Sponge-feeding by the Caribbean starfish Oreaster reticulatus

The common Caribbean starfish Oreaster reticulatus (Linnaeus) feeds on sponges by everting its stomach onto a sponge and digesting the tissue, leaving behind the sponge skeleton. In the San Blas Islands, Republic of Panama, 54.2% of the 1549 starfish examined from February 1987 to June 1990 at eight sites were feeding, and 61.4% of these were feeding on sponges, representing 51 species. Sponges were fed on disproportionately heavily in comparison to their abundance, which was only 9.7% of available prey. In feeding choice experiments, 736 pieces of 34 species of common sponges from a variety of shallow-water habitats, and also 9 ind of a coral, were offered to starfish in individual underwater cages. Acceptance or rejection of sponge species was unambiguous for 31 of the 34 species, and there was a clear relationship between sponge acceptability and sponge habitat. Starfish ate 16 of 20 species that normally grow only on the reefs, but only 1 of 14 species that live in the seagrass meadows and rubble flats surrounding the reefs. The starfish live in the seagrass meadows and rubble flats, and avoid the reefs, and so the acceptable reef sponges are generally inaccessible until a storm fragments and transports them into starfish habitat. After Huricane Joan washed fragments of reef sponges into a seagrass meadow in October 1988, starfish consumed the edible species. When the seagrass meadow was experimentally seeded with tagged reef sponge fragments in June 1994, O. reticulatus consumed edible species and accumulated in the area seeded. Reef sponges that were living in a seagrass meadow, from which O. reticulatus had been absent for at least 4 yr (from 1978 to 1982), were eliminated when the starfish migrated into the area, and the sponges have been unable to recolonize up to June 1994. O. reticulatus feeding and habitat preferences appear to restrict distributions of many Caribbean reef sponge species to habitats without O. reticulatus and may have exerted significant selective pressure on defences of those sponges that live in O. reticulatus habitats.     

The song of the humpback whale Megaptera novaeangliae in the West Indies

Songs of the humpback whale Megaptera novaeangliae were recorded and analyzed from Grand Turks in the Bahamas to Venezuela. The design features of the song are as follows. The basic song evolves through a series of different sounds in a fixed order. The song is produced only in the winter tropical calving grounds, just before the whales arrive on the banks. Redundancy is high in that syllables, motifs, phrases and the entire song are repeated. Low, intermediate, and high-frequency sounds are scattered throughout the song. One sound is associated with blowing. The song appears to be partially different each year and there are some differences within a year between banks which may indicate that dialects are present. It is suggested that songs from other populations are quite different. The apparent yearly changes do not occur at one point in time. Only single individuals produce the song and they are hypothesized to be young, sexually mature males. The implications of these various design features are discussed.     

Some notes on Tubiluchus corallicola (Priapulida) from Barbados,West Indies

The occurrence of Tubiluchus corallicola (van der Land) in a lagoon on the East coast of Barbados, West Indies, is reported. 23 adult and 2 larval specimens were found in a sample taken from a subtidal stromatolite on which the animals presumably inhabited the algal surface layer. A comparison with data from earlier findings shows that the species is not confined to a particular type of substratum, yet morphologically it seems to be well adapted for a life in the interstitial sand habita. For the first time, living animals were observed and photographed. Their behavior and movements are briefly described and an account of morphological and histological details, as seen in squeezing preparations and photomicrographs, is presented.Supported in part by NSF Grant GB-7952     

Host specificity in sponge-encrusting zoanthidea (Anthozoa: Zoantharia) of Barbados,West Indies

Six species of common Caribbean Zoanthidea, Parazoanthus swiftii, P. parasiticus, P. catenularis, P. puertoricense, Epizoanthus cutressi, and Epizoanthus sp., are virtually restricted to living on surfaces of reef-dwelling sponges. Quantitative surveys on Barbados reefs indicate that substrate specificity is relatively high among these zoanthids with three restricted to a single primary host sponge species and three restricted to three closely related sponges. One species, P. swiftii, exhibits a broad range of acceptable secondary substrates, due to its unique ability to execute migrational spread in the adult polyp stage. Variations in substrate specificity have been noted between island populations within the extensive Caribbean range and appear to be due to different species compositions of local sponge communities and slight differences in zoanthid larval settling specificities.     

Ecological energetics of Nerita (Archaeogastropoda,Neritacea) populations on Barbados,West Indies

Population energy budgets estimated on the assumption of steady state conditions for Nerita tessellata Gmelin, N. versicolor Gmelin, and N. peloronta L. on Barbados, W. Indies, are presented. Large differences in population structure, and hence energetics, occurred at different localities along the beach. Relatively high proportions (81 to 88%) of the assimilated energy were lost via metabolism. Assimilation efficiencies ranged from 39 to 43%, net growth efficiencies from 5 to 13%, and ecological efficiencies from 3 to 7%. For each species, production (P), energy flow (A) and total energy consumption (C) were expressed as functions of animal size, in order to facilitate gross estimations of the energy components for other populations for which data on size-frequency and density are available. Respiration studies of all three species in the laboratory failed to detect differences between respiration rates in air or under seawater.     

Significance of ammonia in determining the N:P ratio of the sea water off Barbados,West Indies

N:P atomic ratios calculated on NO₃-N alone for the upper waters of the tropical Atlantic Ocean off Barbados are very low, being only 9.8:1. Absolute values are also low, the integrated values between O and 100 m for NO₃-N and PO₄-P being 0.59 and 0.06 g-at l^-1, respectively. However, when ammonia is included as a nitrogen source the ratio becomes 28.8:1. This is the average value obtained from 42 samples taken over a 21-month period, and suggests that phosphorus, and not nitrogen, is the more critical nutrient in phytoplankton growth off Barbados.     

Light absorption and utilization among hermatypic corals: a study in Jamaica,West Indies

The chlorophyll specific absorption coefficient ( _c) was measured for zooxanthellae from six hermatypic coral species obtained, where possible, from four depths (1, 10, 30, 50 m) on reef sites near Discovery Bay, Jamaica in February and March 1983. Measurements of photosynthetic rates versus irradiance, as well as cellular and areal chlorophyll a, were also performed on these colonies or sister colonies. Together the data were used to compare minimum quantum requirements (1/Φ m) among species and depths and to assess the importance of light utilization to the growth and depth distribution of these corals. Our data suggest that, although _c was found to decrease with depth, interspecific differences in _c do not occur for zooxanthellae from the corals investigated. Minimum quantum requirements (1/Φ m) decreased significantly with depth, thereby reflecting an increase in photosynthetic light utilization efficiency with decreasing irradiance. Interspecific differences in 1/Φ m determinations were suggested but not statistically conclusive. We conclude that interspecific differences in gross photosynthesis, and perhaps growth and depth distribution, are primarily attributable to differences in the light utilization capacity of the whole coral, as reflected by the product of _c ^′ and chlorophyll per unit surface area, and in-situ quantum efficiencies. This research was performed under the auspices of the US Department of Energy under Contract No. DE-AC02-76CH00016     

Differences in the structures of fish assemblages inThalassia testudinum beds in Guadeloupe,French West Indies,and their ecological significance

The structures of fish assemblages in twoThalassia testudinum beds in Guadeloupe, French West Indies, one adjacent to mangroves and the other adjacent to coral reefs, were compared between January 1983 and May 1984. The aim of the study was to compare the influences of mangroves and coral reefs on the utilization of seagrass beds by fishes through examination of species composition, catch rate, size of fishes and temporal changes. The two fish assemblages were similar in terms of the number of species they had in common (nearly 44% of the total number of species collected) and the great abundance of juveniles. They both comprised species that usually inhabit other habitats, i.e., estuaries, open waters or coral reefs. Estuary-associated species (e.g. Gerreidae) were the most abundant species in the seagrass bed near the mangroves, while small pelagic species (e.g. Clupeidae) were the most abundant species in the seagrass bed near the coral reefs. The seagrass bed near the mangroves was preferentially utilized as a nursery area by small juveniles of various species (e.g. Clupeidae, Sparidae, Gerreidae, and at least one coral reef species,Ocyurus chrysurus). The abundance of these species varied frequently, suggesting successive arrivals and departures of juveniles over time. The seagrass bed near the coral reefs was characteristically utilized by fishes that are more able to avoid predation, i.e., fishes that forage over seagrass beds at night and shelter in or near the coral reefs during the day (large juveniles of coral reef species and adults of schooling pelagic species, respectively). The constant migrations of these fishes between the coral reefs and seagrass beds explained the relative stability of the structure of the fish assemblage in the seagrass bed over time. Thus, the two seagrass beds were not equivalent habitats for fishes. The distinct ecological influences of the mangroves (as a nursery for small juveniles) and coral reefs (as a shelter for larger fishes) on the nearby seagrass beds was clearly reflected by the distinct utilizations of these seagrass beds by fishes.     

An assessment of contamination and ecological risk of metals in sediments of the Guaracara,Caparo and Couva rivers in Trinidad,West Indies

The presence of metals in an aquatic environment can serve as a biomarker for pollution and can be used to evaluate its contamination status. Rapid industrialisation in recent decades has propelled Trinidad and Tobago to be one of the most developed nations within the Caribbean region and has stimulated the awareness of potential ecological risks from various industrial activities affecting the rivers of Trinidad. Sediment samples from three rivers along the West coast of Trinidad were analysed for Cd, Cr, Cu, Mn, Ni, Pb and Zn. For all three rivers, the metal concentrations in sediments were in the range of 0.40–2.31?μg/g, 12.77–33.04?μg/g, 14.51–72.89?μg/g, 224.90–4472.83?μg/g, 8.20–43.08?μg/g, 22.63–38.34?μg/g and 92.0–5462.60?μg/g for Cd, Cr, Cu, Mn, Ni, Pb and Zn, respectively. Assessment of the pollution status indicated that all three rivers were considered polluted, with significant contributions from Cr, Cu, Mn, Ni and Zn. The potential ecological risk for all three rivers, however, was low and multivariate statistics revealed that mainly anthropogenic sources contributed to the metal concentrations in sediments of all three rivers.     

The ecology of the molluscs of Thalassia communities,Jamaica, West Indies. II. Molluscan population variability along an environmental stress gradient

Along a composite onshore-offshore gradient, 4 homogeneous areas within beds of the marine angiosperm Thalassia were studied in detail. Eleven environmental variables, and molluscan and echinoderm abundance were sampled at monthly intervals for 1 year. Environmental conditions were generally more extreme, and their variance greatest, nearshore; they decreased significantly with distance from shore. Environmental predictability and cumulative diversity (H) increased with distance from shore, whereas abundance was greatest in the higher-stress environments. Over the year, the population variance (number of species, density, and diversity) was no greater in the unpredictable, low diversity environments than in the more predictable, high-diversity environments. Bivalves collected from the low-diversity environments were markedly eurytopic forms. whereas the highest-diversity area contained predominantly stenotopic taxa. Typical suspension feeders were dominant only in the most diverse area, whereas more generalized feeders dominated the higher-stress environments. There was no correlation between bivalve diversity increased with the variety of available food. Evidence suggests that catastrophes and other long-term phenomena, and biological factors such as predation, are of great importance in determining the differences in fauna between these areas.     

Pollution status,ecological risk assessment and source identification of heavy metals in road dust from an Industrial Estate in Trinidad,West Indies

Road dust in an industrial estate could potentially contain toxic heavy metals as a result of various anthropogenic sources. This study investigated sixteen samples from various locations throughout the Point Lisas Industrial Estate in Trinidad, West Indies. Samples were acid-digested and analysed by Flame Atomic Absorption Spectroscopy, which revealed that concentrations for Cd, Cr, Cu, Mn, Ni, Pb and Zn ranged from 2.48–5.45?μg/g, 14.2–70.5?μg/g, 15.3–130?μg/g, 219–1330?μg/g, 20.0–62.1?μg/g, 43.5–113?μg/g and 105–1154?μg/g, respectively. Different methods (Geoaccumulation index, pollution index, integrated pollution index, enrichment factor and ecological risk assessment) of assessing heavy metal contamination in road dust indicated negligible to moderate degrees of pollution, in which the associated potential ecological risk was considered low. Principal component analysis (PCA) and Cluster analysis (CA) grouped the heavy metals according to potential sources and indicated that the accumulation of heavy metals in the road dust of the Estate were influenced mainly by vehicular and industrial processes.     

Comparison of feeding habits of myctophid fishes and juvenile small epipelagic fishes in the western North Pacific

To examine the potential trophic competition between myctophids and small epipelagic fishes in the nursery grounds in spring, we compared the stomach contents of dominant myctophids (Symbolophorus californiensis, Ceratoscopelus warmingii and Myctophum asperum; n = 179) and juvenile epipelagic fishes (Japanese sardine, Sardinops melanostictus, Japanese anchovy, Engraulis japonicus, chub mackerel, Scomber japonicus, and spotted mackerel, S. australasicus; n = 78) that were simultaneously collected at nighttime with a midwater trawl net around the Kuroshio-Oyashio transition zone in the western North Pacific. It was clear that the neritic copepod Paracalanus parvus s.l. was the most abundant species in NORPAC samples (0.335 mm mesh size) taken at the same stations. Diets of dominant myctophid fishes differed from those of the juvenile epipelagic fishes; Japanese sardine and anchovy mostly preyed upon P. parvus s.l. (23.6% of stomach contents in volume) and Corycaeus affinis (16.1%), respectively. Both chub and spotted mackerels mainly preyed upon the seasonal vertical migrant copepod, Neocalanus cristatus (15.9 and 14.7%, respectively). On the contrary, myctophid fishes probably do not specifically select the abundant neritic copepods. Namely, S. californiensis mostly preyed upon a diel vertical migrating copepod, Pleuromamma piseki (22.7 and 30.6% in stomach of juvenile and adult, respectively), while C. warmingii and M. asperum preyed on Doliolida (43.0% in stomach of juvenile C. warmingii), appendicularians (11.0% in stomach of juvenile M. asperum), and Ostracoda (6.3% in stomach of adult C. warmingii). Feeding habits of myctophid fishes seem adapted to their prey animals; low rate of digested material (less than 30% in volume) in stomachs of S. californiensis may be linked to the movement of P. piseki, hence S. californiensis can easily consume this copepod at night since they are more concentrated at night than daytime. High rate of digested material (over 40%) of M. asperum and adult C. warmingii suggest that they feed not only at night but also during the daytime in the midwater layer. Thus, myctophid fishes actually fed in the surface layer but less actively than the small epipelagic fishes. These results suggest that the potential for direct food competition between myctophids and small epipelagic fishes is low in the nursery ground, but there remains a possibility of indirect effects through their prey items, since the above gelatinous animals feed on common prey items as juveniles of Japanese sardine and anchovy.     

Origins of green turtle (<Emphasis Type="Italic">Chelonia mydas</Emphasis>) feeding aggregations around Barbados,West Indies

Although green turtles (Chelonia mydas Linnaeus) do not nest in Barbados, the easternmost island in the Caribbean archipelago, juveniles are regularly seen foraging in nearshore waters. To examine the stock composition of this foraging population, mitochondrial (mt) DNA control region sequences were analysed from 60 juvenile (31–70 cm curved carapace length) green turtles and compared with data published for key nesting populations in the Atlantic, as well as other feeding grounds (FGs) in the Caribbean. Eight distinct haplotypes were recognised among the 60 individual green turtles sampled around Barbados. Three of the haplotypes found have only previously been reported from western Caribbean nesting beaches, and two only from South Atlantic beaches. The nesting beach origin of one of the Barbados FG haplotypes is as yet unidentified. Stock mixture analysis based on Bayesian methods showed that the Barbados FG population is a genetically mixed stock consisting of approximately equal contributions from nesting beaches in Ascension Island (25.0%), Aves Island/Surinam (23.0%), Costa Rica (19.0%), and Florida (18.5%), with a lesser but significant contribution from Mexico (10.3%). Linear regression analysis indicated no significant effects of rookery population size or distance of the rookery from the FG on estimated contributions from the source rookeries to the Barbados FG. Our data suggest that the similar-sized green turtles sampled on the Barbados FG are a mixed stock of more diverse origins than any previously sampled feeding aggregations in the Caribbean region. The relatively large contribution from the Ascension Island rookery to the Barbados FG indicates that hatchlings from distant rookeries outside the Caribbean basin enter the North Atlantic gyre and become a significant part of the pool from which eastern Caribbean foraging populations are derived. These data support a life cycle model that incorporates a tendency of immatures to migrate from their initial foraging grounds at settlement towards suitable foraging grounds closer to their natal rookeries as they mature.Communicated by P.W. Sammarco, Chauvin     

Active salinity choice and enhanced swimming endurance in 0 to 8-d-old larvae of diadromous gobies,including Sicydium punctatum (Pisces), in Dominica,West Indies

We studied the early life history of diadromous gobies in Dominica, West Indies, from May 1989 to May 1991, emphasising Sicydium punctatum Perugia. The transition of newly hatched larvae from upriver nest sites to the sea was studied in laboratory experiments. Newly hatched larvae are negatively buoyant but avoid settling to the bottom by active swimming during drift to the sea. Laboratory experiments evaluated salinity preferences and effects on swimming endurance. Larvae in haloclines actively selected low to intermediate salinities. Initially (0 to 5-d post-hatch), larvae minimized exposure to salinities >10 ppt, but later (5 to 8-d) occupied increasingly saline water. Larvae in no-choice freshwater or seawater treatments ceased activity at 4 to 5 d, but in haloclines larvae remained active up to 8 d post-hatch. Salinities <10 ppt are important for early survival of sicydiine gobies. Implications for larval survival and transport are discussed.     

Comparative studies on the metabolism of shallow-water and deep-sea marine fishes. II. Red-muscle metabolism in shallow-water fishes

Maximal rates of oxygen consumption in vitro have been measured under standardized conditions at three test temperatures (5°, 15°, 25°C) on minced preparations of red muscle from 10 species of shallow-water marine teleost fishes. These fishes came from three different geographic areas, two with cool average water temperatures (near 15°C: coastal southern California, Galápagos Islands) and one with warm average water temperatures (near 25°C: Hawaiian Islands). The group is made up of post-juvenile or adult epipelagic fishes, which are moderately or very active in terms of their locomotor activities. A large part of the range of phylogenetic diversity among the teleosts is represented, as is the body weight range from a few grams to several kilograms. The purpose of the work is to provide part of a set of tissue-metabolism data on shallow-water fishes for future comparison with similar results from deep-sea species. Of 8 complete curves for oxygen uptake rate versus temperature (R-T curves), 6 are normal in shape (Q₁₀1.5), 1 is normal but with a low Q₁₀, and 1 is partly flat, partly normal. The differences between the species in terms of both absolute positions and slopes of the R-T curves are not related in any consistent way to any of the three testable variables: phylogenetic position, long-term adaptation temperature, and body size. The red muscles of a variety of adult epipelagic fishes, at ecologically realistic temperatures, are shown to be exceptions to the general rule that tissues of ectothermous lower vertebrates have lower metabolic rates than comparable tissues of non-torpid endothermous higher vertebrates. This circumstance probably is a major factor in the great capacities for sustained high-speed swimming shown by most epipelagic fishes. Other physiological and ecological implications of the results are discussed.     

Comparative studies on the metabolism of shallow-water and deep-sea marine fishes. I. White-muscle metabolism in shallow-water fishes

Maximal rates of oxygen consumption in vitro have been measured under standardized conditions at three test temperatures (5°, 15°, and 25°C) on minced preparations of white muscle from 39 species of shallow-water marine teleost fishes. These fishes came from four different geographic areas, two with cool average water-temperatures (near 15°C: coastal southern California, Galápagos Islands) and two with warm average water-temperatures (near 25°C: Hawaiian Islands; Bermuda). The group includes species covering much of the range of variation to be found among the teleosts with respect to five additional variables: phylogenetic position, type of environment, body weight, activity level, and growth stage. The purpose of the work is to provide part of a base line of tissue-metabolism data on shallow-water fishes for comparison with similar results from deep-sea species. Major conclusions from statistical analyses of the results are: four groups of shapes of oxygen-uptake rate versus temperature curves exist: normal, flat, dipped and peaked. Over 50% of curves are normal. Intra-group differences, contributing significantly to the total variance of the results at given test temperatures, are: cool versus warm average environmental temperatures primarily for epipelagic species; epipelagic versus non-epipelagic environments; very active species versus all others; juvenile stages versus adults. In each case, the subgroup first mentioned shows higher muscle oxygen-uptake rates than the other subgroup. Variables not contributing significantly to the total variance are phylogenetic position and body weight. Physiological and ecological implications of these results are discussed.     

Chitinolytic enzymes in the digestive system of marine fishes

Chitinase, exo-N-acetyl--D-glycosaminidase (NAGase) and lysozyme activities were assayed in the digestive tract of 6 species of marine fishes: Myxine glutinosa (cyclostome), Chimaera monstrosa (holocephalan), Squalus acanthias, Etmopterus spinax, Raja radiata (elasmobranchs) and Coryphaenoides rupestris (teleost). Strong chitinase activity was found in the gastric mucosa of the elasmobranchs (S. acanthias, E. spinax and R. radiata) and the teleost (Coryphaenoides rupestris). A remarkably high chitinase activity occurred in the pancreas of the stomachless holocephalan fish Chimaera monstrosa. NAGase activity was strong in the digestive tract of all species. It could be concluded that marine fishes with diets consisting largely of chitinous invertebrates may display high chitinase and NAGase activities in their digestive system; however, only low chitinase activity was found in the intestine of the cyclostome Myxine glutinosa. Coryphaenoides rupestris gastric mucosa chitinase had one optimum activity at pH 1.25, whereas S. acanthias chitinase had two optima, at pH 1.6 and 3.6. The NAGase pH-activity curves from S. acanthias and R. radiata gastric mucosa displayed similar optima, at pH 4.5 and 4.25 respectively. Chimaera monstrosa pancreatic chitinase had a very strong optimum around pH 8 to 10, and one less strong at pH 3. These enzyme activities could not be separated by gel filtration or isoelectric focusing. The pI (isoelectric point) was approximately 4.9 for both enzymes. The molecular weight of the C. monstrosa pancreatic chitinase was estimated to be approximately 43 000. Lysozyme activity was absent or extremely weak in the material studied.     

Variability in abundances of fishes associated with seagrass habitats in relation to diets of predatory fishes

The spatial, diel and tidal variability in the abundance of piscivorous fishes and their teleost prey, and the dietary composition of predatory fishes were investigated in beds of Heterozostera tasmanica within Port Phillip Bay, Australia, from September 1997 to February 1998. Predatory and prey fish assemblages were sampled from beds of H. tasmanica at three locations during each combination of diel (day and night) and tidal (high and low) cycles. Pelagic and benthic crustaceans represented >60% by abundance of the diets of all predatory fishes. Seven species, 54% of all predatory fishes, were piscivorous. These piscivores consumed individuals from seven families, 36.8% of the fish families being associated with seagrass. Western Australian salmon, Arripis truttacea (Arripidae) (n = 174) and yank flathead, Platycephalus speculator (Platycephalidae) (n = 46) were the most abundant piscivores. A. truttacea consumed larval/post-larval atherinids, gobiids and sillaginids. P. speculator consumed late-juvenile/adult atherinids, clinids and gobiids. While the abundances of piscivores varied between locations (P < 0.001) and diel periods (P = 0.028), the relative differences in piscivore abundance between sites and diel periods were not consistent between tides. The abundances of A. truttacea varied in a complex way amongst sites, diel period and tidal cycle, as shown by a three-way interaction between these factors (P = 0.026). Only during diurnal periods at St. Leonards was the abundance of A. truttacea significantly higher during high than low tides (P < 0.001). During the other diel periods at each site, the abundance of A. truttacea did not vary. P. speculator was significantly more abundant nocturnally (P = 0.017). The abundance of small (prey) fishes varied significantly amongst sites (P < 0.001). During the day, the abundance of small fishes did not vary between high and low tides (P = 0.185), but their nocturnal abundance was greater during low tide (P < 0.001). Atherinids (n = 1732) and sillaginids (n = 1623) were the most abundant families of small fishes. Atherinids were significantly more abundant nocturnally (P = 0.005) and during low tides (P = 0.029), and varied significantly amongst sites (P < 0.001). Sillaginids varied significantly only amongst sites (P < 0.001). Seagrass beds provide a foraging habitat for a diverse assemblage of predatory fishes, many of which are piscivorous. Anti-predator behaviour and amongst-location variability in abundances of piscivorous fishes may explain some of the diel and tidal, and broad-scale spatial patterns in small-fish abundances. Received: 23 July 1999 / Accepted: 18 January 2000