Loading...
12 results
Search Results
Now showing 1 - 10 of 12
- Behavioral and olfactory responses of female Salaria pavo (Pisces : Blenniidae) to a putative multi-component male pheromonePublication . Serrano, Rui M.; Barata, E. N.; Birkett, Michael A.; Hubbard, Peter; Guerreiro, Patrícia; Canario, Adelino V. M.The peacock blenny, Salaria pavo (Risso 1810), typically breeds in rocky shores of the Mediterranean and adjacent Atlantic coast. Males defend a territory around a hole or cavity wherein females deposit eggs that the male guards until hatching. A pair of exocrine glands on the anal fin (anal glands) of males produces a putative pheromone involved in attraction of reproductively competent females to the nest. We used behavioral assays to assess speciesspecific attraction of reproductively competent females to putative male pheromones, including the anal gland pheromone. Additionally, chromatographic fractions of anal glands and male-conditioned water were tested for olfactory potency in females by electro-olfactogram analysis (EOG). In a flow-through tank or fluviarium, reproductive females were attracted to male-conditioned water and to the anal gland macerate from conspecifics but not to those of a closely related heterospecific. In addition, attraction of reproductive females to conspecific anal gland macerate occurred only during their initial upstream movement in the fluviarium; this was an ephemeral response when compared with the response to male-conditioned water that attracted females throughout the entire period of observation (5 min). Reproductive females also were attracted during the entire period of observation to water-conditioned by conspecific males whose anal glands had been removed. However, the attraction was more variable than that to water conditioned by intact males. Moreover, females were not attracted to male (without anal glands) odor during their initial upstream movement in the fluviarium. Finally, non-reproductive females were not attracted to the conspecific anal gland macerate. The EOG responses of females to molecular weight fractions and solid-phase extraction and high-performance liquid chromatography fractions of anal gland macerates and male-conditio ned water (with and without anal glands) suggest that the anal glands release hydrophilic odorants that consist mainly of molecules smaller than 500 Da. Furthermore, males released potent odorants that do not originate from the anal glands. We hypothesize that females respond to a multi-component male pheromone to find mates. The putative anal gland pheromone is possibly comprised of hydrophilic odorants, whereas the other component(s), presumably of gonadal origin, may be less water-soluble.
- Possible disruption of pheromonal communication by humic acid in the goldfish, Carassius auratusPublication . Hubbard, Peter; Barata, E. N.; Canario, Adelino V. M.Humic acids are large, complex, organic molecules which are ubiquitous components of aquatic environments as products of degradation of plant material. In aqueous solution they form microvesicles. As many teleost pheromones are steroidal in nature, we hypothesised that they would preferentially dissolve in the organic, hydrophobic core of these vesicles instead of in water and therefore be unavailable for detection. This would have obvious and profound effects on many aspects of fish biology. To test this hypothesis we recorded electro-olfactogram (EOG) response of the goldfish (Carassius auratus) olfactory epithelium to the pheromones 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P), its sulphated conjugate (17,20β-P-SO4) and prostaglandin F2α (PGF2α), all at 10−11 to 10−8 M, in the absence and presence of humic acids (1–1000 mg l−1). At nearly all concentrations of humic acid tested, there was a significant attenuation of the amplitude of the initial (phasic) response to 17,20β-P compared to 17,20β-P alone. At higher concentrations of humic acid, the EOG response to 17,20β-P was often completely obliterated, suggesting that the concentration of the pheromone available to the olfactory epithelium was below the threshold of detection. Exposure of the olfactory epithelium to humic acid did not cause any short-term loss of sensitivity to 17,20β-P per se. Furthermore, simultaneous recording of electro-encephalograms from the olfactory bulb demonstrated that the nervous activity evoked by the same concentration of 17,20β-P was less intense in the presence of humic acid than its absence. PGF2α is non-steroidal and much more soluble in water. In contrast to 17,20β-P, only the higher concentrations of humic acid (100 and 1000 mg l−1) significantly diminished the EOG amplitude. 17,20β-P-SO4 is detected via a distinct olfactory mechanism to the free form. Given that the sulphate group increases the water solubility, we predicted that the effect of humic acid would be reduced. However, the effect of humic acid on EOG amplitude in response to 17,20β-P-SO4 was similar to that of the free form. We suggest that the steroid portion of the molecule adsorbs onto the surface of the humic acid microvesicles and is still effectively unavailable for olfactory detection. In conclusion, humic acid may significantly reduce the concentration of 17,20β-P and 17,20β-P-SO4 available for detection by Carassius auratus in natural environments. Furthermore, as many teleost pheromones are steroid derivatives, this phenomenon may be applicable to chemical communication systems in teleosts in general.
- Seasonal cell differentiation and olfactory potency of secretions by the anal glands of male peacock blenny Salaria PavoPublication . Serrano, Rui M.; Lopes, Orlando; Hubbard, Peter; Araújo, J.; Canario, Adelino V. M.; Barata, E. N.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.
- Olfactory sensitivity of the marine flatfish Solea senegalensis to conspecific body fluidsPublication . Fatsini, Elvira; Carazo, Ignacio; Chauvigne, Francois; Manchado, Manuel; Cerda, Joan; Hubbard, Peter; Duncan, Neil J.Chemical communication is better understood in freshwater fish than marine fish. The Senegalese sole (Solea senegalensis) is a marine flatfish wherein one of the problems in aquaculture is the poor reproductive performance of hatchery-bred males. Is chemical communication involved in the reproduction of this species? Urine, intestinal fluid and mucus samples were taken from adult fish (wild-caught and hatchery-bred) over the spawning season (March-May), and assessed for olfactory potency using the electro-olfactogram (EOG). The effect of stimulation of the olfactory system with adult female urine on circulating luteinizing hormone (LH) levels was also tested in males. Intestinal fluid and urine were potent olfactory stimuli for both juvenile and adult conspecifics, evoking large-amplitude, concentration-dependent EOG responses, with thresholds of detection at approximately 1:10(6). However, the amplitude of the response to urine depended on the sex and state of maturity of both the donor and the receiver. Most olfactory activity could be extracted by C18 solid-phase cartridges. Urine from mature females evoked a slight, but significant, increase in circulating LH levels in mature males 30 min after exposure. Furthermore, the olfactory potency of urine differed between wild-caught and hatchery-bred fish; however, contrary to expectations, urine from wild-caught females was less potent than that from hatchery-bred females. Taken together, these results strongly suggest that faeces-and urine-released odorants are involved in reproduction in the Senegalese sole, and establish a basis for further investigation into pheromonal communication in marine teleosts.
- Olfactory transduction pathways in the Senegalese sole Solea senegalensisPublication . Velez, Zélia; Hubbard, Peter; Barata, E. N.; Canario, Adelino V. M.This study tested whether differences in sensitivity between the upper and lower olfactory epithelia of Solea senegalensis are associated with different odorant receptors and transduction pathways, using the electro-olfactogram. Receptor mechanisms were assessed by cross-adaptation with amino acids (L-cysteine, L-phenylalanine and 1-methyl-L-tryptophan) and bile acids (taurocholic acid and cholic acid). This suggested that relatively specific receptors exist for 1-methyl-L-tryptophan and Lphenylalanine (food-related odorants) in the lower epithelium, and for taurocholic acid (conspecificderived odorant) in the upper. Inhibition by U73122 [a phospholipase C (PLC) inhibitor] suggested that olfactory responses to amino acids were mediated mostly, but not entirely, by PLC-mediated transduction (IC50; 15–55 nM), whereas bile acid responses were mediated by both PLC and adenylate cyclase–cyclic adenosine monophosphate (AC–cAMP) (using SQ-22536; an AC inhibitor). Simultaneous application of both drugs rarely inhibited responses completely, suggesting possible involvement of non-PLC and non-AC mediated mechanisms. For aromatic amino acids and bile acids, there were differences in the contribution of each transduction pathway (PLC, AC and non-PLC and non-AC) between the two epithelia. These results suggest that differences in sensitivity of the two epithelia are associated with differences in odorant receptors and transduction mechanisms.
- 11-ketotestosterone stimulates putative sex pheromone production in the male peacock blenny, Salaria pavo (Risso 1810)Publication . Serrano, Rui M.; Lopes, Orlando; Hubbard, Peter; Araújo, J.; Canario, Adelino V. M.; Barata, E. N.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.
- Olfactory sensitivity to steroid glucuronates in Mozambique tilapia suggests two distinct and specific receptors for pheromone detectionPublication . Keller-Costa, Tina; Canario, Adelino V. M.; Hubbard, PeterCichlids offer an exciting opportunity to understand vertebrate speciation; chemical communication could be one of the drivers of African cichlid radiation. Chemical signals mediate key aspects in the lives of vertebrates and often are species specific. Dominant male Mozambique tilapia [Oreochromis mossambicus (Peters 1852)] release a sex pheromone, 5 beta-pregnan-3 alpha,17 alpha,20 beta-triol 3-glucuronate and its 20 alpha-epimer, via their urine. The objective of this study was to assess the sensitivity, specificity and versatility of the olfactory system of O. mossambicus to other steroids and their conjugates using the electro-olfactogram. Oreochromis mossambicus was sensitive to several 3-glucuronidated steroids, but did not respond to prostaglandins, unconjugated steroids or 17- or 20-conjugated steroids. Stimulation of the olfactory epithelium with increasing concentrations (1 pmol l(-1) to 10 mu mol l(-1)) of 5 beta-pregnan-3 alpha, 17 alpha,20 beta-triol 3-glucuronate, 5 beta-pregnan-3 alpha, 17 alpha,20 beta-triol 3-glucuronate, 3 alpha,17 alpha-dihydroxy-5 beta-pregnan-20-one 3-glucuronate, etiocholanolone 3 alpha-glucuronate and 17 beta-estradiol 3-glucuronate produced characteristic sigmoidal concentration-response curves. However, tilapia were most sensitive to 17 beta-estradiol-3-glucuronate, which also had the lowest apparent EC50 and maximal response amplitude. Cross-adaptation and binary mixture experiments suggested that 5 beta,3 alpha-reduced pregnan-and androstan-3-glucuronates share (a) common olfactory receptor(s), whereas 17 beta-estradiol 3-glucuronate is detected via (a) distinct olfactory receptor(s). In conclusion, the Mozambique tilapia has evolved high olfactory sensitivity and specificity to 3-glucuronidated steroids through two distinct olfactory receptor types; one detecting a male sex pheromone and a second detecting 17 beta-estradiol 3-glucuronate, a putative female-derived signal. However, O. mossambicus differs markedly in its olfactory perception from the more recently derived East African cichlid Astatotilapia burtoni, suggesting that chemical communication could, indeed, be involved in speciation.
- Evidence for functional asymmetry in the olfactory system of the senegalese sole ( solea senegalensis )Publication . Velez, Zélia; Hubbard, Peter; Barata, E. N.; Canario, Adelino V. M.The two olfactory epithelia of flatfish of the family Soleidae are essentially in contact with two distinct environments; the upper (right) side samples open water while the lower (left) side samples interstitial water. This study assessed whether there are differences in the responsiveness of the two epithelia by use of the electro‐olfactogram in the Senegalese sole (Solea senegalensis). The upper epithelium was significantly more responsive to the basic amino acids (l‐lysine and l‐arginine), glycine, and l‐threonine than the lower epithelium. The lower epithelium was significantly more responsive to aromatic amino acids (l‐tryptophan, l‐tyrosine, l‐DOPA, and l‐phenylalanine), l‐leucine, and l‐asparagine than the upper. Both epithelia had similar responsiveness to the sulphur‐containing amino acids (l‐cysteine and l‐methionine), l‐alanine, l‐serine, and l‐glutamine. Neither side was responsive to the acidic amino acids (l‐aspartate and l‐glutamate) or the D‐isomers of any amino acid tested. The upper olfactory organ was much more responsive to conspecific‐derived stimuli (bile and intestinal fluid) than the lower organ. We suggest that these differences in responsiveness may be related to different functional roles of the upper and lower epithelia in feeding and chemical communication.
- Production, release and olfactory detection of sex steroids by the tench (Tinca tinca L.)Publication . Pinillos, M. L.; Guijarro, A. I.; Delgado, M. J.; Hubbard, Peter; Canario, Adelino V. M.; Scott, A. P.The present study is concerned with pheromone communication in tench (Tinca tinca L.), establishing firstly whethermales have a high olfactory sensitivity to some typical teleost sex steroids and prostaglandins; and secondly whether males and females might be able to synthesise and release some of these steroids into the water. The C21 steroid, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P)was found to give large electro-olfactogram responses with an estimated threshold of detection of 10−12 M. The male tench were equally sensitive to glucuronidated 17,20β-P (10−11.6 M) but 100 times less sensitive to sulphated 17,20β-P (11−9.7 M). Preliminary data from cross-adaptation studies suggest that both the free and conjugated forms are detected by the same olfactory receptor(s). Male tench also had high olfactory sensitivity to prostaglandin F2α (PGF2α) and 15-keto PGF2α (11−11.5 and 10−11.4 M). They were relatively insensitive, however, to testosterone (T), androstenedione (AD), 11-ketotestosterone (11-KT), 17β-oestradiol (E2), 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P) and 17,20α-dihydroxy-4-pregnen-3- one (17,20α-P). Radioimmunoassays were used to measure the steroids in plasma and water and all samples were processed for themeasurement of free, sulphated and glucuronidated fractions. In females, free 17,20β-P, 17,20α-P, free and glucuronidated T, and AD in plasma showed the largest increases in response to injection with mammalian gonadotropin-releasing hormone analogue (GnRHa) or Ovaprim (a mixture of GnRHa and a dopamine inhibitor). Free 17,20β-P was released into the water at the greatest rate. Plasma concentrations of the two conjugated forms of 17,20β-P were also elevated 18 h after the administration of GnRHa, but not by as much as the free steroid. In males, AD and 11-KT showed the greatest increase in response to GnRHa and were moreover released into the water at a higher rate in the treated group than in the control. The data support a possible pheromonal role for free and glucuronidated 17,20β-P.
- A sterol-like odorant in the urine of mozambique tilapia males likely signals social dominance to femalesPublication . Barata, E. N.; Fine, J. M.; Hubbard, Peter; Almeida, O. G.; Frade, P.; Sorensen, P. W.; Canario, Adelino V. M.Many species of freshwater fish with relatively simple mating strategies release hormonally derived sex pheromones in urine. However, it is not known whether species with more complex reproductive strategies use specialized urinary chemical signals. We addressed this by using the Mozambique tilapia (Oreochromis mossambicus Peters 1852), a lek-breeding species in which males establish dominance hierarchies and visiting females mate preferentially with territorial/dominant males. We measured urination frequency of territorial males in social isolation and in the presence of females that were either ready to spawn or had finished spawning. In groups of fish, we monitored the volume of urine stored in subordinate and dominant males to determine if urine volume and olfactory potency (by recording electro-olfactograms, EOG, in females) are related to the male’s social rank. Dominant, territorial males stored more urine than subordinates and released it in short pulses, the frequency of which increased in the presence of females ready to spawn but not in the presence of post-spawn females. Urine from subordinate and dominant males was fractionated by liquid chromatography and fractions tested for olfactory potency by using the EOG, with the most potent fraction analyzed by mass spectrometry (MS). The olfactory system of females was sensitive to a urinary compound that was more abundant in the urine of dominant males than in that of subordinates. MS analysis suggested the compound is a sulfated aminosterol-like compound with a formula of C29H40N2O10S. Therefore, we suggest that dominant/territorial tilapia males dramatically increase urination frequency in the presence of females ready to spawn and that the urinary odorant acts as a pheromonal signal of dominance, thereby influencing female spawning.