Dietary accumulation of UV-absorbing mycosporine-like amino acids (MAAs) by the green sea urchin (Strongylocentrotus droebachiensis)

The bioaccumulation of ultraviolet radiation-absorbing mycosporine-like amino acids (MAAs) by Strongylocentrotus droebachiensis (Müller) was determined in specimens maintained on MAA-rich and MAA-deficient diets. Individuals were fed either the red alga Mastocarpus stellatus (Stackhouse), which has a high concentration of the MAA shinorine (6.98 nmolmg^–1 dry wt), and trace amounts of the MAAs porphyra-334, asterina-330 and palythine, or the brown alga Laminaria saccharina (Lamouroux), which contains no detectable MAAs. Reproductively spent urchins were fed ad libitum during a 9 mo period in 1992 to 1993 until they were once again gravid. To monitor accumulation, samples of urchin tissues and ingested food were taken throughout the 9 mo period from males and females maintained on each diet, and the concentrations of MAAs determined using high performance liquid chromatography. Urchins maintained on a diet of M. stellatus showed an ovarian shinorine concentration (8.33 nmol mg^–1 dry wt) 25 times higher than those fed L. saccharina. There was no change in MAA content of testes or somatic tissues in either feeding group. More than 99% of the MAAs present in an experimental meal of M. stellatus were removed during passage through the gut. Previous studies have inferred dietary accumulation of MAAs by comparing MAAs present in animal tissues with the consumer's potential diet in the field. This is the first study to have monitored MAA accumulation in animal tissues in conjunction with a controlled diet having a known MAA composition. Concentrating MAAs in the ovaries may provide eggs released into the water column with protection from damaging solar ultraviolet radiation.     

Dietary study of the midwater polychaete Poeobius meseres in Monterey Bay,California

This study presents the first quantification of the diet of a gelatinous midwater organism on a temporal basis. Using the Monterey Bay Aquarium Research Institute's remotely operated vehicle Ventana, regular collections of the polychaete Poeobius meseres (Heath, 1930) over a 1 yr period (October 1990 to November 1991) in Monterey Bay yielded intact organisms for the study of feeding behavior and quantitative analysis of stomach contents. In situ observations showed P. meseres feeding in two different ways: (1) by deployment of a mucus web in the water column that passively collects particles for consumption; and/or (2) by grasping detrital material in the water column with its ciliated tentacles. Stomach-content analyses showed that P. meseres is primarily coprophagic, its diet being dominated by fecal pellets from euphausiids and copepods. These fecal pellets appear to provide P. meseres with essentially all its carbon. Although fecal pellets were the most important food item volumetrically, P. meseres also consumed large numbers of diatoms and small numbers of dinoflagellates, chrysophytes, radiolarians, foraminiferans and eggs. The diet of P. meseres appears to reflect primary productivity in the surface waters, with different food items predominant in the diet at different times of the year. Pennate diatoms were most abundant in the diet during the fall, centric diatoms were most abundant during the sumnier, and fecal pellets during the winter. The composition of P. meseres diet suggests that this and other midwater gelatinous organisms have a significant role in the remineralization of particles as they sink from the surface to the deep sea.     

Age-related settlement success by cyprids of the barnacleBalanus amphitrite,with special reference to consumption of cyprid storage protein

Newly molted (0-d-old) cyprids of the barnacleBalanus amphitrite Darwin were prevented from settling for 0 to 14 d at four different temperatures (25, 20, 15 and 5°C treatments). The effect on settlement success of prolonging the cyprid lifetime was evaluated using a nitrilocellulose membrane assay. In addition, protein extract prepared from these cyprids was analyzed using gel electrophoresis to characterize the effect of age on protein content and composition. Settlement success was significantly affected for larvae aged at 25 (P < 0.001), 20 (P < 0.001) and 15°C (P < 0.05), while differences in settlement success between age groups was negligible at 5°C (P = 0.09). Settlement success of cyprids increased with time for up to 3 d (P < 0.001, Phase 1), following which settlement success significantly declined (P < 0.001, Phase 11). Temperature had no significant effect on settlement in Phase I (P = 0.17), but did enhance the decline in settlement success with age during Phase II (P < 0.001). Gel electrophoresis revealed a significant decline in the quantity of the cyprid storage protein CMP (Cyprid Major Protein) with increasing age at 25, 20 and 15°C, but CMP levels remained constant at 5°C. These results suggest that, upon molting to the cyprid stage, larvae may still require a settlement-competence attainment period. This may be achieved by CMP utilization during Phase I, depletion of which during Phase II may be responsible for reduction in settlement success with cyprid age such that remaining CMP stores can no longer support the production of adult structures following settlement.     

Colonization of Europe by two American genetic types or species of the genus Marenzelleria (Polychaeta: Spionidae). An electrophoretic analysis of allozymes

Allozyme electrophoresis was conducted in an attempt to identify the origin ofMarenzelleria sp. found in the North Sea and Baltic Sea. The analysis covered eight enzymes with ten loti from nine populations found on the North American Atlantic toast, these populations in the North Sea and five populations in the Baltic. The North Sea spionids correspond to the Type IMarenzelleria from North American coastal waters between Barnstable Harbor (Massachusetts) and Cape Henlopen (Delaware). Nei's genetic distance between these North American populations and those from the North Sea wasD = 0.010 to 0.020. TheMarenzelleria sp. found in the Baltic Sea very probably stems from North American populations of Type II found from the region of Chesapeake Bay (Trippe Bay) south to the Currituck Sound (North Carolina). The genetic distance between these North American populations and the Baltic populations isD = 0.000 to 0.001. The invaders appear to have lost little of their genetic variation while colonizing the North and Baltic Seas. Probably, both colonizing events tan be attributed to large numbers of individuals reaching Europe simultaneously on one or more occasions. In addition, aMarenzelleria Type III was found by electrophoresis among specimens from Currituck Sound (North Carolina), rohere it is sympatric withMarenzelleria Type II. Salinity is discussed as an important factor for the establishment ofMarenzelleria Type I in the North Sea and Type II in the Baltic Sea.     

The application of geographic information systems to geochemical studies in Jamaica

The Centre for Nuclear Sciences (CNS) uses a raster based geographic information system (GIS), integrated with a relational database to store information on point sampled data, including concentrations of over 50 elements and/or ions in a variety of sample materials. These data are filtered in the GIS to create surface layers and are assigned colours according to percentile ranges allowing visual inspection to be used to identify significant features and trends. The database currently contains raster map layers for soils and geologic features, point site data for water and air, and vector data for roads, rivers and streams. While data are still being added to the database interesting results are already being obtained and a few instances where the GIS was used to assist in the data interpretation are reported.     

Relation of RNA/DNA ratios to growth for the scallop Euvola (Pecten) ziczac in suspended culture

We examined the relation of RNA/DNA ratios to growth for three size groups of the tropical scallop Euvola ziczac maintained in suspended culture at 8, 21 and 34 m in depth in the Golfo de Cariaco, Venezuel. Various growth parameters indicated that production decreased with depth. This was more likely due to a decrease in seston quality with depth than to temperatures or seston abundance (which were similar at the various depths studied). The RNA/DNA ratio was correlated with the G-index of muscle growth for juveniles (r ²=0.55). A much weaker correlation was observed for the maturing scallops (r ²=0.18), probably because of the interaction between reproductive and somatic growth. In fully mature scallops, somatic growth was negligible and the RNA/DNA ratios appeared to be inversely related to the level of physiological stress of the scallops. Whereas RNA/DNA ratios are difficult to interpret for maturing E. ziczac, because an increased ratio can be due to either increased gonadal or somatic growth, they are useful in predicting growth in juveniles and physiological stress in fully mature scallops.     

Early development and estimated life cycle of the mesopelagic copepod Pareuchaeta elongata in the southern Japan Sea

Life cycle of the mesopelagic copepod Pareuchaeta elongata was investigated combining laboratory rearing data on the eggs, nauplii, and early copepodites with field growth data on the late copepodites. Examination and incubation at near the in situ temperature (0.5°C) of egg sacs collected from the field indicated that the clutch size was 13 to 24 eggs (mean: 20), hatching time was 39.4d (mean), and hatchability was low (mean: 28.5%). The development time at 0.5°C was 2.4 d for Nauplius Stage 1 (N1), 4.6 d for N2, 6.2 d for N3. 7.4 d for N4, 7.1 d for N5, 20.8 d for N6, 36.7 d for Copepodite Stage 1 (C1) and 65.3 d for C2. From the numerical analysis of seasonal samples collected from the field, the development time was estimated as 1 mo for C3, 2 mo for C4 and 2.5 mo for C5. Thus, the egg hatching time plus the integrated development time by stage was 355 d or nearly 1 yr (i.e. span of one life cycle). Duration of the C6 (adult) was estimated as>2.5 mo. Combining the present data on development times of each stage with published data on the major spawning season (August to October) and ontogenetic migration, a schematic representation of the life cycle of this copepod was developed. Between-stage comparison of wet, dry, and ash-free dry weights of all developmental stages of preserved wild specimens revealed that there is almost no gain in weight during naupliar stages, and the greatest weight increment over the life cycle was during the C4 stage. The present results are compared with those for the same and related species living in other regions.     

Settlement of larvae of the giant scallop,Placopecten magellanicus,in 9-m deep mesocosms as a function of temperature stratification,depth, food,and substratum

In January and February 1992 an experiment was conducted in a 10.5-m deep tank (diameter: 3.7 m, volume: 117 m³) to examine the effects of food distribution with respect to a stable thermocline, depth, and substratum type on the settlement and metamorphosis of larvae of the giant scallop, Placopecten magellanicus (Gmelin). Polyethylene tube bags (diameter: 0.60 m) were used to enclose 9-m deep columns of seawater which were then used as treatment replicates. A sharp thermocline (i.e. 7 to 11°C gradient) was created between a depth of 4.0 and 5.0 m. At the beginning of the experiment, one million 6-d old larvae were added to the surface of each tube. Two or three replicate tubes of each of four feeding treatments were established: (1) food (Isochrysis galbana) added to the top 1 m of the water column (top-fed, n=3); (2) food added to the bottom 1 m of the water column (bottom-fed, n=3); (3) food added throughout the water column (mixed, n=3); and (4) no food added (unfed, n=2). Settlement collectors were placed in two replicate tubes of each treatment at depths of 0.1, 4, 5, and 9 m and contained two different substrata, Polysiphonia lanosa (a red filamentous alga) and aquarium filter-wool as an algal mimic. Spat settlement in the different feeding treatments was a function of larval growth rate. Most spat were collected in the mixed tubes. Fewer individuals were collected in the top-fed treatment and fewer still in the bottom-fed treatment; minimal numbers of spat were found in the unfed tubes. Filter-wool collected more spat than P. lanosa, but this was evident only in the 4-m deep collectors in the mixed tubes. Most spat were found in the 0.1-m or 4-m deep collectors; generally few were located below the thermocline in collectors at 5 or 9 m. We suggest that, in areas of intense stable stratification, spat collection of the giant scallop may be enhanced by the placement of collectors with appropriate substratum material at or above the zone of stratification, rather than near the bottom. Furthermore, we propose that natural settlement may be increased in areas where a stratification layer intersects with the sea floor or where the layer is disrupted by turbulent mixing.Contribution to the programs of OPEN (Ocean Production Enhancement Network, one of the 15 Networks of Centres of Excellence supported by the Government of Canada) and GIROQ (Group Interuniversitaire de Recherches Océanographiques du Québec)     

Environmental health in minority and other underserved populations: Benign methods for identifying lead hazards at day care centres of New Orleans

This study tests the hypothesis that exterior sources of lead dust are more important than interior sources in the route of exposure of children. Benign field methods were used to distinguish between potential and actual lead exposure problems. Utilising hand wipe and surface wipe techniques, hand and environmental samples were obtained from selected day care centres at different locations within New Orleans. Previous research has shown that soil lead is determined by location within the city. Private and public day care centres were selected from inner and outer city areas to estimate the extent of hand lead exposure. To measure and identify the extent of environmental lead exposure, hand wipes were taken before and after playing outdoors. Results of preliminary findings show that outdoor lead dust is a more potent contaminant of hands than indoor lead dust. An association was found between the amount of lead on children's hands after playing outdoors and the lead content in the exterior dust and soil. Although two girls out of forty children had exceptionally high hand lead quantities after playing outdoors, in general, boys have higher hand lead levels than girls. The private inner-city day care centre had a severe contamination problem in its outdoor play area. By contrast, the outdoor play area of the public inner city day care centre is of such a high quality that the quantity of lead dust is independent of location in the city.     

Food limitation stimulates metamorphosis of competent larvae and alters postmetamorphic growth rate in the marine prosobranch gastropodCrepidula fornicata

The effects of food limitation on growth rates and survival of marine invertebrate larvae have been studied for many years. Far less is known about how food limitation during the larval stage influences length of larval life or postmetamorphic performance. This paper documents the effects of food limitation during larval development (1) on how long the larvae ofCrepidula fornicata (L.) can delay metamorphosis in the laboratory after they have become competent to metamorphose and (2) on postmetamorphic growth rate. To assess the magnitude of nutritional stress imposed by different food concentrations, we measured growth rates (as changes in shell length and ash-free dry weight) for larvae reared in either 0.45-m filtered seawater or at phytoplankton concentrations (Isoehrysis galbana, clone T-ISO) of 1 × l0³, 1 × 10⁴, or 1.8 × 10⁵ cells ml^–1. Larvae increased both shell length and biomass at 1 × 10⁴ cells ml^–1, although significantly more slowly than at the highest food concentration. Larvae did not significantly increase (p > 0.10) mean shell length in filtered seawater or at a phytoplankton concentration of only 1 × 10³ cells ml^–1, and in fact lost weight under these conditions. To assess the influence of food limitation on the ability of competent individuals to postpone metamorphosis, larvae were first reared to metamorphic competence on a high food concentration ofI. galbana (1.8 × 10⁵ cells ml^–1). When at least 80% of subsampled larvae were competent to metamorphose, as assessed by the numbers of indlviduals metamorphosing in response to elevated K⁺ concentration in seawater, remaining larvae were transferred either to 0.45-m filtered seawater or to suspensions of reduced phytoplankton concentration (1 × 10³, 1 × 10⁴, or 5 × 10⁴ cells ml^–1), or were maintained at 1.8 × 10⁵ cells ml^–1. All larvae were monitored daily for metamorphosis. Individuals that metamorphosed in each food treatment were transferred to high ration conditions (1.8 × 10⁵ tells ml^–1) for four additional days to monitor postmetamorphic growth. Competent larvae responded to all food-limiting conditions by metamorphosing precociously, typically 1 wk or more before larvae metamorphosed when maintained at the highest food ration. Surprisingly, juveniles reared at full ration grew more slowly if they had spent 2 or 3 d under food-limiting conditions as competent larvae. The data show that a rapid decline in phytoplankton concentration during the larval development ofC. fornicata stimulates metamorphosis, foreshortening the larval dispersal period, and may also reduce the ability of postmetamorphic individuals to grow rapidly even when food concentrations increase.