Histological and histochemical changes in the gills of the yellowtail Seriola quinqueradiata exposed to the Raphidphycean flagellate Chattonella marina

The gills of the yellowtail Seriola quinqueradiata, exposed to Chattonella marina a red tide species, were examined histologically and histochemically. The pavement cells of primary lamellae were swollen in the exposed specimens. This presumably indicates that C. marina contains undetermined toxic substances. The number of mucous cells containing mucous decreased in proportion to the duration of exposure. The loss of the mucous substance in the cells is probably due to the ichthyotoxic stimulus caused by C. marina. A decrease of carbonic anhydrase activity in the secondary lamellae was confirmed, when mucous substances were lost in most mucous cells. Since the carbonic anhydrase usually exists in the epithelia of the secondary lamellae, it was presumably resolved by C. marina. The decrease of the carbonic anhydrase activity may cause certain physiological disadvantages to the fish exposed to C. marina.     

New development in the MOCNESS,an apparatus for sampling zooplankton and micronekton

Four variants of the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) have been constructed to sample a broad size spectrum of oceanic animals from microzooplankton to micronekton. The systems differ in mouth opening dimensions (ranging from 1/4 to 20 m²), the number of nets carried (from 5 to 20), and the mesh size of the netting (from 64 m to 3.0 mm). A new electronics package enables an operator to send commands down a single conductor, armored cable to open/close the nets and provides 12-bit resolution for the environmental (temperature, depth, conductivity) and net operation data (flow, net-frame angle, net-bar release), which are transmitted up the cable to the deck unit at 2-s intervals. A microcomputer system, interfaced to the deck unit, calculates salinity, volume filtered by a net, net trajectory velocity, and vertical velocity. The data are printed out and stored on disc, and profiles of temperature and salinity versus depth are plotted during the course of the tow. Analysis of the relationship between the geometry of the MOCNESS under tow and the past and present methods used to estimate the water filtered by a net revealed that significant bias is introduced when the ascent or descent angle of a net is disregarded. The bias is a function of the ratio of vertical velocity to net trajectory velocity and results in an underestimate of volume filtered while shooting a net and an overestimate while hauling.     

Origin and nature of spermatophoric mass of the spiny lobster Panulirus homarus

In the spiny lobster Panulirus homarus (Linnaeus) the spermatophoric mass consists of a highly convoluted tube, containing the sperm mass and a gelatinous matrix. The spermatophoric components have their origin in the proximal vas deferens and the completed spermatophoric mass is stored within the distal dilated part of the vas deferens. In the proximal vas deferens the inner glandular epithelial cells give rise to leaf-like typhlosoles which gradually diminish in size and finally disappear in the distal vas deferens. The secretions originating from the typhlosole form the outer gelatinous matrix of the spermatophoric mass. Histochemical observations reveal that the wall of the spermatophore tube consists of neutral mucopolysaccharide, whereas the sperm mass and the gelatinous matrix are rich in acidic mucopolysaccharides. Both polyacrylamide gel electrophoresis and agarose gel electrophoresis were used to separate the acidic mucopolysaccharide (AMPS) complexed with the proteins and the simple proteins. In addition, AMPS have been isolated following the method of Rahemtulla and Lovtrup (1974) and used for electrophoresis. In both the polyacrylamide gel electrophoresis and agarose gel electrophoresis, the extracted acid mucopolysaccharides give only a single fraction which, in comparison with the standard acid mucopolysaccharides, corresponds to chondroitin sulphate. The functional significance of the chondroitin sulphate and neutral mucopolysaccharides in the spermatophoric components of P. homarus is discussed in relation to their functional role in spermatophore hardening and protection of the delicate spermatozoa during their prolonged storage on the sternum of the female.     

Ultrastructural alterations on chloride cells of the yellowtail Seriola quinqueradiata,following exposure to the red tide species Chattonella antiqua

By means of scanning and transmission electron microscopy, the influence of the red tide species Chattonella antiqua was examined with respect to the surface ultrastructures of chloride cells of the yellowtail Seriola quinqueradiata. Conspicuous ultrastructural alterations occurred on the apical surface of these cells. The majority of chloride cells in the control gills showed an apical surface with numerous cellular extensions, while more than half the chloride cells affected by red tide organisms exhibited an apical surface with fewer and smaller extensions, a wrinkled apical surface, or a protruded apical surface. These ultrastructural alterations of chloride cell surface may be due to the partial disturbance of salinity by C. antiqua, and reflect the changes of the ion-transport function in yellowtail gills exposed to red tide water.     

Nitrogen uptake and growth of the germlings and mature thalli of Fucus distichus

Fucus distichus L. was collected near Vancouver, Canada, in late fall and early winter, 1981. The effects of the forms of nitrogen (nitrate, ammonium or urea) and periodic exposure to air on growth, rhizoid development and nitrogen uptake in germlings was investigated. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development twofold. Nitrate and ammonium uptake rates of the germlings were higher than for the mature thalli (20 to 40 times for nitrate and 8 times for ammonium), while the halfsaturation constant (K _s) values for nitrate were similar (1 to 5 M). The germlings showed saturable uptake kinetics but the mature thalli did not. When germlings were exposed to air it caused a 70% decrease in nitrate uptake, but not change in ammonium uptake. Ammonium uptake in the mature thalli was proportional to the ambient ammonium concentration. Nitrate uptake in the mature thalli appeared to follow saturation kinetics at low nitrate concentrations, but showed a non-saturable component at concentrations greater than 10 M. Presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings.     

In-situ measurements of nitrogenous nutrient uptake by kelp (Ecklonia maxima) and phytoplankton in a nitrate-rich upwelling environment

Nitrogen uptake by the kelp Ecklonia maxima Osbeck and phytoplankton was examined under different conditions of nutrient availability in a kelp bed off the Cape of Good Hope by measuring nutrient depletion in large plastic bags by the kelp and ¹⁵N uptake by phytoplankton. E. maxima took up nitrate and ammonia, but not urea, and showed only a weak preference for reduced nitrogen. Phytoplankton absorbed all three forms of nitrogen available, with a preference for ammonia and urea. Ambient nitrate concentration exhibited a marked and rapid decrease with northerly winds and an increase in response to offshore southerly winds. Nitrogen uptake by E. maxima was linearly related to ambient concentration and did not saturate even at nitrate concentrations >20g-at N l^-1, resulting in a significantly higher tissue nitrogen content under upwelling conditions. Nitrate imported by upwelling was the chief source of nitrogen utilised within the kelp bed. Locally regenerated nitrogen (ammonia and urea) was calculated to contribute only ca 4% of total nitrogen uptake during upwelling and 30% during the relaxation or downwelling phase.     

Availability of copper from phytoplankton and water for the bivalveMacoma balthica. II. Uptake and elimination from64Cu-labelled diatoms and water

The amount of copper taken up via algae and water byMacoma balthica from the Oosterschelde sea arm, S.W. Netherlands, was established using the radioisotope⁶⁴Cu. As far as we know, this isotope has never been used before in marine flod chain studies. As a model food source the marine diatomPhaeodactylum tricornutum was allowed to accumulate⁶⁴Cu for 1 d. These labelled algae were fed to the clams in the presence of the complexing agent EDTA (0.27mM). EDTA was added to prevent uptake of dissolved⁶⁴Cu that could be leaking from the labelled diatoms. In control experiments, unlabelled diatoms were fed toM. balthica in the presence of dissolved⁶⁴Cu (with and without EDTA) in order to assure a similar filtration activity. In repeated experiments with varying particulate/dissolved copper ratios, uptake through food always turned out to be at least as efficient as uptake from the water. It was concluded that Cu, associated with food, is well available for uptake byM. balthica.     

Population structure of the Spanish sardine Sardinella aurita: natural morphological variation in a genetically homogeneous population

The importance of larval dispersal in determining the distribution and abundance of benthic marine organisms is well recognized; however, the contribution of post-larval dispersal has not been measured. I compared the dispersal of swimming larvae with that of rafting colonies in a population of compound ascidians, Botrylloides sp., living attached to leaves of the eelgrass Zostera marina in Tomales Bay, California, USA in 1990–1992. Colonies rafting on broken eelgrass traveled over 200 times farther and had comparable recruitment success relative to swimming larvae. The recruitment of rafting colonies into new habitats was facilitated by the ability of thesecolonial animals to grow asexually onto surrounding substrata. Rafting colonies brooded larvae that were subsequently relased after the colony settled into a new habitat. These results suggest that colonization of new habitats can occur by post-larvae as well as larvae, and that long-range dispersal by species with short-lived larvae may occur by post-larval rafting.     

Isolation and sequence of cDNA encoding a 3-methylcholanthrene-inducible cytochrome P450 from wild red sea bream,Pagrus major

We have isolated a cDNA clone of mRNA for the cytochrome P450 from a 3-methylcholanthrene (MC)-treated red sea bream,Pagrus major, using a cDNA fragment for rat P4501A2 as a probe. The cloned cDNA is ca. 1.8 kb long and contains an open reading frame of 1545 nucleotides for polypeptides of 515 amino acids. The deduced N-terminal amino acid sequence of the cDNA is very similar to that for purified cytochrome P450 protein from the marine fish scup, which was reported previously (Klotz et al. 1983). A conserved amino acid sequence containing a putative heme-binding cysteine is present in the equivalent position proximate to the C-terminus of the molecules. The deduced amino acid sequence shows more than 50% positional identity with known members of the mammalian aromatic hydrocarbon-inducible P450 family. RNA blot analysis indicates that P450 mRNA (s) is expressed in the liver, kidney, gill and gut of the MC-treatedP. major.     

Spatial patterns and temporal succession in soft-bottom macroinvertebrate assemblages surrounding an ocean outfall on the southern San Diego shelf: relation to anthropogenic and natural events

Spatial patterns and temporal succession in soft-bottom macroinvertebrate assemblages are described for an area of the southern San Diego shelf which is influenced by both anthropogenic and natural events. The study transect covered 19 km along the 60 m-depth contour and spanned the terminus of the Point Loma wastewater outfall (32°40N; 117°17W). Ordination and classification analyses revealed that eight major benthic assemblages occurred in the study area from 1986–1990. These analyses further indicated that: (1) the impact of wastewater discharge on the benthos was asymmetric about the outfall, and (2) primary and secondary impact zones existed within the outfall footprint. The primary impact extended only 0.5 km south, but usually up to 1 km north, of the point of discharge, reflecting the prevailing northerly flow of currents along the San Diego coast. Stations within the primary impact zone usually supported similar faunal assemblages at any point in time. A lessened, or secondary, impact was apparent at stations 1 to 2 km south and 2 km north of the outfall. The two stations 9 km to the north appeared to be outside the outfall footprint. Assemblages in the three zones did not differ greatly in species composition, but did differ with respect to organismal density, relative abundances (dominance hierarchy) of component species, and temporal persistence. Biostimulation of the benthos, manifest as increased species richness and organismal abundance, was apparent in the primary impact zone from 1986–1988, although dominance was relatively low. Dominance increased at these sites during 1989 and 1990 due to large increases in populations of a few small species, such as the polychaete Myriochele sp. M and the ostracod Euphilomedes carcharodonta. Biomass was slightly elevated in the primary impact zone during 1986–1987; however, this trend was not sustained. Communities within the outfall footprint were much less persistent over time than those beyond it. The observed shifts in benthic assemblages within the outfall footprint corresponded to natural oceanographic cycles (i.e., the transition from El Niño to La Niña conditions) and anthropogenic changes (i.e., changes in wastewater output). These observations suggest that the Point Loma outfall has a localized effect on the stability of infaunal communities. Possible destabilization mechanisms are explored. Finally, comparisons with pre-discharge data taken during 1956–1957 revealed that about half of the species present prior to construction of the outfall were still common in 1990, after 27 yr of wastewater discharge, although large increases in species diversity and abundance seem to have occurred at all stations.