Observations on the biological traits of the rare shark Oxynotus centrina (Chondrichthyes: Oxynotidae) in the Hellenic Seas.

New records of the rare angular rough shark Oxynotus centrina from the Hellenic Seas are presented. Its occurrence is reported for the first time in the Corinthian Gulf. Some aspects of the species' biology are described and compared with previous studies.

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 small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed.

Age estimation of juvenile European hake Merluccius merluccius based on otolith microstructure analysis: a slow or fast growth pattern?

The main goal of this study was to examine otolith microstructure and to estimate the age and growth of European hake Merluccius merluccius from the eastern Mediterranean Sea. One hundred and twenty-nine specimens ranging from 102 to 438 mm in total length (LT ) were used. Age estimations were based on the study of the otolith microstructure, which was revealed after grinding both frontal sides of otoliths. The enumerations of the daily growth increments (DGI) as well as their width (WDGI ) measurements were made on calibrated digital images. The number of DGI in otoliths ranged between 163 and 717. Four phases in the WDGI evolution were distinguished: (1) larval-juvenile pelagic phase, with an increasing trend in WDGI up to the 60th DGI, (2) settlement phase, with a short-term deceleration in WDGI between the 61st and 150th DGI, (3) juvenile demersal phase, characterized by a stabilization of WDGI from 151st to 400th DGI and (4) adult phase, with a decreasing trend in WDGI after the 400th DGI. Age, sex and month of formation were found to affect the WDGI in all phases, with the exception of age at the juvenile demersal phase. The power curve with intercept model described best the relationship of M. merluccius LT with age (TDGI ), according to Akaike criteria, revealing differences in growth between females [LT = 65 · 36(TDGI )(0 · 40) - 388 · 55] and males [LT = 69 · 32(TDGI )(0 · 37) - 352 · 88] for the sizes examined. The mean daily growth rates were 0·61 mm day(-1) for females and 0·52 mm day(-1) for males, resulting in an LT of 283 and 265 mm at the end of their first year of life. In comparison with previous studies on the Mediterranean Sea, the results of this study showed a greater growth rate, similar to results from tagging experiments and otolith microstructure analyses for M. merluccius in other geographic areas.

Evidence of a high percentage of intersex in the Mediterranean swordfish (Xiphias gladius L.).

The first evidence of the presence of intersexuality in a wild population of Mediterranean swordfish (Xiphias gladius L.) is reported. Forty of 162 specimens (25%) macroscopically classified as males, showed the presence of female germ cells within the testes. In two specimens grouped previtellogenic oocytes were present; all the other specimens possessed single scattered previtellogenic oocytes. The presence of vitellogenin was demonstrated immunohistochemically in the liver of both intersex and normal males. These findings could be due to the exposure to oestrogen-mimicking substances.

Histochemical study of glycoconjugates in the toadfish Halobatrachus didactylus oesophagus epithelium.

The carbohydrate expression in the epithelium lining the oesophagus of the toadfish Halobatrachus didactylus was studied by means of conventional and lectin histochemistry. The stratified epithelium was constituted by basal cells, polymorphous cells in the intermediate layer, pyramidal and flattened cells in the outer layer and contained two types of large secretory cells: goblet cells and sacciform cells. PAS, Alcian blue pH 2.5 and pH 1.0 stained very strongly the goblet cells, weakly the surface of the other epithelial cells but did not stain the sacciform cells. The goblet cells cytoplasm contained oligosaccharides with terminal Galbeta1,3GalNAc, alpha/betaGalNAc, Galbeta1,4GlcNAc, alphaL-Fuc and internal betaGlcNAc residues (PNA, SBA, RCA120, UEA I, LTA and KOH-sialidase-WGA affinity). Galbeta1,4GlcNAc, alphaL-Fuc and internal betaGlcNAc were also found in the glycocalyx. The sacciform cells expressed sialyloligosaccharides terminating with Neu5Acalpha2,3Galbeta1,4GlcNac, Neu5Acbeta2,6Gal/GalNAc, Neu5AcForssman pentasaccharide (MAL II, SNA, KOH-sialidase-DBA staining) as well as asialo-glycoconjugates with terminal/internal alphaMan (Con A affinity) and with terminal Galbeta1,3GalNAc, Forssman pentasaccharide, Galbeta1,4GlcNAc, GalNAc (HPA and SBA reactivity), alphaGal (GSA I-B4 reactivity), D-GlcNAc (GSA II labelling), alphaL-Fuc. The basal cells cytoplasm exhibited terminal/internal alphaMan and terminal Neu5Acalpha2,6Gal/GalNAc, Galbeta1,4GlcNAc, alpha/betaGalNAc, alphaGal, GlcNAc, alphaL-Fuc. Intermediate cells showed oligosaccharides with terminal/internal alphaMan and/or terminating with Neu5Acalpha2,6Gal/GalNAc, Galbeta1,4GlcNAc in the cytoplasm and with Neu5Acalpha2,3Galbeta1,4GlcNac, alpha/betaGalNAc, alphaGal, GlcNAc, alphaL-Fuc in the glycocalyx. The pyramidal cells expressed terminal/internal alphaMan and terminal Neu5Acalpha2,6Gal/GalNAc, alpha/betaGalbeta1,4NAc, alphaGal, alphaL-Fuc in the entire cytoplasm, terminal Neu5Acalpha2,3Galbeta1,4GlcNac and Forssman pentasaccharide in the apical extension, internal betaGlcNAc and/or terminal alphaL-Fuc in the luminal surface, Neu5Acalpha2,3Galbeta1,4GlcNac, Neu5Acalpha2,6Gal/GalNAc, Galbeta1,4GlcNAc, alphaGal in the basolateral surface. The flattened cells displayed glycans with terminal/internal alphaMan and terminal Neu5Acalpha2,6Gal/GalNAc, alpha/betaGalNAc, alphaGal, D-GlcNAc in the entire cytoplasm, glycans terminating with Galbeta1,3GalNAc and/or internal betaGlcNAc in the sub-nuclear cytoplasm.

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 beta-elimination reaction, N-Glycosidase F and sialidase digestion. Leydig cells expressed O-linked glycans with terminal alphaGalNAc (HPA reactivity) and N-glycans with terminal/internal alphaMan (Con A affinity). The basement membrane showed terminal Neu5Acalpha2,6Gal/GalNAc, Galbeta1,3GalNAc, alpha/betaGalNAc, and GlcNAc (SNA, PNA, HPA, SBA, GSA II reactivity) in O-linked oligosaccharides, terminal Galbeta1,4GlcNAc (RCA120 staining) and alphaMan in N-linked oligosaccharides; in addition, terminal Neu5acalpha2,3Galbeta1,4GlcNac, Forssman pentasaccharide, alphaGal, alphaL-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-Galbeta1,4GlcNAc, Neu5Ac-betaGalNAc as well as internal GlcNAc in O-linked glycans, alphaMan in N-linked glycoproteins and terminal Neu5Acalpha2,6Gal/ GalNAc in both O- and N-linked oligosaccharides. Spermatogonia exhibited cytoplasmic N-linked glycoproteins with alphaMan residues. The spermatocytes cytoplasm expressed terminal Neu5Acalpha2,3Galbeta1,4 GlcNAc and Galbeta1,3GalNAc in O-linked oligosaccharides, terminal Galbeta1,4GlcNAc and alpha/betaGalNAc in N-linked glycoconjugates. The Golgi region showed terminal Neu5Acalpha2,3Galbeta1,4GlcNac, Galbeta1,4GlcNAc, Forssman pentasaccharide, and alphaGalNAc in O-linked oligosaccharides, alphaMan and terminal betaGal in N-linked oligosaccharides. The acrosomes of Golgi-phase spermatids expressed terminal Galbeta1,3GalNAc, Galbeta1,4GlcNAc, Forssmann pentasaccharide, alpha/betaGalNAc, alphaGal and internal GlcNAc in O-linked oligosaccharides, terminal alpha/betaGalNAc, alphaGal and terminal/internal alphaMan in N-linked glycoproteins. The acrosomes of cap-phase spermatids lacked internal Forssman pentasaccharide and alphaGal, while having increased alpha/betaGalNAc. The acrosomes of elongated spermatids did not show terminal Galbeta1,3GalNAc, displayed terminal Galbeta1,4GlcNAc and alpha/betaGalNAc in N-glycans and Neu5Ac-Galbeta1,3GalNAc in O-linked oligosaccharides.