Biología reproductiva y desarrollo embrionario de Squalus blainvillei en el este del mar Mediterráneo

A total number of 526 Squalus blainvillei was sampled from the bottom trawl and bottom longline catches in the eastern Mediterranean Sea from December 2004 to December 2009. Females outnumbered males and the overall sex ratio was 1.26:1. Females ranged from 182 to 779 mm in total length and males from 180 to 799 mm. Both females and males showed allometric growth (b > 3) and we found statistically significant differences in the relationship between length and weight. Out of the specimens examined, 36% of females and 63% of males were sexually mature. Males reached sexual maturity at smaller sizes than females. The smallest sexually mature female was 523 mm in total length, while the smallest sexually mature male was 425 mm in total length. Mean length at 50% maturity was estimated at 564.4 mm for females and 457.7 mm for males. Sexually mature specimens of both sexes with mature gonads and high GSI were present in high proportions in every season of the year, which indicates a continuous reproductive cycle. Ovarian oocytes continued to develop throughout gestation. Females carrying near-term embryos had large, equally developed ovarian oocytes, which suggests that they ovulate soon after parturition. Ovarian fecundity ranged from 1 to 7 and uterine fecundity ranged from 1 to 6. Embryo length and yolk sac weight were negatively correlated.Un total de 526 Squalus blainvillei procedentes de pescas de arrastre de fondo y palangres de fondo se muestrearon en el este del Mar Mediterráneo, desde diciembre de 2004 hasta diciembre de 2009. Las hembras excedieron en número a los machos y el cociente de sexos fue 1.26:1. Las hembras midieron entre 182 y 779 mm de longitud total y los machos de 180 a 799 mm. Tanto machos como hembras mostraron un crecimiento alométrico (b > 3), pero se encontraron diferencias estadísticamente significativas en la relación talla y peso. De los especímenes examinados, el 36% de las hembras y el 63% de los machos eran sexualmente maduros. Los machos alcanzaron la madurez sexual a tamaños más pequeños que las hem- bras. La hembra sexualmente madura de menor talla tenía una longitud total de 523 mm, mientras que el macho sexualmente maduro más pequeño tenía una longitud total de 425 mm. La talla media al 50% de madurez, se estimó en 564.4 mm para las hembras y en 457.7 mm para los machos. Los especímenes de ambos sexos sexualmente maduros, con gónadas maduras y alto GSI estuvieron presentes en elevadas proporciones en todas las estaciones del año, indicando un ciclo reproductivo continuo. Los oocitos ováricos continuaron desarrollándose durante la gestación. Las hembras que llevaban embriones desarrollados tenían grandes oocitos ováricos igualmente desarrollados, lo que hace pensar que ovulan pronto después del parto. La fecundidad ovárica varió de 1 a 7 y la fecundidad uterina de 1 a 6. La longitud de los embriones y el peso del saco vitelino estuvieron correlacionados negativamente

Estimación de la edad del bonito del Atlántico en el Mediterráneo Este usando las espinas dorsales y validación del método

Growth parameters were studied in 397 specimens of the Atlantic bonito caught in the eastern Mediterranean Sea (Aegean and Ionian Seas) ranging from 7.2 to 72.5 cm in fork length and from 2 to 5400 g in total weight. The study of the growth bands in spine sections showed that one translucent ring is formed annually during the cold season. The growth parameters estimated (L∞ = 82.99 cm, K = 0.24, t0 = -0.77) express the growth of the species more realistically than previous studies in the Mediterranean Sea and the Atlantic Ocean.Se estudiaron los parámetros de crecimiento en 397 especimenes de bonito del Atlántico capturados en el Mediterráneo Este (mares Egeo y Jónico) entre 7.2 y 72.5 cm de longitud total y de 2 a 5400 g de peso total. El estudio de las bandas de crecimiento en secciones de espinas mostró que anualmente, durante la estación fría, se forma un anillo translucido. Los parámetros de crecimiento estimados (L∞ = 82.99 cm, K = 0.24, t0 = -0.77) expresan el crecimiento de la especie de manera más realista que en previos estudios en el Mediterráneo y el Atlántico

Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/ Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the smallspotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed

Evidence of high genetic connectivity for the longnose spurdog Squalus blainville in the Mediterranean Sea

Squalus blainville is one of the least studied Mediterranean shark species. Despite being intensively fished in several locations, biological knowledge is limited and no genetic structure information is available. This is the first study to examine the genetic structure of S. blainville in the Mediterranean Sea. Considering the high dispersal potential inferred for other squalid sharks, the hypothesis of panmixia was tested based on a 585 bp fragment of the mitochondrial DNA cytochrome c oxidase subunit I gene from 107 individuals and six nuclear microsatellite loci from 577 individuals. Samples were collected across the Ionian, Aegean and Libyan Seas and off the Balearic Islands. Twenty three additional sequences of Mediterranean and South African origin were retrieved from GenBank and included in the mitochondrial DNA analysis. The overall haplotype diversity was high, in contrast to the low nucleotide diversity. Low and non-significant pairwise ΦST and FST values along with a Bayesian cluster analysis suggested high connectivity with subsequent genetic homogeneity among the populations studied, and thus a high dispersal potential for S. blainville similar to other squalids. The historical demography of the species was also assessed, revealing a pattern of population expansion since the middle Pleistocene. These findings could be considered in species-specific conservation plans, although sampling over a larger spatial scale and more genetic markers are required to fully elucidate the genetic structure and dispersal potential of S. blainville

Combining selection models and population structures to inform fisheries management: a case study on hake in the Mediterranean bottom trawl fishery

The reduction of juvenile catch and discards are important targets in fisheries policy. This work examines how selection models can predict the size structure (LFD) of discards and landings considering the effects of area, time period, gear and fisher behaviour. Additional exploitation indicators related to the gear used, fisher's selection pattern, and discards were also estimated. The approach is demonstrated in a study concerning hake in the Mediterranean trawl fishery, focusing on high (HRA) and low (LRA) recruitment areas in the Saronikos Gulf (Eastern Mediterranean) during two periods (June, September) using two codends (40 mm square-40S, 50 mm diamond-50D mesh). The predicted discards LFDs revealed generally higher percentages in the HRA in June when using the 50D. The predicted landings LFDs showed higher percentages in the LRA in September for both codends, but undersized hake were always included. LFDs and exploitation indicators indicated that both codends were inappropriate for sustainable fishing of hake in the HRA, where 50D performed worse than the 40S. Fishing with both codends in the LRA in September revealed the lowest discards rates and minimum sizes of landings close to MCRS (minimum conservation reference size). These results can provide information to fisheries management aiming to protect juveniles and reduce discards through spatio-temporal fishing closures

Starost, rast i morfometrija otolita palamide (Sarda sarda Block, 1793) iz istočnog Sredozemnog mora

The otoliths of the Atlantic bonito, Sarda sarda (Bloch, 1793), were examined with the aim to estimate the age and growth of the species in the eastern Mediterranean Sea and to reveal possible relationships between otolith shape or size and age. All specimens used in this study, ranging from 7.2 to 70.4 cm in fork length and from 20 to 4889 g in total weight, were caught in the Aegean and Ionian Seas during the period 1997-2010. Otolith morphometry was studied using image analysis techniques for all intact sagittae ranging in weight from 0.6 to 11.3 mg and four shape indices were calculated. No statistical significant differences between left and right otolith morphometric variables were found. The age of fish was estimated by counting the pairs of opaque and translucent bands in transversal thin sections of otoliths. The estimated ages ranged from 0+ to 7 years and the von Bertalanffy growth parameters were determined ((L∞=79.9 cm, k=0.261 and to=-1.230 years)). The examination of the type of growth bands at the outside margin of each otolith per month showed that one translucent band is formed annually during the cold season. The results revealed statistically significant relationships between otolith morphometric variables and fish length or age. Among the variables, otolith weight was the one that showed the highest correlation with age (R=0.77). Therefore, otolith weight could represent a valuable criterion for age estimation in Atlantic bonito that is objective, economic and easy to perform compared to annuli counting method in hard parts.Kako bi se odredila starost i rast palamide Sarda sarda (BLOCH, 1793), koja obitava u Sredozemnom moru, analizirani su njeni otoliti. Isto tako se analizom morfometrijskih parametara otolita palamide pokušala utvrditi korelacija između oblika samog otolita i očitane starosti. Vilična dužina i masa svih analiziranih jedinki palamide, koje su prikupljene na području Jonskog i Egejskog mora u razdoblju od 1997. god. do 2010. god., kretala se u rasponu od 7.2 cm do 70.4 cm odnosno od 20 g do 4889 g. Morfometrijske značajke neoštećenih otolita, čija masa je bila od 0,6 mg do 11,3 mg, su definirane preko četiri parametra oblika istih. Nije utvrđeno da postoji statistički značajna razlika između lijevog i desnog otolita. Starost palamide, dobivena očitavanjem i brojanjem zona prirasta na otolitu, istraživanih jedinki je kolebala od 0+ do 7 godina starosti te su definirani von Bertalanffy parametri rasta ((L∞=79.9 cm, k=0.261 i t_o =-1.230 god.)). Analizirajući zone prirasta na otolitu uočeno je da tijekom jedne godine nastaje jedan hijalini (proziran) prsten i to u hladnijem dijelu godine. Utvrđena je statistički značajna korelacija između morfometrijskih parametara otolita i dužine ribe kao i starosti. Osobito značajna korelacija (R=0,77) je uočena između mase otolita i dužine istraživane jedinke, što upućuje na to da bi se u budućnosti navedeni parametar – masa otolita, mogla koristiti kao indikator starosti s obzirom da se radi o metodi koja bi u svakom slučaju bila dosta ekonomičnija i jednostavnija

Histochemical analysis of glycoconjugates in the domestic cat testis

The localization and characterization of oligosaccharide sequences in the cat testis was investigated using 12 lectins in combination with the ßelimination reaction, N-Glycosidase F and sialidase digestion. Leydig cells expressed O-linked glycans with terminal aGalNAc (HPA reactivity) and N-glycans with terminal/internal aMan (Con A affinity). The basement membrane showed terminal Neu5Aca2,6Gal/GalNAc, Galß1,3GalNAc, a/ßGalNAc, and GlcNAc (SNA, PNA, HPA, SBA, GSA II reactivity) in O-linked oligosaccharides, terminal Galß1,4GlcNAc (RCA120 staining) and aMan in N-linked oligosaccharides; in addition, terminal Neu5Aca2,3Galß1,4GlcNac, Forssman pentasaccharide, aGal, aL-Fuc and internal GlcNAc (MAL II, DBA, GSA I-B4, UEA I, KOH-sialidase-WGA affinity) formed both O- and N-linked oligosaccharides. The Sertoli cells cytoplasm contained terminal Neu5Ac- Galß1,4GlcNAc, Neu5Ac-ßGalNAc as well as internal GlcNAc in O-linked glycans, aMan in N-linked glycoproteins and terminal Neu5Aca2,6Gal/ GalNAc in both O- and N-linked oligosaccharides. Spermatogonia exhibited cytoplasmic N-linked glycoproteins with aMan residues. The spermatocytes cytoplasm expressed terminal Neu5Aca2,3Galß1,4 GlcNAc and Galß1,3GalNAc in O-linked oligosaccharides, terminal Galß1,4GlcNAc and a/ßGalNAc in N-linked glycoconjugates. The Golgi region showed terminal Neu5aca2,3Galß1,4GlcNac, Galß1,4GlcNAc, Forssman pentasaccharide, and aGalNAc in O-linked oligosaccharides, aMan and terminal ßGal in N-linked oligosaccharides. The acrosomes of Golgi-phase spermatids expressed terminal Galß1,3GalNAc, Galß1,4GlcNAc, Forssmann pentasaccharide, a/ßGalNAc, aGal and internal GlcNAc in O-linked oligosaccharides, terminal a/ßGalNAc, aGal and terminal/internal aMan in N-linked glycoproteins. The acrosomes of cap-phase spermatids lacked internal Forssman pentasaccharide and aGal, while having increased a/ßGalNAc. The acrosomes of elongated spermatids did not show terminal Galß1,3GalNAc, displayed terminal Galß1,4GlcNAc and a/ßGalNAc in N-glycans and Neu5Ac-Galß1,3GalNAc in O-linked oligosaccharides