Physiological development of brooded larvae from two pocilloporid corals in Taiwan

In southern Taiwan, brooded larvae of Pocillopora damicornis and Seriatopora caliendrum are released year-round in synchrony with new moons, and each larval release occurs over multiple days. Using P. damicornis and S. caliendrum as a model system, we describe within-brood variation in larval phenotypes and test for release-day effects that influence larval performance in the pelagic phase. Research was conducted in 2010 using larvae from corals collected in June and July from Nanwan Bay (21°56.179??N, 120°44.85??E). In June, larval phenotypes of both species were characterized immediately following release, and their competency to settle assessed. In July, larvae of P. damicornis were collected on 3?days over the peak release period and incubated for 7?C11?days at 28.0?°C and 320???mol?quanta?m^?2?s^?1; their phenotypes and settlement competency were measured every 2?days. P. damicornis larvae released close to peak release were 1.6 times larger in size, contained twice the number of Symbiodinium larva^?1, and were 44?% more likely to settle in the first 24?h than larvae released early in the brood. In addition, peak-release larvae respired at a lower rate than larvae released late in the brood. Similarly, S. caliendrum larvae released close to peak release were 1.4 times larger in size and were 33?% more likely to settle in the first 5?h than larvae released early in the brood. In July, P. damicornis larvae differed between early (2?days prior to peak), peak, and late (2?days after peak) release. Protein content of early-release larvae was lower than peak- and late-release larvae, and this difference persisted throughout the development. Further, release day affected the way larval respiration varied throughout development. By showing that brooded coral larvae differ between release days and display maternal effects influencing performance in the swimming phase, our results suggest that pocilloporid corals utilize bet-hedging to increase reproductive success.     

Color patterns of the shrimps Heptacarpus pictus and H. paludicola (Caridea: Hippolytidae)

Color patterns of the shallow-water shrimps Heptacarpus pictus and H. paludicola are formed by chromatosomes (usually termed chromatophores) located beneath the translucent exoskeleton. Development of color patterns is related to size (age) and sex. The color expressed is determined by the chromatosome pigment dispersion, arrangement, and density. In populations with well-developed coloration (H. pictus from Cayucos, California, 1976–1978, H. paludicola from Argyle Channel, San Juan Island, Washington, June–July, 1978), prominent coloration was a characteristic of maturing females, breeding females, and some of the larger males. In the Morro Bay, California, population of H. paludicola (sampled 1976–1978), color patterns were poorly developed except in a few large females. In both species, most shrimp lose color at night because of pigment retraction in certain chromatosomes. In both species, there are 5 basic morphs: 1 transparent and 4 colored morphs. In the colored morphs, the color patterns are composed of bands, stripes, and spots which appear to disrupt the body outline. Each color morph also has a common environmental color in its color pattern, e.g the green of green algae, the whites and pinks of dead and living coralline algae, and various shades of tidepool litter. These shrimps are apparently under heavy predation pressure by fish, and it is suggested that the color patterns are camouflage against such visually-hunting predators.     

Parthenogenetic reproduction of Diaphanosoma celebensis (Crustacea: Cladocera): influence of salinity on feeding, survival, growth and neonate production

 Effect of salinity on the feeding rate and parthenogenetic reproduction of asexual females of the cladoceran Diaphanosoma celebensis Stingelin was studied. Short-term (10 h) grazing experiments were conducted using Isochrysis galbana as feed at 5, 17, 25 and 30 psu salinity. Gut pigment concentration showed a significantly higher rate of feeding at lower salinities. Survival, growth, maturity attainment and neonate production of asexual females reared in the above four test salinities indicated preference for lower salinities (5 and 17 psu). The mean size of adult females decreased from 909 to 593 μm, mean life span from 24 to 5 d, mean neonate production from 12 to 2 and mean size of neonates from 434 to 400 μm as the salinity increased from 5 to 30 psu. Salinity variations also affected the size and age of primiparous females. Resting egg formation and sexual reproduction did not occur at the tested salinities. The results indicate that D. celebensis is adapted to low saline, estuarine environments. Received: 14 January 2000 / Accepted: 24 March 2000     

Seasonal growth of the giant kelp Macrocystis pyrifera in New Zealand

The seasonal growth pattern of Macrocystis pyrifera (L.) C. Agardh in New Zealand was determined from measurements of blade-elongation rates between March 1986 and December 1987. Growth rates remained relatively constant throughout most of the year, but declined significantly during the summer months. Seawater nitrate levels had a marked seasonal cycle, with concentrations of 0.3 μM detected in summer. The timing of the decline in internal nitrogen concentrations varied for different-aged blades, but occurred ∼1 mo after the decrease in seawater nitrate concentrations. Sufficiently high irradiance levels and seawater nutrient concentrations support active growth for most of the year, but growth is nutrient-limited during summer. No carbon accumulation during summer was observed. Between March and August 1988, growth estimates were also derived from node-initiation rates and stipe-elongation rates to permit comparisons with previous studies from the northern and southern hemispheres. Direct comparisons of the three growth parameters determined for non-terminated canopy and sub-surface fronds were used to assess possible differential resource allocation in the two frond classes. Received: 16 May 1997 / Accepted: 28 May 1997     

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Editorial

Publisher’s Note     

Genetic differentiation in a pelagic crustacean (Meganyctiphanes norvegica: Euphausiacea) from the North East Atlantic and the Mediterranean Sea

Meganyctiphanes norvegica (M. Sars)is a pelagic crustacean that plays a key role in marine food webs of North Atlantic Ocean and marginal seas. We studied eight population samples collected in the European Atlantic and Mediterranean Sea. By means of single strand conformation polymorphism analysis (SSCP) and direct sequencing, we investigated a segment of 158 base pairs of the mitochondrial gene coding for the subunit 1 of NADH dehydrogenase. We found 12 sequence variants among the 385 individuals studied. Analysis of molecular variance (AMOVA) showed that 14.75% of the total genetic variability was explained by differences between populations, thus indicating absence of panmixia for these populations. Pairwise comparisons revealed three distinct genetic pools: the first one represented by Cadiz Bay, the second one by the Ligurian Sea, and the third one included all the NE Atlantic samples. We also investigated one population from the Alboran Sea (within the Mediterranean basin, east of the Strait of Gibraltar). This population was found to be genetically intermediate between the NE Atlantic samples and the Ligurian sample, suggesting that the restriction to the gene flow is not associated with the Strait of Gibraltar, but possibly with the Oran–Almeria oceanographic front. The present work indicates that M. norvegica, although endowed with a high dispersal capacity because of its pelagic habit, can develop separate breeding units inside the same oceanic basin (the Atlantic). Furthermore, the Ligurian sample should be considered as a distinct evolutionary entity, separated from the Atlantic population. Received: 2 May 1999 / Accepted: 26 November 1999     

Sparse PCA and investigation of multi-elements compositional repositories: theory and applications

The geochemistry of floodplain sediments is fundamental to monitor environmental changes and to quantify their contribution to natural and anthropic processes. A floodplain sediment composition is a vector of positive elements which sum to a fixed constant. The analysis of high-dimensional compositions requires methods that produce results involving only a small portion of the original variables. On the other hand, the analysis must take into account the additional constraints specific to compositions. With the purpose of studying these problems, a new procedure for sparse PCA is proposed on European floodplain sediment samples.     

Venoms from six species of marine fish: lethal and hemolytic activities and their neutralization by commercial stonefish antivenom

A specimen of the stonefish Synanceja verrucosa was captured in Okinawa in March 1988. Live specimens of the scorpionfish Inimicus japonicus were purchased from the Tokyo Central Wholesale Market in November 1988 and those of four species of zebrafish Pterois lumulata, P. volitans, P. antennata and Dendrochirus zebra from an aquarium in December 1988. Crude venoms were extracted from dorsal spines of the six species. All venoms exhibited lethal activity against mice and hemolytic activity specific for rabbit erythrocytes. The lethal activity (or hemolytic activity) of each venom was very unstable to freezing, lyophilization and heating. Both lethal and hemolytic activities of S. verrucosa venom were remarkably neutralized by the commerical stonefish (Synanceja trachynis) antivenom. This antivenom was also effective, to some extent, in counteracting the other venom activities. The neutralizing capacities of the antivenom were calculated to be 7310 LD₅₀ ml^-1 for S. verrucosa venom and 1 220 to 2 990 LD₅₀ ml^-1 for the other venoms. Results of neutralization tests suggest that venoms from the six species were comparable in terms of antigenecity.