Loading...
21 results
Search Results
Now showing 1 - 10 of 21
- Evidence that olfactory sensitivities to calcium and sodium are mediated by different mechanisms in the goldfish Carassius auratusPublication . Hubbard, Peter; Canario, Adelino V. M.The current study investigated whether the olfactory sensitivity to Ca2+ and Na+ is mediated by the same mechanism in the goldfish, a freshwater teleost. The olfactory responses, as assessed by recording the electro-encephalogram (EEG) from the olfactory bulb, to changes in external [Ca2+] and to [Na+] were recorded in the absence and presence of increasing concentrations of the other ion. Low concentrations of Na+ (0–1.0 mM) had no significant effects on the olfactory response to changes in [Ca2+] in terms of EC50, Imax or Hill co-efficient (n = 8). A relatively high concentration of Na+ (10 mM) significantly reduced the Imax and increased the EC50. One hundred millimolars Na+reduced the olfactory response to Ca2+ to undetectable levels. Conversely, low concentrations of Ca2+ (0.1 and 1.0 mM) significantly attenuated the olfactory response to changes in environmental [Na+], reducing the amplitude of response and increasing the threshold of detection (n = 7). However, a high concentration of Ca2+ (10 mM) failed to attenuate the olfactory response to Na+ completely. Taken together, these results suggest that, at normal environmental concentrations of these ions, Ca2+ and Na+ are detected by distinct and separate cellular mechanisms. However, there seems to be a degree of overlap between the two mechanisms. The exact mechanisms involved, and their biological roles, remain to be established.
- 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.
- Identification, release and olfactory detection of bile salts in the intestinal fluid of the Senegalese sole (Solea senegalensis)Publication . Velez, Zélia; Hubbard, Peter; Welham, K.; Hardege, Jörg D.; Barata, E. N.; Canario, Adelino V. M.Olfactory sensitivity to bile salts is wide-spread in teleosts; however, which bile salts are released in suYcient quantities to be detected is unclear. The current study identiWed bile salts in the intestinal and bile Xuids of Solea senegalensis by mass spectrometry–liquid chromatography and assessed their olfactory potency by the electro-olfactogram.
- Olfactory sensitivity to conspecific bile fluid and skin mucus in the European eel Anguilla anguilla (L.)Publication . Huertas, Mar; Hubbard, Peter; Canario, Adelino V. M.; Cerda, J.The present study assessed the olfactory potency of conspecific bile fluid and skin mucus in the European eel Anguilla anguilla by the electro-olfactogram. Immature males showed high olfactory sensitivity to conspecific bile, giving large amplitude responses in a concentrationdependent manner with estimated thresholds of detection of <1:107 (n = 6). Mucus also proved to contain highly potent odorants with thresholds of detection of c. 1:106 (n = 6). Crude solidphase extraction of bile fluid (C-18 and C-2/ENV+ cartridges) showed that the majority of olfactory activity in bile fluid was contained in the eluate of C-18 cartridges (n = 6). There were quantitative differences, however, between the sexes; female bile fluid had a higher proportion of activity in this fraction. Similar solid-phase extraction of mucus showed that it contains a higher proportion of odorants in the C-18 filtrate than bile fluid. Mucus from mature eels, however, had a higher proportion of olfactory activity in the eluate than immature fish (n = 6). Cross-adaptation experiments suggest that there are qualitative differences in the odorants contained in bile and mucus depending on both the sex and state of sexual maturation of the donor (n = 6). These results are consistent with a role for chemical communication in the reproduction of the European eel and suggest that both bile and mucus are potential sources of the odorants involved.
- Adaptation to reduced salinity affects the olfactory sensitivity of Senegalese sole (Solea senegalensis Kaup 1858) to Ca2+ and Na+ but not amino acidsPublication . Velez, Zélia; Hubbard, Peter; Barata, E. N.; Canario, Adelino V. M.The Senegalese sole is a marine flatfish, which often penetrates into estuarine waters to feed. It cannot, however, survive in full freshwater. The current study investigated the effect of adaptation to low salinity (10‰) on olfactory responses to changes in environmental [Ca2+] and [Na+] and amino acids by the electro-encephalogram (EEG) recorded from the olfactory bulb. The sole showed olfactory responses to increases in environmental [Na+] and decreases in environmental [Ca2+]; sensitivity to Na+ was greater at 10‰ whereas sensitivity to Ca2+ was greater at 35‰. Decreased environmental [Na+] increased sensitivity to changes in [Ca2+] whereas increased environmental [Ca2+] decreased bulbar responses to changes in [Na+]. Sensitivity to amino acids was unaffected by external salinity. However, the absence of external Na+ strongly decreased bulbar responses to amino acids in fish adapted to 35‰ seawater but not in those at 10‰. The absence of external Ca2+ had no such effect at either salinity. This suggests that odorant-receptor binding and/or olfactory transduction is reliant on external Na+ (but not Ca2+) at higher salinities but the olfactory system is able to adapt to lower environmental [Na+]. Taken together, these results suggest that reductions of external salinity modulate olfactory sensitivity to environmental Ca2+ and Na+ but not amino acids. However, at low salinities, olfactory sensitivity to amino acids is maintained by decreasing reliance on external Na+.
- Independent effects of seawater pH and high P-CO2 on olfactory sensitivity in fish: possible role of carbonic anhydrasePublication . Velez, Zélia; Costa, Rita; Wang, Wenjing; Hubbard, PeterOcean acidificationmay alter olfactory-driven behaviour in fish by direct effects on the peripheral olfactory system; olfactory sensitivity is reduced in CO2-acidified seawater. The current study tested whether this is due to elevated P-CO2 or the consequent reduction in seawater pH and, if the former, the possible involvement of carbonic anhydrase, the enzyme responsible for the hydration of CO2 and production of carbonic acid. Olfactory sensitivity to amino acids was assessed by extracellularmulti-unit recording from the olfactory nerve of the gilthead seabream (Sparus aurata L.) in normal seawater (pH similar to 8.2), and after acute exposure to acidified seawater (pH similar to 7.7) but normal P-CO2 (similar to 340 mu atm) or to high P-CO2 seawater (similar to 1400 mu atm) at normal pH (similar to 8.2). Reduced pH in the absence of elevated P-CO2 caused a reduction in olfactory sensitivity to L-serine, L-leucine, L-arginine and L-glutamine, but not L-glutamic acid. Increased P-CO2 in the absence of changes in pH caused reduced olfactory sensitivity to L-serine, L-leucine and L-arginine, including increases in their threshold of detection, but had no effect on sensitivity to L-glutamine and L-glutamic acid. Inclusion of 1 mmol l(-1) acetazolamide (a membrane-permeant inhibitor of carbonic anhydrase) in the seawater reversed the inhibition of olfactory sensitivity to L-serine caused by high P-CO2. Ocean acidification may reduce olfactory sensitivity by reductions in seawater pH and intracellular pH (of olfactory receptor neurones); the former by reducing odorant-receptor affinity, and the latter by reducing the efficiency of olfactory transduction. The physiological role of carbonic anhydrase in the olfactory receptor neurones remains to be explored.
- Olfactory sensitivity to bile fluid and bile salts in the European eel (Anguilla anguilla), goldfish (Carassius auratus) and Mozambique tilapia (Oreochromis mossambicus) suggests a 'broad range' sensitivity not confined to those produced by conspecifics alonePublication . Huertas, Mar; Hagey, L.; Hofmann, A. F.; Cerda, J.; Canario, Adelino V. M.; Hubbard, PeterTeleosts have high olfactory sensitivity to bile salts. To assess whether this phenomenon is involved in intra-specific chemical communication alone, or is part of a more ‘broad range’ sensitivity to bile salts produced by heterospecifics, we investigated possible differences in the odour of bile between the sexes and among different species – the eel (Anguilla anguilla), goldfish (Carassius auratus) and Mozambique tilapia (Oreochromis mossambicus) – using the electro-olfactogram (EOG). We also identified the main bile constituents by liquid chromatography and mass spectrometry. There were marked differences in olfactory response of the eel to thin-layer chromatography fractions of bile from both sexes, and mature and immature conspecifics. Smaller differences were seen in the potency of fractions of bile from male and female goldfish and tilapia. Eels, goldfish and tilapia demonstrated similar olfactory sensitivity to bile from a range of different species, with no apparent correlation between the olfactory potency of bile and a phylogenetic closeness and/or similarity of diet of the donor to the receiver. The three species were able to detect odorants in thin-layer chromatography fractions of heterospecific bile even in the absence of activity in conspecific bile. Eels, goldfish and tilapia responded to both sulphated C27 bile salts (5-scymnol-sulphate and 5-cyprinol sulphate) and to taurine-conjugated C24 bile salts (taurochenodeoxycholic acid, taurolithocholic acid and taurocholic acid), irrespective of whether these bile salts were present in conspecific bile. Together, these results suggest that teleosts have a broad-range olfactory sensitivity to bile salts, with potential roles in both intra-specific chemical communication and in inter-specific interactions.
- 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 that 1-methyl-l-tryptophan is a food-related odorant for the Senegalese sole (Solea senegalensis)Publication . Velez, Zélia; Hubbard, Peter; Hardege, Jörg D.; Welham, K.; Barata, E. N.; Canario, Adelino V. M.Nocturnal animals often rely heavily on olfactory cues to locate their food. This is especially true for fish whose prey live buried in the substrate. The aim of the current study was to identify non-polar odorants released by the ragworm (Hediste diversicolor) that are detected by the olfactory system of the Senegalese sole (Solea senegalensis) and therefore may be food-related cues. Ragworm-conditioned water was passed through a C18 solid-phase extraction cartridge (to remove polar compounds) and the eluate fractionated by reverse phase high-performance liquid chromatography (HPLC). The fractions were then tested for olfactory activity in the sole by the electro-olfactogram (EOG). Most olfactory activity was found in the first two fractions to elute from the HPLC column (0–4 min). Liquid chromatography-mass spectrometry (LC/MS) of both fractions revealed a base peak with a molecular mass of 219.4 Da and a fragment of 205.3 Da. These data are consistent with a methylated form of tryptophan; synthetic 1-methyl-l-tryptophan had a similar HPLC retention time (2.8 min) and similar LC/MS spectra. Furthermore, sole showed olfactory sensitivity to 1-methyl-l-tryptophan with the lower (left) epithelium being more sensitive than the upper (right). Cross-adaptation (using EOG recording) suggested that the olfactory receptors responding to 1-methyl-l-tryptophan are different in the lower epithelium from the upper. These results suggest that ragworms release 1-methyl-l-tryptophan, or similar tryptophan derivative, and that sole may use this chemical cue to locate and/or identify one of their main prey species. This may help the formation of artificial feeds that are more attractive to sole.
- Prey odour enhances swimming activity and feed intake in the Senegalese solePublication . Barata, E. N.; Hubert, F.; Conceição, L. E. C.; Velez, Zélia; Rema, P.; Hubbard, Peter; Canario, Adelino V. M.Olfaction is important in many aspects of the life-history of fishes including feeding, and more so in nocturnal benthic feeders. In the current study we assessed the importance of olfaction in food-search behaviour of the Senegalese sole, an economically important marine species both as farmed and wild-caught. Whole-body homogenates of the polychaete Diopatra neapolitana were fractionated by solid-phase extraction (SPE) using C18 cartridges and the olfactory potency of the resultant fractions (hydrophobic eluate and hydrophilic filtrate) was assessed by the electro-olfactogram in juvenile sole. In addition, the effect of both the homogenate and SPE fractions on sole locomotion was assessed in a flow-through tank (fluviarium). Finally, whole-body homogenate was added to commercial feed pellets and tested whether it could enhance food consumption by sole. The SPE hydrophilic filtrate contained the majority of the olfactory activity found in the whole-body homogenate. Both the homogenate and filtrate, but not the eluate, increased number of movements, time moving, linear velocity, distance travelled and time swimming upstream of sole in the fluviarium; ablation of the olfactory epithelia disrupted these behavioural responses to the homogenate. Intact sole consumed more pellets flavoured with worm homogenate than those without. These results show that olfaction plays an important role in food-search behaviour of the Senegalese sole and that the hydrophilic fraction of D. neapolitana whole-body homogenate contains key substances affecting sole search behaviour; moreover, ingestion by sole was enhanced by addition of worm homogenate to the dry feed pellets.
- «
- 1 (current)
- 2
- 3
- »