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Candidate Species (candidate + species)
Selected AbstractsOffspring performance and the adaptive benefits of prolonged pregnancy: experimental tests in a viviparous lizardFUNCTIONAL ECOLOGY, Issue 4 2009Geoffrey M While Summary 1Offspring locomotor performance has been shown to influence fitness related traits in a wide range of taxa. One potential mechanism by which viviparous animals can increase the performance (e.g. sprint speed) of their offspring is by prolonging pregnancy (beyond that required for complete development). However, to date studies examining this potentially important maternal effect have been largely descriptive. 2The skink Egernia whitii is an ideal candidate species to examine the consequences of delayed parturition on the performance of offspring as it routinely gives birth asynchronously despite synchronous offspring development. 3Using correlative data from a natural population and experimental manipulations of birthing asynchrony, we tested the prediction that, within litters, last born offspring have a better locomotor performance than first born offspring. 4We show that prolonged pregnancy does significantly influence average offspring locomotor performance; however, contrary to predictions, the direction of this effect is dependent on gestation length and thus offspring date of birth. Last born offspring had significantly poorer performance than first born offspring in litters early in the season with this pattern reversed late in the season. 5These results do not support the hypothesis that prolonged retention of fully formed offspring consistently increases offspring performance; however, they may help us understand the asymmetries in offspring competitive ability generated by birthing asynchrony. [source] Effect of rearing techniques on skeletal deformities and osteological development in red porgy Pagrus pagrus (Linnaeus, 1758) larvaeJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2010J. Roo Summary Red porgy is a candidate species for marine aquaculture diversification. The objective of the present study was to describe the osteological development in this species and the occurrence of skeletal deformities in relation to the intensification of the rearing system. Fish samples were periodically collected along the development from hatching to juveniles (95 days after hatching). Osteological development and the presence of skeleton abnormalities were evaluated. Larvae reared under S-IS showed a better growth in terms of total length in comparison with IS reared ones. Regarding to osteological development for red porgy, this was similar between fish from both culture systems, but differing in timing of apparition and ossification of skeletal elements. X-ray studies revealed a high number of fish with skeletal deformities (Semi-intensive: 38.8%; Intensive: 46.5%), but no significant effect of the rearing technique on the incidence of deformities such as lordosis or fused vertebrae was found. However, cranial abnormalities and kyphosis incidences were significantly higher in intensive system cultured red porgy. These results, suggest a relationship among rearing technique, osteological development and the apparition of certain deformities. [source] Responsible estuarine finfish stock enhancement: an Australian perspectiveJOURNAL OF FISH BIOLOGY, Issue 2 2005M. D. Taylor The responsible approach to marine stock enhancement is a set of principles aimed at maximising the success and benefits of artificially re-stocking depleted fisheries. The benefits of such an approach are evident in the 400% increase in survival of stocked striped mullet in Hawaii through refinement of release techniques, however financially or temporally constrained stocking programs in Australia have not adhered to all principles. A pragmatic approach to address these principles is proposed, using international examples and Australian marine finfish pilot stockings of barramundi, mulloway, sand whiting, dusky flathead and black bream. Biological ranking of candidate species by estuarine residency, a low natural-mortality to growth ratio, a large L, and comparison by recreational value and available rearing technologies, show that mulloway, barramundi and sea mullet are ideal species for stocking in Australia. Australian intermittently closed opening landlocked lagoons and recreational fishing havens, especially near cities, provide experimental opportunities to apply this approach and stock suitable species through small-scale pilot experiments. This would allow evaluation of production and carrying capacity, and density dependent processes with respect to optimal stocking strategies unconfounded by emigration and commercial fishing practices. Twenty per cent of Australians fish each year, and harvest approximately 27 000 t of finfish. Stocking recreationally important species in Australia should give a greater financial benefit, which is spread across a larger cross-section of the community, compared to stocking to enhance commercial fisheries. The pragmatic application of the responsible approach, and stocking of fast growing estuarine residents into recreational fishing havens would enhance the benefit from marine stocking. [source] The Effect of Temperature on First Feeding, Growth, and Survival of Larval Witch Flounder Glyptocephalus cynoglossusJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2001Deborah A. Bidwell Witch flounder Glyptocephalus cynoglossus has recently been identified as a candidate species for aquaculture in the northeastern United States and the Canadian Atlantic Provinces. This study investigated the optimal temperatures for witch flounder larval first feeding and for long term larval culture from hatching through metamorphosis. Maximum first feeding occurred between 15.0 and 16.2 C. Larvae did not survive beyond first feeding when reared at mean temperatures of 5.1, 10.4, or 19.5 C and were unable to initiate feeding at mean rearing temperatures below 6.0 C. At a rearing temperature of 15.0 C in 16-L tanks, mean larval survival to 60 days post hatch (dph) was 14.1%. Mean overall length-specific growth rate for larvae reared to 60 dph at 15.0 C was 3.5%/d and mean absolute growth was 0.62 mm/d. Subsequent larval growth at 15.6 C began to taper off towards 70 dph at the onset of weaning which overlapped with larval metamorphosis. Growth plateaued at 85 dph, followed by a rebound between 90 and 95 dph. Survival was 100% when weaning onto a dry, pelleted diet was initiated at 70 dph with a 10-d live diet co-feeding period. These results are favorable and encourage the further pursuit of commercial witch flounder culture. [source] Origin, diversification and conservation status of talus snails in the Pinaleño Mountains: a conservation biogeographic studyANIMAL CONSERVATION, Issue 3 2010K. F. Weaver Abstract For many taxa, determining conservation status and priority is impeded by lack of adequate taxonomic and range data. For these problematic groups, we propose combining molecular techniques with careful geographic sampling to evaluate the validity, extent and phylogenetic relatedness of the proposed units of diversity. We employed such a strategy to document monophyletic lineages, range extents and phylogenetic relatedness for talus snails (genus Sonorella) in the Pinaleño Mountains of Arizona, an isolated range that has the most vertical relief of any of the sky islands in Arizona. Three of the four species found in the Pinaleño Mountains have been considered candidate species for protection under the Endangered Species Act. Further, one of these taxa, Sonorella macrophallus, is of particular concern and was protected under an USFS conservation agreement until 2004, due to its presumed endemicity to a narrow portion of one canyon. We collected a large dataset of 12S and COI mitochondrial DNA, and subsamples of reproductive morphology from specimens collected throughout the Pinaleños and from adjacent ranges (e.g. the Huachucas, Chiricahuas and Santa Catalinas). We generated a phylogeny based on the mitochondrial data, and matched clades with named species utilizing reproductive morphology. Our results show that both S. macrophallus and Sonorella imitator are relatively widespread across the Pinaleños while Sonorella grahamensis and Sonorella christenseni are restricted to very small areas. These results dramatically change our previous knowledge about range extents, especially for S. macrophallus. Given these results, land managers may need to reassess the status of all four Sonorella species. Finally, all Sonorella species from the Pinaleños are more closely related to each other than to other taxa on other ranges. This result strongly suggests that diversification of the four Sonorella species in the Pinaleños occurred in situ. [source] Protein requirement for maintenance and maximum growth of two-banded seabream (Diplodus vulgaris) juvenilesAQUACULTURE NUTRITION, Issue 1 2009R.O.A. OZÓRIO Abstract The effects of various dietary protein levels on growth performance, whole body composition and nutrient utilization were studied in two-banded sea bream (Diplodus vulgaris), a candidate species for aquaculture. Fish (initial weight 6.1 g) were fed to satiety six iso-energetic diets, containing 5%, 12.5%, 25%, 35%, 45% or 55% of crude protein during 72 days. Fish fed 35% and 45% protein attained better growth and feed utilization than the other groups (P < 0.05). Daily growth index and feed conversion ratio were the poorest for fish fed 5% and 12.5% protein (P < 0.001), while the 25% and 55% protein groups had intermediate performance. Lipid retention increased significantly from 13.7% to 30.1% (P < 0.0001) and protein retention decreased from 35.5% to 21.3% (P < 0.01) with increasing protein levels from 12.5% to 45%. Muscle protein, lipid and energy concentrations were not significantly affected by dietary protein level. The estimated protein requirement for maintenance and maximum growth of two-banded seabream growing from 6 to 20 g were 7.5% and 35.7%, respectively. Protein requirements as calculated from body protein gain were 2.3 and 6.5 g of protein intake per kilogram body weight per day. [source] Precocious sex change and spermatogenesis in the underyearling Malabar grouper Epinephelus malabaricus by androgen treatmentAQUACULTURE RESEARCH, Issue 2 2010Ryosuke Murata Abstract The Malabar grouper Epinephelus malabaricus is an important candidate species for commercial aquaculture in tropical and subtropical areas. In nature, this species requires more than 10 years to change sex from female to male and have active spermatogenic tissues in the testis. Thus, it is essential to find a means of producing sperm for seed production. This is the first report of artificial sex change in underyearling E. malabaricus. Female E. malabaricus with immature ovaries at 144 days post-hatch (DPH) were fed a diet with 17,-methyltestosterone (MT) at 50 ,g g,1 diet for 6 months. Sex change occurred in most of the treated fish, which had testis with all stages of spermatogenic germ cells including spermatozoa. In contrast, most of the control fish had immature ovaries. These results, which reveal that germ cells in the underyearling grouper have the ability to produce spermatozoa in response to exogenous androgen, demonstrate that sex change can be artificially induced during ovarian development. [source] Biological and technical evaluation of the potential of marine and anadromous fish species for cold-water maricultureAQUACULTURE RESEARCH, Issue 2 2002N R Le François Abstract Concern about the overexploitation of wild aquatic resources, the slow recovery of the groundfish fisheries and the need to encourage the diversification of the mariculture industry of the province of Quebec (Canada) all provided strong incentive to explore the potential of a wide selection of marine and anadromous fish species for cold-water mariculture. Starting from a list of over 45 indigenous fish species of potential commercial interest, a biotechnical review was initiated. Technical sheets for each species were produced and aquaculture-based selection criteria covering three aquaculture approaches of development (complete life cycle, on-growing and stock enhancement) were examined. Species were ranked according to their degree of suitability for the given biological parameters. The final classification analysis within the complete life cycle production strategy positioned the Atlantic wolffish as the top candidate species (91%) followed by the spotted wolffish and Arctic charr (87%). Growth rate, optimal growth temperature, duration of the weaning period, minimal lethal temperature, larval size and feed requirements were the determining criteria. The on-growing scenario final results ranked Arctic charr first (84%) followed by Atlantic cod (79%) and Atlantic halibut (74%) mostly owing to their growth rate at low temperature and optimal growth temperature criteria. Stock enhancement programmes should concentrate their efforts on the striped bass (56%), the haddock (54%) and the Atlantic sturgeon (34%) based on their growth rate, fishery status, landing price and the availability of impact studies. [source] Anaerobic degradation of benzene by a marine sulfate-reducing enrichment culture, and cell hybridization of the dominant phylotypeENVIRONMENTAL MICROBIOLOGY, Issue 1 2008Florin Musat Summary The anaerobic biodegradation of benzene, a common constituent of petroleum and one of the least reactive aromatic hydrocarbons, is insufficiently understood with respect to the involved microorganisms and their metabolism. To study these aspects, sulfate-reducing bacteria were enriched with benzene as sole organic substrate using marine sediment as inoculum. Repeated subcultivation yielded a sediment-free enrichment culture constituted of mostly oval-shaped cells and showing benzene-dependent sulfate reduction and growth under strictly anoxic conditions. Amplification and sequencing of 16S rRNA genes from progressively diluted culture samples revealed an abundant phylotype; this was closely related to a clade of Deltaproteobacteria that includes sulfate-reducing bacteria able to degrade naphthalene or other aromatic hydrocarbons. Cell hybridization with two specifically designed 16S rRNA-targeted fluorescent oligonucleotide probes showed that the retrieved phylotype accounted for more than 85% of the cells detectable via DAPI staining (general cell staining) in the enrichment culture. The result suggests that the detected dominant phylotype is the ,candidate species' responsible for the anaerobic degradation of benzene. Quantitative growth experiments revealed complete oxidation of benzene with stoichiometric coupling to the reduction of sulfate to sulfide. Suspensions of benzene-grown cells did not show metabolic activity towards phenol or toluene. This observation suggests that benzene degradation by the enriched sulfate-reducing bacteria does not proceed via anaerobic hydroxylation (mediated through dehydrogenation) to free phenol or methylation to toluene, respectively, which are formerly proposed alternative mechanisms for benzene activation. [source] | |||||||||||||