Gender Identification in Great Sturgeon (Huso huso) Using Morphology, Sex Steroids, Histology and Endoscopy

Comparative study on accuracy of mucosal estradiol-17β, testosterone and 11-ketotestosterone, for maturity, and cutaneous vitellogenin gene expression in goldfish (Carassius auratus)

Providing a non-invasive procedure to track fish maturity remains a priority in broodstocks' management. In the present study, the main goal was to assess reproduction status by measuring sex steroids and vitellogenin (VTG) in the skin mucosa, as a non-invasive method. For this purpose, the present study compared the levels of estradiol-17β (E₂ ), testosterone (T), 11-ketotestosterone (11-KT), VTG and calcium (Ca) in skin mucosa and blood plasma of goldfish (Carassius auratus). Skin mucosal and blood samples were collected, as well as gonad tissues, from goldfish, as a seasonal spawner. Histological analysis confirmed the gender and maturity status from females' ovaries (as primary-growth, cortical-alveoli, initial and late-vitellogenesis) and males' testes (as spermatogenesis and spermiation). Furthermore, vitellogenin (vtg) expression was observed in skin, liver and gonads. The results indicate that mucosal E₂ concentrations were significantly higher during initial and late vitellogenesis than the other stages. Mucosal 11-KT concentrations significantly increased at spermiation (P < 0.05). E₂ /T and 11-KT/E₂ ratios significantly increased at early vitellogenesis and spermatogenesis, respectively (P < 0.05). Females' mucosal VTG levels were significantly fluctuated according to the maturity stage. Ca showed a similar trend, but Ca was more accurate for sex identification than the VTG. Although mucus showed high levels of VTG, ovarian vtg expression was strongest while liver and skin had the similar results. These results show that measuring the mucosal androgens could be considered as an accurate, non-invasive method to monitor fish maturity.

Sex identification of the ornamental amazon fish Astronotus ocellatus by videoceloscopy and gonadal biopsy

This study was conducted to evaluate and validate the efficacy and safety of videoceloscopy and gonadal biopsy as sexing methods for the A. ocellatus. A total of 31 adult individuals were used. Florfenicol (50 mg/kg) and morphine (5 mg/kg) were administered intramuscularly during the pre-surgical period. Animals were maintained in a supine position preceding a ventral midline incision and endoscope optics were then utilized for gonad visualization and sex identification. A gonadal fragment was collected using laparoscopic forceps and conditioned in 10 % formalin. To suture the cavity, polyamide yarn was used in a simple and continuous pattern. At 15 days subsequent to surgery, healing was evaluated, and the stitches were removed. Videoceloscopy accuracy and gonadal biopsy effectiveness were 97 % and 83 %, respectively. Total time devoted in the videoceloscopy, gonadal biopsy and surgery was longer for animals identified as males compared to females The survival rate was 100 %. There were differences regarding food consumption at 24 and 36 h post-surgery when compared to control specimens (pre-surgical) Regarding position in the water column, differences were observed at 24 and 72 h after surgery when compared individually to the control specimens. There were differences for interaction behavior at 24, 36 and 60 h, and regarding search for hiding places at 12 and 24 h after surgery in relation to the control specimens. The applied videoceloscopy and gonadal biopsy surgical techniques are, therefore, effective and safe for A. ocellatus sexing procedures.

Ultrasound imaging identifies life history variation in resident Cutthroat Trout

Human activities that fragment fish habitat have isolated inland salmonid populations. This isolation is associated with loss of migratory life histories and declines in population density and abundance. Isolated populations exhibiting only resident life histories may be more likely to persist if individuals can increase lifetime reproductive success by maturing at smaller sizes or earlier ages. Therefore, accurate estimates of age and size at maturity across resident salmonid populations would improve estimates of population viability. Commonly used methods for assessing maturity such as dissection, endoscopy and hormone analysis are invasive and may disturb vulnerable populations. Ultrasound imaging is a non-invasive method that has been used to measure reproductive status across fish taxa. However, little research has assessed the accuracy of ultrasound for determining maturation status of small-bodied fish, or reproductive potential early in a species’ reproductive cycle. To address these knowledge gaps, we tested whether ultrasound imaging could be used to identify maturing female Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi). Our methods were accurate at identifying maturing females reared in a hatchery setting up to eight months prior to spawning, with error rates ≤ 4.0%; accuracy was greater for larger fish. We also imaged fish in a field setting to examine variation in the size of maturing females among six wild, resident populations of Westslope Cutthroat Trout in western Montana. The median size of maturing females varied significantly across populations. We observed oocyte development in females as small as 109 mm, which is smaller than previously documented for this species. Methods tested in this study will allow researchers and managers to collect information on reproductive status of small-bodied salmonids without disrupting fish during the breeding season. This information can help elucidate life history traits that promote persistence of isolated salmonid populations.

Use of magnetic resonance imaging to assess ovarian maturation in live Rhinogobio ventralis (Sauvage & Dabry de Thiersant, 1874)

The aim of this study is to evaluate the application of magnetic resonance imaging (MRI) to assess ovarian maturation in live female Rhinogobio ventralis (Sauvage & Dabry de Thiersant, 1874). The fish were randomly collected from the Jiangjin area of the Yangtze River between January and April 2014. Magnetic resonance imaging was performed using a 3.0 T clinical MRI scanner with a brain coil and two pulse sequences (IDEAL and 3D CUBE) were employed. Magnetic resonance and histologic images at different stages of ovarian maturation (I-IV) were acquired. An empirical equation (y = -0.1 + 1.56 × x) was derived by traditional method to describe the relationship between the gonadosomatic index (y) and the percentage volume of the ovary (x). A significant correlation (R(2) = 0.977, P < 0.01, N = 53) was found between measurements of the percentage volume of the ovary by MRI and traditional methods. The research findings suggested that MRI was a reliable, rapid, and noninvasive method to assess stages of ovarian maturity in female R. ventralis.