Optimization of the larviculture of the tropical fish cobia Rachycentron canadum in Vietnam

Cobia is a potential fish species for marine aquaculture due to its rapid growth and succulent flesh. However, shortage of high quality fingerlings remains a bottle neck for further propagation of the species. This PhD thesis aimed to study the effects of feeds, feeding frequency and rearing density on the performance of cobia larvae and early juveniles, with focus on the co-feeding and weaning stage. During weaning, growth and survival of cobia juveniles were affected by the rearing density, but not by the feeding frequency. A commercial dry feed (NRD®, INVE Aquaculture SA) showed its advantages in comparison with the use of the home-made moist diet or minced trash fish in terms of growth and survival improvement. The study results also revealed the acceptance of the dry diet of cobia juveniles during weaning stage. Cobia larvae grow very fast and they may need high amounts of nutrition from the onset of exogenous feeding onwards. Use of umbrella-stage of Artemia franciscana (UAF) revealed that cobia larvae are able to ingest and digest UAF since the first feeding. Replacing enriched rotifers by UAF as starter food for cobia larvae had very little effect on larval growth by 8 dph and appeared to have no significant negative effect on larval quality, growth or survival by 18 dph. In order to balance and improve the nutritional condition of the larvae, early co-feeding of Proton® from 8 dph was conducted and resulted in better growth. The use of the experimental diet with a higher n-3HUFA content and DHA/EPA ratio, compared to Proton® or NRD®, significantly improved growth and survival of cobia at the stage of 20-38 dph, but was not appropriate for early co-feeding at the stage 8-23 dph. Cobia larvae retain DHA rather than other fatty acids in their body: the content of DHA and other fatty acids in the larval tissues decreased according to their age (0-12 dph), but the DHA/EPA ratio increased. Higher levels of dietary DHA and DHA/EPA ratios resulted in a better growth and survival of cobia juveniles (12-30 dph). Levels of DHA and DHA/EPA ratio in the juvenile tissues and in the diets could not be correlated, but the best survival in the transportation test was recorded in the treatments fed high dietary DHA content and DHA/EA ratio. In conclusion, our study revealed that cobia larvae are able to ingest and digest UAF from first feeding onwards. Growth, survival and quality of cobia juveniles can be improved by manipulation of early co-feeding of formulated diets, appropriate rearing density and feeding frequency as well as appropriate dietary DHA and DHA/EPA ratio. More researches for further improvement of UAF and formulation of the appropriate weaning diets were suggested

Expression of Hormone Receptors and HER-2 in Benign and Malignant Salivary Gland Tumors

With the advent of targeted therapies, expression of sex hormone receptors and HER-2 in salivary gland tumors (SGTs) is of clinical interest. Previous reports of estrogen (ER) and progesterone (PR) receptor expression have varied. Androgen receptor (AR) and HER-2 overexpression are frequently reported in salivary duct carcinoma (SDC), but have not been studied systematically in other SGTs. This study examines ER, PR, AR, and HER-2 expression in SGTs. Immunohistochemistry for ER, PR, AR, and HER-2 was performed on 254 SGTs (134 malignant). ER, PR, and AR expression was scored using Allred system. HER-2 expression was scored using Dako HercepTest guidelines. FISH for HER-2 amplification was performed on select cases with HER-2 overexpression (2-3+). No SGT demonstrated strong expression of ER or PR. Combined strong AR and HER-2 expression was seen in 22 carcinomas: 14/25 SDC, 3/16 poorly differentiated, two oncocytic, and one each carcinoma ex pleomorphic adenoma, squamous cell, and intraductal carcinoma. Eighteen additional high grade carcinomas had HER-2 overexpression with absent, weak, or moderate AR expression; eight high grade carcinomas had isolated strong AR expression with 0-1+ HER-2 staining. Of 15 tested cases, six demonstrated HER-2 amplification by FISH, all of which had 3+ immunoreactivity. Neither benign nor malignant SGTs had strong expression of ER or PR. None of the benign SGTs overexpressed AR or HER-2. Coexpression of AR and HER-2 should not define SDC, but immunostaining should be considered in high grade salivary carcinomas, as some show overexpression and may benefit from targeted therapy

Effect of early co-feeding and different weaning diets on the performance of cobia (Rachycentron canadum) larvae and juveniles

Cobia (Rachycentron canadum) is a very fast growing species. This can only be achieved if sufficient amounts of feed are provided from early larval development onwards. In this study, we examined the effects of early co-feeding and different co-feeding formulated diets on growth, survival and vitality of cobia larvae and juveniles. Two experiments were conducted to test the possibility of early co-feeding of the two formulated diets for cobia larvae (8–18 dph) and one experiment was conducted to compare the effect of three formulated diets for cobia juveniles (20–38 dph). During the larval stage, two formulated diets: Proton® and an experimental diet (INVE, Belgium) were used along with live food from eight days post hatch (dph) and 13 dph compared to 18 dph as the control. Results from the study indicated that early co-feeding of Proton® from eight dph had a significantly positive effect on growth (P 0.05), but not on survival and stress resistance in a salinity stress test (P > 0.05) of cobia larvae. In the second trial, no significant difference (P > 0.05) was detected between all treatments in terms of growth, vitality and survival. However, high mortality occurred in the treatment with the experimental diet as of 12 dph. The study suggested that early co-feeding of Proton® to cobia larvae from eight dph is possible and research on the appropriate nutritional composition of weaning diets needs to be addressed. In the juvenile stage, three formulated diets, i.e. the experimental diet, Proton® and NRD® (INVE Aquaculture NV) were evaluated for growth performance and survival of early cobia juveniles (20–38 dph). The diets were manually introduced from 22 dph at a feeding frequency of every 2 h until satiation, while feeding of enriched EG Artemia was maintained until 30 dph. Average length and weight of the 38-dph juveniles fed the experimental diet were significantly higher (P 0.05) compared to larvae fed Proton® and NRD®. However, the coefficient of size variation as well as the cumulative stress index in a salinity challenge test was not significantly different (P > 0.05). Survival in the Proton® treatment was the lowest, while no significant difference was evident between the experimental diet and NRD® treatments. The mortality rate of all three treatments had two peaks: one at the beginning of the experiment and one when live food feeding was discontinued. This result indicates that the nutritional requirements of cobia are age-dependent and prolongation of live food co-feeding during weaning may be necessary. The higher DHA/EPA ratio in the experimental diet can be a clue for the improvement of growth and survival of cobia during the weaning stage