The toxicity, absorption and excretion of rotenone in oysters (Ostrea edulis), and its degradation in seawater at temperatures near 0°C

A rapid extraction procedure and a HPLC method for quantitative measurements of the concentration of rotenone in oysters (Ostrea edulis) and in seawater is presented. The absorption rate of rotenone by oysters was rapid. With an average rotenone concentration in the seawater of 26 ppb, the concentration in the oysters reached 4.6 ppm after 4 days of exposure. The t_1/2 of the excretion of rotenone was 40 h at 10°C. The absorption rate was highly affected by both the rotenone concentration in the seawater and the seawater temperature. Rotenone was quite stable in seawater at low temperatures. At an average temperature close to 0°C, 18% of the rotenone added was still present 45 days after preparing the solution (1 ppm Gullviks rotenone mixture) in seawater. The acute mortality observed was closely related to the measured concentration of rotenone in the oysters.     

Do extracellular products of Aeromonas salmonicida induce thrombosis by entering the fish coagulation system at factor X?

Abstract. Thrombosis of minute vessels is a common feature of acute furunculosis in Atlantic salmon. Crude extracellular products (F.CP) of Aeromans, salmonicida injected into the dorsal aorta of cannulated fish elicited an activation of the coagulations systems of the fish When screened with a number of chromogenic substrates, the ECP protease revealed a factor-X like activity. Thus, it may he hypothesized that the ECP induces thrombosis by entering the fish coagulation systems at factor X. and that thrombus formation is a way of creating a site of infection.     

The GnRH systems in the brain and pituitary of normal and hCG treated European silver eels

The distribution of immunoreactive GnRH was studied in the brain and pituitary gland of normal and human chorionic gonadotrophin (hCG) injected silver eels. It was found that the general organization of GnRH systems in this species is similar to that reported in other teleosts. Cell bodies were present in the olfactory bulbs, ventral telencephalon, periventricular hypothalamus and dorsal tegmentum. No positive perikarya could be detected in the preoptic region. Only scarce fibers were observed in the proximal neurohypophysis. Treatment with hCG does not modify the distribution of GnRH but it increases the density of positive structures, in particular at the level of the pituitary. The results are discussed in relation with the present status of knowledge of the mechanisms underlying the blockage of sexual maturation in the European eel at the silver stage.     

Intestinal histological alterations in farmed red-bellied pacu Piaractus brachypomus (Characiformes: Serrasalmidae) heavily infected by roundworms

The farmed red-bellied pacu Piaractus brachypomus is a valuative commercial fish widely exploited in fish farming. Histopathologic alterations in small intestine of this fish were associated with heavy roundworms infection. Of a total of thirty-five fish examined, all were parasitized with a prevalence of 100%, intensity of 290–6403, and mean intensity of infection of 4467.5 parasites per fish. According to the morphological features of whole nematodes examined using light and electronic microscopy, the parasite was identified as Rondonia rondoni Travassos. Rev Vet e Zoot 10, 59–70; 1920. The fish intestinal tissue alterations include fusion of villi, edema, disorganization of epithelial cells, epithelial abrasion, and flaking of the villus at mucosa layer level and submucosa layer with some regions of necrosis and lymphocyte infiltrate. This is the first report of histopathological alterations caused by infection of the atractid nematode R. rondoni in a farmed population of P. brachypomus in the Peruvian Amazon. The study points out the need of improving the strategies of parasitic prevention and control in order to better prevent future disease outbreaks.

     

In vitro steroidogenesis by gonads of the Russian sturgeon, Acipenser gueldenstaedti Brandt

Ovaries and testes from the Russian sturgeon at different stages of sexual maturity were incubated with ;sup3;H-androstenedione or ³H-pregnenolone. The major metabolites of androstenedione in both sexes were testosterone and 5- and 5ß-androstanediols, but no evidence was found for the gonadal production of 11-oxygenated androgens. Pregnenolone was converted to 17-hydroxyprogesterone, androstenedione and testosterone together with reduced metabolites. 11-Oxygenated androgens were found in female serum by gas chromatography-mass spectrometry (GC-MS), in serum of both sexes by radioimmunoassay (RIA), and was detectable by RIA in interrenal but not gonadal tissue. The results suggest that sturgeon may differ from teleosts in that 11-oxygenation may take place in extragonadal tissues.     

Ion levels in the gastrointestinal tract content and plasma of four teleosts with different feeding habits

The levels of various ions (Na⁺, Cl⁻, Ca²⁺, Mg²⁺, K⁺) in the fluid phase of the gastrointestinal contents and of the plasma were determined in four teleosts with different feeding habits: traira (Hoplias malabaricus), hassar (Hoplosternum littorale), silver catfish (Rhamdia quelen), and grass carp (Ctenopharyngodon idella). The results showed that most ionic levels in the fluid phase of the gastrointestinal tract seem to be affected by feeding habit and that these levels can be different from those found in the plasma. In practical terms, these results suggest that ionic levels of the gastrointestinal contents should be considered when preparing solutions for studies of intestinal absorption in fishes.     

Live microbial feed supplement in aquaculture for improvement of stress tolerance

Two bacterial strains, Lactobacillus fructivorans, isolated from sea bream (Sparus aurata) gut, and Lactobacillus plantarum, isolated from human faeces, were administered simultaneously, during sea bream development, using Brachionus plicatilis and/or Artemia salina as vectors. The probiotic treatment significantly affected gut colonization. To test the probiotic influence on stress responsiveness, sea bream fry, 47 days post-hatching (p.h.), were subjected to pH stress (from 8.6 to 6.3) and cumulative mortality, cortisol levels and HSP70 gene expression were analysed. Cortisol was selected, since under stress conditions its level increases. HSP70 was selected with consideration of its wide involvement in response to a great number of injuries, and because it protects cells probably by binding and refolding damaged proteins. The results obtained indicated that the administration of probiotic to sea bream fry induced higher HSP70 levels, indicating a greater potentiality to respond to the harmful conditions possibly present in fish farms. This hypothesis is supported by the fact that the levels of cortisol found were significantly lower (P < 0.05) in both groups under probiotic treatment. When pH was used as a stressor, it induced a higher cumulative mortality in the control; the mortality was found to be significantly lower in both treated groups. Interestingly, a significant increase (P < 0.05) in HSP70 gene expression was observed in all stressed groups. These results suggest an improvement in tolerance to acute stress of fry fed with probiotics.     

Artificial insemination in tench, Tinca tinca L.

Abstract. The sperm of tench, Tinca tinca L., is characterized by a milky colour and consistency, and is of very low density. After collecting the sperm, motion of spermatozoa was recorded even without water activation. A better motility value (value 4·36 on average) was observed in spermatozoa collected in immobilizing solution (collecting medium) and stored for 3h, when compared with spermatozoa without collecting medium. Average total and relative numbers of spermatozoa were 12·16 × 10⁹ per male and 18·50 × 10⁹ per kg of body weight, respectively. When testing the effect of activating solution in artificial propagation of tench, the highest fertilization rates (81·3 and 85% in two cases) were found for NaCl solution with an osmotic concentration of 34 or 69 mOsmol and for fresh water, respectively. The fertility rate was reduced significantly ( P < 0·01) by any increase above 105 mOsmol in NaCl concentration in the activating solution. In the tests of optimal method of artificial fertilization, the highest hatching rate of sac fry (71·35%) was found in sperm collected into immobilizing solution. The application of immobilizing solution significantly increased the number of sac fry at the levels P < 0·1 and P < 0·01, if compared with intact sperm stored for 3 h and fresh sperm, respectively.     

Water temperature regimes affect cataract development in smolting Atlantic salmon, Salmo salar L.

The effect of fluctuation in water temperature during the freshwater rearing stage on cataract development in Atlantic salmon was investigated. Presmolts were exposed to either constant low or high temperatures, or high temperature with cold-water fluctuations. Temperature fluctuations caused the fastest growth rate and most severe cataracts, whilst low temperature resulted in slow growth and minor cataracts. The fish were then individually marked and maintained together in a seawater net pen for 7 months. Cataract progressed in all groups, fish from the low temperature group showed the fastest subsequent growth, and developed cataracts to the same degree as fish from the other groups. There were no statistically significant differences in selenium-dependent glutathione peroxidase levels in pooled samples of aqueous humour, lens and plasma from fish with or without cataract, except from the last freshwater samples, where cataractous fish showed lower plasma activity. Plasma cortisol and glucose levels did not differ, nor did whole eye riboflavin levels. Higher concentrations of some free amino acids in whole eyes were found in fish with cataract. This study shows that fluctuation in water temperature may cause both increased growth rate and cataract development in Atlantic salmon and that cataract development initiated in the freshwater rearing phase continues after transfers to seawater.