Feeding deterrence properties of apo-fucoxanthinoids from marine diatoms. II. Physiology of production of apo-fucoxanthinoids by the marine diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana,and their feeding deterrent effects on the copepod Tigriopus californicus

The marine diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana have been shown to produce apo-fucoxanthinoid compounds which act as feeding deterrents against the harpacticoid copepod Tigriopus californicus. The amounts and types of apo-fucoxanthinoids produced were species specific. Th. pseudonana produced small quantities of apo-12-fucoxanthinal and apo-13-fucoxanthinone only during senescence, while P. tricornutum produced much greater quantities of these two compounds during both log and senescence phases, in addition to producing a third compound, apo-10-fucoxanthinal, only during senescence. For both species, production of apo-fucoxanthinoids increased as the cells entered senescence phase due to phosphate limitation. The amounts of apo-fucoxanthinoids necessary to reduce feeding in T. californicus by 50% ranged from 2.22 to 20.2 ppm. This range was approximately 1000 times lower than the total apo-fucoxanthinoid concentration in P. tricornutum. The amounts of apo-fucoxanthinoids necessary to cause a 50% mortality in a population of T. californicus ranged from 36.8 to 76.7 ppm. Thus, these compounds are present in concentrations which may have ecological significance in the control of bloom formation and grazing. The production of apo-fucoxanthinoids may be a phenomenon common to many diatoms, particularly as they enter senescence due to nutrient limitation.     

Metabolism of a nonylphenol isomer by Sphingomonas sp. strain TTNP3

For elucidation of the metabolism of the endocrine disruptor nonylphenol by Sphingomonas sp. strain TTNP3, the degradation of an isomer of nonylphenol, 4(2,6-dimethyl-2-heptyl)-phenol, has been studied. As in the case of 4(3,5-dimethyl-3-heptyl)-phenol, the metabolism of this nonylphenol isomer leads to the formation of the NIH-shifted product 2(2,6-dimethyl-2-heptyl)-1,4-benzenediol (NIH: National Institute of Health), but also to the alkoxy derivative 4(2,6-dimethylheptan-2-yloxy)phenol as additional metabolite. To the best of our knowledge, this is the first report describing the formation of alkoxyphenol as a degradation product of nonylphenol. Additionally, these results provide for the first time evidence for slight differences in the biodegradation of the isomers of nonylphenol.     

What is the sex ratio of harpacticoid copepods in the deep sea?

The sex ratios of deep-sea harpacticoids have been thought to be greatly skewed toward females. The representation of males is notably more equitable (approximately 1:2) at three deep-sea sites (San Diego Trough: 32°52.4N, 117°45.5W, 1 050 m, January 1987; Porcupine Seabight: 51°36.85N, 12°57.30W, 1 369 m, August 1984; northwest Atlantic, 40°27N, 62°20W, 4 820 m, July 1982, June 1983). This ratio conceals extensive variation at the species level. For some species, males are unknown. For other species, males are more numerous than females. Sampling bias against males can occur and may explain the more extreme reports of male rareness in the literature.     

Feeding mechanism of Pelagia noctiluca (Scyphozoa: Semaeostomeae); laboratory and open sea observations

The behaviour of the oral arms of Pelagia noctiluca (Forsskål) has been investigated in open sea predation and in predation induced both in the laboratory and the natural environment. Specimens were first studied in the field and then collected from coastal aggregations in the Gulf of Trieste, North Adriatic Sea, in December 1985 (Lat. 13°40 E, Long. 45°42 N) and in June 1986 (Lat. 13°39 E, Long. 45°43 N). The results of laboratory experiments and in situ observations, recorded on videotapes and photographs, show that the marginal tentacles are utilized to: (1) paralyze the prey; (2) contract and bend inward towards the nearest oral arm. Occasionally the tentacle does not contract and the prey is released; thus prey selection may occur. The oral arms are therefore involved in the: (1) transport of prey from the tentacle to the gastric cavity; (2) catching of motionless prey; (3) anchoring the medusa to the substratum. A similar feeding pattern can explain the survival of several specimens of P. noctiluca near the bottom during the winter of 1985/1986 in the Gulf of Trieste (North Adriatic Sea) in spite of the severe climatic conditions.     

Autotoxic antibiotic production by a marine Chromobacterium

An antibiotic-producing Chromobacter was isolated from a sea-water sample from the North Pacific Gyre. The bacterium produces 3 bromine-containing metabolites: tetrabromopyrrole, 2-(2-hydroxy-3, 5-dibromophenyl)-3, 4, 5-tribromopyrrole, and hexabromo-2, 2-bipyrrole. It also synthesizes n-propyl 4-hydroxybenzoate and 4-hydroxybenzaldehyde. Some of these compounds were shown to be responsible for autoinhibition of the Chromobacterium itself, as well as for antibiotic action against other kinds of bacteria.     

Fouling organisms in the port of Mar del Plata (Argentina). I. Siphonaria lessoni: ecological and biometric aspects

The present paper deals with ecological aspects of the pulmonate gastropod Siphonaria lessoni (Blainville, 1824), a common member of fouling communities in Mar del Plata's port (38°0817 S, 57°3118 W). Populations on colonized panels of an experimental raft were studied during three annual cycles, to determine feeding habits, growth and various factors which restrict their distribution on floating substrata. Although S. lessoni is harmless as a fouling organism, its grazing on the algal belt clears a part of the substratum's surface, which is then quickly colonized by truly aggressive organisms such as Balanus amphitrite.     

Ecological investigations of the late-stage phyllosoma and puerulus larvae of the western rock lobster Panulirus longipes cygnus

The distribution and abundance of the late-stage phyllosoma larvae of Panulirus longipes cygnus George and the distribution and densities of the final larval stage, the puerulus, both in the plankton and at settlement along the coast, were investigated. A total of 3,617 late-stage phyllosoma (Stages VI to IX) and 301 puerulus larvae were caught at 187 plankton stations during the July to November periods 1974, 1975 and 1976 off the west coast of Australia between 29°00 to 32°30S and 113°30 to 115°00E. The depth range sampled was 0 to 35 m on the continental shelf and 0 to 90 m off the shelf. During onshore/offshore cruises with similar sampling effort on and off the shelf, 1,169 late-stage phyllosoma larvae were taken, of which only 9 were caught on the shelf, and these near the outer edge. A series of cruises sampling two areas beyond the shelf near 29°30 and 32°00S yielded 2448 late-stage phyllosoma, with greater densities of larvae in the northern location. The settlement of puerulus-stage larvae along the coast in the same geographical range was also greater in the north than in the south. The data from the onshore/offshore cruises showed a definite effect of moon phase on numbers of puerulus larvae caught on the shelf, with higher catches near new moon. The low numbers of puerulus larvae (usually 0, 1 or 2 individuals) caught at all stations showed that the puerulus stage is sparsely distributed in the plankton. Fewer puerulus larvae were present at the surface than at lower depths, but it was not possible to determine a depth preference for the puerulus between 10 m and the lowest depths sampled because of the low catch numbers. No relationships were found between puerulus larvae density and surface-water temperature, salinity, or plankton biomass at each station. Data on the larval distributions indicate that, near the end of their planktonic existence, the majority of the late-stage phyllosoma larvae of P. longipes cygnus are not carried onto the shelf, where mixing of oceanic and continental shelf waters occurs only on the outer third, but are transported southward by oceanic circulation beyond the shelf. The puerulus moults from the last phyllosoma stage beyond the shelf and completes the larval cycle by swimming across the shelf and settling in the shallow reef areas.     

Importance of the fatty acids 20:5ω 3 and 22:6ω 3 in the diet of plaice (Pleuronectes platessa) larvae

The requirement of plaice (Pleuronectes platessa L.) larvae for the fatty acids 20:5 3 and 22:6 3 was studied. Larvae were reared from first feeding to beyond metamorphosis on Artemia sp. nauplii (EG brand), whose nutritional content had been manipulated by enrichment. Some larvae were fed Artemia rich in 20:5 3 and 22:6 3, and others were fed nauplii with no 22:6 3 and low levels of 20:5 3 (1.9% of the total fatty acids). The differences in diet had no significant difference on growth or survival of the plaice larvae. The results indicate that the plaice larvae in this study did not require 22:6 3 in their diet, even when the levels of 20:5 3 were low.     

Dominance of larval forms in euphausiid (Crustacea:Eucarida) ontogenesis

Variability and dominance of Euphausia superba Dana larval forms (Furcilia-I and Furcilia-II stages) in the plankton of the Scotia and Weddell Seas have been investigated. New forms (1, 2, 3 and 14) have been recorded. The dominant forms of Furcilia-I stage are proposed to represent the initial dominants. In accordance with the initial dominance, five types of larval form combinations have been established. During the initial dominance change — from 5 to 2, the larval form number increases. This phenomenon is due to parallel development of euphauiid larvae; it results from a developmental pathway change in the main larval mass. Such deviations are reflected in an initial dominance change. In each pathway, the larvae pass through an unequal number of moults before reaching Form 5 (in accordance with the proposed moult scheme of Furcilia-I stage larvae). In the case of initial dominance of less-developed forms, the presence of different parallel pathways increases. As a result, the total number of larval forms present in the plankton changes, causing increased variability of the total number of larval forms. Each type of larval form combination is the result of summation of all larval forms, which derive from different developmental pathways of the larvae in different localities. The most usual developmental pathway for Euphausia superba is through Form 5, which may, thus, be regarded as the main developmental pathway for this species. This pathway probably corresponds to optimal environment conditions for larval growth and morphogenesis with maximal synchronisation of both processes. Consequently, it may be suggested that changes in developmental pathways of larvae are connected with suboptimal environmental conditions.     

An instance of bacterial inhibition in oceanic surface water

Water from the 150 surface film 50 miles north of Puerto Rico at 19°30 N, 66°30W supported only a negligible microflora compared to that of adjacent stations. Bacteriostasis was indicated when a ten-fold dilution of the sample resulted in a ninety-fold increase in cultivable microorganisms. The surviving organisms, atypical pseudomonads, were biochemically inactive in comparison to isolates from the other stations. Net phytoplankters at this station were similar in relative composition and abundance to those at the adjacent station.     

Growth and spatial distribution of Cassidulus mitis (Echinodermata: Echinoidea) on a sandy beach in Southeastern Brazil

Using a hand dredge, a population of Cassidulus mitis Krau, 1954 was sampled monthly from February 1986 to January 1987 at 15 stations offshore from Vermelha Beach (22°5718 S; 43°948 W), in water depths ranging from 0 to 6 m. The sex ratio indicated a slight numerical dominance of females for adults and a larger numerical female dominance for juveniles. A von Bertalanffy growth curve was estimated as L=71.00 (1-e^(-0.390t)), where L=length (mm) and t=time (yr). The instantaneous natural mortality rate (M) was estimated as 0.812. The population occupies a zone parallel to the beach, and displays a spatially aggregated pattern, with higher densities in areas characterized by coarse and very well sorted sand containing low amounts of organic matter.     

Aggregation and foraging behavior of whirligig beetles (Gyrinidae)

Summary Whirligig beetles aggregate in the daytime into dense single-and multispecies groups (rafts) of hundreds or thousands of individuals. On the 22km shoreline of Lake Itasca in northern Minnesota, these aggregations were on the average 0.8 km apart, and they were usually found day after day in the same ocations.Most beetles apparently do not home to the aggregation of their origin after dispersing at night because (a) the species composition of some aggregations changed greatly, and (b) paint-marked beetles (Dineutus horni) moved overnight from one aggregation as far as 4km, joining 11 of the 14 large (>300 beetles) D. horni groups on the lake.Throughout the night, the largest concentrations of beetles remained within 100m of the diurnal aggregation sites. Beetles reconvened into the compact rafts before daybreak, in part by following each other in sometimes long single files or trains. Their forward motion stopped after they joined large number of other beetles. We infer that following behavior enables those individuals that have dispersed from their original aggregations (during their nocturnal foraging) to find and join other aggregations before daylight.Naive fish ate the beetles despite their noxious secretions. However, fish living near rafting sites and feeding on insects on the water surface in daylight should soon learn to avoid the beetles. The rafting sites would then become safe places. We observed fish attacking only those beetles that had been either dispersed from their rafts or released into open water away from raft sites in the daytime. We speculate that the evolutionary significance of the aggregation behavior is related to predator (fish) avoidance.     

Comparison of three techniques for administering radiolabeled substrates to sediments for trophic studies: uptake of label by harpacticoid copepods

Microbial grazing by two species of meiofaunal harpacticoid copepods (Heteropsyllus nunni and Thompsonula hyaenae) was determined by uptake of radioactive labels following their introduction into natural sediments from a low-energy intertidal site in Florida (29°5440N; 84°3130W) in May 1986. Grazing was related to three methods of radioactive-label introduction: injection, porewater replacement, and slurry. Uptake of label by harpacticoids was examined using two dual-label combinations, ³H-thymidine/¹⁴C-bicarbonate and ³H-thymidine/¹⁴C-acetate. The injection and porewater-replacement methods yielded statistically indistinguishable results. Results obtained by the slurry method differed significantly from the other two methods. We suggest that the unique results obtained in the slurry method were a consequence of the disruption of microbial-meiofaunal spatial relationships.     

Influence of irradiance on the nutritional value of two phytoplankton species fed to larval Japanese scallops (Patinopecten yessoensis)

Japanese scallop (Patinopectin yessoensis Jay) larvae grew faster and were larger after 18 d when fed a diet of high-light(HL)-grown Chaetoceros simplex or HL Pavlova lutheri relative to diets of the same phytoplankton species grown at low light (LL). When provided as saturating rations to larval scallop, these diets could be ranked: HL C. simplex>LL C. simplex>HL P. lutheri>LL P. lutheri. In both phytoplankton species, HL-grown cells contained more of the short-chain saturated fatty acid (FA), 16:0 than LL-grown cells. Scallop growth rates were a significant function of the amounts (mg g^-1 dry wt) and the proportions (as percentage of total FAs) of the FAs 14:0 and 14:0+16:0 (total saturated FAs) in their diet. The proximate biochemical composition of HL- versus LL-grown phytoplankton showed no significant differences in protein, total lipid, carbon, carbohydrate or nitrogen per cell which were consistently associated with the greater nutritional value of HL cells. In spite of this high variability in proximate composition, the larval growth rate was a significant function of the average carbon content, nitrogen content and cell volume of the phytoplankton cells. Increased amounts of the essential polyunsaturated FAs 20:5 3 and 22:6 3 in the phytoplankton were negatively correlated with larval scallop growth rates. Thus HL-grown phytoplankton cells were nutritionally superior to LL-grown cells. This nutritional superiority seems to be determined by the fatty acid composition of the cells which, in turn, is controlled by variation in irradiance. The general tendency of predator FA profiles to resemble that of their prey was not observed in larvae fed P. lutheri. The much greater amounts of 18:4 3, 20:5 3, and 22:6 3 FA in P. lutheri relative to C. simplex were not evident in the scallop larvae fed these cells.     

Potential effects of a resuspension event on the vertical distribution of copepod eggs in the sea bed: a laboratory simulation

Adult female Acartia tonsa and Labidocera aestiva were obtained from inshore marine waters near Turkey Point, Florida (29°54.5N;84°31W) during April and May 1991. For each species, eggs spawned overnight in the laboratory were collected, mixed with sediment, and added to a plastic tube (26 to 29 cm longx5 cm diam) to yield a 2 cm-thick layer. This tube was connected to a 245 cm-long tube, seawater was added and the contents were thoroughly mixed by turning the assembly end-over-end several times. The vertical distribution of eggs in the sediments following resuspension varied according to the grain size of the sediments. For sediments of 125 m particle-diameter, 68 to 72%, and 70 to 73% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm.For sediments 63 to <125 m particle-diameter, 34 to 36% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm. For sediments of <63 m particle-diameter, egg distribution was uniform for both species throughout the 2 cm layer. The results indicate that the vertical distribution of eggs in the sea bed following a resuspension event should be highly dependent upon the grain-size composition of the sediments.     

Descriptions and durations of premolt setal stages in female Dungeness crabs,<Emphasis Type="Italic"> Cancer magister</Emphasis>

For crustaceans with a well-defined annual molting season, such as adult female Dungeness crabs (Cancer magister Dana), setal molt staging can, in principle, be used to predict molting destiny of individual crabs. Size-specific predictions of molting probability could, in turn, be useful for estimating mortalities due to molting. Female Dungeness crabs were collected January–March 1997 at depths of 10–30 m off the California coast, USA (41°N). Intermolt stage A₁–C₄ and premolt stages D₀, D₁, D₁, D₁ and D₂ were described based on features of the branchial epipod. Laboratory experiments suggested that stage D₁ was the earliest stage beyond which eventual molting was inevitable so that molting destiny could be determined. Estimated mean number of days from the beginning of stage D₁ to molting was 85. Estimated individual stage durations, based on laboratory experiments, were 24, 51, –4, 18, and 20 days, respectively, for stages D₀, D₁, D₁, D₁, and >D₂. The estimated –4 days for stage D₁ suggests that this stage must be very brief and raises a question of its utility in designation of molt stages. Molt staging of three field samples, 300–600 crabs in each, collected prior to the 1997 annual molting season, indicated an increase in the size and frequency of crabs staged D₁ or later as the time to molt approached, although crabs of 150 mm carapace width and larger showed few signs of molt preparation. Because the duration of the molting season (approximately 120 days) for adult female C. magister in northern California exceeds the estimated maximum duration of reliable prediction of molting destiny (85 days), it does not appear that molt staging can be used to predict molting destiny in this population. However, the procedures that we have used in this paper for application to female C. magister might be used with success for other crustaceans if the duration of stages D₁ to molting exceeds the duration of the molting season, and furthermore may be used for describing temporal molting trends.Communicated by J.P. Grassle, New Brunswick     

Two new records of Planctosphaera larvae (Hemichordata: Planctosphaeroidea)

Two specimens of the rarely found Planctosphaera larva have been taken in the North Atlantic near Challenger Bank north of the Azores and in the North Equatorial Current, latitude 19°33 N, longitude 40°01 W.This research was supported by Grant 6027-X from the U.S. National Science Fonndation and is Contribution No. 2380 from the Woods Hole Oceanographic Institution.     

Response of gametophytes of Ecklonia radiata (Laminariales) to temperature in saturating light

Gametophytes of Ecklonia radiata (C.Ag.)J.Ag. from two New Zealand locations with different field temperature ranges were exposed to temperatures of 5° to 26°C in saturating light. Plants from Goat Island Bay (Lat. 36° 16S, Long. 174°48E) grew in 9.3° to 25°C and reproduced in 9.3° to 24°C. There was no growth at 8°C and plants died at 26°C. Plants from the cooler location, Houghton Bay (Lat. 41°20S, Long. 174°40E), grew from 8° to 24°C and reproduced up to 15°C but not at 21.5°C. The plants did not grow at 6°C and died at 26°C. The timing of the first cell division and subsequent growth rate were retarded close to the upper and lower tolerance limits. Reproduction was a broad optimum of roughly 12° to 20°C. Within this range, fertile female gametophytes grown at lower temperatures had fewer, larger cells and thus fewer potential ova than those grown at higher temperatures.     

Observations of planktonic bioluminescence in the euphotic zone of the California Current

The distributions of bioluminescence, temperature, salinity, oxygen. pH, and chlorophyll a were measured at 10 m intervals, to a depth of 100 m at a station (33°46N; 119°36W) in the California Current from 17 to 20 July 1982. The distribution of bioluminescence showed a marked day-night change which was consistent over the sampling period. The nighttime maximum was at the surface, and the daytime maximum was between 30 and 40 m. The shapes of the day and night distributions were independent of the absolute intensity of bioluminescence and were also insensitive to advection, as inferred from changing temperature-salinity relationships. The nighttime depth distribution broadened during a period of high wind Day to night differences in the color spectrum at the depth of maximum bioluminescence suggest that the luminescent organisms differed from day to night.     

The structure of plankton communities of the Indian Ocean

Species diversity and trophic structure of plankton communities have been considered as most important biological features. The Fisher () and Simpson () indices and the information index H=- pi log₂ pi (Margalef) were used for evaluation of species diversity. The indices have been calculated within the group of filter feeders by numbers ( and H) and biomass ( and H) of the species; the best results were obtained in the latter case. The index H=- pi log₂ pi is proposed for the quantitative evaluation of trophic structure, where a portion of an individual trophic group is taken as pi. The plankton material was collected by the R.V. Vityaz in the northern Indian Ocean in January through February, 1960. Analysis of characteristics of zooplankton distribution, species and trophic diversity in connection with characteristics of the water regime resulted in the definition of 3 types of the plankton communities: (a) those in intensive divergence zones; (b) those in poor divergence zones; (c) those in regions with stable water stratification or with feebly marked convergence, distiguished by different values of biomass, species diversity, and trophic group ratios.