[Show abstract][Hide abstract] ABSTRACT: The genetic structure and the phylogenetic relationships among five Balkan populations of trout Salmo trutta that have been classified earlier into five different taxa were studied, using microsatellite and mitochondrial DNA (mtDNA) analyses. The pattern of population differentiation observed at microsatellites differed to that depicted by mtDNA variation, yet both methods indicated a very strong partitioning of the genetic variation among sampling locations. Results thus suggest that conservation strategies should be directed towards preserving the genetic integrity and uniqueness of each population.
Journal of Fish Biology 12/2011; 79(7):1950-60. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Adult gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax were exposed for 24 and 48 h, respectively, to two concentrations of ammonia each (mean values of 3·34 and 13·10 mg l(-1) TA-N in S. aurata; 2·99 and 11·90 mg l(-1) TA-N in D. labrax). Light microscopy and computerized morphometry were used to evaluate ammonia-induced alterations in skin structure during exposure and following recovery in normal water. In S. aurata, ammonia exposure induced a concentration-dependent increase in the number (hyperplasia) of neutral mucous cells (mc), with peak values at 24 h recovery after exposure. An increase in the dispersion of melanosomes in skin melanocytes was also observed in the dermis and occasionally in the epidermis of S. aurata, with peak values at 24 h of ammonia exposure. Exposure of D. labrax to ammonia had, likewise, concentration-dependent effects on mucous secretion. Of the two types of mc in this species, there was an increase in the number of the neutral mc and a reduction in the much more numerous acid mc, with peak values at 24 and 48 h, respectively, of ammonia exposure. The more intense mucous secretion in D. labrax compared to S. aurata could be related to the lower tolerance to ammonia in D. labrax, as reported elsewhere. Finally, the increase in melanosome dispersion was less evident in D. labrax, due to highly variable control values. These morphological alterations to the skin could be useful indicators of non-specific stress in cultured fishes.
Journal of Fish Biology 04/2011; 78(4):1152-69. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The yearly gonadal cycle of two Kinneret teleosts, Barbus longiceps and Capoeta damascina and of their hybrid, was assessed by measuring the gonadosomatic index (GSI) in both sexes, as well as the spermatozoan index (SPI) in the males. SPI was established through a computerized analysis system, using light microscopy images of histological preparations of the testes.Barbus longiceps specimens had highest GSI in March, 6.31 for males and 1.40 for females. Capoela damascina had highest GS1 in January, 6.63 for males and 6.88 for females. In the male-like hybrids, the highest GSI was 5.57 in February, and in female-like hybrids 1.83 in March; no gametes were ever formed in hybrid gonads. The highest SPI appeared in B. longiceps in April, while in C. damascina the highest SPI was found in March. In both species, the highest SPI was attained several weeks after the highest GSI was observed. It is suggested that the peak of the breeding season of both species is actually represented by the highest SPI. In males, the decreasing GSI, which corresponds to the highest SPI, represents the loss of gonad weight, which is due to the elimination of the spermatid residual bodies, prior to spermiation. In the females the decreasing GSI is the result of ovulation, and characterizes the peak of spawning activity.
Journal of Fish Biology 04/2005; 43(6):865 - 875. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Testicular ultrastructure was studied in Barbus longiceps, Capoeta damascina and their natural hybrid. The testes of these teleosts belong to the unrestricted or lobular type. Germ cell morphology is similar in the parental males. In the hybrid, spermatogenesis does not extend beyond the pachytene of the first meiotic division, probably due to the unsuccessful pairing of the homologous chromosomes. Hybrid testes are occupied mainly by degenerating primary spermatocytes, at the leptotene and pachytene stages. In both parents and the hybrid, Sertoli and Leydig cells are characterized by the presence of granular endoplasmic reticulum and of mitochondria with tubular cristae. Due to the arrest of spermatogenesis, the male germ cell protective barrier is absent in the hybrid. Germ cell nuclear size was measured by a computerized analysis system, using light-microscopy images. In the parents and the hybrid, germ cells attain a uniform inter-individual nuclear size when they reach the first meiotic prophase. The nuclear size of primary spermatocytes is similar among the three groups of fish, possibly reflecting their close genetic relationship.
Journal of Fish Biology 03/2005; 49(3):458 - 468. · 1.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gonad development and somatic growth were studied in the hybrid between Barbus longiceps and Capoeta damascina (Pisces: Cyprinidae) from Lake Kinneret (Lake Tiberias), during the years 1987–1990. Reproductive eriods of both parental species were considerably overlapping. Among 39 hybrid specimens sampled, 5 were found to be males with arrested spermatogenesis, 31 were females with abnormal gonads and 3 were structural hermaphrodites with arrested gametogenesis. In all hbrids gonad development was impaired. No ripe eggs or spermatozoa were ever observed in histological sections of the hybrid gonads. However, during the breeding season the hybrids possessed secondary sex characteristics, similar to those present in the parental species. Hybril somatic growth was intermediate between that of the parental species. The hybrid dressing rate was also intermediate between that of the parental species.ZusammenfassungGonadenentwicklung und somatisches Wachstum eines intergenerischen Hybriden karpfenartiger Fische aus dem See Genezareth, IsraelDie Gonadenentwicklung und das Wachstum wurden am Hybriden zwischen Barbus longiceps und Capoeta damascini (Pisces: Cyprinidae) aus dem See Genezareth (See Tiberias) in den Jahren 1987 bis 1990 untersucht. Die Vermehrungsperiode beider Elternarten überlappen erheblich. Fünf der 39 untersuchten Hybriden waren Männchen mit stagnierender Spermatogenese; 31 Weihchen hatten abnormale Gonaden und 3 Tiere waren strukurell als Hermahroditen mit gehemmter Gametogenese einzustufen. Die Entwicklung war in allen Hybriden-Gonaden gehemmt. In keinem Fall wurden reife Eier oder Spermatozoen in den histologischen Schnitten der Hybridengonaden gefunden. Trotzdem besaßen die Hybriden während der Laichzeit sekundäre Geschlechtsmerkmale, ähnlich denen der Elternarten. Das somatische Wachstum der Hybriden war im Vergleich zu den Elternarten intermediär Die Schlachtausbeute der Hybriden lag ebenfalls zwischen derjenigen der Elternarten.