Gonadal histology and plasma sex steroid concentrations in maturing and mature spring migrants of Caspian lamprey Caspiomyzon wagneri in the Shirud River, southern Caspian Sea, Iran

The role of temperature and daytime as indicators for the spawning migration of the Caspian lamprey Caspiomyzon wagneri Kessler, 1870

“…Lampreys often cannot travel upstream of the bridge unless there is low discharge of water, thus this bridge base as an obstacle and a high water discharge can delay their upstream migration. Spending time in freshwater and at warmer temperatures has been associated with sexual maturation in Pacific lamprey ( Entosphenus tridentatus ; Clemens et al., ) and Caspian lamprey (Farrokhnejad et al., ). As we observed, until partway through the migration season, none of the Caspian lampreys passed the bridge.…”

“…Total length (1 mm), total mass (0/1 g) and sex of each lamprey was recorded. Sex determination of the migrating fish was done by identification of external secondary sex characteristics (males with well‐developed urogenital papillae and females with obvious eggs in the abdominal cavity and/or swollen base of second dorsal fin and a crescent‐shaped extra ‘anal fin’ (Farrokhnejad et al., ). After careful examination of their bodies for general health, the lampreys were returned to the river above the Shirud bridge.…”

“…Recent studies suggest that Caspian lamprey abundance has declined steadily, thus this species is classified as ‘near threatened’ on the IUCN Red List (IUCN, ; Kiabi et al., ; Farrokhnejad et al., ). Habitat loss, river obstacles, dredging and sand removal from the riverbeds, sea conditions, excessive fishing in some places as well as water pollution have all probably contributed to the decline.…”

Gonadal Development and Associated Changes in Estradiol, Thyroid Hormones, and Sex-Related Genes During Different Growth Stages in Cultured Female Rainbow Trout (Oncorhynchus Mykiss) in Yunnan

“…In teleost, it is well known that the hypothalamic-pituitary-gonadal (HPG) axis regulates the vitellogenesis and the nal oocyte maturation during individual growing that mediate gonadotropic hormones (GtHs) actions via steroids secreted by the follicular cells surrounding the oocyte [5]. Correlation between changes in levels of sexual steroids (testosterone and 17β-estradiol (E 2 )) and oocyte development have been well documented in sh [6][7][8]. Moreover, studies showed that the hypothalamus-pituitary-thyroid (HPT) axis is also involved in gonad development [9].…”

Use of sex steroid profiles and hematological indices to identify perinucleolus and migratory gonadal stages of captive Siberian sturgeon Acipenser baerii (Brandt, 1869) females

“…Hence, analysis of blood signs is considered to be a valuable guide in sturgeon aquaculture in assessing the biological status (Asadi et al., ; Sepúlveda et al., ). Regarding the relationship in fish between sex steroids and hematological factors with the maturation stage (Farrokhnejad et al., ), a few studies present data on hematological factors and broodstock quality in sturgeon species (Falahatkar et al., ; Barannikova et al., ; Semenkova et al., ; Matsche and Gibbons, ). As sturgeon broodstock in different stages of maturation deal with various physiological factors, the present study was designed to: (i) characterize relationships between the reproductive stage of female fish and serum steroids, and (ii) determine whether sex steroids and hematological indices differ among females in the perinucleolus and migratory stages.…”