Particle interception,transport and rejection by the feather star Oligometra serripinna (Echinodermata: Crinoidea), studied by frame analysis of videotapes

Suspension feeding by a stalkless crinoid (Oligometra serripinna) was studied at Lizard Island, Australia, in 1985. The crinoids were placed in a laboratory flume with a slow, unidirectional current of seawater. Nutritive and non-nutritive particles (15 to 180 m) were introduced upstream from the crinoid, and feeding behavior was recorded at high magnifications on videotape for frame analysis. These direct observations showed that each intercepted particle (whether a dejellied clam egg, Sephadex bead or latex sphere) contacts a single, evidently adhesive tube foot and is rapidly transferred to the pinnular food groove by a bend of the tube foot. The tube foot bends in about 0.1 s and returns to its extended position in 1 to 2 s. Spheres less than 20 m in diameter cause only the intercepting tube foot to bend. In contrast, larger spheres cause the coordinated bending of the intercepting tube foot plus many of the neighboring tube feet: the stimulus spreads through the reacting group of tube feet at about 1 cm s^-1. After transfer to the pinnular food groove, the nutritive particles (dejellied clam eggs) travel at about 1 cm min^-1 to the arm axis and thence down the arm food groove at about 4 cm min^-1 to the mouth; in contrast, non-nutritive particles (Sephadex beads and latex spheres) are discarded from the pinnular food groove between 1 and 30 s after capture. Tube-foot bending is presumably triggered when arriving particles (whether nutritive or non-nutritive) are detected by sensory cells in the tubefoot epithelium: mechanoreception by itself appears sufficient to initiate bending, although chemoreception may modify the reaction. Then, soon after captured particles have been transferred to the pinnular food groove, the crinoid discards those judged unsuitable (probably by contact chemoreceptors in the food-groove epithelium). Clam eggs with intact jelly layers temporarily hang up on tube feet they contact and then float away in the curent: the jelly evidently interferes with mechanoreception and/or chemoreception by the tube-foot epithelium. Some previous studies of crinoid feeding have suggested that particles are trapped in extensive nets or strands of mucus: we found no evidence for this in O. serripinna, which captures particles predominantly be the direct interception method of the aerosol filtration model.     

Mytilus edulis planulatus: an “integrator” of cadmium pollution?

Mussels, Mytilus edulis planulatus, were collected from Port Phillip Bay, Victoria, Australia, in February 1984, to test the assumption that they are integrators of cadmium pollution. Groups of mussels were subjected to the same average dose of cadmium (21 g l^-1), administered according to different dosing regimes over 4 wk (Regimes 1, 2, 3, 5); other groups received twice the average dose (42 g l^-1) in half the time (Regime 4). During each regime, the mussels were exposed to the different cadmium concentrations for one week at each concentration. Nominally, the regimes were: (1) 36 g (Wk 1) to 26 g (Wk 2) to 16 g (Wk 3) to 6 g (Wk 4) Cd l^-1; (2) 6 to 16 to 26 to 36 g Cd l^-1; (3) 21 to 21 to 21 to 21 g Cd l^-1; (4) 42 to 42 g Cd l^-1; (5) 42 to 42 g Cd l^-1 to background (<0.5 g) to background. Differences in cadmium accumulation by mussels from Regimes 1 and 4 were not statistically significant, nor were differences in accumulation between mussels from Regimes 2 and 3. However, mussels from Regimes 1 and 4 had accumulated significantly more cadmium than had mussels from Regimes 2 and 3. Accumulation by mussels from Regime 5 was not significantly different from that by mussels from any of the other regimes. These results suggest that, at least for cadmium, the assumption that mussels are integrators of pollution should be treated with caution. They also have implications with regard to the quantitative biological monitoring of pollution. For example, even in a carefully controlled monitoring program, using mussels of standard size and condition, significant differences in cadmium content between mussels need not indicate exposure to different levels of contamination. Rather, these differences could reflect differences in the regime by which the contamination was received.     

Distribution and variability in abundance ofSchistomysis spiritus (Crustacea: Mysidacea) in the Bristol Channel in relation to environmental variables,with comments on other mysids

Mysids are important components of the zooplankton biomass of estuaries and coastal regions. Twelve species were identified from the Bristol Channel and Severn Estuary (British Isles). The most abundant species wasSchistomysis spiritus (Norman), the majority of which occurred in the Channel within a salinity range of 27 to 34 S. The seasonal distribution and numerical abundance of this species are described over the period November 1973 to February 1975. The peak of abundance ofS. spiritus occurred in the Inner Channel in September (mean of 14 individuals m^-3, ca. 250 individuals m^-2 for this sub-region) when it represented 76% of the omnivore biomass (g C m^-3); for the 364 d from 4 November 1973, the species contributed 43% of the total integrated omnivore standing stock. This peak of biomass was the product of the development of the juveniles from the reproductive period in the spring. Correlation analyses were carried out betweenS. spiritus biomass and 10 physical and biotic variables for 2 mo, November 1973 and September 1974. Temperature and salinity, which are simple indices of seasonal change, exhibited significant correlations with the mysid's abundance in both months. These correlations do not necessarily imply causal relationships or mechanisms between the distribution and abundance of the species and these variables. Clearly, in such a complex environment as an estuarine ecosystem a single variable is unlikely to control the abundance of a species, it is more the result of the combined influence of a number of variables acting in concert.     

A comparison of the efficiency of the bottom samplers used in benthic studies off Cochin

The efficiency of the van Veen and Foerst Petersen grabs used in sampling the bottom fauna near the Cochin Harbour area has been compared in two selected stations having different hydrographic and substratic conditions. The results indicate that the heavier grab is generally more efficient than a lighter one, especially when the substratum is sandy. An examination of the quantity of the sediment and the total number of species brought by the two grabs showed that the design of the van Veen is superior to the Petersen type grab used in the present study. However, due to the highly patchy distribution of the organisms the superiority of the van Veen was less evident when a comparison was made of the total number of animals sampled by the two grabs. When the distribution is bunched it is suggested that samples are drawn, as far as possible, from the same sampling position. The grabs should also be of the same weight and biting area.     

Dependence of phytoplankton production on rhythm and rate of elimination

This paper investigates the dependence of phytoplankton production upon rhythm and rate of zooplankton grazing and presents a mathematical model for calculating the most important parameters. Both uniform and non-uniform grazing are described mathematically. Non-uniform grazing, expressed by a sinusoidal curve, is usually found in bathyplanktonic ecosystems with migratory consumers. Phytoplankton production depends on the time of grazing; the nearer grazing occurs toward nightfall, the higher is the phytoplankton production. In order to calculate phytoplankton productivity and the amount of food consumed by the zooplankton, experimental data on generation time of phytoplankters, their mortality rates, initial and final standing stocks, and information on diurnal grazing rhythms must be available. If the distribution of grazing rates is sinusoidal and mortality rate constant, the equations presented allow the calculation of phytoplankton productivity with an error of about 6%.     

The annual reproductive cycles of Uca annulipes,Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) from the South-west coast of India

Employing the gonad index method, the reproductive cycles of three decapod crustaceans, Uca annulipes (Latreille), Portunus pelagicus (Linnaeus) and Metapenaeus affinis (Milne-Edwards) have been studied. In these crustaceans breeding is not continuous all the year round, but extends over several months of the year with distinct peak periods of gonadal activity. The male and female reproductive cycles are not concurrent. The peak of the reproductive cycle of males occurs slightly earlier in the breeding season than that of females. These studies indicate the possibility of production of successive broods of eggs during the same breeding season. In these species, the low saline conditions of the monsoon period are unfavourable for breeding. The medium and high saline conditions during the post-monsoon and pre-monsoon months, respectively, with plenty of planktonic food for the larvae, seem to be the favourable periods for breeding activity.     

Insecticidal activity of the plant Phyllanthus amarus against Tribolium castaneum

The plant Phyllanthus amarus is used as folk medicine since the year 1800 and has been established for its important medicinal properties particularly for liver ailments. The present communication explores the insecticidal activity of ethanolic extract of aerial and root parts of this plant against stored grain pest Tribolium castaneum. LC 50 values of ethanolic aerial part were 895.77, 473.91, 279.89 and 260.85 microg/cm2, while 512.62, 376.96, 248.88 and 209.79 microg/cm2 for ethanolic root part at the exposure of 3, 5, 7, 9 and 11 days respectively. Ethanolic root extract possessed significant insecticidal activity against T. castaneum.     

Effects of Aquarium Collectors on Coral Reef Fishes in Kona, Hawaii

Abstract:   No previous studies have conclusively documented the magnitude of the effect of aquarium collecting on natural populations. In Hawaii concern over the effects on reef fish populations of collecting for the aquarium trade began in the early 1970s, primarily in response to multiple-use conflicts between aquarium-fish collectors and recreational dive-tour operators. In 1997–1998 we used a paired control-impact design to estimate the effect of aquarium collectors. We compared differences in fish abundance along visual belt transects between collection sites, where collecting was known to occur, and control sites, where collecting was prohibited. To test the assumptions of our observational design, we surveyed a combination of species captured by aquarium collectors and those not captured. The extent of bleaching, broken coral, and coral cover was also surveyed. Seven of the 10 aquarium species surveyed were significantly reduced by collecting. The abundance of aquarium fish at collection sites ranged from 38% lower ( Chaetodon multicinctus ) to 75% lower ( C. quadrimaculatus ) than that at control sites. In contrast, only two of the nonaquarium species displayed a significant collection effect. There were no significant differences in damaged coral between control and collection sites to indicate the presence of destructive fishing practices. In addition, there were no increases in the abundance of macroalgae where the abundance of herbivores was reduced by aquarium collecting. Although our results suggest that aquarium collectors have a significant effect on the abundance of targeted aquarium fishes, better knowledge of the intensity and location of collecting activities is required to make a rigorous assessment of the effects of collecting on nearshore fish populations. Several lines of evidence suggest that the current system of catch reporting underestimates actual removals.     

Incorporation and utilization of bacterial lipids in theSolemya velum symbiosis

We undertook a detailed analysis of the lipid composition ofSolemya velum (Say), a bivalve containing endosymbiotic chemoautotrophic bacteria, in order to determine the presence of lipid biomarkers of endosymbiont activity. The symbiont-free clamMya arenaria (L.) and the sulfur-oxidizing bacteriumThiomicrospira crunogena (Jannasch et al.) were analyzed for comparative purposes. The ¹³C ratios of the fatty acids and sterols were also measured to elucidate potential carbon sources for the lipids of each bivalve species. Both fatty acid and sterol composition differed markedly between the two bivalves. The lipids ofS. velum were characterized by large amounts of 18: 17 (cis-vaccenic acid), 16:0, and 16 : 17 fatty acids, and low concentrations of the highly unsaturated plant-derived fatty acids characteristic of most marine bivalves. Cholest-5-en-3-ol (cholesterol) accounted for greater than 95% of the sterols inS. velum. In contrast,M. arenaria had fatty acid and sterol compositions similar to typical marine bivalves and was characterized by large amounts of the highly unsaturated fatty acids 20 : 53 and 22 : 63 and a variety of plant-derived sterols. The fatty acids ofT. crunogena were similar to those ofS. velum and were dominated by 18:17, 16:0 and 16:17 fatty acids. Thecis-vaccenic acid found inS. velum is almost certainly symbiontderived and serves as a potential biomarker for symbiontlipid incorporation by the host. The high concentrations ofcis-vaccenic acid (up to 35% of the total fatty acid content) in both symbiont-containing and symbiont-free tissues ofS. velum demonstrate the importance of the endosymbionts in the lipid metabolism of this bivalve. The presence ofcis-vaccenic acid in all the major lipid classes ofS. velum demonstrates both incorporation and utilization of this compound. The ¹³C ratios of the fatty acids and sterols ofS. velum were significantly lighter (–38.4 to –45.3) than those ofM. arenaria (–23.8 to – 24.2) and were similar to the values found for the fatty acids ofT. crunogena (–45); this suggests that the lipids ofS. velum are either derived directly from the endosymbionts or are synthesized using endosymbiontderived carbon.Woods Hole Oceanographic Institution Contribution No. 7356Please address all correspondence and reprint requests to Dr Conway at her present address: Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA     

Respiration and nitrogen metabolism of Atlantic halibut eggs (Hippoglossus hippoglossus)

Naturally spawned and fertilized eggs of Atlantic halibut,Hippoglossus hippoglossus L., were analysed for protein, free amino acids (FAA), ammonium ions and energy content. The chemical composition was found to be size-dependent but varied little during egg development. Ammonium ions did, however, accumulate during the late embryonic stage, and the trend in FAA content was downward during the same period. Rates of O₂ uptake and NH₃ excretion followed exponential patterns. A total of 1µmol O₂ was consumed and 120 nmol NH₃ excreted between the time intervals of fertilization and 1 d post hatch. Derived O:N ratios indicated that the dominant portion of the energy metabolism was lipid- or carbohydrate-based during the mid-development period but switched to FAA as hatch was approached.Correspondence should be addressed to: Zoological Laboratory, University of Bergen, Allégt. 41, N-5007 Bergen, Norway