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- Sexually mature European eels (Anguilla anguilla L.) stimulate gonadal development of neighbouring males: possible involvement of chemical communicationPublication . Huertas, Mar; Scott, A. P.; Hubbard, Peter; Canario, Adelino V. M.; Cerda, J.This study was aimed to investigate whether sexual maturation of immature male eels could be stimulated indirectly by placing them in contact with either male (Minj) or female (Finj) eels in which sexual maturation had been stimulated directly by weekly injections of human chorionic gonadotropin (hCG) or salmon pituitary extract (SPE), respectively. Untreated males were placed either in the same tank or in a separate tank that was linked to the injected Wsh via a recirculation system. The hormonal treatments stimulated spermatogenesis and spermiation in Minj, and ovulation in Finj as well as an increase of the ocular (Io) and gonadosomatic (GSI) indices in both sexes. Plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) increased in Minj and T and 17 -estradiol (E2) in Finj. A small peak of plasma 17,20 -dihydroxypregn-4-en-3-one (17,20 P) occurred during ovulation, while the plasma levels of 17 -hydroxypregn-4- ene-3,20-dione (17P) were undetectable in both males and females. The water conditioned by Minj and Finj induced signiWcant, though relatively minor, increases in Io and GSI in uninjected males. In addition, uninjected Wsh showed small changes in plasma T and 11-KT levels, apparently related to the timing of spermiation and ovulation of Minj and Finj, respectively, as well as an activation of spermatogenesis (but not spermiation). Injected Wsh released free and conjugated T, 11-KT and E2 into the water, although immature eels were unable to smell (by electro-olfactogram) any of these steroids or prostaglandin F2 . However, immature males were highly sensitive to water extracts conditioned by spermiating Minj and pre-ovulatory and ovulated Finj. These preliminary results suggest the existence of chemical communication between maturing eels and immature males that stimulates gonad development, although the putative pheromone(s) involved has/have not yet been identiWed.
- Evidence for involvement of chemical communication in reproduction of the eel Anguilla anguillaPublication . Huertas, Mar; Hubbard, Peter; Scott, A. P.; Canario, Adelino V. M.; Cerda, J.The European eel (Anguilla anguilla) is characterised by long transoceanic migration to spawning sites during which the fish become sexually mature. A previous study demonstrated that mature eels may induce physiological and behavioural changes in immature conspecifics. This raises the possibility that chemical communication may be involved in this process. The aim of the current study was, therefore, to assess the olfactory sensitivity of eels to conspecific-derived odours and to establish whether these odours differ according to sex and/or state of maturity.