Black Soldier Fly (Hermetia illucens) larvae-meal as an example for a new feed ingredients’ class in aquaculture diets

Regarding the growing demand for fishmeal, soybean meal and other feed ingredients in livestock feeding and especially in aquaculture, alternative protein carriers are an increasing concern of the animal feed industry. Beside the possibility to use animal by-products of non-ruminant origin, such as blood- and meat-meals in aquafeeds - according to the EU-regulation (EC) 56/2013 - the use of insect-based feed ingredients is progressively discussed among fish-feed producers, scientists and policy makers.Thus the possibility of mass-rearing flies on organic substrates was rediscovered. The black soldier fly, BSF (Hermetia illucens) occurring in tropical and subtropical countries all over the world including the Mediterranean states and European countries north of the alps proved to be an ideal candidate (Bondary et al. 1981; St-Hilaire et al. 2007 ). This organism can be reared on a wide range of organic (waste)-material which is currently deposited or burned or used in biogas plants in the best case. The developing stages of the fly can use the potential of this waste-material and reduce the volume of those substrates by up to 50%, producing biomass with a protein content of about 42% and a fat content of up to 35 % (Sheppard et al., 1994, Stamer et al. 2007). The suitability of the Hermetia pre-pupae meal as a protein source in feedstuff had been proven in poultry and pigs and also in warm water fish species (i.e. channel catfish and tilapia) (Bondari, Sheppard, 1981; Hale, 1973; Newton et al., 1977). For carnivorous cold water fish species (e.g. Salmonidae, Scophthalmidae) only limited data is available regarding the use of insect meals instead of fish meal (Kroeckel et al. 2012; St-Hilaire et al. 2007). The present study shows results of a feeding-trial on rainbow trout (Oncorhynchus mykiss) fed with two BSF-larvae meal containing diets

Tilapia sex determination: Where temperature and genetics meet

This review deals with the complex sex determining system of Nile tilapia, Oreochromis niloticus, governed by the interactions between a genetic determination and the influence of temperature, shown in both domestic and wild populations. Naturally sex reversed individuals are strongly suggested in two wild populations. This can be due to the masculinising temperatures which some fry encounter during their sex differentiation period when they colonise shallow waters, and/or to the influence of minor genetic factors. Differences regarding a) thermal responsiveness of sex ratios between and within Nile tilapia populations, b) maternal and paternal effects on temperature dependent sex ratios and c) nearly identical results in offspring of repeated matings, demonstrate that thermosensitivity is under genetic control. Selection experiments to increase the thermosensitivity revealed high responses in the high and low sensitive lines. The high-line showed ~ 90% males after 2 generations of selection whereas the weakly sensitive line had 54% males. This is the first evidence that a surplus of males in temperature treated groups can be selected as a quantitative trait. Expression profiles of several genes (Cyp19a, Foxl2, Amh, Sox9a,b) from the gonad and brain were analysed to define temperature action on the sex determining/differentiating cascade in tilapia. The coexistence of GSD and TSD is discussed

Supplementary Material for: Germline Development of Genetically Female Nile Tilapia (Oreochromis niloticus) Reared under Different Temperature Regimes

In teleosts, elevated temperature during embryogenesis can act on germline cell development, which in turn plays a role for sexual fate. In Nile tilapia, a species with high-temperature-induced masculinization, little is known about the effects of increased temperature on gonadal development in non-masculinized females. The aim of the present work was to investigate persistent effects on the germline of genetically female (XX) Nile tilapia reared at normal (28°C) or elevated temperature (36°C) during the critical time of gonadal sex differentiation at 10 to 20 days post fertilization. Non-sex-reversed females were compared to control females to determine persistent effects of temperature on subsequent ovarian development using histological approaches. Germline stem cells were identified using the germline marker Vasa in combination with the proliferation marker PCNA. Vasa- and PCNA-positive germline stem cells were found in ovaries of both high-temperature-treated and control females. In both groups, ovarian germline stem cells were located at the germinal epithelium of the ovigerous lamellae. Although no detrimental effects of high temperature on gonadal development in female Nile tilapia were observed, implications on the reproductive fitness caused by elevated temperature need to be investigated in greater depth