16 resultados para TERDIGITATA BONNATERRE


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We predicted that the probability of egg occurrence of salamander Salamandrina perspicillata depended on stream features and predation by native crayfish Austropotamobius fulcisianus and the introduced trout Salmo trutta. We assessed the presence of S. perspicillata at 54 sites within a natural reserve of southern Tuscany, Italy. Generalized linear models with binomial errors were constructed using egg presence/absence and altitude, stream mean size and slope, electrical conductivity, water pH and temperature, and a predation factor, defined according to the presence/absence of crayfish and trout. Some competing models also included an autocovariate term, which estimated how much the response variable at any one sampling point reflected response values at surrounding points. The resulting models were compared using Akaike's information criterion. Model selection led to a subset of 14 models with Delta AIC(c) <7 (i.e., models ranging from substantial support to considerably less support), and all but one of these included an effect of predation. Models with the autocovariate term had considerably more support than those without the term. According to multimodel inference, the presence of trout and crayfish reduced the probability of egg occurrence from a mean level of 0.90 (SE limits: 0.98-0.55) to 0.12 (SE limits: 0.34-0.04). The presence of crayfish alone had no detectable effects (SE limits: 0.86-0.39). The results suggest that introduced trout have a detrimental effect on the reproductive output of S. perspicillata and confirm the fundamental importance of distinguishing the roles of endogenous and exogenous forces that act on population distribution.

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The evolution of the general microscopic structure of the ovary of Thunnus albacares related to the gonad index, and the ovocyte maturation process were studied. Some stages of the males sexual maturation were characterized.

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Se llevó a cabo una comparación entre la morfología de las células de la sangre periférica de 9 tiburones nodriza, de una raya americana y 9 peces teleósteos; además, se determinó la fórmula leucocitaria y la cantidad total de eritrocitos y leucocitos/mm 3 de sangre para cada pez estudiado. English Abstract This work is a comparation of the blood cells morphology between 9 nurse sharks, southern stingray and 9 bone fishes, moreover, it was maked a differential leucocytes count, red and white cells counts by blood mm3 for any fish.

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La presente tesi vuole colmare le conoscenze biologiche ed ecologiche dello squalo di profondità Dalatias licha. Attualmente le conoscenze riguardanti le popolazioni di questo squalo nel Mediterraneo sono scarse dato il numero limitato di studi affrontati. La biologia e l’ecologia di questo squalo è stata studiata attraverso la stima di alcune caratteristiche importanti come la sex ratio, la maturità sessuale degli individui, gli indici di condizione (epatosomatico e gonadosomatico) e le analisi dei contenuti stomacali. I 78 esemplari (16 femmine e 62 maschi) osservati sono stati campionati tra il 2001 e il 2003 dal bycatch di motopescherecci a strascico della marineria di Genova porto, operanti sul piano batiale del Golfo di Genova (Mar Ligure). Le catture sono state eseguite ad una batimetria compresa tra -450 e -800 m, tra Genova e Sestri Levante. I risultati, sebbene basati su un numero limitato di individui, sono di particolare interesse visto il deficit conoscitivo inerente a questa specie in ambito nazionale e mediterraneo

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In the present study we have investigated the population genetic structure of albacore (Thunnus alalunga, Bonnaterre 1788) and assessed the loss of genetic diversity, likely due to overfishing, of albacore population in the North Atlantic Ocean. For this purpose, 1,331 individuals from 26 worldwide locations were analyzed by genotyping 75 novel nuclear SNPs. Our results indicated the existence of four genetically homogeneous populations delimited within the Mediterranean Sea, the Atlantic Ocean, the Indian Ocean and the Pacific Ocean. Current definition of stocks allows the sustainable management of albacore since no stock includes more than one genetic entity. In addition, short-and long-term effective population sizes were estimated for the North Atlantic Ocean albacore population, and results showed no historical decline for this population. Therefore, the genetic diversity and, consequently, the adaptive potential of this population have not been significantly affected by overfishing.

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In 1987 we found a juvenile yellowfin tuna, Thunnus albacares (Bonnaterre, 1788), in the stomach of a longnose lancetfish, Alepisaurus ferox Lowe, 1833. Analysis of published information on lancetfish food habits (Haedrich, 1964, 1969; Haedrich and Nielsen, 1966; Parin, 1968; Parin et al., 1969; Fourmanoir, 1969; Grandperrin and Legand, 1970; Kubota and Uyeno, 1970; Legand et al., 1972; Kubota, 1973; Fujita and Hattori, 1976; Matthews et al., 1977) led us to conclude that this was the first record of a yellowfin tuna found in a lancetfish stomach.

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Ceylon’s fishery for the tunas is presently limited to the coastal waters which in the present context have an off-shore limit of 15 miles and our contribution to the world tuna production is a little over 1%. Four varieties of tuna are largely exploited in the coastal waters. Of these, Baleya or the skipjack (Katsuwonus pelamis Linn. 1758) is the predominant variety followed by attavalla or mackerel tuna (Euthynnus ajfinis, Cantor, 1850), kelawalla or yellowfin (Thunnus albacares, Bonnaterre, 1788) and alagoduwa or frigate mackerel (Auxis thazard Lacepede, 1802). Other varieties like the thora-baleya or bonito (Sarda orientalis) and asgedi kelawalla or big eye tuna (Thunnus obesus) are also landed frequently but in extremely small quantities. Figure 1 illustrates the relative composition of the tuna varieties in the catch and their percentage composition further sub-divided according to the type of effort applied. It is evident that Ceylon's coastal fishery for tunas is greatly influenced by the production of smaller varieties of the tunas.

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The following trematodes are part of a collection made by the author at Suva, Fiji in 1951. 1. Prosorhynchus squamatus Odhner, 1905 is believed to be distinct from P. crucibulus and most other species in the genus on the basis of its oval-shaped rhynchus. It thus remains, as originally, the type species of the genus. 2. Prosorhynchus thapari n. sp. is described from Plectropoma maculatum (Bloch) from Suva, Fiji. The "P. facilis (Ozaki, 1924)" of Nagaty (1937) is considered to be a synonym. 3. Neidhartia polydactyli n. sp. is described from Polydactylus plebius (Bonnaterre) from Suva, Fiji.

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This study is on albacore (Thunnus alalunga, Bonnaterre 1788), an epi- and mesopelagic oceanic tuna species cosmopolitan in the tropical and temperate waters of all oceans including the Mediterranean Sea, extending in a broad band between 40°N and 40°S. What it’s known about albacore population structure is based on different studies that used fisheries data, RFLP, mtDNA control region and nuDNA markers, blood lectins analysis, individual tags and microsatellite. At the moment, for T. alalunga six management units are recognized: the North Pacific, South Pacific, Indian, North Atlantic, South Atlantic and Mediterranean stocks. In this study I have done a temporal and spatial comparison of genetic variability between different Mediterranean populations of Thunnus alalunga matching an historical dataset ca. from 1920s composed of 43 individuals divided in 3 populations (NADR, SPAIN and CMED) with a modern dataset composed of 254 individuals and 7 populations (BAL, CYP, LIG, TYR, TUR, ADR, ALB). The investigation was possible using a panel of 94 nuclear SNPs, built specifically for the target species at the University of Basque Country UPV/EHU. First analysis done was the Hardy-Weinberg, then the number of clusters (K) was determined using STRUCTURE and to assess the genetic variability, allele frequencies, the average number of alleles per locus, expected (He) and observed (Ho) heterozygosis, and the index of polymorphism (P) was used the software Genetix. Historical and modern samples gives different results, showing a clear loss of genetic diversity over time leading to a single cluster in modern albacore instead of the two found in historical samples. What this study reveals is very important for conservation concerns, and additional research endeavours are needed.

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Yellowfin tuna (Thunnus albacares, YFT, Bonnaterre 1788) is one of the most important market tuna species in the world. The high mortality of juveniles is in part caused by their bycatch. Indeed, if unregulated, it could permanently destabilize stocks health. For this reason investigating and better knowing the stock boundaries represent a crucial concern. Aim of this thesis was to preliminary investigate the YFT population structure within and between Atlantic and Pacific Oceans through the analysis of genetic variation at eight microsatellite loci and assess the occurrence of barriers to the gene flow between Oceans. For this propouse we collected 4 geographical samples coming from Atlantic and Pacific Ocean and selected a panel of 8 microsatellites loci developped by Antoni et al., (2014). Samples 71-2-Y and 77-2-Y, came from rispectively west central pacific ocean (WCPO) and east central pacific ocean (ECPO), instead samples 41-1-Y and 34-2-Y derive from west central atlantic ocean (WCAO) and east central atlantic ocean (ECAO). Total 160 specimens were analyzed (40 per sample) and were carried out several genetic information as allele frequencies, allele number, allelic richness, HWE (using He and Ho) and pairwise Fst genetic distance. Results obtained, may support the panmictic theory of this species, only one of pairwise Fst obtained is statistically significant (Fst= 0.00927; pV= 0.00218) between 41-1-Y and 71-2-Y samples. Results suggest low genetic differentiation and consequent high level of gene flow between Atlantic and Pacific populations. Furthermore, we performed an analysis of molecular taxonomy through the use of ATCO (the flaking region between ATPse6 and cytochrome oxidase subunit III genes mt DNA, to discriminate within the gener Thunnus two of the related species (Yellofin and bigeye tuna) according with their difficult recognition at certain size (<40 cm). ATCO analysis in this thesis, has provided strong discriminate evidence between the target species proving to be one of the most reliable genetic tools capable to indagate within the genus Thunnus. Thus, our study has provided useful information for possible use of this protocol for conservation plans and management of this fish stocks.

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Mode of access: Internet.

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Mode of access: Internet.