Iranian Journal of Fisheries Sciences
Volume:6 Issue: 2, Jan 2007

Apoptosis is a programmed cell death that has been attributed to theaction of stress hormones, such as cortisol. We investigated the in vitro effect ofcortisol in goldfish (Carassius auratus) mature (GSI: 2٫75-4٫65) or immature (GSI: 1٫94-2٫4) testes. Testes were taken out and transferred into culture medium (M 199), cut into 20μm thick slices and supplemented with fetal bovine serum (FBS), addeddifferent doses of cortisol (0, 50, 100, 200, 400, 750 and 800 ng/ml) and incubatedfor 24h, 48h or 72h at 18°C. Samples were rinsed and homogenized with phosphatebuffered saline (PBS) after incubation period. Duplicates or triplicates processed forcaspase-3 activity. The results showed a significant increase in caspase-3 activity inimmature testes after 72h treatment with 750ng/ml of cortisol (P<0٫05), and also at400ng/ml (P<0٫05). In contrast, no significant differences were observed betweennon-treated and cortisol-treated samples from mature goldfish testes. In this studywe have demonstrated, for the first time that the stress hormone cortisol inducesapoptosis in the goldfish testis in a stage-specific manner (immature testis).

The salinity tolerance and hydromineral regulation capabilities of juvenilegreat sturgeon, Huso huso, of different age and size groups (I: 35days, BW: 0٫60±0٫02g &TL: 4٫80±0٫13cm; II: 35 days, BW: 2٫23±0٫20g & TL: 7٫19±0٫17cm; III: 35days, BW: 9٫91±0٫23g & TL: 11٫86±0٫24cm; IV: 50 days, BW: 3٫97±0٫25g & TL: 9٫34±0٫18cm; V: 50 days, BW: 22٫27±1٫9g & TL: 17٫25±0٫35cm; VI: 65 days, BW: 6٫3±0٫67g & TL: 11٫1±0٫37cm; n = 90 for each group) in freshwater (FW: 0٫5‰), estuary water (EW: 9٫5 ‰) and the Caspian Sea water (CSW: 12٫5‰) wereinvestigated. The fishes are directly transferred from FW to EW and CSW. Thepossible repercussions of osmoregulatory processes on some indicators of classicalwere examined at the end of 168 hours fish acclimation. Mortality was observed (higher than 50٪ after 72 hours) only in Ist group in EW and CSW. Somehaematological parameters, namely haematocrit (Hct), red and white blood cellscount (RBC, WBC), mean cell volume (MCV), haemoglobin concentration (Hb), mean cell haemoglobin concentration (MCHC), the amount of haemoglobin pererythrocyte (MCH), levels of cortisol, osmolarity and ion concentration (Na+, K+, ∗ Corresponding author 16 S. M. Farabi et al., Ca+2 and Mg+2) in the plasma were determined. The functional levels of the mechanism of osmotic and ionic homeostasis were similar in different groups (II to VI) but differed in experimental media (P<0٫05). Significant differences were observed between the levels of serum Na+ concentration in different groups in EW and CSW media (p<0٫05). Serum Na+ and Ca+2 concentrations were higher than those of FW and EW media, but lower than in CSW media. The Hct, MCV and MCH decreased with increase in fish age, and decreased from FW media to CSWmedia with increasing salinity; RBC, WBC and MCHC did not change. The trend ofincreasing levels of cortisol were observed at higher salinity in each group (P<0٫05). However, Hct, MCV, MCHC, cortisol, osmolarity and ion concentration values didnot return to initial values (P<0٫05), showing that osmoregulatory processes causedmajor physiological changes in this species.

The impact of two principal parasitic digenetic trematodes, Meiogymnophallus minutus and Himasthla spp., on the growth (weight and length) of the cockle, Cerastoderma edule, in Arcachon Bay (France) was studied. The experiment was conducted in the land-based mesocosms. The velocity of infestation with both trematodes was far more rapid during summer in the cockles already parasitized with these trematodes (0٫35 to 0٫45 metacercariae day-1) than those of healthy ones (approximately 0٫01 metacercariae day-1). The parasitism had also an effect on the growth rates of cockles. During 190 days of the experiment, the daily growth speed varied from 0٫001mm. day-1 to 0٫021mm. day-1. On average, the growth was slightly more important in healthy cockles after the start of experiments (0٫014mm. day-1) than those initially infested cockles (0٫011mm. day-1). Theexperiment also showed that infestation of hosts with trematodes could perhapsdisturb their immunity system, as the intensification with trematode parasites hadbeen favored by already infested cockles.

The efficiency of different types of traps for catching of the Caspian Seacrayfish, Astacus leptodactylus eichwaldi, was investigated from Mar. 2002 to Feb. 2003. Totally 56 traps of four most commonly used types, “Rectangular trap”, “Round trap”, “Opera house trap” in two colors of “black” and “blue”, and “Fathoms plus” only in black were installed in depths of 35, 45, 55 and 65 metersalong two transects in Anzali coastal area. The results revealed no significant differences (P≥0٫05) in the average length, weight and sex ratio among the crayfish in different months and applied traps. However, significant differences (P<0٫05) in CPUE of different traps in variousmonths of the study year were observed. Mean annual of CPUE in Opera housetraps “blue” was the greatest (5٫09±0٫29) and the lowest was found in “Fathomsplus” traps (0٫28±0٫05). In general, all blue color traps performed better catch thanthe black ones.

A sex steroid-binding protein (SBP) that binds to 17β-estradiol with highaffinity and moderate capacity was identified in the plasma of female and juvenile ofkutum (Rutilus frisii kutum) sampled during the early stage of gonadal maturation inOctober and prior to spawning in March. Mean maximum specific binding (Bmax) and equilibrium dissociation constant (Kd) of the fish were as follows: In early stage of gonadal development (October), Bmax =5800±970fmol E2/mg protein, Kd 4٫1±0٫6nM, and prior to spawning (March) Bmax =4000±895fmol E2/mg protein, Kd 2٫9±0٫3nM. In juvenile sampled in October Bmax =1600±130fmol E2/mg protein, Kd 2٫1±0٫2nM and in March samples Bmax = 3500±780fmol E2/mg protein, Kd 2٫2±0٫2nM. Plasma estradiol binding characteristics ofthe adult samples in October and March differed from the juvenile samples in havingboth Bmax and Kd significantly higher than juveniles. Plasma SBP levels displayed amoderate correlation with GSI (r2 = 0٫52) and CF (r2 = 0٫51) and a weak correlationwith HSI (r2 = 0٫28). Affinity was moderately correlated with CF (r2 = 0٫68) andHIS (r2 = 0٫50). A strong correlation was obtained between Bmax and Kd, high Bmaxvalues coincided with high Kd values and vice versa.

The experiments with Beroe ovata showed that this ctenophore cansurvive and reproduce in the Caspian Sea water, though at far lower rate than in theBlack Sea; larval growth in the Caspian Sea water was also slower and mortalityhigher. Maximum fecundity of 2210 and 240 eggs recorded in laboratories ofTurkey and Iran, respectively. About 34 to 100٪ of eggs in the Caspian Sea watercould not develop and hatch. Larvae were at different stages of development, usuallywith size between 1٫2 to 2mm. The highest number of eggs and larvae were obtainedin tanks where Beroe individuals were together with Mnemiopsis leidyi. The poorreproduction of B. ovata in the Caspian Sea water could be due to both theacclimation stress to low salinity and possible damage of individuals during thetransportation.

The effectiveness of two kinds of dopamine antagonist (DA), metoclopramide (Met) and domperidone (Dom) combined with the gonadotropinreleasing hormone analogue (D-Ala6, Des Gly10 ethylamide) GnRHa was assayed onthe ovulation success, latency period, ovulation index (OI) and fertilization successof kutum, Rutilus frisii kutum (Kamenskii, 1901). Broodfish were injected intraperitoneallyas follows: 2 mg/kg b. w. of carp pituitary extract (CPE) as a control, 5μg + 2٫5mg, 10μg + 5mg and 20μg + 10mg/kg b. w. of GnRHa + Met or Dom in asingle injection. Based on the ovulation and fertilization success, no significant differencesbetween similar doses of Dom and Met when combined with similar doses ofGnRHa were found (P>0. 05). However, in some groups, the OI and latency periodwere greater when Dom was used as a DA instead of Met (P<0. 05). In general, theresults of this study showed that the potency of Dom was nearly same as Met whencombined with GnRHa and used as a DA in kutum. It is strongly recommended torepeat the experiment under different conditions to find out definite conclusion.

Ensiling as one of the best methods for utilization of tuna wastes wasinvestigated. docosahexaenoic acid [DHA C22: 6 (n-3)]- rich products were obtainedfrom the wastes (viscera and dark meat) of four tuna species, namely longtail, skipjack, yellowfin and kawakawa by a procedure involving ensiling in organicacids followed by neutralization. Identification of fatty acids in the samples wasperformed by comparison with chromatograms of fatty acids standard. Total lipid content of silages varied from 10٫41٪ in skipjack dark meat silage to22٫01٪ in kawakawa viscera silage, but all lipids contained high percentages ofDHA and EPA [eicosapanteoneic acid C20: 5 (n-3)]. The highest DHA ratio (15٪ oftotal lipids) was found in the lipid of skipjack viscera silage and the highest ratio ofEPA (11٪ of total lipids) belonged to the lipids of kawakawa dark meat silage. ANOVA test results indicated that DHA ratio was significantly high before silagepreparation and linolenic acid [C18: 3 (n-3)] content significantly differed betweenthe species (P<0٫05).

Some reproduction characteristics of keeled mullet, Liza klunzingeri, were studied during Apr. 2003 to Feb. 2004 in Khuzestan waters of the Persian Gulf. A total of 836 samples were monthly collected from two fish landings of Bahrekanand Hendijan; 727 specimens were studied from point of sex determination, and 60specimens were studied from the fecundity point of view. This species was found tohave more abundance in autumn (esp. Oct-Nov). The samples composed of89 (12٫2٪) male, 467 (64٫2٪) female and 171 (23٫6٪) immature; the sex ratio wasM: F = 1: 5. The advanced stages of maturity (4th & 5th) were found in Octoberonward. The highest Gonadosomatic Index was in December and the lowest was inJune. The maximum absolute and relative fecundities were 183040 and 2232, respectively; the minimum absolute and relative fecundities were 44700 and 582, respectively. The minimum and maximum egg diameter was 0٫04mm (stage 2nd) and0٫75mm (stage 6th).