Induction of ovulation and spawning in the Mediterranean red porgy, Pagrus pagrus, by controlled delivery and acute injection of GnRHa

Gonadotropin-releasing hormone analogue (GnRHa) in the form of saline injections or sustained-release microspheres was used to induce oocyte maturation, ovulation, and spawning in captive red porgy (Pagrus pagrus). Individually tagged vitellogenic females (n = 9 or 10) were treated at the beginning of the spawning season (March) with 20 μg/kg body weight (bw) GnRHa-loaded microspheres, a single injection of 20 μg/kg bw dissolved in saline, or physiological saline (control). Females were placed in tanks (one tank per treatment) connected to overflow egg collectors and monitored for 11 days. In addition to the eggs collected from the tank overflow, eggs were stripped from the fish on a daily basis. Only one spawn was obtained from the control fish, probably from a single female, given the small relative fecundity (700 eggs/kg bw). On the contrary, treatment with a GnRHa injection produced two spawns (9 and 11 days after treatment) and 50% of the fish ovulated. Treatment with GnRHa microspheres induced seven spawns (3 and 6-11 days after treatment) and 100% of the females ovulated. Females did not spawn all the eggs ovulated on a particular day, evident from the significant number of eggs obtained by manual stripping. Egg quality did not significantly differ among treatments, whereas number of spawned eggs and total relative fecundity were significantly higher in fish treated with GnRHa microspheres (ANOVA, p<0.05). The results demonstrate the potential of GnRHaloaded microspheres to induce spawning in red porgy, as a method of overcoming spawning failures in commercial hatcheries

Lack of genetic structure in euryhaline Chelon labrosus from the estuaries under anthropic pressure in the Southern Bay of Biscay to the coastal waters of the Mediterranean Sea

Over the last decade, xenoestrogenic effects have been reported in populations of thicklip grey mullet Chelon labrosus from contaminated estuaries in the Bay of Biscay, resulting in intersex condition. To understand the level of gene flow in individuals of different Basque estuaries microsatellite markers were used to evaluate the population structure and connectivity of C. labrosus from estuaries of the Basque coast. 46 microsatellites were tested and 10 validated for the analysis of 204 individuals collected from 5 selected Basque estuaries and 2 outgroups in the Bay of Cadiz and Thermaic Gulf. The polymorphic microsatellites revealed 74 total alleles, 2–19 alleles per locus. The mean observed heterozygosity (0.49 ± 0.02) was lower than the expected one (0.53 ± 0.01). There was no evidence of genetic differentiation (FST = 0.0098, P = 0.0000) among individuals or sites. Bayesian clustering analysis revealed a single population in all sampled locations. The results of this study indicate widespread genetic homogeneity and panmixia of C. labrosus across the current sampling areas spanning the Atlantic and Mediterranean basins. The hypothesis of panmixia could therefore be well supported so individuals inhabiting estuaries with high prevalence of intersex condition should be considered as members of the same single genetic group as those inhabiting adjacent estuaries without incidence of xenoestrogenicity.This work was funded by the Spanish Ministry of Science. Innovation and Universities and EU-FEDER/ERDF (BORN2bEGG PGC2018-101442-B-I00) and the Basque Government (Grants to consolidated research groups IT1302-19 and IT1743-22). A.N. is a recipient of a pre-doctoral grant PIF17/172 from the University of the Basque Country (UPV/EHU). Authors wish to thank the help of two anonymous reviewers for significantly helping in better focusing the aim of the present work

New Fisheries-related data from the Mediterranean Sea (April 2015)

In this second Collective Article with fisheries-related data from the Mediterranean Sea we present the evaluation of bony structures in aging of Barbus tauricus, otolith dimensions-body length relationships for two species (Trachinus draco and Synchiropus phaeton), information on the growth of juvenile Thunnus thynnus and of Ruvettus pretiosus, weight-length relationships for three species (Aulopus fiamentosus, Thunnus thynnus and Tylosurus acus imperialis) and data on feeding habits and reproduction of Aulopus fiamentosus

A Sexual Shift Induced by Silencing of a Single Insulin-Like Gene in Crayfish: Ovarian Upregulation and Testicular Degeneration

In sequential hermaphrodites, intersexuality occurs naturally, usually as a transition state during sexual re-differentiation processes. In crustaceans, male sexual differentiation is controlled by the male-specific androgenic gland (AG). An AG-specific insulin-like gene, previously identified in the red-claw crayfish Cherax quadricarinatus (designated Cq-IAG), was found in this study to be the prominent transcript in an AG cDNA subtractive library. In C. quadricarinatus, sexual plasticity is exhibited by intersex individuals in the form of an active male reproductive system and male secondary sex characters, along with a constantly arrested ovary. This intersexuality was exploited to follow changes caused by single gene silencing, accomplished via dsRNA injection. Cq-IAG silencing induced dramatic sex-related alterations, including male feature feminization, a reduction in sperm production, extensive testicular degeneration, expression of the vitellogenin gene, and accumulation of yolk proteins in the developing oocytes. Upon silencing of the gene, AG cells hypertrophied, possibly to compensate for low hormone levels, as reflected in the poor production of the insulin-like hormone (and revealed by immunohistochemistry). These results demonstrate both the functionality of Cq-IAG as an androgenic hormone-encoding gene and the dependence of male gonad viability on the Cq-IAG product. This study is the first to provide evidence that silencing an insulin-like gene in intersex C. quadricarinatus feminizes male-related phenotypes. These findings, moreover, contribute to the understanding of the regulation of sexual shifts, whether naturally occurring in sequential hermaphrodites or abnormally induced by endocrine disruptors found in the environment, and offer insight into an unusual gender-related link to the evolution of insulins

Morphometric identification of Tylosurus acus imperialis in the North Aegean Sea

Increasing numbers of Tylosurus needlefishes together with common Belone needlefishes appeared in Thermaikos Gulf (North Aegean Sea, Greece) from 2012 to 2014, especially from May to August. The Tylosurus individuals were identified because of the absence of gill rakers and the presence of black thin lateral keel on caudal peduncle. From June 2013 to July 2014, 112 specimens of Tylosurus needlefishes were collected from commercial fisheries and a detailed morphometric and meristic analysis was applied for species identification. Measurements were recorded on each specimen, for six distance characters (TL, SL, FL, BL, HL, MBH). The length of fins (pectoral, ventral, dorsal, anal) was measured, various proportions between body and fin length were estimated and the number of fin rays was counted. Total length (TL) ranged from 59.3 to 111.6 cm. The soft rays in ventral fins were 6, in dorsal fin were 23-26 (mainly 24 with 53%) and in anal fin were 21-23 (mainly 22 with 51%). Body length to head length (BL/HL) ranged from 2 to 2.82, BL to pectoral fins length (BL/P) ranged from 8.3 to 10.8, BL to ventral fins length (BL/V) ranged from 10.9 to 17.7, BL to anterior dorsal fin lobe height (BL/D) ranged from 10.5 to 15.3 and BL to anterior anal fin lobe height (BL/A) ranged from 9.3 to 14.3. The anal fin lobe ranged from 4.9 to 7.4% of standard length. Moreover, the specimens had greater size in length, greater values in morphometrics (i.e. BL/P etc) and higher values in meristics than those reported for the congeneric species Tylosurus choram (Rüppell, 1837) and Tylosurus crocοdilus (Péron & Lesueur, 1821). The resulted diagnostic features are in accordance to the literature for the systematics of Tylosurus acus imperialis (Rafinesque, 1810). Thus, specimens were identified as T. acus imperialis confirming its occurrence in Thermaikos Gulf waters appearing the northern geographic expansion in the Aegean Sea

Gonadal changes and blood sex steroids levels during natural sex inversion in the protogynous Mediterranean red porgy, Pagrus pagrus (Teleostei : Sparidae)

Changes in gonadal structure and serum levels of sex steroids were investigated during natural sex inversion from female to male in reared populations of the protogynous Mediterranean red porgy, Pagrus pagrus. Four developmental phases were identified by histological observation: female, early transitional (ETr), late transitional (LTr), and male phases. At female phase, a few nests of spermatogonia were observed at the posterior-ventral part of the gonad mainly in females out of the breeding season. At ETr phase, spermatogonial proliferation occurred while perinucleolar oocytes showed signs of degeneration. At LTr phase, seminiferous lobules were formed and spermatogonial proliferation expanded along the ovary which degenerated. All types of male germ cells could be found. At male phase, functional testis underwent active spermatogenesis while small ovarian remnants associated to fat tissue could be detected. Both 17 beta-estradiol (E2) and estrone (E1) blood levels were significantly lower in fish at transitional and male phases in comparison to breeding females, while levels of 11-ketotestosterone (11-KT) and testosterone (T) gradually increased in the transitional and male phases. In conclusion, the protogynous P. pagrus possess a delimited type bisexual gonad with a medio-dorsal ovarian area and a latero-ventral testicular zone. Sex inversion starts mainly after the female breeding season with an active spermatogonial proliferation. The testis tissues develop while ovarian tissues regress to disappear completely in the functional male. This process is accompanied by a sharp decrease of estrogens levels and a progressive increase of androgens levels. The physiological significance of such endocrine changes is discussed. (c) 2006 Elsevier Inc. All rights reserved

Endocrine changes during the annual reproductive cycle of the red porgy, Pagrus pagrus (Teleostei, Sparidae).

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