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Seasonal variations and reaction norms for vertebral number ( V) in response to incubation water temperature were estimated in adult and juvenile naturally spawning chum salmon Oncorhynchus keta. The mean V of adults varied according to spawning time; the early-spawning population had higher V values than the late-spawning population. Moreover, the mean V values in the early-spawning population decreased with seasonal changes, whereas V values in the late-spawning population remained stable. Chum salmon embryos in three full-sib families were incubated at five different temperatures until hatching, and the V values of the resulting juveniles were analyzed. The V reaction norm to incubation water temperature showed a V-shaped curve that was lowest at an intermediate temperature. The mean V at the same incubation temperature varied among the three families. These results suggest that V values in chum salmon are influenced by genetic components and incubation water temperatures. V may be a useful parameter for estimating the environmental conditions during ontogenesis and the genetic background by detecting population changes. [ABSTRACT FROM AUTHOR]

Abstract: This study examines seasonal changes in the activities of selected biomarkers in carp (Cyprinus carpio L.) from Karakaya Dam Lake and evaluates the influence of gender and environmental factors on those activities. Physicochemical characteristics of water were evaluated in the lakewater. Fish were sampled on seasonal basis, and liver ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase, glutathione reductase, plasma lactate dehydrogenase, aspartate and alanine aminotransferase, and brain acetylcholinesterase (AChE) activities were assayed. Plasma vitellogenin level and hepatosomatic index and condition factors were also determined. Strong seasonal variations were observed but there were no gender differences among selected markers. The highest vitellogenin level of male fish was detected as 606ng/mL which represents the estrogenicity of water in the lake in September 2005. In addition, the seasonal changes of some biomarkers such as EROD and AChE showed that the lake may be at risk of pollution by some xenobiotics arising from agricultural and/or industrial activities. [Copyright &y& Elsevier]

To examine whether metabolic compensation during seasonal acclimatization at the liver mitochondrial level is consistent with that at the whole-animal level, respiration rates of liver mitochondria and resting metabolic rates in winter- and summer- acclimatized southern catfish (Silurus meridionalis Chen) were measured. At 12.5, 17.5, 22.5, 27.5 and 32.5°C, the mean values of state 3 respiration rates were 12.21, 13.84, 18.96, 24.78 and 32.01 nmol O2 min-1 mg-1 mitochondrial protein in the winter group, and 8.56, 9.20, 17.32, 22.74 and 26.32 nmol O2 min-1 mg-1 in the summer group, respectively. At the five assay temperatures the resting metabolic rates were 24.86, 42.68, 61.59, 84.10 and 125.65 mg O2 h-1 kg-1 body mass in the winter group, and 22.89, 40.59, 52.94, 75.13 and 109.35 mg O2 h-1 kg-1 in the summer group, respectively. Total mitochondrial respiration rates in the liver organ were estimated based on state 3 respiration rates, mitochondrial protein content and organ mass, and the mean values were 72.96, 71.87, 112.47, 167.35 and 183.27 nmol O2 min-1 in the winter group, and were 47.89, 47.39, 105.67, 138.18 and 132.29 nmol O2 min-1 in the summer group, respectively. Metabolic compensation caused by seasonal acclimatization occurred at the liver mitochondrial level and compensation at the liver organ level was found to be more efficient because of an increase in metabolic capacity of mitochondria and a boost in organ mass. Metabolic compensation at the whole-animal level was not detected. During seasonal acclimatization, the effect of metabolic compensation at liver mitochondrial level is inconsistent with that at the whole-animal level in the southern catfish. This may be due to different degrees of regulation of metabolic mechanisms among various tissues and organs in an acclimatized organism [Current Zoology 57 (1): 109-115, 2011]. [ABSTRACT FROM AUTHOR]

Abstract: Nitric oxide (NO) is a well-recognized versatile signaling molecule. It is produced by catalytic action of nitric oxide synthase (NOS) on L-arginine in a variety of animal tissues. Existence of different isoforms of NOS has been shown in mammalian testis, but report on their presence in the testis of ectothermic vertebrates is non-existent. This study demonstrates the differential expressions of two isoforms of nitric oxide synthase (neuronal-nNOS and inducible-iNOS) like molecules in different cell types in the testis of seasonally breeding catfish, Clarias batrachus through immunohistochemistry. Positive immunoprecipitation of nNOS and iNOS like molecules were detected in germ cells as well as interstitial cells only in the recrudescing and fully mature fish. The immunoreactions differed in intensity and varied with changing reproductive status. Treatment of adult male fish with NO donor, sodium nitroprusside, and a NOS inhibitor, N-nitro-L-arginine methyl ester (L-NAME) increased and decreased the total nitrate and nitrite concentration in the testis, respectively. Sodium nitroprusside and L-NAME also induced simultaneous decline and rise in the testicular testosterone level, respectively. These findings, thus, suggest that NOS isoforms are expressed variedly in different cell types in the testis of reproductively active fish. This investigation also suggests that NO inhibits testosterone production in the testis. [Copyright &y& Elsevier]

Abstract: In the present study, tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine synthesis) activity was demonstrated in the ovary of the catfish to elucidate the possible physiological role of catecholamines in the gonad. The ovary is innervated by seven pairs of nerves, originating from the paired sympathetic chain lying dorsal to the posterior kidney. Ovarian TH activity showed a significant annual variation (P <0.001, one-way ANOVA), correlating with gonado-somatic index. Activity was low from December to February (resting phase), increased from March to July (recrudescent phase) and then decreased in post-spawning phase (August–November). The annual pattern was similar to that of the brain. An intraperitoneal injection of 100IU hCG/fish induced significant periovulatory changes in TH activity with the peak rise at 16h, and the activity decreased after egg-stripping (P <0.001, one-way ANOVA). Brain TH activity showed similar periovulatory changes. The results suggest that catecholamine synthesis is increased during both ovarian recrudescence and spawning of the annual reproductive cycle, implying a functional role in ovarian growth, maturation and ovulation. [Copyright &y& Elsevier]

Abstract: PPAR isotypes have been previously identified in the teleost brown trout (Salmo trutta f. fario) and their organ distribution pattern established. Being that the liver is a vital metabolic organ presenting expression of all isotypes and also knowing that estrogens/estrogen receptors seem to interact with PPARs, we hypothesized that the latter may very well change seasonally. So, we studied the expression of these receptors in the liver, along the annual reproductive cycle and in both genders. According to real-time RT-PCR, PPARα mRNA expression in females was significantly higher in May and lower in September than in other seasons. No significant variation was observed along the year in males. A significant difference between genders occurred in May, when PPARα expression was higher for females. PPARβ expression showed little variation along the reproductive cycle in females, but in males it was significantly higher in December than in the other seasons. No significant differences existed between genders. PPARγ was more expressed in February than in September and December, for females. As to males, it was more expressed in February than in all other seasons. No significant differences were observed between genders. The study proved our hypothesis that PPARs gene expression varies along the year. Moreover, PPARα expression in females followed the same annual variation pattern as peroxisome volumes and enzyme activities, and an inverse pattern relatively to the salmonid type annual plasma estradiol levels. The data agrees with the idea that PPARα is under estradiol modulation and that cross-talk between this receptor and the estrogen receptor possibly exists. [Copyright &y& Elsevier]

We measured the δ15N of particulate organic matter (POM), Daphnia pulex (D), Holopedium gibberum (H), Leptodiaptomus tyrelli (LT), Epischura nevadensis (E), and Chaoborus trivittatus (C) over an annual cycle in Council Lake, a pristine, oligotrophic, fishless lake. Annual averages of the δ15N of plankton (C, LT, E > D, H > POM) matched expected differences in trophic position, but seasonal patterns differed among species. During midsummer, the δ15N of D, H, and LT increased above the δ15N of E and C, despite little temporal or spatial variation in the δ15N of POM (<41 µm). Larger size fractions of POM (41–200 µm) helped explain some of the temporal variability of zooplankton δ15N. Body size of zooplankton was correlated with δ15N for D, C, and E, which could indicate size-based, trophic-level variation; selective feeding; or physiological differences in 15N enrichment. We propose that detailed time series of δ15N for multiple zooplankton species can help determine the seasonal variability of trophic structure in zooplankton assemblages. [ABSTRACT FROM AUTHOR]