Oogenesis in the bluefin tuna, Thunnus thynnus L. A histological and histochemical study

Histology and histochemistry are useful tools to study reproductive mechanisms in fish and they have been applied in this study. In the bluefin tuna, Thunnus thynnus L., oocyte development can be divided into 4 principal phases based on the morphological features of developing oocytes and follicles. The primary growth phase includes oogonia and basophilic or previtellogenic oocytes classified as chromatin-nucleolus and perinucleolus stages. The secondary growth phase is represented by vitellogenic oocytes at early (lipid globule and yolk granule 1), mid (yolk granule 2) and late (yolk granule 3) vitellogenesis stages. The maturation phase involves postvitellogenic oocytes undergoing maturation process. During the spawning period, both postovulatory follicles, which indicate spawning, and atretic follicles can be distinguished in the ovary. Carbohydrates, lipids, proteins and specially those rich in tyrosine, tryptophan, cystine, arginine, lysine and cysteine, as well phospholipids and/or glycolipids and neutral glycoproteins were detected in yolk granules. Moreover, affinity for different lectins (ConA, WGA, DBA and UEA) was detected in vitellogenic oocytes (yolk granules, cortical alveoli, follicular layer and zona radiata), indicating the presence of glycoconjugates with different sugar residues (Mannose- Man- and/or Glucose -Glc-; N-acetyl-D-glucosamine- GlcNAc- and/or sialic acid- NANA-; N-acetyl-D-galactosamine- GalNAc-; LFucose -Fuc-). Histochemical techniques also demonstrated the presence of neutral lipids in globules (vacuoles in paraffin sections) and neutral and carboxylated mucosubstances in cortical alveoli. By using anti-vitellogenin (VTG) serum, immunohistochemical positive results were demonstrated in yolk granules, granular cytoplasm and follicular cells of vitellogenic oocytes. Calcium was also detected in yolk granules and weakly in follicular envelope. In females, the gonadosomatic index (GSI) increased progressively from May, during early vitellogenesis, until June during mid and late vitellogenesis, where the highest values were reached. Subsequently, throughout the maturation-spawning phases (July), GSI decreased progressively reaching the minimal values during recovering-resting period (October)

Histochemical aspects of the yol k-sac and digestive tract of larvae of the Senegal sole, Solea senegalensis (Kaup, 1858)

Histochemical distribution of glycoproteins, carbohydrates and proteins rich in different aminoacids were studied using histological and histochemical procedures, in Senegal sole, Solea senegalensis (Kaup, 1858) larvae from hatching until day 15. Glycogen, proteins and glycoproteins were detected in the yolk-sac of the larvae at hatching and during the yolk-resorption. The epithelia1 digestive system (brush border, enterocytes and goblet cells) contained neutral and acid mucins (carboxylated andlor sulphated). Glycogen was observed in the cytoplasm of the digestive absortive cells (enterocytes) and in the liver (hepatocytes) on day 3-4 posthatching. Protein reactions, and specially those that showed proteins rich in arginine, tyrosine and tryptophan, were very intense in the zymogen granules of the pancreatic cells. Oesophageal and intestinal goblet cells contained glucose N-acetyl and sialic acid residues, but the mucin content of these mucous cells did not show affinity towards Con-A, suggesting the absence of glycoproteins with Mannose andlor glucose residues. WGA showed a very intense positivity in the microvilli of the digestive epithelium of the larvae and positive granules for both lectins, specially for Con-A, were detected in the cytoplasm of the anterior intestinal enterocytes

Histochemical study of skin and gills of Senegal sole, Solea senegalensis larvae and adults

A battery of horseradish peroxidaseconjugated lectins (Con A, WGA and DBA), as well as conventional histochemical techniques (PAS, saponification, Alcian Blue pH 0.1, 1, 2.5, chlorhydric hydrolisis, neuraminidase, Bromophenol blue, Tioglycollate reduction and Ferric-ferricyanide-FeIII) were used to study the content and distribution of carbohydrates, proteins and glycoconjugate sugar residues on the skin and gills of Senegal sole, Solea senegalensis larvae and adults. During larval development of Solea senegalensis (from hatching until day 45 posthatching), epidermal sacciform, as well as branchial and epidermal chloride cells were unreactive with all cytochemical tests performed in this paper. Mucous or goblet cells of the corporal skin and gills containing strongly sulphated acid glycoproteins were evident on days 15-20 of larval development, as well as in epidermal and branchial mucous cells of adult specimens, which also contained GlcNAc andlor sialic acid. In adult specimen, the proteic content was higher in branchial mucous cells than in epidermal cells. In larvae, variable amounts of glycoproteins containing sialic acid, GlcNAc, GalNAc, Man andlor Glc residues were observed in epithelia1 cells and/or cuticle. GlcNAc andlor sialic acid sugar residues were only weakly detected in glycoproteins of some epidermal and branchial mucous cells of larvae by day 45, because from hatching until metamorphosis, lectin reactions (WGA, Con A and DBA) were negative in mucous cells

Histochemical study of lymphocystis disease in skin of gilthead seabream, Sparus aurata L.

A battery of horseradish peroxidasecorijugated lectiris (Con A, WGA arid DBA). as well as coriventional histochemical techniques (PAS. saponification, Alcian Blue pH 0.1 , 1. 2.5. chlorhydric hydrolisis. sialidasc, Bromophenol blue, Tioglycollate reduction and Ferric-ferricyanide-FeIlI) were used to study the coritent and distribution of carbohydrates, proteins and glycoconjugatc sugar residues on the skin and on the lymphocystis-infected cells of gilthead seabrcain, Spcrrus uurntcr. Variable ari-iounts of glycoproteins containing sialic acid, N-acetyl-Dglucosainine, N-acetyl-D-galactosarnine; mannose andlor glucose residues were observed in the cuticle and mucous cells of the c o r ~ o r a ls kin. tails and f ins . ~ ~ Germinative and epithelial cells of the epidermis contained glycogen. proteins. carboxylated groups, as well as glycoproteins with mannose andlor glucose and N-acetyl-U-galactosamine residues. Hyaline capsule of the mature lyniphocystis-infected cells was strongly stained with PAS, Alcian Blue (pH 0.5 and 2.5) and weakly positive with Alcian Blue (pH 1 ) . Con A reacted with the granular cytoplasm, specially around hyaline capsule. and with the basophilic intracytoplasinic inclusions developed in mature lymphocystis-infected cells of Spcrrrrs crlirntu skin. These sugar residues (niannose andlor glucose), as well as N-acetyl-Drrlucosamine andlor sialic acid and N-acetvl-D- L galactosamine were not detected in the hyaline capsule of the lyr.iphocysti5 disease