The spermatozoa of seven fishes belonging to Cyprinid family are examined. They have no acrosome, like all Teleost fishes, a spheroidal or slightly elliptic nucleus, always eccentrically placed on the tail, two variously oriented centrioles, and a postnuclear cytoplasmic region of various size that contains some mitochondria (2 to 10) and surrounds a periaxonemal postnuclear canal. The tail is of modcrate length (from 36 to 60 pm) and contains a "9 + 2" axoneme: both dynein arms are present. Comparative examination of the spermatozoa in the seven species shows that significant differences occur among them, even when they belong to the same genus. These concern the tail length; the position of the centrioles, the proximal with respect to the central one and with respect to the nucleus; the number of mitochondria, which is in relationship to the depth of the postnuclear canal. In the uniform general pattern of the ultrastructure of the Cyprinid spermatozoa, each species is characterized by a particular organization of the sperm organelles; in this respect, the two species examined by us, Leuciscus cephalus and souffia, are more closely related, even if easily recognizable one from the other. From a phylogenetic point of view, the comparative spermatology of the Cyprinid fishes suggests that the mitochondria1 number is a good character, which enables us to order them in a phylogenetic arrangement.

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Two bacterial strains Lactobacillus fructivorans (AS17B), isolated from adult seabream (Sparus aurata L.) gut, and Lactobacillus plantarum (906), isolated from human faeces, were administered contemporaneously during seabream development using Brachionus plicatilis and/or Artemia salina and dry feed as vectors. Experimental group A received the probiotic strains already via rotifers from day 5 post-hatch (ph), whereas treatment of group B began with Artemia feeding from day 27 ph. Fish were sampled at day 28 ph (group A and control) and day 99 ph (groups A, B and control) for electron microscopy, histology and immunohistochemistry with the polyclonal antiserum ORa against homologous serum Ig and the mAb G7 specific for seabream acidophilic granulocytes. In all groups, timing and pattern of differentiation of the digestive tract did not differ. Furthermore, neither tissue damage nor manifest inflammation was provoked by probiotic administration. At day 28 ph, the developing GALT already housed mucosal leucocytes, including Ig(+) cells but no acidophilic granulocytes. No differences were seen between experimental groups. At day 99 ph, the density of Ig(+) cells (+51%) and acidophilic granulocytes (+284%) was significantly higher (p<0.05) in group A than in controls. Also group B had a higher density of Ig(+) cells (+17%) and acidophilic granulocytes (+130%) compared with controls, although less pronounced. Light and electron microscopy observations detailed the occurrence of heterogeneous populations of lymphocytes and granulocytes in the developing intestinal mucosa, and highlighted the net expansion of G7(+) acidophilic granulocytes (A +536%, B +292% vs. control) due to probiotic administration. Evidence is provided that early feeding with probiotic-supplemented diet increased the number of Ig(+) cells and acidophilic granulocytes in seabream gut and that the effects were more pronounced when administration started during gut metamorphosis. These results point to a stimulatory effect of probiotics on the gut immune system that correlates with improvement of fry survival.

The morphological organization of the male brood pouch skin of three different species of syngnathids (Nerophis ophidion, Syngnathus abaster and Hippocampus hippocampus), investigated using light and electron microscopy, showed that each pouch had a skin with a different ultrastructure. This reflected different relationships between the paternal body and the developing embryos. In N. ophidion, the bilayered epidermis of the pouch consisted mainly of pavement cells (filament-containing cells) typical of fish skin. In S. abaster, pavement cells were interspersed with many mitochondria-rich cells. These cells varied in number during the different functional stages of the pouch and died by apoptosis after the breeding period. Modified secretory ' flame cone cells ' rich in vesicles and granules characterized the epidermis of H. hippocampus. Although there were specific differences, the vascularized dermis was the only feature common to all three types of pouch. These findings suggest that the brood pouch in Syngnathidae has different functions, which may be related to the different reproductive strategies and ecology of each species.

ZAM is an env-containing member of the gypsy family of retrotransposons that represents a possible retrovirus of invertebrates. In this paper, we traced ZAM mobilization to get information about a potential path a retroelement may take to reach the germ line of its host. In situ hybridization on whole-mount tissues and immunocytochemistry analyses with antibodies raised against ZAM Gag and Env proteins have shown that all components necessary to assemble ZAM viral particles, i.e., ZAM full-length RNAs and Gag and Env polypeptides, are coexpressed in a small set of follicle cells surrounding the oocyte. By electron microscopy, we have shown that ZAM viral particles are indeed detected in this somatic lineage of cells, which they leave and enter the closely apposed oocyte. Our data provide evidence that the vesicular traffic and yolk granules in the process of vitellogenesis play an important role in ZAM transfer to the oocyte. Our data support the possibility that vitellogenin transfer to the oocyte may help a retroelement pass to the germ line with no need of its envelope product.ZAM is a 8.4-kb retroelement that resides within the genome of Drosophila melanogaster (11). On the basis of sequence similarity and gene organization, ZAM is a member of a group of retrotransposons that bears a striking resemblance to the vertebrate retroviruses. These elements are flanked by long terminal repeats (LTRs) that direct the transcription of fulllength RNAs representing potential templates for reverse transcription during mobilization. The LTRs flank three open reading frames (ORFs) analogous in position and coding potential to the retroviral gag, pol, and env genes ( Fig. 1). Among the diverse classes of eukaryotic retrotransposons, the presence of a third env-like ORF (ORF3) is unique to ZAM and a small group of other members of this family, including gypsy, 297, 17.6, Idefix, and nomad in D. melanogaster (3,8,14,19,26), tom in Drosophila ananassae (25), Osvaldo in Drosophila buzzatii (15), TED in the lepidopteran Trichoplusia ni (5), and Yoyo in the medfly Ceratitis capitata (28). An envelope protein expressed in vivo has been identified for only three of these elements (gypsy, tom, and TED) (16,21,24,25), and only one of them, gypsy, has been shown to date to have infectious properties (9,22). Although retroviral Env proteins are known to be involved in viral infectivity through host cell receptor recognition and fusion of viral and cellular membranes, the role of the Env glycoproteins encoded by these elements is still unclear since no budding has ever been visualized for any of them.ZAM was first identified as a spontaneous insertion at the white locus, giving rise to the w IR6RevI allele in a line of D. melanogaster subsequently called RevI (11). This mutation occurred in the course of a massive amplification of ZAM elements in this line due to their mobilization, which remains active in this stock of flies (3). The existence of RevI and its parental line, w IR6 , which displays a low copy number of stable ZAM elemen...

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Eggs, larvae, post-larvae and sexually immature juveniles of the teleost Dicentrarchus labrax (L.) were assayed for the expression of genes encoding the T cell receptor beta and CD8alpha. RT-PCR of RNA extracted from larvae revealed TCRbeta transcripts from day 25 post-hatching (ph) and CD8alpha transcripts from 26 days later. At day 51 ph, CD8alpha and TCRbeta mRNAs were localised by in situ hybridisation in thymocytes of the outer and lateral zones of the thymic paired glands. From day 75 ph onwards the signal was mainly detected in the outer region, drawing a cortex-medulla demarcation. In 1-year-old fish, CD8alpha+ and TCRbeta+ thymocytes almost filled the cortex and extended in large cords in the medulla. A CD8alpha(-)TCRbeta+ subcapsular lymphoid zone was evident near the septa coming from the inner connective capsule that delimited the thymus. The localisation of CD8alpha and TCRbeta transcripts demonstrated a compartmentalisation of the juvenile thymus due to distinct localisation of thymocytes at different developmental stages.