Tilapia male urinary pheromone stimulates female reproductive axis

Mozambique tilapia males congregate in leks where they establish dominance hierarchies and attract females to spawn in sandy pits. Dominant males store more urine than subordinates and the pattern of urination and the high sensitivity of females to male urine suggest chemical signalling via the urine. Here we show that pre-ovulated and post-spawn females when exposed to dominant male urine increased significantly, in less than 1 h, the release rate of the maturation-inducing steroid 17,20bdihydroxypregn- 4-en-3-one which is maintained elevated for at least 6 h. This indicates a pheromonal role for male urine in the synchronisation of spawning. Furthermore, we show that the lack of affinity of 17,20bP to sex steroid binding globulin explains, at least partly, its rapid release and lack of detection in the blood. Thus tilapia urine involvement in several communication processes confirms that cichlids have evolved a sophisticated chemical signalling system together with their complex visual, acoustic and behavioural displays

The effect of nest aggregation on the reproductive behaviour of the peacock blenny Salaria pavo (Risso)

The effect of nest aggregation in courtship behaviour was tested experimentally in an ecologically constrained, sex-role reversed population of the peacock blenny Salaria pavo. Mixed sex groups of eight males and eight females were tested in experimental tanks, containing eight potential nests either aggregated or dispersed. In the aggregated treatment, males spent more time inside their nests and monopolized other potential nests, causing a female-biased operational sex ratio (OSR). In the aggregated treatment, females also expressed more courtship behaviour. The results in general support the prediction that the aggregation of nests promotes male monopolization of potential nests, resulting in fewer nest-holding males and therefore a female-biased OSR that leads to the reversal o f sex roles

Genomics toolbox for farmed fish

International audienceThe last decade has seen dramatic technological developments which have resulted in massive production of genome and transcriptome sequence information from a variety of organisms, at all levels of complexity, including several fish species. While hitherto most applications of genomic data have been in biomedicine, biotechnology, and agriculture, there is a growing interest in applying genomic approaches to animal production. This review will describe the basic tools and resources that are currently available and how they are being used for advancing aquaculture. Finally it will discuss current trends that are likely to have some impact for the benefit of aquaculture

Olfactory Sensitivity to Amino Acids in the Blackspot Seabream (Pagellus Bogaraveo, Brünnich 1768): How Effective is the Electro-olfactogram in Seawater?

Intensive aquaculture is heavily dependent on high-quality fishmeal to meet their protein requirements. However, due to the increased demand, decreased availability, raising costs and the potential presence of organic and inorganic contaminants, it is of economical and environmental interest to replace fishmeal by a renewable protein sources. This is particularly challenging since replacing fishmeal may lack appropriate chemical stimulants for active consumption. Fish have a well-defined olfactory sensitivity to L-amino acids (Hara, 1994), and this phenomenon is generally held to be involved in the location and identification of food (Carr et al., 1996). Olfactory sensitivity in fish can be assessed by electro-olfactogram (EOG); a field potential recorded from just above the olfactory epithelium (Scott and Scott-Johnson, 2002). Due to the high electrical conductivity of seawater, EOG responses recorded in marine fish are, however, of lower amplitude than those recorded in freshwater fish (Silver et al., 1976). It is unclear, however, to what extent EOG recording in seawater may underestimate the olfactory sensitivity of a given species when compared to more invasive recording methods, such as multi-unit recording from the olfactory nerve. The blackspot seabream is a promising new species for the finfish aquaculture industry; however, little is known about its biology. The current study investigated its olfactory sensitivity to amino acids and compared the efficacy of two different experimental approaches: multi-unit recording from the olfactory nerve and the electro-olfactogram (EOG). Cited references: Carr W.E.S., J.C. Netherton, R.A. Gleeson and C.D. Derby. 1996. Stimulants of feeding behavior in fish: analyses of tissues of diverse marine organisms. Biological Bulletin 190: 149-160. Hara T.J. 1994. The diversity of chemical stimulation in fish olfaction and gustation. Reviews in Fish Biology and Fisheries 4: 1-35. Scott J.W. and P. E. Scott-Johnson. 2002. The electro-olfactogram: a review of its history and uses. Microscopy Research and Technique 58: 152-160. Silver W.L., J. Caprio, J.F. Blackwell and D. Tucker. 1976. The underwater electro-olfactogram: a tool for the study of the sense of smell of marine fishes. Experientia 32: 1216-1217

11-Ketotestosterone stimulates putative sex pheromone production in the male peacock blenny, Salaria pavo (Risso 1810)

Male peacock blennies (Salaria pavo) release odors from their anal glands and, possibly, from their gonads that attract reproductive females. The current study investigated the effects of 11-ketotestosterone (KT) on development of the anal glands, testes, and accessory testicular organs as well as the subsequent olfactory potency of their secretions. After 3 wk of KT treatment (5 mg/kg in silastic implants), clusters of cells secreting neutral mucins differentiated in the anal gland of all treated males, whereas this occurred in only one control male. Secretions by anal glands from KT-treated males elicited greater olfactory responses, as assessed by electro-olfactography, than those from controls. Treatment with KT stimulated testicular gland growth and sialomucin secretion but had no clear effect on the germinal region of the testis; KT also stimulated enlargement of, and fluid secretion in, the blind pouches (paired evaginations of the spermatic ducts). Secretions by the testes and fluid in blind pouches from KT-treated males elicited greater olfactory responses than those from controls. In conclusion, KT stimulates development of the anal glands and testicular accessory organs and promotes odorant secretion, the putative multicomponent male peacock blenny pheromone

Seasonal cell differentiation and olfactory potency of secretions by the anal glands of male peacock blenny

The current study shows cytological differences between the anal glands of pre-spawning and spawning peacock blennies Salaria pavo. The cytological differences in the anal gland coincide with higher olfactory potency of their secretions in spawning males, suggesting that seasonal differentiation of cell clusters secreting neutral mucins is related to the production and release of the putative sex pheromone

Putative pheromones from the anal glands of male blennies attract females and enhance male reproductive success.

Parental males of several blenniid species have a pair of glands on the anal fin. These are thought to be a source of pheromones for female attraction and/or of antimicrobials for egg protection. In Salaria pavo, we tested the female attraction hypothesis and whether the anal glands are essential for egg parental care. In S. pavo and Salaria fluviatilis, we tested whether anal glands affect female mate choice. In a Y-maze, reproductive females were attracted to water conditioned by males with anal glands and macerated anal glands but not to substances released by conspecific females, water conditioned by males that had the anal glands removed or to macerated anal fin rays. Females preferred to spawn in nests of males with anal glands than in those of males without anal glands. In the laboratory, neither hatching success nor development time was affected by the removal of the anal glands from parental males. In contrast, most of the eggs without parental care did not complete their development. We suggest that the anal glands are specialized in the secretion of a pheromone that attracts reproductive females, and blenniids have evolved true chemical communication, possibly through the selective pressure of female mate choice

Empowering marine science through genomics

Marine scientists in Europe summarize their successes with genome technologies in the marine sciences and make a plea for a concerted international effort to raise greater public education for support

The LIFECYCLE project: greater basic knowledge on fish biology will help find long-term solutions to aquaculture production bottlenecks

International audienc

The LIFECYCLE project: greater basic knowledge on fish biology will help find long-term solutions to aquaculture production bottlenecks

International audienc