Effect of salinity adaptation on nitrogen metabolism in the freshwater fish Tilapia mossambica. I. Tissue protein and amino acid levels

Water, proteins and total free amino acids were estimated in different tissues of the euryhaline fish Tilapia mossambica after adaptation to various strenghts of sea water. The water content did not vary significantly in any tissue on salinity adaptation. The soluble and insoluble proteins displayed a general and considerable decrease in muscle, liver and heart; the decrease in the soluble fraction in the heart and the proteins of the muscle in 75% sea water (100% sea water=32.5 S) were significant. The gill proteins did not alter with salinity; the kidney proteins tended to increase slightly in 100% sea water (SW). The total free amino-acid content decreased insignificantly in all tissues on adaptation to 25% SW; in higher salinities, however, the content increased significantly. This increase was sudden and steep in 50% SW, and gradual and less steep in 75 and 100% SW. It is suggested that constancy in water content may contribute to the great adaptability of T. mossambica to heterosmotic media, and that the total free amino acids may be involved in isosmotic intracellular regulation. The possibility of amino acid increase as a result of protein breakdown is also indicated.     

Über den einfluß des hydrostatischen druckes auf die ultrastrukturen von zellen und geweben. IV. Der effekt der temperatur auf die druckresistenz der membran-, filament- und mikrotubulisysteme verschiedener gewebe mariner muscheln und Branchiostoma lanceolatum

Temperature-pressure experiments have been carried out on gill epithelium of Modiolus modiolus and Mytilus edulis (Baltic and North Seas), as well as on the skin, pharynx, and trunk muscles of Branchiostoma lanceolatum (Pallas), employing the technique of pressure fixation. Temperatures of 0°, 5° and 15°C have been combined with pressures up to 800 atm. Low temperature (0°C) intensifies disintegration of ultrastructures by pressure in comparison to 5°C. The highest degree of structural disorganization can be observed at 600 atm and 0°C. Increased temperature (15°C) increases pressure resistance, but the structural difference is more quantitative than qualitative. In pressure experiments, temperature probably affects cell organelles at the molecular level.     

Über den einfluß des hydrostatischen druckes auf die ultrastrukturen von zellen und geweben. III. Untersuchungen an filament-und mikrotubulisystemen verschiedener gewebe mariner muscheln und Branchiostoma lanceolatum

Employing the technique of pressure fixation, the effect of high hydrostatic pressure (1 to 800 atm) at 5°C has been investigated on cilia of the gill epithelium in Modiolus modiolus, Mytilus edulis (Baltic and North Seas), and on the skin and muscle cells of Branchiostoma lanceolatum (Pallas). With increasing pressure, the filaments and tubuli are increasingly disorganized to an electron-dense material, which seems to be a conglomeration of the globular structure units. Minimum pressure causing disintegration of filaments and tubules is 300 atm; 600 atm is critical, especially for filaments in skin cells of B. lanceolatum. Whereas the filaments do not show any intermediate stages of damage at any one pressure, microtubules show different stages of disorganization. There seems to be a direct relation between motility and structural organization of cilia. Probably the mechanisms of disintegration of filaments and microtubules are related to the enzymatic activities and the protein-protein-interactions of the subunits. The difference between di-and monomer enzymatic systems in the structures may be important for pressure resistance of the organelles.     

Life histories of large and small murexes (Prosobranchia: Muricidae)

One can predict the major features of a muricid's life history from its adult size. Most adults do not grow, and juveniles of all species grow 1 to 2 mm/month, so that larger adults have had fonger juvenile periods. Larger females deposit larger egg capsules and, since each of these contains more eggs, their clutches are larger. Small females deposit several clutches each year, and thus have relatively large annual fecundities. However, large females live longer, so each spawns many more eggs in her life-time than would a smaller female. From 90 to 99% of the juveniles die within their first year. However hatchings of small species are much more likely to complete their first year; a newly hatched Urosalpinx cinerea is 25 times more likely to survive long enough to breed once than a newly hatched Ceratostoma foliatum (Gmelin, 1791).     

Fitness benefits of multiple mating versus female mate choice in the cellar spider (Pholcus phalangioides)

Recent studies have demonstrated that mating with multiple males can be beneficial for females and her offspring even if males contribute nothing but sperm. This was mainly established for species in which sperm from several males mix in the reproductive tract of the female, thus allowing sperm competition and/or female sperm choice. However, in species with last male sperm precedence, female re-mating decides against the previous male by strongly limiting his reproductive success. We tested the effect of female re-mating behaviour using the cellar spider Pholcus phalangioides, which shows strong last males sperm precedence and moderate levels of polyandry under natural situations. We predicted that females prevented from remating even though they are receptive would show reduced reproductive success compared to females that accept two copulations and females that reject a second male, since the latter two treatments were allowed to behave according to their decisions. However, if the number of matings per se had an effect on oviposition or on offspring performance, double-mated females should perform better compared to both treatments of once-mated females. We measured female fecundity and fertility over a period of 140 days, comparable to the species' natural reproductive peak season. Two thousand one hundred and fifty-two offspring from 67 first egg sacs were reared under two feeding levels. We registered development time and survival, and measured offspring adult size and mass. We found a positive effect of double mating, as in this treatment, oviposition probability was higher compared to the other treatments. Interestingly, adult female offspring of the DM treatment that were raised under low food level had a higher condition index compared to those from FS and RM, but development time, size and mass at adulthood were not affected by mating treatment. Female choice only seemed to affect hatching latency of the offspring. Overall, the main predictor of female reproductive output and success was female body size.     

Phylogenetic relationships within Ovulidae (Gastropoda: Cypraeoidea) based on molecular data from the 16S rRNA gene

Closely interacting groups, such as hosts and parasites, sometimes provide useful models to study evolution and adaptive processes. In Ovulidae, a widespread family of specialised browsing carnivorous molluscs that feed on polyps and tissues of Anthozoa, close association with the host has produced a plethora of adaptations affecting shell morphology, colour pattern and mantle shape. These morphological characters have been widely used in ovulid taxonomy, although putative differences are often based on trivial and inconsistent variations. In this work we used a molecular approach to generate the basal phylogeny of the family. Phylogenetic analyses of mitochondrial 16S rRNA gene sequences of 32 species from 23 genera reveal unexpected taxonomic groupings from the genus up to the family level, as well as unexpected phenomena of homoplasy in conchological features. Since molecular phylogenies also provide an evolutionary framework where character transformations are polarised, we used this basal ovulid phylogeny to explore the specificity of the association and the degree of morphological adaptation to the host.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-005-1566-0.Communicated by R. Cattaneo-Vietti, Genova     

Feeding habits of the dungeness crab Cancer magister as determined by the index of relative importance

Specimens of the Dungeness crab Cancer magister, were collected subtidally and intertidally from an estuary in Washington State, USA in June and September 1980, and January, April, May and July, 1981. Gut contens of freshly collected crabs were analyzed by the Index of Relative Importance; for each prey taxon, this method measured frequency of occurrence, percentage of total biomass, and percentage of total numbers consumed. The most important higher taxon eaten was fish; however, the most important prey genus was the shrimp Crangon spp. There was greater predation on Crangon spp. at night at the intertidal site, and during winter and spring when the shrimp were most abundant there. Feeding activity, as indicated by a weight-specific gut-fullness index, showed no consistent diel pattern. There were significant ontogenetic changes in feeding patterns: first-year crabs preyed primarily on very small bivalves or small crustaceans including their conspecifics; second-year crabs preferred Crangon spp. and fish, and third-year crabs preyed less on Crangon spp. and more on fish. Such changes in feeding habits with ege could be purely due to mechanics of food handling, but might also reduce competition among age groups of crabs, possibly partitioning resources within the estuary. Findings are discussed in terms of optimal foraging and compared to other similar studies.Contribution No. 599, School of Fisheries, University of Washington, Seattle, Washington 98195, USA     

Cadmium accumulation and toxicity in the kidney of the bay scallop Argopecten irradians

Specimes of bay scallops, Argopecten irradians, collected from shallow-water eel-grass beds near Beaufort, North Carolina (USA) in September 1979, were exposed to 0.7 ppm cadmium in flowing seawater for 5 d. This exposure resulted in a massive extrusion of the calcified concretions of most of the kidney epithelial cells, although marked morphological damage consisting of cytoplasmc degeneration was apparent in only a few focal areas of the kidney. In addition, unique cytoplasmic membrane-bound bodies were observed in epithelial cells of cadmium-treated but not control scallop kidneys. In some cells, these bodies appeared to fuse with the main concretion vacuole. Kidneys of cadmium-treated scallops accumulated cadmium to 200 ppm on a wet wt basis; of this 60% was associated with concretions (2 000 ppm dry wt) and 38% with the membranous pellet obtained after ultracentrifugation at 105 000 g for 1 h. Approximately 2% of total kidney cadmium was associated with the cytosolic fractions but, unlike zinc or manganese, which were bound to either high or low molecular weight species, a large component of the cadmium in this fraction was bound to a protein peak of approximately 21 000 daltons. Results of this study indicate that kidney concretions of A. irradians play a major role in the control of renal cadmium accumulation and excretion and hence the toxicity of cadmium to this organism.