoms.Contribution No. 100 from the Mukaishima Marine Biological Station.     

Observations on the biochemical changes in gonads and other organs of Uca annulipes,Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) during the reproductive cycle

The fluctuations in biochemical constituents such as water, nitrogen, non-protein nitrogen, protein, lipid and glycogen in gonad, muscle and hepatopancreas have been followed in 3 decapod crustaceans, Uca annulipes (Latreille), Portunus pelagicus (Linnaeus) and Metapenaeus affinis (Milne-Edwards). The water and ash content of the entire body show no systematic fluctuation in relation to the annual reproductive cycle. The water content of the ovary diminishes as it matures. In the ovary of these crustaceans, the lipid fluctuated greatly in relation to the reproductive cycle. The maturing ovary contains more lipid than an immature or spent ovary per unit tissue weight. The changes in the biochemical constituents in the testis are not so pronounced as in the ovary, since the testicular cycle is often drawn-out and almost continuous in these crustaceans. There is an inverse relationship between water content and lipid content of the hepatopancreas; the greater the fat content, the lesser the water content. The hepatopancreas in these crustaceans is apparently a storage organ and contains much lipid and glycogen. At the height of the breeding season, when gonad production is intense, there is an indication of the mobilisation of at least a part of the lipid from hepatopancreas to gonad.Dissertation for the award of a Doctorate Degree of the Kerala University.Formerly the Marine Biological Laboratory.