Biología reproductiva del pepino de mar Holothuria sanctori (Echinodermata: Holothuroidea)

The reproductive biology of the sea cucumber Holothuria sanctori was studied over 24 months (February 2009 to January 2011) at Gran Canaria through the gonad index and a combination of macro- and microscopic analysis of the gonads. Holothuria sanctori showed a 1:1 sex ratio and a seasonal reproductive cycle with a summer spawning: the mean gonad index showed a maximum (3.99±0.02) in summer (June-July) and a minimum (0.05±0.04) between late autumn (November) and early spring (March). Females had significantly wider gonad tubules than males. First maturity occurred at a size of 201 to 210 mm, a gutted body weight of 101 to 110 g and a total weight of 176 to 200 g. Holothuria sanctori shows a typical temperate species reproduction pattern. These results could be useful for managing current extractions of H. sanctori in the Mediterranean and in case a specific fishery is started in the eastern Atlantic region.Se estudió la biología reproductiva del pepino de mar Holothuria sanctori durante 24 meses (Febrero de 2009 a Enero de 2010) en la isla de Gran Canaria, mediante el índice gonadal y una combinación de análisis macro y microscópicos de sus gónadas. Holothuria sanctori presentó una relación de sexos de 1:1 y un solo ciclo reproductivo anual con desove en los meses estivales: el índice gonadal medio presentó un máximo (3.99±0.02) en verano (Junio-Julio) y un mínimo (0.05±0.04) entre finales de otoño (Noviembre) y primeros de primavera (Marzo). Las hembras presentaron túbulos gonadales significativamente más anchos que los de los machos. La primera madurez tuvo lugar con una talla de 201-210 mm, un peso eviscerado de 101-110 g y un peso total de 176-200 g. Holothuria sanctori presenta un patrón de reproducción típico en especies de zonas templadas. Estos resultados pueden ser útiles para gestionar las capturas actuales de H. sanctori en el Mediterráneo y en el caso de que una pesquería específica empezase en la región oriental del Atlántico

Natural variation and the capacity to adapt to ocean acidification in the keystone sea urchin Strongylocentrotus purpuratus

A rapidly growing body of literature documents the potential negative effects of CO2-driven ocean acidification (OA) on marine organisms. However, nearly all this work has focused on the effects of future conditions on modern populations, neglecting the role of adaptation. Rapid evolution can alter demographic responses to environmental change, ultimately affecting the likelihood of population persistence, but the capacity for adaptation will differ among populations and species. Here, we measure the capacity of the ecologically important purple sea urchin Strongylocentrotus purpuratus to adapt to OA, using a breeding experiment to estimate additive genetic variance for larval size (an important component of fitness) under future high-pCO2/low-pH conditions. Although larvae reared under future conditions were smaller than those reared under present-day conditions, we show that there is also abundant genetic variation for body size under elevated pCO2, indicating that this trait can evolve. The observed heritability of size was 0.40 ± 0.32 (95% CI) under low pCO2, and 0.50 ± 0.30 under high-pCO2 conditions. Accounting for the observed genetic variation in models of future larval size and demographic rates substantially alters projections of performance for this species in the future ocean. Importantly, our model shows that after incorporating the effects of adaptation, the OA-driven decrease in population growth rate is up to 50% smaller, than that predicted by the \u27no-adaptation\u27 scenario. Adults used in the experiment were collected from two sites on the coast of the Northeast Pacific that are characterized by different pH regimes, as measured by autonomous sensors. Comparing results between sites, we also found subtle differences in larval size under high-pCO2 rearing conditions, consistent with local adaptation to carbonate chemistry in the field. These results suggest that spatially varying selection may help to maintain genetic variation necessary for adaptation to future OA. © 2013 John Wiley & Sons Ltd

Does the embryonic response to temperature and salinity by four species of Caribbean sea urchins parallel the reproductive synchrony?

Populations of four species of sea urchins, Lytechinus variegatus, Echinometra lucunter, Echinometra viridis and Tripneustes ventricosus, overlap in distribution on the shallow insular shelf of southwest Puerto Rico yet they exhibit distinctly different degrees of reproductive synchrony. Populations of L. variegatus and T. ventricosus possess gravid individuals for many months of the year while the Echinometra species have a synchronous spawning period with gravid individuals present only for the two fall months that coincide with the sea temperature maximum. These species all broadcast spawn and possess planktotrophic larvae. Little is known about the response of the embryos and larvae of these species to the environment. Perhaps the embryos of those species with highly synchronous reproduction are more sensitive to physical factors that those of the less synchronous ones. To determine developmental responses to temperature and salinity, a 3x3 factorial experiment over a temperature range of 20 to 30° C and a salinity range of 31.5 to 38.5 ‰ was performed for each species. Developmental stage was measured at 3h intervals for 48h. Response surface analysis of cleavage stages revealed that all species were more sensitive to temperature than salinity in the ranges tested and that the most synchronous species were most responsive to temperature differences. At the blastula stage, the least synchronous L. variegatus and T. ventricosus exhibit the broadest and narrowest lethal limits, respectively; while the more synchronous Echinometra species exhibit intermediate ones. Environmental influences seem to be manifested at a number of sites during the developmental process

Nutritional ecology of sea urchin larvae: influence of endogenous and exogenous nutrition on echinopluteal growth and phenotypic plasticity in Tripneustes gratilla

1. Marine invertebrates use egg nutrients to develop the functional feeding larva and then enter a facultative feeding period (FFP) when development can proceed without food because larvae are supported by maternal reserves. Facultative feeding reduces starvation risk and so is important for larval success. It may also influence egg size evolution because FFP length correlates with egg size. 2. We quantified energetic lipid (triglyceride, TG) utilisation in unfed and fed larvae as an index of larval nutritive condition in the tropical echinoid Tripneustes gratilla during the FFP to determine if fed larvae would use the buffer provided by endogenous provisions to improve their condition or accelerate development. We predicted that: (i) the condition of unfed and fed larvae should diverge before egg TG is exhausted and/or (ii) that the size of fed larvae should outstrip that of unfed larvae. 3. Temperate echinoplutei exhibit phenotypic plasticity, increasing the length of their food capture apparatus (arms) in nutrient-poor conditions. We examined the generality of this phenomenon in a morphometric analysis of growth in the tropical larva of T. gratilla. We hypothesized that plastic arm growth in starved larvae would occur before the FFP ends as a bet hedging strategy to prepare for hard times ahead when lack of reserves may render this response impossible. 4. We found that fed larvae diverged in condition (higher TG) but not in size compared with starved larvae before egg energetic lipids were exhausted. In addition, unfed larvae showed plastic arm growth before the end of the FFP. 5. Lack of divergence in growth of unfed and fed larvae suggests there may be an imperative to maintain a nutrient storage buffer against starvation due to unpredictable future planktonic food supply. The FFP of T. gratilla exceeds 8 days, considerably longer than that of other echinoids with similarly sized eggs, emphasizing that egg quality may be more important than egg size as a predictor of the FFP in fecundity-time models of egg evolution.M. Byrne, M. A. Sewell and T. A. A. Prows

Simultaneous 16S and 18S rRNA fluorescence in situ hybridization (FISH) on LR White sections demonstrated in Vestimentifera (Siboglinidae) tubeworms

Traditional morphological identification of invertebrate marine species is limited in early life history stages for many taxa. In this study, we demonstrate, by example of Vestimentiferan tubeworms (Siboglinidae, Polychaeta), that the simultaneous fluorescence in situ hybridization (FISH) of both eukaryotic host and bacterial symbiont cells is possible on a single semi-thin (1 μm) section. This allows the identification of host specimens to species level as well as offering visualization of bacteria distributed within the host tissue. Previously published 18S rRNA host-specific oligonucleotide probes for Riftia pachyptila, Tevnia jerichonana and a newly designed Oasisia alvinae probe, as well as a 16S rRNA probe targeting symbionts found in all host species, were applied. A number of standard fixation and hybridization parameters were tested and optimized for the best possible signal intensity and cellular resolution. Ethanol conserved samples embedded in LR White low viscosity resin yielded the best results with regard to both signal intensity and resolution. We show that extended storage times of specimens does not affect the quality of signals attained by FISH and use our protocol to identify morphologically unidentifiable tubeworm individuals from a small data set, conforming to previous findings in succession studies of the Siboglinidae family