29 research outputs found
Genetic validation of the unexpected presence of a tropical tuna, bigeye tuna (Thunnus obesus), in the Mediterranean
Bigeye tuna (Thunnus obesus, Lowe, 1839) is one of the eight recognized species of the genus Thunnus. It is considered a tropical species distributed in the Atlantic, Pacific and Indian Oceans. To date, no validated presence of this species has been reported inside the Mediterranean Sea. This study, however, confirms, for the first time, the presence of three young individuals of this species within the Mediterranean Sea.VersiĂłn del editor1,83
Larval Retention and Homing Behaviour Shape the Genetic Structure of the Bullet Tuna (Auxis rochei) in the Mediterranean Sea
Background: The bullet tuna (Auxis rochei) is an epipelagic fish with a worldwide distribution that is highly targeted by fisheries. Genetic diversity and population genetics are good
indicators of population structure and thus, essential tools for fisheries management. Knowing which
factors (biotic and abiotic) might be shaping such structure is crucial for management plans. In the
present study, we assessed the population structure of the bullet tuna in the western and central
Mediterranean Sea. Methods: We used two types of genetic data: the mitochondrial DNA control
region and seven microsatellite loci. The analysis of 431 sequences with a length of 386 bp from the
mtDNA CR and the results from 276 individuals were genotyped by seven microsatellite loci. Results: Both types of markers coincided in showing significant genetic differences between an Iberian
PeninsulaâStrait of Gibraltar stock in comparison with a North African stock. Conclusions: We argue
that this differentiation pattern is likely caused by reproductive strategies such as coastal spawning,
larval retention, and natal homing behavior. These results should endorse the implementation of
management plans for a resource that currently is not being managed. Thus, to ensure sustainability,
these new policies should consider the presence of at least two genetically identified stocks
Implications for fishery management in small tunas the case of genetic population structure of bullet tuna in the west Mediterranean
Knowledge of population structure of species is needed to establish appropriate management
regulations. Of particular concern are those commercial species; these exploited fish populations
can undergo loss of genetic variability that ultimately may lead the loss of regional small
populations. This situation could occur in the small tuna species, which in some cases are heavily
targeted by artisanal fisheries. Here, we focused on the Bullet tuna (Auxis rochei) with an
extensive sampling (n = 431) along the north and south coast of the west Mediterranean and one
location on the east Atlantic. The analysis of the mtDNA control region revealed that seven (about
1.6%) individuals were not identified as Bullet tuna suggesting a species misidentification with
possible implications in stock assessment. Population genetics results showed clear genetic
differentiation between the Iberian Peninsula and North African locations. These results have a
clear impact on the conservation and management strategies, and if it is confirmed in other small
pelagic species, the pattern of population structure in the Mediterranean is more complex than
initially expected
Population genetic of Atlantic bonito in the north east Atlantic and Mediterranean
This study assesses the stock structure of Atlantic bonito (Sarda sarda) using the mitochondrial
control region as a genetic marker. About 615 individuals distributed in seven locations were
analyzed. Two of the locations were in the Mediterranean Sea (MD/BIL95) (Spain and Tunis),
three in the northeast Atlantic (AT-NE/BIL94B) (Portugal, Tunis, Morocco and Mauritania), and
one in the southeast Atlantic (AT-SE/BIL97) (CĂŽte dâIvoire). All these samples were obtained
thanks to the participation of all authors in two Small Tuna Research Programs funded by
ICCAT. The analysis of the genetic variability of the sequence of mitochondrial control regions
depicts a clear heterogeneity among locations. The shared genetic pool that comprises the
locations within the Mediterranean (Spain and Tunis), including also a sample from the northeast
Atlantic (Portugal), is clearly different from the African locations (Senegal and CĂŽte dâIvoire).
Moreover, these two African locations are also genetically differentiated between them. Morocco
and Mauritania locations seems to be located in an intermediate situation between these two
groups of locations. These results can be used to infer a management policy by ICCAT on the
fisheries of this specie
Final report of the short-term contract for ICCAT SMYTP for the biological samples collection for growth, maturity and genetics studies â Year #2
This document is the final report of the second year of the short-term contract of the Small Tuna
Year Program by ICCAT. In 2018, the Small Tuna Species Group decided to prioritize Little
tunny (LTA) (Euthynnus alletteratus) Atlantic bonito (BON) (Sarda sarda) and Wahoo (WAH)
(Acanthocybium solandri), based on their economic importance and the deficiency of knowledge
of their biology. The objectives of the contract for three species were: i) Collect biological
samples for estimating growth parameters, assessing the maturity and stock structure analysis
(populations genetics), and ii) Conclude the analysis of the stock structure for at least one of the
three species and provide preliminary results for the remaining. The obtained samples for
growth, maturity and stock structure analysis was almost completed for Little tunny and Atlantic
bonito, whereas for Wahoo the samples are scarce. The analysis of stock structure for Little tunny
and Atlantic bonito revealed that the observed dif
Deep genetic differentiation in the little tunny from the Mediterranean and east Atlantic.
In this study we present the analysis of the stock structure of Little tunny (Euthynnus alletteratus) using the mitochondrial control region as a genetic marker. More than 500 individuals distributed in six locations were analyzed. Samples were from three main regions: Mediterranean (Tunisia and Spain), and northeast Atlantic (Portugal and Senegal) and southeast Atlantic (CĂŽte dâIvoire and Gabon). Deep genetic differences were found between these locations. The phylogenetic tree showed a complete reciprocal monophyly association of the individuals in two main regions: Portugal, Spain and Tunisia; and Senegal, CĂŽte dâIvoire and Gabon. The level of genetic differentiation between these two areas is similar to the differences found between species of the genus Euthynnus. These results suggest a scenario of having two species of Little tunny in its Mediterranean-Atlantic distribution. Further evidence with other non-linked genetic markers along morphological and meristic data is necessary to fully confirm these two putative species. However, based on these results a separate management unit can be considered: i) Northeast Atlantic/Mediterranean (Portugal, Spain and Tunisia), and ii) the northeast/Southeast Atlantic (Senegal, CĂŽte dâIvoire and Gabon).
RĂSUMĂ
Dans cette Ă©tude, nous prĂ©sentons l'analyse de la structure du stock de la thonine commune (Euthynnus alletteratus) en utilisant la zone mitochondriale de contrĂŽle comme marqueur gĂ©nĂ©tique. Plus de 500 spĂ©cimens rĂ©partis sur six sites ont Ă©tĂ© analysĂ©s. Les Ă©chantillons provenaient de trois rĂ©gions principales : MĂ©diterranĂ©e (Tunisie et UE-Espagne), Atlantique Nord-Est (Portugal et SĂ©nĂ©gal) et Atlantique Sud-Est (CĂŽte d'Ivoire et Gabon). De profondes diffĂ©rences gĂ©nĂ©tiques ont Ă©tĂ© constatĂ©es entre ces endroits. L'arbre phylogĂ©nĂ©tique affichait une association monophylique rĂ©ciproque complĂšte des spĂ©cimens dans deux rĂ©gions principales : lâUE-Portugal, lâUE-Espagne et la Tunisie ; et le SĂ©nĂ©gal, la CĂŽte d'Ivoire et le Gabon. Le niveau de diffĂ©renciation gĂ©nĂ©tique entre ces deux rĂ©gions est similaire aux diffĂ©rences constatĂ©es entre les espĂšces du genre Euthynnus. Ces rĂ©sultats suggĂšrent un scĂ©nario de prĂ©sence de deux espĂšces de thonidĂ©s mineurs dans sa distribution mĂ©diterranĂ©enne-atlantique. Des preuves supplĂ©mentaires avec d'autres marqueurs gĂ©nĂ©tiques non liĂ©s ainsi que des donnĂ©es morphologiques et mĂ©ristiques sont nĂ©cessaires pour confirmer pleinement ces deux espĂšces supposĂ©es. Toutefois, sur la base de ces rĂ©sultats, une unitĂ© de gestion distincte peut ĂȘtre envisagĂ©e : i) Atlantique Nord-Est/MĂ©diterranĂ©e (UE-Portugal, UE-Espagne et Tunisie) et ii) Atlantique Nord-Est/Sud-Est (SĂ©nĂ©gal, CĂŽte d'Ivoire et Gabon).
RESUMEN
En este estudio presentamos el anĂĄlisis de la estructura del stock de la bacoreta (Euthynnus alletteratus) utilizando la regiĂłn de control mitocondrial como marcador genĂ©tico. Se analizaron mĂĄs de 500 ejemplares distribuidos en seis localizaciones. Las muestras procedĂan de tres regiones principales: MediterrĂĄneo (TĂșnez y España), AtlĂĄntico nororiental (Portugal y Senegal) y AtlĂĄntico suroriental (CĂŽte d'Ivoire y GabĂłn). Se hallaron profundas diferencias genĂ©ticas entre las tres localizaciones: El ĂĄrbol filogenĂ©tico presentaba una asociaciĂłn monofilĂ©tica recĂproca completa de los ejemplares en dos regiones principales: Portugal, España y TĂșnez; y Senegal, CĂŽte d'Ivoire y GabĂłn. El nivel de diferenciaciĂłn genĂ©tica entre estas dos zonas es similar a las diferencias halladas entre especies del gĂ©nero Euthynnus. Estos resultados sugieren un escenario con dos especies de bacoreta en su distribuciĂłn atlĂĄntica-mediterrĂĄnea. Son necesarias mĂĄs pruebas con otros marcadores genĂ©ticos no vinculados con datos morfolĂłgicos y nerĂticos para confirmar mĂĄs estas dos especies putativas. Sin embargo, en base a estos resultados, puede considerarse una unidad de ordenaciĂłn separada: i) AtlĂĄntico nororiental/MediterrĂĄneo (Portugal, España y TĂșnez) y ii) AtlĂĄntico suroriental/nororiental (Senegal, CĂŽte d'Ivoire y GabĂłn).N
Final report of the short-term contract for ICCAT SMYTP for the biological samples collection for growth, maturity and genetics studies â Year #3
This document is the final report of the third year of the short-term contract of the Small Tuna Year
Program by ICCAT, with the objectives of: a) conduct additional sampling aiming to fill the specific gaps
of the biological samples for estimating the growth and maturity parameters for BON and LTA; b)
estimate the referred parameters for both species, and preliminary provide preliminary results for WAH;
and, c) refine the sampling and stock structure analysis for BON, LTA and WAH. A total of 374
individuals were collected: 145 of BON, 139 of LTA and 90 WAH. Initial target size class was
accomplished only for BON in the Mediterranean. Small individuals are need in the Northeast and no
samples were obtained in Southeast Atlantic. For LTA, total target sizes were not completely achieved in
any case. However, preliminary results were obtained for growth and reproductive parameters. For
BON, with samples arrived from Morocco, no genetic differentiation was detected, and the hypothesis
provided in the previous contract is maintained. The population genetic analysis of WAH presents a
scenario of homogeneous distribution.En prensa
Population genetic of Atlantic bonito in the north east Atlantic and Mediterranean
This study assesses the stock structure of Atlantic bonito (Sarda sarda) using the mitochondrial
control region as a genetic marker. About 615 individuals distributed in seven locations were
analyzed. Two of the locations were in the Mediterranean Sea (MD/BIL95) (Spain and Tunis),
three in the northeast Atlantic (AT-NE/BIL94B) (Portugal, Tunis, Morocco and Mauritania), and
one in the southeast Atlantic (AT-SE/BIL97) (CĂŽte dâIvoire). All these samples were obtained
thanks to the participation of all authors in two Small Tuna Research Programs funded by
ICCAT. The analysis of the genetic variability of the sequence of mitochondrial control regions
depicts a clear heterogeneity among locations. The shared genetic pool that comprises the
locations within the Mediterranean (Spain and Tunis), including also a sample from the northeast
Atlantic (Portugal), is clearly different from the African locations (Senegal and CĂŽte dâIvoire).
Moreover, these two African locations are also genetically differentiated between them. Morocco
and Mauritania locations seems to be located in an intermediate situation between these two
groups of locations. These results can be used to infer a management policy by ICCAT on the
fisheries of this specie
Final report of the short-term contract for ICCAT SMYTP for the biological samples collection for growth, maturity and genetics studies â Year #2
This document is the final report of the second year of the short-term contract of the Small Tuna
Year Program by ICCAT. In 2018, the Small Tuna Species Group decided to prioritize Little
tunny (LTA) (Euthynnus alletteratus) Atlantic bonito (BON) (Sarda sarda) and Wahoo (WAH)
(Acanthocybium solandri), based on their economic importance and the deficiency of knowledge
of their biology. The objectives of the contract for three species were: i) Collect biological
samples for estimating growth parameters, assessing the maturity and stock structure analysis
(populations genetics), and ii) Conclude the analysis of the stock structure for at least one of the
three species and provide preliminary results for the remaining. The obtained samples for
growth, maturity and stock structure analysis was almost completed for Little tunny and Atlantic
bonito, whereas for Wahoo the samples are scarce. The analysis of stock structure for Little tunny
and Atlantic bonito revealed that the observed dif
Dual estrogenic regulation of the nuclear progestin receptor and spermatogonial renewal during gilthead seabream (Sparus aurata) spermatogenesis
11 pages, 6 figuresStudies in teleosts suggest that progestins have crucial functions during early spermatogenesis. However, the role of the different progestin receptors in these mechanisms is poorly understood. In this work, we investigated the expression pattern and hormonal regulation of the classical nuclear progestin receptor (Pgr) in the gilthead seabream at three different stages of spermatogenesis: the resting (postspawning) phase, onset of spermatogenesis, and spermiation. Immunolocalization experiments using a seabream specific Pgr antibody revealed that the receptor was expressed in Sertoli and Leydig cells, and also in a subset of spermatogonia type A, throughout spermatogenesis. Short-term treatment of testis explants with 17ÎČ-estradiol (E2) increased pgr mRNA expression at all stages, while the progestin 17α,20ÎČ-dihydroxy-4-pregnen-3-one (17,20ÎČP) had the opposite effect. At the resting stage, Sertoli cell Pgr expression was positively correlated with the occurrence of proliferating spermatogonia type A in the tubules, and both processes were incremented in vitro by E2 likely through the estrogen receptor alpha (Era) expressed in Sertoli and Leydig cells. In contrast, treatment with 17,20ÎČP downregulated Pgr expression in somatic cells. The androgen 11-ketotestosterone (11-KT) upregulated pgr expression in Leydig cells and promoted the proliferation of mostly spermatogonia type B, but only during spermiation. No relationship between the changes in the cell type-specific expression of the Pgr with the entry into meiosis of germ cells was found. These data suggest a differential steroid regulation of Pgr expression during seabream spermatogenesis and the potential interplay of the E2/Era and 17,20ÎČP/Pgr pathways for the maintenance of spermatogonial renewal rather than entry into meiosisThis work was supported by the CERCA Programme/Government of Catalonia and partially funded by the Spanish Ministry of Science and Innovation (AGL2013-41196-R) to J.C. Participation of J.P. was financed by an award of the Biotechnology Overseas Associateship, Indian Ministry of Science and TechnologyPeer Reviewe