A population of the Mediterranean red gorgonian Paramuricea clavata has exhibited unexpected resilience after being impacted by 2 anomalous mortality events in 1999 and 2003. To understand the recovery mechanisms, we examined the population reproductive structure and reproductive output based on data collected via non-destructive sampling techniques. The overall population sex ratio was balanced, though the spatial distribution of sexes was significantly segregated. Dividing the population into 14 size classes on the basis of their measured average annual growth revealed a decreasing monotonic trend of abundance of larger classes. The Recruitment class was consistently dominant. The minimum size at first reproduction was 8.5 cm in height, corresponding to an age of ~3 yr. The percentage of fertile colonies increased with size, reaching 90% in size Class 9. Polyp fecundity increased with colony size and did not differ signif- icantly between healthy and damaged colonies. As the number of mature oocytes produced by a colony is a function of polyp fecundity and of the number of reproductive polyps, colony reproduc- tive output increased exponentially with size. The population reproductive output (145 × 103 mature oocytes m−2 yr−1) was one-fifth of that measured in stable, undamaged populations and came mainly from the medium size classes. After the catastrophic mortality, the population has been recovering, albeit with reduced reproductive output. Moreover, it has exhibited a 2-fold increase in recruitment rate, 3-fold greater than that measured in other, undisturbed populations. Our findings are consistent with a strict density-dependent recruitment control operating in crowded, stable P. clavata populations
In the olfactory and vomeronasal systems of vertebrates, the morphology of the receptor neurons, the receptor gene family they express, the G-protein coupled with the receptor (in particular the G-protein alpha subunit), and their projection to the olfactory bulb are correlated. Much information about this complicated system have been collected in different groups, but nothing is known about Chondrichthyes. In this work, the presence and distribution of immunoreactivity for different types of G-protein alpha subunit (Ga o , Ga q and Ga s/olf ) were investigated in the olfactory mucosa and olfactory bulb of the shark Scyliorhinus canicula. Only Ga olike immunoreactivity was detected in the olfactory mucosa and bulb, both in tissues and homogenates. Its distribution was partially similar to that found in other vertebrates: it was localized in the microvillous receptor neurons, in numerous axon bundles of the fila olfactoria, in the stratum nervosum and in the most of glomeruli in the stratum glomerulosum. No immunoreactivity was instead observed in the crypt neurons, the second type of olfactory neurons present in cartilaginous fish. The projections of crypt neurons to olfactory bulb probably correspond to the few ventrallylocated glomeruli which were negative to the antiserum against Ga o . These data suggest, in S. canicula, different olfactory neuron types send projections to the olfactory bulb with a segregated distribution, as observed in other vertebrates. Anat Rec, 292:1771Rec, 292: -1779Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.
Echinoderms are valuable test species in marine ecotoxicology and offer a wide range of biological processes appropriate for this approach. Regenerating echinoderms can be regarded as amenable experimental models for testing the effects of exposure to contaminants, particularly endocrine disrupter compounds (EDCs). As regeneration is a typical developmental process, physiologically regulated by humoral mechanisms, it is highly susceptible to the action of pseudo-hormonal contaminants which appear to be obvious candidates for exerting deleterious actions. In our laboratory experiments, selected EDCs suspected for their antiandrogenic action (p,p'-DDE and cyproterone acetate) were tested at low concentrations on regenerating specimens of the crinoid Antedon mediterranea. An integrated approach which combines exposure experiments and different morphological analyses was employed; the obtained results suggest an overall pattern of plausible endocrine disruption in the exposed samples, showing that processes such as regenerative growth, histogenesis, and differentiation are affected by the exposure to the selected compounds. These results confirm that (1) regenerative phenomena of echinoderms can be considered valuable alternative models to assess the effects of exposure to exogenous substances such as EDCs, and (2) these compounds significantly interfere with fundamental processes of developmental physiology (proliferation, differentiation, etc...) plausibly via endocrine alterations. In terms of future prospects, taking into account the increasing need to propose animal models different from vertebrates, echinoderms represent a group on which ecotoxicological studies should be encouraged and specifically addressed.
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