Water flow and prey capture by three scleractinian corals, Madracis mirabilis, Montastrea cavernosa and Porites porites, in a field enclosure

Scleractinian corals experience a wide range of flow regimes which, coupled with colony morphology, can affect the ability of corals to capture zooplankton and other particulate materials. We used a field enclosure oriented parallel to prevailing oscillatory flow on the forereef at Discovery Bay, Jamaica, to investigate rates of zooplankton capture by corals of varying morphology and polyp size under realistic flow speeds. Experiments were carried out from 1989 to 1992. Particles (Artemia salina cysts) and naturally occurring zooplankton attracted into the enclosures were used as prey for the corals Madracis mirabilis (Duchassaing and Michelotti) (narrow branches, small polyps), Montastrea cavernosa (Linnaeus) (mounding, large polyps), and Porites porites (Pallas) (wide branches, small polyps). This design allowed corals to be used without removing them or their prey from the reef environment, and avoided contact of zooplankton with net surfaces. Flow speed had significant effects on capture rate for cysts (M. mirabilis), total zooplankton (M. mirabilis, M. cavernosa), and non-copepod zooplankton (M. mirabilis). Zooplankton prey capture increased with prey concentration for M. mirabilis and M. cavernosa, over a broad range of concentrations, indicating that saturation of the feeding response had not occurred until prey density was over 10⁴ items m⁻³, a concentration at least an order of magnitude greater than the normal range of reef zooplankton concentrations. Location of cyst capture on coral surfaces was not uniform; for M. cavernosa, sides and tops of mounds captured most particles, and for P. porites, capture was greatest near branch tops, but was close to uniform for M. mirabilis branches in all flow conditions. The present study confirms laboratory flume results, and field results for other species, suggesting that many coral species experience particle flux and encounter rate limitations at low flow speeds, decreasing potential zooplankton capture rates. Received: 17 September 1996 / Accepted: 22 November 1997     

Zooplankton capture by two scleractinian corals,Madracis mirabilis andMontastrea cavernosa,in a field enclosure

Capture of zooplankton by scleractinian corals has been noted for several species, yet quantitative information on rates of capture and differential capture by prey taxon has been lacking. We used field enclosures to examine prey capture for two coral species,Madracis mirabilis (Duchassaing and Michelotti) andMontastrea cavernosa (Linnaeus), on the north coast of Jamaica (Discovery Bay) in November 1989, February and March 1990, and January 1992.M. mirabilis has small polyps and a branching colony morphology (high surface/volume ratio), whereasM. cavernosa has large polyps and mounding colonies (low surface/volume ratio). Corals were isolated front potential prey, then were introduced into enclosures with enhanced zooplankton concentrations for 15- to 20-min feeding periods. Corals were fixed immediately after the experiment to prevent digestion, and coelenteron contents were examined for captured zooplankton. Plankton pumps were used to sample ambient zooplankton in the enclosures near the end of each run. Selectivity and capture rates were calculated for each prey taxon in each experiment; both indices were high for relatively uncommon large prey, and low for copepods, which were often the most common items in the plankton. Sizes of zooplankton captured by both species were generally larger than those available considering all prey taxa combined, but were almost the same for both coral species, even though the corals' polyp sizes are very different. This occurred primarily because small copepods, with low capture rates, dominated most plankton samples. For specific prey species, or group of species, there were few significant differences in size between the prey available and the prey captured.M. mirabilis, with small polyps, also captured far more prey per unit coral biomass than didM. cavernosa, with much larger polyps. We hypothesize that the large differences in capture rate of prey taxa are related to escape or avoidance behavior by those potential prey, and to the mechanics of capture, rather than to any selectivity by the corals.     

A histological study of reproduction in the serpulids<Emphasis Type="Italic"> Pomatoceros triqueter</Emphasis> and<Emphasis Type="Italic"> Pomatoceros lamarckii</Emphasis> (Annelida: Polychaeta)

The reproductive cycles of the serpulid polychaetes Pomatoceros lamarckii (Quatrefages, 1865, as Vermilia) and P. triqueter (Linnaeus, 1767, as Serpula triquetra) were studied by histological examination during 1999 and 2000 at Bantry Bay, south-west Ireland. Gametogenesis, sex ratios and hermaphroditism were also investigated. The male/female ratio in P. lamarckii was approximately equal, but in P. triqueter it deviated significantly in favour of females. There was no significant variation in the sex ratios throughout the year in either species. Results confirm that the species are protandric hermaphrodites. In P. lamarckii, but not in P. triqueter, sexual dimorphism was exhibited in body size, the females being larger than the males of the same species. In both species, the proportion of females increased with increasing body size. Simultaneous hermaphroditism was recorded in P. lamarckii, but not in P. triqueter. There was no clearly defined annual gametogenic cycle in either species. Both species appear to have an extended reproductive season, with numerous small-scale peaks in reproductive maturity that can vary annually. Spawning was broadly synchronous between sexes. Visual observation alone (i.e. without histology) was insufficient to accurately assess reproductive condition in individuals not in, or close to, a ripe state.     

Elevated levels of nitrogen and phosphorus reduce fertilisation success of gametes from scleractinian reef corals

Spawned gametes were collected from colonies of Acropora longicyathus at One Tree Island and Goniastrea aspera at Magnetic Island, Great Barrier Reef, Australia, for use in fertilisation trials. Mean fertilisation rates were significantly reduced compared with controls (P<0.003), when gametes from the branching coral A. longicyathus were exposed to elevated ammonium concentrations at 1 µM and above in one cross (60-64% reduction), and at 100 µM in another cross (16% reduction). Mean fertilisation success of A. longicyathus gametes was also significantly reduced compared with controls in both crosses (P=0.000) at concentrations of 1 µM phosphate and above (35-75% reduction), and at 1 µM ammonium plus 1 µM phosphate and all higher concentrations (68-74% reduction). Similarly, the mean percentage of regular embryos that were developing normally was significantly reduced in most nutrient treatments compared with controls (P=0.000). Fertilisation trials using gametes from the brain coral G. aspera resulted in a significantly lower percentage of regular embryos (P=0.001) and a significantly higher percentage of deformed embryos (P=0.001) developing after exposure to elevated nutrient treatments compared with controls. Mean fertilisation rates for this species were only significantly reduced (P=0.034) in the 50 µM ammonium plus phosphate treatment in one cross (8% reduction), compared with the control. Therefore, ammonium and phosphate enrichment significantly impairs fertilisation success and embryo development in scleractinian reef corals.     

Biological patterns and near-bottom population characteristics of two pasiphaeid decapod crustacean species, Pasiphaea sivado and P. multidentata, in the north-western Mediterranean Sea

Biological aspects of the only two epi-/mesopelagic pasiphaeid species distributed along the continental marginof the north-western Mediterranean Sea were studied over the period 1991-1994. The annual reproductive cycle, reproductive output, sex and size distributions by depth (near-bottom distribution), and growth were analysed using 4156 specimens of Pasiphaea sivado (Risso, 1816) and 5491 specimens of P. multidentata Esmark, 1866. The reproductive cycle in the shallower-dwelling species, P. sivado, was nearly continuous, in contrast to the reproductive cycle in P. multidentata, which was markedly seasonal in nature. Both species exhibited similar size and population structure patterns with depth, with individual size increasing along the bottom depth gradient. The shallower-dwelling species had a significantly higher reproductive output level, in terms of the relative number of eggs, than the deeper-dwelling species. Biological trends for each of the species have been compared. The comparative results for these two congeneric species revealed that the biological parameters analysed were closely linked to their population structure. The slight differences in the depth range inhabited by each species have been considered the main environmental factor affecting the life histories of these two species. The data presented supported the hypothesis that depth exerted an important influence on the biological patterns of deep-water species, with the seasonality of reproductive processes increasing in deeper-dwelling species.     

Temporal reproductive isolation and gametic compatibility are evolutionary mechanisms in the<Emphasis Type="Italic"> Acropora humilis</Emphasis> species group (Cnidaria; Scleractinia)

Patterns of interbreeding between individuals are fundamental to the structure and maintenance of evolutionary boundaries between species. In corals, both hybridisation and reproductive isolation appear to be important evolutionary mechanisms. In this study, I examine evolutionary boundaries using morphological, molecular and reproductive criteria within the Acropora humilis species group at Lizard Island on the Great Barrier Reef, Australia. Five species and seven morphs are recognised on the basis of morphological appearance of features traditionally used to identify corals of the genus Acropora. In a molecular phylogenetic analysis, I examine relationships for the mitochondrial DNAs putative control region, using maximum-parsimony and maximum-likelihood methods. The reproductive criteria explore whether species and morphs are reproductively isolated on the basis of temporal or fertilisation barriers. Timing of gamete maturity is surveyed for each species and morph, from the month prior to and 3 months after the mass spawning. Time of spawning is documented at the levels of night and hour of spawning, and time taken for egg-sperm bundles to separate. Laboratory fertilisation experiments tested the potential of species and morphs to interbreed. High levels of intraspecific and extremely low or zero fertilisation levels between the five species indicated that they are valid species. Based on the combined assessment of morphological, molecular and reproductive criteria, A. humilis and A. gemmifera appear to be the most closely related species, which are most closely related to the remaining species in the following order: A. samoensis, A. monticulosa and A. digitifera. Evidence derived from one or more of these criteria suggest that the morphs (1) are at various stages of divergence from the species with which they share morphological characters, and (2) may indicate possible zones of speciation and hybridisation. Identification of morphs avoided the possibility of taxonomic error and was essential for accurate interpretation of evolutionary boundaries. Confirmation of morphology as an informative character of evolutionary boundaries is of great significance because most coral research projects rely on morphology as the primary tool for identification of species.Communicated by M.S. Johnson, Crawley     

Interspecific infection of aposymbiotic juveniles of <Emphasis Type="Italic">Codakia</Emphasis><Emphasis Type="Italic">orbicularis</Emphasis> by various tropical lucinid gill-endosymbionts

Previous molecular phylogenetic analyses have shown that five tropical lucinid species living in or near Thalassia testudinum seagrass beds are colonized by the same bacterial symbiont species. In addition, a new lucinid species belonging to the genus Anodontia, which inhabits reducing sediment found near seagrass beds and in mangrove swamps, has been included in the present study. Endosymbiosis in Anodontia alba was examined according to symbiont phylogenetic and gill ultrastructural analysis. Phylogenetic analysis showed that partial 16S rDNA sequences of A. alba- and Codakia orbicularis-symbionts were 100% identical at all nucleotide positions determined, suggesting that A. alba also harbors the same symbiont species as C. orbicularis (and, consequently, as C. orbiculata, C. pectinella, Linga pensylvanica and Divaricella quadrisulcata). Based on light and electron microscopy, the cellular organization of the gill filament appeared similar to those already described in other lucinids. The most distinctive feature is the lack of "granule cells" in the lateral zone of A. alba gill filaments. In order to confirm the single-species hypothesis, purified fractions of gill bacterial symbionts obtained from the gills of each of the six tropical lucinids cited above were used to infect aposymbiotic juveniles of C. orbicularis. In each case, aposymbiotic juvenile batches were successfully infected by the gill-endosymbiont fractions, whereas, during the experiments, juveniles from the negative control were still uninfected. These experimental data confirm the phylogenetic data and also demonstrate that chemoautotrophic bacterial endosymbionts from their host cells can colonize aposymbiotic juveniles. The conclusion also follows that intracellular gill-endosymbionts still have the capacity to recognize and colonize new host generations. Lucinids provide a unique model for the study of sulfide-oxidizing symbiosis, even if symbionts remain unculturable.     

Chromosomal and nuclear characteristics of deep-sea hydrothermal-vent organisms: correlates of increased growth rate

A range of tissue and cell types from adult and juvenile stages of vent- and non-vent-dwelling deep-sea and shallow-water organisms were compared for signs of cell division, in preparation for a cytogenetic study of the different groups. Virtually all the Mid-Atlantic Ridge (MAR) vent species (bresiliid shrimp, bathymodiolid mussel, branchipolynoid polychaete, and a range of small gastropods) showed an abundance of metaphase chromosome spreads, indicating a generally high intrinsic rate of cell division, irrespective of their phylogenetic group. In comparison, similar tissues and life-history stages (i.e. gonad, developing eggs and gill) from two deep-sea bathypelagic crustaceans, Hymenodora and Gnathophausia, failed to yield any convincing evidence of cell division. This indicated that rates of growth and reproduction in the rest of the deep sea are extremely low. While much has been written about the contrasting growth rates of vent versus non-vent organisms, this is the first direct evidence of differences in cell-division rate between vent and non-vent species, which undoubtedly reflects contrasting conditions relating to food availability and temporal stability in these two deep-sea environments. The cells of shallow-water marine invertebrates (Mytilus, Nucella, Littorina, Pomatoceros and Crangon), based on the results of previous cytogenetic investigations, occupy an intermediate position with respect to their cell-division kinetics. When chromosome numbers, DNA content and nuclear diameters were compared between vent and non-vent species, this showed that no change had occurred in these characters since the time of vent colonisation. Representative chromosome spreads from hydrothermal-vent organisms are shown here for the first time.     

Ecological and genetic aspects of reproductive isolation by different spawning times in<Emphasis Type="Italic"> Acropora</Emphasis> corals

In Okinawa, Japan, we found several species of the coral genus Acropora that spawn 1.5-3 h earlier than other mass-spawning acroporids. In six early-spawning species, gamete bundles appear on the surface of the colony ("setting") about 1 h before sunset, whereas setting occurs about 1 h after sunset in the more common late mass spawners. These early spawners are divided further into two sub-groups: three species that release their gametes within 1 h after setting and three that release their gametes 1.5-2 h after setting. DNA phylogenetic analyses show that each of these groups forms an independent genetic clade. These genetic relationships suggest that different spawning times form the basis of reproductive isolation among these broadcast-spawning corals. Late spawning appears to be the ancestral state, and the shift of spawning to earlier times may have played a role in the speciation process in these sympatric species.     

Molecular taxonomy of vestimentiferans of the western Pacific and their phylogenetic relationship to species of the eastern Pacific. I. Family Lamellibrachiidae

Phylogenetic relationships among vestimentiferans in the family Lamellibrachiidae collected from ten sites in the western Pacific were analyzed on the basis of the nucleotide sequence of part of a mitochondrial gene for cytochrome oxidase I. The 103 individuals analyzed were tentatively classified into five species: namely, Lamellibrachia satsuma, three tentative species inhabiting Japanese waters and one tentative species from the Manus Basin. Phylogenetic analysis of the four tentative species, L. satsuma, and two lamellibrachiids, whose sequences had been reported previously, namely L. columna from the Lau Basin and L. barhami from the Oregon Margin and the Middle Valley, revealed that the lamellibrachiids from Japanese waters were not monophyletic. While two tentative species from Japanese waters and L. columna formed a monophyletic group, the other tentative species from Japanese waters was closely related to the tentative species from the Manus Basin. L. satsuma was shown to be phylogenetically distinct from other lamellibrachiids of the western Pacific. A lamellibrachiid that had been collected from the Nikko Seamount was also demonstrated to be L. sastuma.     

A systematic study of some Black Corals species (Antipatharia,Hexacorallia) based on rDNA internal transcribed spacers sequences

A phylogenetic analysis based on rDNA internal transcribed spacers (ITS) sequences was performed on 15 species of black corals assigned to the genera Antipathes, Stichopathes, Cirrhipathes, Rhipidipathes, Antipathella, Myriopathes and Cupressopathes recorded from the Messina Strait (Mediterranean Sea) and the Bunaken Marine Park (Celebes Sea, Indonesia). The phylogenetic analysis shows that the examined species are grouped in two main branches corresponding to the families Antipathidae-Aphanipathidae and Myriopathidae. While among the Myriopathidae species there is a very small genetic distance, the Antipathidae-Aphanipathidae clade shows a high degree of divergence between different genera. According to this study, the taxon Antipathes? sp. 3 characterised by a bush-like corallum without a well-defined axis, probably belongs to a new undescribed genus of the family Antipathidae.     

Characterization of urease activity in three marine phytoplankton species,<Emphasis Type="Italic"> Aureococcus anophagefferens</Emphasis>,<Emphasis Type="Italic"> Prorocentrum minimum</Emphasis>, and<Emphasis Type="Italic"> Thalassiosira weissflogii</Emphasis>

The availability of different forms of nitrogen in coastal and estuarine waters may be important in determining the abundance and productivity of different phytoplankton species. Although urea has been shown to contribute as much as 50% of the nitrogen for phytoplankton nutrition, relatively little is known of the activity and expression of urease in phytoplankton. Using an in vitro enzyme assay, urease activities were examined in laboratory cultures of three species: Aureococcus anophagefferens Hargraves et Sieburth, Prorocentrum minimum (Pavillard) Schiller, and Thalassiosira weissflogii (Grunow) Fryxell et Hasle. Cultures of P. minimum and T. weissflogii were grown on three nitrogen sources (NO₃^m, NH₄⁺, and urea), while A. anophagefferens was grown only on NO₃^m and urea. Urease was found to be constitutive in all cultures, but activity varied with growth rate and assay temperature for the different cultures. For A. anophagefferens, urease activity varied positively with growth rate regardless of the N source, while for P. minimum, urease activity varied positively with growth rate only for cultures grown on urea and NH₄⁺. In contrast, for T. weissflogii, activity did not vary with growth rate for any of the N sources. For all species, urease activity increased with assay temperature, but with different apparent temperature optima. For A. anophagefferens, in vitro activity increased from near 0-30°C, and remained stable to 50°C, while for P. minimum, increased in vitro activity was noted from near 0-20°C, but constant activity was observed between 20°C and 50°C. For T. weissfloggii, while activity also increased from 0°C to 20°C, subsequent decreases were noted when temperature was elevated above 20°C. Urease activity had a half-saturation constant of 120-165 wg atom N l^у in all three species. On both an hourly and daily basis, urease activity in A. anophagefferens exceeded nitrogen demand for growth. In P. minimum, urease activity on an hourly basis matched the nitrogen demand, but was less than the demand on a daily basis. For T. weissflogii, urease activity was always less than the nitrogen demand. These patterns in urease activity in three different species demonstrate that while apparently constitutive, the regulation of activity was substantially different in the diatom. These differences in the physiological regulation of urease activity, as well as other enzymes, may play a role in their ecological success in different environments.     

Chromosomal evolution in Mugilidae: karyotype characterization of Liza saliens and comparative localization of major and minor ribosomal genes in the six Mediterranean mullets

This study continues a comparative cytogenetic analysis of the fish family Mugilidae, reporting the karyotype characterization of the leaping mullet, Liza saliens, by C-banding, Ag- and fluorochrome-staining, and completing the fluorescence in situ hybridization (FISH)-mapping of the 18S and 5S rRNA genes (rDNA) to the chromosomes of the six Mediterranean mullets, namely L. saliens, L. ramada, L. aurata, Mugil cephalus, Chelon labrosus and Oedalechilus labeo. In all species, except M. cephalus, the 5S rDNA sites were localized on a medium-sized acrocentric chromosome pair, which was considered homeologous in all of them. In L. saliens, an additional 5S rDNA site was detected in a location close to the one shown by major ribosomal genes in M. cephalus, i.e. the subtelomeric region of chromosome pair 1. The 5S rDNA site in M. cephalus is located on the smallest chromosome pair of the complement, which, on the other hand, though on a different position, bears 18S rDNA in all the species of Liza and Chelon examined. The heterochromatin composition and the major and minor ribosomal gene locations suggest that the karyotype of L. saliens (subgenus Protomugil) can be considered intermediate between the karyotype of the more primitive M. cephalus and those of the other Liza (subgenus Liza) species and of the representatives of the more derived genera Chelon and Oedalechilus.     

Larval survivorship, competency periods and settlement of two brooding corals, Heliopora coerulea and Pocillopora damicornis

Larval dispersal and recruitment are important in determining adult coral distribution; however, few studies have been made of coral larval dispersal. This study examined the larval behavior, survivorship competency periods and settlement of two brooding corals, Heliopora coerulea and Pocillopora damicornis, in relation to different potential larval dispersal patterns. We also examined the lipid content of H. coerulea as a means of flotation and a source of energy. Planulae of H. coerulea were on average 3.7 mm in length, lacked zooxanthellae, and were mostly benthic, probably because of restricted movement and low lipid content (54% by dry weight). Planulae of P. damicornis were on average 1.0 mm in length, had zooxanthellae and swam actively. The competency period of H. coerulea was shorter (30 days) than that of P. damicornis (100 days). Forty percent of H. coerulea planulae crawled onto the substrata within 1 h of release, and 47% settled within 6 h. By contrast, fewer than 10% of P. damicornis planulae crawled onto the substrata within the first hour and 25% settled within 6 h of release. The planulae of H. coerulea may have a narrower dispersal range than those of P. damicornis, settling and recruiting near parent colonies. Thus, brooding corals exhibit variations in larval dispersal patterns, which are characterized by their position in the water column and competency periods.     

Annual population development and production by Calanus finmarchicus, C. glacialis and C. hyperboreus in Disko Bay, western Greenland

The populations of the copepod species Calanus finmarchicus, C. glacialis and C. hyperboreus were investigated in Disko Bay during a 14-month period in 1996-1997. The three species were predominant in the copepod community. The biomass reached a maximum at the beginning of June (127 mg C m^-3). From the end of July until the end of April the following year, the biomass was <1-6 mg C m^-3. All three species showed seasonal ontogenetic migration. The spring ascent for all three species was just prior to or in association with the break-up of sea ice and the development of the spring bloom, whereas descent occurred over a larger time span during summer. The main overwintering stages were CV for C. finmarchicus, CIV and CV for C. glacialis and C. hyperboreus. Peak abundance of juvenile copepodites, representing the new generation, was in August for C. finmarchicus, in July for C. glacialis and in May/June for C. hyperboreus. From the timing of reproduction and the population development, the life cycles were deduced to be 1 year for C. finmarchicus and at least 2 years for C. glacialis and C. hyperboreus. Secondary production and potential grazing impact of the Calanus community were estimated by two methods based on specific egg-production rates and temperature-dependent production. The Calanus community was not able to control the primary producers during the spring bloom but probably did during post-bloom. The estimates also indicated that grazing on ciliates and heterotrophic dinoflagellates contributes as an essential food source in the post-bloom period.     

In situ feeding rates and grazing impact of zooplankton in a South African temporarily open estuary

Recent studies in temporarily open estuaries of South Africa have shown that phytoplankton biomass is at times low, when compared to the high standing stock of the grazers. In situ grazing rates of the dominant zooplankton species were estimated at the Mpenjati Estuary once during the winter closed phase, in August 1999, and once during the summer open phase, in February 2000. The study aimed at determining what proportion of the energetic demands of the dominant grazers of the estuary is met by the available phytoplankton. Results show that the gut of all species exhibited higher pigment concentrations during the night than during the day, both in winter and summer. Gut pigment contents ranged from 0.27 to 5.38 ng pigm individual^-1 in the mysid Gastrosaccus brevifissura, from 0.16 to 1.63 ng pigm individual^-1 in the copepod Pseudodiaptomus hessei, from 0.12 to 0.45 ng pigm individual^-1 in the copepod Acartia natalensis, and from 0.8 to 5.44 ng pigm individual^-1 in the caridean Palaemon sp. [where pigm is the sum of chlorophyll-a (chl-a) and phaeopigments]. During the winter closed phase, gut evacuation rates for G. brevifissura, P. hessei, and A. natalensis were 0.62, 0.42, and 0.46 h^-1, respectively. In summer, gut evacuation rates were 0.68, 0.48, and 0.46 h^-1 for G. brevifissura, P. hessei, and Palaemon sp., respectively. The rate of gut pigment destruction for G. brevifissura was 99.6% of the total ingested, one of the highest values ever recorded for any crustacean. A gut pigment destruction of 79.0% was measured for Palaemon sp., 95.7% for P. hessei, and 93.8% for A. natalensis. During winter the total grazing impact of the dominant zooplankton species ranged from 5.05 to 22.7 mg chl-a m^-2 day^-1 and accounted for 34-69% of the available chl-a in the water column. During summer, the grazing impact ranged between 0.45 and 0.65 mg chl-a m^-2 day^-1, accounting for 17-41% of the available chl-a in the water column. This shows that the dominant zooplankton species of the Mpenjati have a very high grazing impact on algal cells. At times this may exceed 100% of the available phytoplankton production, suggesting that the zooplankton community may often resort to other food sources to meet all its energetic demands.     

Cross-shelf variation in calanoid copepod production during summer 1996 off the Oregon coast, USA

The fecundity of nine species of adult female calanoid copepods, and molting rates for copepodite stages of Calanus marshallae were measured in 24 h shipboard incubations from samples taken during the upwelling season off the Oregon coast. Hydrographic and chlorophyll measurements were made at approximately 300 stations, and living zooplankton were collected at 36 stations on the continental shelf (<150 m depth) and 37 stations offshore of the shelf (>150 m depth) for experimental work. In our experiments, maximum egg production rates (EPR) were observed only for Calanus pacificus and Pseudocalanus mimus, 65.7 and 3.9 eggs fem^-1 day^-1 respectively, about 95% of the maximum rates known from published laboratory observations. EPR of all other copepod species (e.g., C. marshallae, Acartia longiremis and Eucalanus californicus) ranged from 3% to 65% of maximum published rates. Fecundity was not significantly related to body weight or temperature, but was significantly correlated with chlorophyll a concentration for all species except Paracalanus parvus and A. longiremis. Copepod biomass and production in on-shelf waters was dominated by female P. mimus and C. marshallae, accounting for 93% of the adult biomass (3.1 mg C m^-3) and 81% of the adult production (0.19 mg C m^-3 day^-1). Biomass in the off-shelf environment was dominated by female E. californicus, P. mimus, and C. pacificus, accounting for 95% of the adult biomass (2.2 mg C m^-3) and 95% of the adult production (0.08 mg C m^-3 day^-1). Copepodite (C1-C5) production was estimated to be 2.1 mg C m^-3 day^-1 (on-shelf waters) and 1.2 mg C m^-3 day^-1 (off-shelf water). Total adult + juvenile production averaged 2.3 mg C m^-3 day^-1 (on-shelf waters) and 1.3 mg C m^-3 day^-1 (off-shelf waters). We compared our measured female weight-specific growth rates to those predicted from the empirical models of copepod growth rates of Huntley and Lopez [Am Nat (1992) 140:201-242] and Hirst and Lampitt [Mar Biol (1998) 132:247-257]. Most of our measured values were lower than those predicted from the equation of Huntley and Lopez. We found good agreement with Hirst and Lampitt for growth rates <0.10 day^-1 but found that their empirical equations underestimated growth at rates >0.10 day^-1. The mismatch with Hirst and Lampitt resulted because some of our species were growing at maximum rates whereas their composite empirical equations predict "global" averages that do not represent maximum growth rates.     

Morphological, reproductive, and genetic variability among three populations of Crucibulum quiriquinae (Gastropoda: Calyptraeidae) in northern Chile

Crucibulum quiriquinae (Lesson, 1830) is the only species of Crucibulum currently recognized in northern Chile. Recent analysis of three Crucibulum populations obtained in northern Chile demonstrates the existence of morphological, genetic, and reproductive differences among populations. Two populations present in Bahía Tongoy (30°15'S), one inhabiting the shells of the snail Turritella cingulata and the other shells of the pectinid Argopecten purpuratus, showed morphological differences. However, both had planktonic larval development and show low genetic divergence (D=0.002). A third population from Bahía La Herradura (29°58'S), which also inhabits the shells of T. cingulata, did not show morphological differences compared with its counterpart from Bahía Tongoy. However the Bahía La Herradura population had intracapsular development and metamorphosis, and a larger genetic distance (D=0.06) from both Tongoy populations. The results of the reproductive and genetic analyses strongly suggested that the two Tongoy populations, although showing morphological differences, are biologically the same species, Crucibulum quiriquinae, whereas the La Herradura population is a new species.     

Reproductive cycle of two commercial species of sea cucumber (Echinodermata: Holothuroidea) from Caribbean Panama

The reproductive status of the holothuroid species Isostichopus badionotus (Selenka, 1867) and Holothuria mexicana (Ludwig, 1875) was studied over 16 months in Bocas del Toro (Panama), from November 1999 to February 2001. Sexual reproduction was evaluated by the gonad index method, and by histology of gonad development. In addition, population structure was assessed based on sex ratio, minimum reproductive size, and length and weight distributions of males and females. The sex ratio in both species was 1:1, with a unimodal population distribution composed mainly of mature individuals. The minimum reproductive length and weight were 13-20 cm and 150 g, respectively, for both species, although reproductive individuals 10 cm in length were also found. A consistently higher gonad index was observed in H. mexicana, due to a high proportion of mature females and males and high gonad indices in most monthly samples. Gametogenesis and spawning patterns seemed to occur throughout the year, with periods of enhanced activity. Two periods of maximum reproductive activity were tentatively identified: July-November for I. badionotus and February-July for H. mexicana, but neither species had a single, sharply defined annual spawning event. Further work on these exploited holothuroids should examine the relationships between reproduction and environmental factors and between reproductive status and recruitment.     

Seasonal and sex-specific variations in levels of photo-protecting mycosporine-like amino acids (MAAs) in soft corals

This study focusses on the nature and extent of variation in mycosporine-like amino acids (MAAs) in relation to annual cycles in solar radiation, seawater temperature, and reproduction in reef-flat populations of two soft coral species. The results show MAA tissue concentrations in shallow water colonies of Lobophytum compactum and Sinularia flexibilis to be significantly correlated to annual cycles in solar radiation (P<0.0006 and P<0.0005, respectively) and seawater temperature (P<0.0006 and P<0.0004, respectively). Evidence of seasonal cycles in MAA levels in the tissues of shallow-reef invertebrates positively correlating with annual cycles in solar radiation and temperature suggests that they are an integral component of the soft corals' biochemical defence system against high irradiance and/or temperature stress and thus bleaching. This is further corroborated by the higher production of MAAs in females than males prior to spawning (up to 67% and 56% for L. compactum and S. flexibilis, respectively), presumably to provide a high level of protection against irradiance stress for progeny.