Using molecular markers for pedigree reconstruction of the greater amberjack (Seriola dumerili) in the absence of parental information.

Ensuring appropriate levels of genetic diversity in captive populations is essential to avoid inbreeding and loss of rare alleles by genetic drift. Pedigree reconstruction and parentage analysis in the absence of parental genotypes can be a challenging task that relies in the assignment of sibship relationships among the offspring. Here, we used eight highly variable microsatellite markers and three different assignment methods to reconstruct the most likely genotypes of a parental group of wild Seriola dumerili fish based on the genotypes of six cohorts of their offspring, to assess their relative contributions to the offspring. We found that a combination of the four most variable microsatellites was enough to identify the number of parents and their contribution to the offspring, suggesting that the variability of the markers can be more critical than the number of markers. Estimated effective population sizes were lower than the number of breeders and variable among years. The results suggest unequal parental contribution that should be accounted for breeding programs in the future.

Effects of a diet lacking HUFA on lipid and fatty acid content of intestine and gills of male gilthead seabream (Sparus aurata L.) broodstock at different stages of the reproductive cycle.

A feeding experiment was carried out to determine the effect of a diet lacking n-3 and n-6 highly unsaturated fatty acids (HUFA) on lipid and fatty acid content in intestine and gills of male gilthead seabream (Sparus aurata L.) broodstock at different stages of the reproductive cycle: November (pre-spermatogenesis), March (spermatogenesis), and June (post-spermatogenesis). For this purpose, gilthead seabream broodstock were fed either a control diet (C) or an n-3 and n-6 HUFA-deficient diet (D). The results showed no changes in fatty acid content of polar lipids of intestine and gills from fish fed diet C at different stages of the reproductive cycle. However, significant changes were observed in the fatty acid content of neutral lipids in intestine but not in gills in this group. Thus, between November and March, saturates and n-3 HUFA decreased while monoenes increased. In June, the contents of these fatty acids had returned to their initial values (November). Moreover, in fish fed diet D, the fatty acid content of neutral lipid changed in both intestine and gills. In intestine NL, a decrease in saturates and n-3 HUFA and an increment in monoenes were observed from November to June. In gills, a decrease was also observed in n-3 HUFA from NL along the cycle. Nevertheless, n-6 HUFA content remained unchanged. These results show both tissue specificity in seasonal mobilization of fatty acids linked to reproductive processes and the influence of dietary fatty acids on body composition.

Lipid and fatty acid content in wild white seabream (Diplodus sargus) broodstock at different stages of the reproductive cycle.

The lipid and fatty acid content of the gonads, liver and muscle of wild white seabream males and females was studied at different stages of the reproductive cycle. Samples were taken from mature white seabream at pre-spawning (November), mid-spawning (March) and post-spawning (June) stages. The results showed that lipid accumulates in gonads and muscle from November to March. The gonadosomatic index (GSI) was also increased during this period. Male gonads showed a greater increase in polar lipid (PL) than neutral (NL), while female gonads displayed the reverse. The increase in both neutral and polar lipid was higher in the muscle of males than in females. In the same period, male livers showed no changes either in lipid content or the hepatosomatic index (HSI), while female livers registered an increase in both lipid content and HSI. Between March and June, in both males and females, total, neutral and polar lipid decreased sharply in the gonads and muscle. Muscular lipid content reduction was more pronounced in males than females. On the other hand, the lipid content of the liver in males and females remained relatively constant. In general terms, the amounts of major fatty acids (16:0, 18:1n-9, 20:5n-3 and 22:6n-3) in gonadal and muscular polar and neutral lipid in both males and females increased from November to March and declined thereafter. Variations of the liver fatty acid content were less extreme. In the period from mid-spawning to post-spawning, the presence of 20:4n-6 in polar and neutral lipid increased to a notable extent in all organs studied.

Lipid dynamics and plasma level changes of 17beta-estradiol and testosterone during the spawning season of gilthead seabream (Sparus aurata) females of different ages.

The present study was undertaken to evaluate whether the age of brood stock females of Sparus aurata affects the mobilization of lipids from muscle and liver towards the gonads to aid in oocyte development. Taking into account the role some hormones play in lipid mobilization the production of 17beta-estradiol (E2) and testosterone (T) was also measured throughout the spawning season. Four groups of fish were established consisting of 3-, 4-, 5- and 6-year-old females (1.3, 1.5, 2.3 and 2.8 kg average weight, respectively), maintained in separate tanks together with a number of two-year-old males. The results for all four groups showed no variations in fish total length between the beginning and end of the experimental period. However, losses were recorded both of body weight and condition factor. In general terms, there were no significant differences in the plasma levels of E2, T and the gonadosomatic (GSI) and hepatosomatic (HSI) index among the four groups throughout the spawning season. In all groups, the plasma levels of E2, T, GSI and HSI were at their lowest at the end of spawning. Between December (pre-spawning) and March (mid-spawning), all groups suffered depletion of the lipid content of liver and muscle, while gonad lipid content remained constant. The mobilization of lipids from liver and muscle to contribute to the upkeep of the gonadal lipid involved the mobilization of all the fatty acid groups, saturates, monoenes, n-6, n-3, and n-3 HUFA. A good correlation existed between the percentage of the various fatty acid groups transferred from muscle and the age of the reproductive females. However, the greater lipid mobilization from muscle matching the greater age of the reproductive females did not result in greater lipid gonadal reserves or greater body size, suggesting that reproduction on the part of older females requires greater effort. Despite this, the results as a whole indicated that lipogenic capacity, considered as the mobilization of lipids from muscle and liver towards the gonad for the development of oocytes, is unaffected by age in reproductive 3- to 6-year-old gilthead seabream females.