Percorrer por autor "Couto, Elsa"
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- Endocrine correlates of intra-specific variation in the mating system of the St. Peter's fish (Sarotherodon galilaeus)Publication . Ros, A. F. H.; Canario, Adelino V. M.; Couto, Elsa; Zeilstra, IIja; Oliveira, R. F.The Challenge Hypothesis postulates that androgen levels are a function of the social environment in which the individual is living. Thus, it is predicted that in polygynous males that engage in social interactions, androgen levels should be higher than in monogamous animals that engage in parental care. In this study, we tested this hypothesis at the intra-specific level using a teleost species, Sarotherodon galilaeus, which exhibits a wide variation in its mating system. Experimental groups of individually marked fish were formed in large ponds with different operational sex-ratios (OSR) to study the effects of partner availability on blood plasma levels of sex steroids [11-ketotestosterone (11-KT), testosterone (T), and 17,20B-dihydroxy-4-pregnen-3-one (17,20B-P)] and gonadosomatic index (GSI). Polygyny mostly occurred in the female biased OSR groups. 17,20B-P and gonadosomatic index did not differ among OSR groups. However, 11-KT was high in male biased OSR and positively correlated with aggressive challenges, thereby supporting the central postulate of the Challenge Hypothesis. The results of T were the inverse of those of 11-KT, probably because 11-KT is metabolized from T. 11-KT levels of polygynous males did not differ neither from those of monogamous males, nor from those of males that participated in parental care. These results do not support the expected relationships between polygyny, parental care, and androgen levels. The differences from expectations for 11-KT may be related to the fact that in S. galilaeus, the mating and the parenting phase are not clearly separated and thus, males may still fight and court while they are brooding.
- Fecundity and sex steroid profile in boarfish Capros aperPublication . Sequeira, Vera; Couto, Elsa; Neves, Ana; Vieira, Ana Rita; Canario, Adelino; Gordo, Leonel SerranoThe boarfish Capros aper is one of the most commonly discarded non-commercial species in the International Council for the Exploration of the Sea (ICES) Subdivision VIII in the Atlantic. An increasing interest in this fishery and an incomplete knowledge on the status of the stock justified the present investigation focused on the determination of fecundity type and its estimation, supported by sex steroid profiles for 17 beta-oestradiol (E2), 11-ketotestosterone and 17,20 beta-dihydroxypregn-4-en-3-one (17,20 beta-P). C. aper was found to have indeterminate fecundity with a mean relative batch fecundity during the spawning peak of 50 oocytes g(-1) eviscerated weight (W-E) and a mean relative annual fecundity of 4020 oocytes g(-1) W-E. E2 variations throughout the year indicated the existence of at least two important spawning events, one in winter (January-February) and the other in summer (June-August), with concentrations in females increasing from those with growing oocytes in the developing phase to those in the spawning capable phase. Higher E2 concentrations were also found from 2000 to 2400 hours and from 0800 to 1200 hours suggesting more intense vitellogenesis activity during the night and in the morning, in contrast to 17,20 beta-P concentrations, which were higher between 1200 and 2000 hours, suggesting a more intense spawning activity during this period.
- Free androgens and progestins and their conjugated forms in serum and urine of stellate sturgeon (Acipenser stellatus Pallas) malesPublication . Bayunova, L.; Canario, Adelino V. M.; Semenkova, T.; Couto, Elsa; Gerasimov, A.; Barannikova, I.Stellate sturgeon (Acipenser stellatus Pallas) males from Volga River treated with LH-RH-A showed an increase of free, sulfated and glucuronided sex steroid levels in serum and urine at spermiation. Conjugated forms of sex steroids could act as pheromones in sturgeon.
- How integrated are behavioral and endocrine stress response traits? A repeated measures approach to testing the stress-coping style modelPublication . Boulton, Kay; Couto, Elsa; Grimmer, Andrew J.; Earley, Ryan L.; Canario, Adelino V. M.; Wilson, Alastair J.; Walling, Craig A.It is widely expected that physiological and behavioral stress responses will be integrated within divergent stress-coping styles (SCS) and that these may represent opposite ends of a continuously varying reactive-proactive axis. If such a model is valid, then stress response traits should be repeatable and physiological and behavioral responses should also change in an integrated manner along a major axis of among-individual variation. While there is some evidence of association between endocrine and behavioral stress response traits, few studies incorporate repeated observations of both. To test this model, we use a multivariate, repeated measures approach in a captive-bred population of Xiphophorus birchmanni. We quantify among-individual variation in behavioral stress response to an open field trial (OFT) with simulated predator attack (SPA) and measure waterborne steroid hormone levels (cortisol, 11-ketotestosterone) before and after exposure. Under the mild stress stimulus (OFT), (multivariate) behavioral variation among individuals was consistent with a strong axis of personality (shy-bold) or coping style (reactive-proactive) variation. However, behavioral responses to a moderate stressor (SPA) were less repeatable, and robust statistical support for repeatable endocrine state over the full sampling period was limited to 11-ketotestosterone. Although post hoc analysis suggested cortisol expression was repeatable over short time periods, qualitative relationships between behavior and glucocorticoid levels were counter to our a priori expectations. Thus, while our results clearly show among-individual differences in behavioral and endocrine traits associated with stress response, the correlation structure between these is not consistent with a simple proactive-reactive axis of integrated stress-coping style. Additionally, the low repeatability of cortisol suggests caution is warranted if single observations (or indeed repeat measures over short sampling periods) of glucocorticoid traits are used in ecological or evolutionary studies focussed at the individual level.
- Levels of free and conjugated androgens and progestins in coelomic fluid and serum of stellate sturgeon (Acipenser stellatus Pallas) femalesPublication . Bayunova, L.; Semenkova, T.; Canario, Adelino V. M.; Couto, Elsa; Gerasimov, A.; Barannikova, I.Stellate sturgeon (Acipenser stellatus Pallas) females from the Volga River were analysed for sex steroids after hormonal stimulation. The results show a significant increase of sulfated sex steroid levels in serum and coelomic fluid (CF) at final maturation (FM). It is hypothesized that the steroid metabolites could be part of a chemical communication system related to reproduction.
- Non-invasive assessment of reproductive status and cycle of sex steroid levels in a captive wild broodstock of Senegalese sole Solea senegalensis (Kaup)Publication . Garcia-Lopez, A.; Anguis, V.; Couto, Elsa; Canario, Adelino V. M.; Canavate, J. P.; Sarasquete, C.; Martínez-Rodriguez, G.Senegalese sole, Solea senegalensis, intensive culture is currently limited mainly due to the low control on reproduction in captivity. Comprehensive knowledge of reproductive biology and physiology for this species is needed in order to improve tank spawning success. This work describes for the first time the seasonal profiles of plasma levels of sex steroids (17β-estradiol, testosterone, 11- ketotestosterone, and 17,20β-dihydroxy-4-pregnen-3-one [17,20β-P]) in a S. senegalensis captive wild broodstock held under natural conditions, during two consecutive reproductive cycles. Changes in apparent maturation in females, dynamics of sperm release in males, and the condition factor (K) were monitored. Sixmaturation stages were established for females according to apparent size of the ovary and external abdominal swelling: early, intermediate and final ovarian development (F2+, F3+ and F4+, respectively), and partially spawned, mid spawned and spawned out or regressed (F3−, F2−, and F1−, respectively). During summer, F1− and nonrunning males (NRM) were predominant in association with low K and plasma steroid levels. At the end of summer, a new cycle of gonadal development started, denoted by the increase in reproductive parameters (K and steroid levels) and the appearance of F2+. By middle autumn, some females reached advancedmaturation stages (F3+ and F4+)while the proportion of runningmales (RM) showed a maximum. An occasional spawning could be registered during this season (November 2002). Towards the end of winter and beginning of spring, ovarian development reached its maximum. At this point, the proportion of F3+, F4+ and RM, K (specially in females), and steroid concentrations were the highest in concordance with the starting of the main spawning period (lasting from January to June 2003 and fromMarch to June 2004). Throughout this period, concomitantly with oocyte and sperm release, the proportion of F3−, F2−, F1− and NRMprogressively increased, while steroid levels and K progressively declined (concentration of steroids could fluctuate under a decreasing trend). The relatively elevated levels of 17,20β-P correlating with some parts of the spawning periods makes it a candidate for the role of the maturation-inducing steroid in S. senegalensis. Seasonal variations of measured parameters were consistent with the reproductive cycle of this species in the wild, and comparable to those found in other asynchronous multi-spawning fish.
- Ovarian development and plasma sex steroid levels in cultured female Senegalese sole Solea senegalensisPublication . Garcia-Lopez, A.; Couto, Elsa; Canario, Adelino V. M.; Sarasquete, C.; Martínez-Rodriguez, G.Ovarian development was studied in cultured female Senegalese sole Solea senegalensis. Females with regressed ovaries, mainly occupied by perinucleolar oocytes, predominated throughout summer exhibiting low condition factor (K), gonadosomatic index (IG), and plasma 17β-estradiol and testosterone levels. Throughout autumn and winter (ovaries at early and intermediate maturation), oocytes progressed to cortical alveoli and vitellogenic stages accompanied by increasing K, IG, and plasma 17β-estradiol and testosterone levels. At late winter/early spring, ovarian development reached its maximum with the predominance of females at intermediate and final maturation (the latter occupied by late vitellogenic oocytes and few early maturation oocytes) and peak values of K, IG, and 17β-estradiol and testosterone concentrations. Steroid levels were lower (especially testosterone) than those for naturally-spawning females, which might cause extensive atresia without final oocyte maturation (no spawning was observed). This degenerative process reduced de size of the ovary (initial and intermediate phases of regression) in association with declining K, IG, and plasma 17β-estradiol and testosterone levels and increasing proportions of perinucleolar oocytes. The circulating 17,20β-dihydroxy-4-pregnen-3-one levels, the proposed maturation-inducing steroid, remained relatively constant throughout the experimental period, suggesting that oocytes were unable to respond adequately to its stimulation. We propose the inadequate seasonal thermal regime as the main cause of such dysfunction.
- Plasma steroid hormone levels in female flounder Platichthys flesus and the influence of fluctuating hydrostatic pressurePublication . Damasceno-Oliveira, A.; Fernández-Durán, B.; Gonçalves, J. M. S.; Couto, Elsa; Canario, Adelino V. M.; Coimbra, JoséThe reproductive cycle in teleosts is timed to guarantee that eggs hatch in the right place at the right time, with environmental factors playing important roles in entraining and controlling the entire process. The effects of some environmental factors, like temperature and photoperiod, are now well understood. There are only a few studies regarding the effects of hydrostatic pressure (HP) on the reproductive cycle, in spite of its importance as a ubiquitous factor in all biological environments and affecting all living organisms. Hydrostatic pressure is of particular importance in fish because they can also experience rapid and cyclic changes in HP due to vertical movements in the water column. The aim of the present research was to investigate the effects of vertical migrations on the reproductive steroids of maturing female flounder. After a 14 day exposure to cyclic hydrostatic pressure (with a period of 12.4 h and with a maximum peak of 800 kPa of absolute hydrostatic pressure), fish showed significantly lower plasmatic concentrations of “5β,3α” steroids, metabolites of the putative maturation-inducing steroid in flounder (17α,20β-dihydroxy-4-pregnen-3-one). Results indicate that environmentally realistic cyclic changes of hydrostatic pressure can influence the metabolism of reproductive steroids. This suggests a physiological role of tidally-associated vertical migrations, affecting oocyte maturation and retarding the reproductive cycle in this species until the spawning ground is attained.
- Sex steroids and oocyte maturation in the sterlet (Acipenser ruthenus L.)Publication . Semenkova, T.; Canario, Adelino V. M.; Bayunova, L.; Couto, Elsa; Kolmakov, Nikolai N.; Barannikova, I.Sturgeon oocytes, like those of other vertebrates, are arrested in early meiosis and require a steroid or steroids to trigger meiosis resumption or maturation. The identity of the maturation-inducing steroid in sturgeons has present study was designed to investigate in sterlet the follicular secretion and relative blood changes of free and conjugated 17,20βP, 20βS and of the androgens T, 11KT, in response to hormonal treatment and to determine the relative potencies of the progestagens, 17,20β-P, 20βS, P4 and S, in inducing oocyte final maturation in vitro.
- Sex steroids of black scabbardfish, Aphanopus carbo, in relation to reproductive and migratory dynamicsPublication . Farias, I.; Couto, Elsa; Lagarto, N.; Delgado, J.; Canario, Adelino; Figueiredo, I.Black scabbardfish, Aphanopus carbo, is a commercially important species that takes distant migrations throughout its life cycle. Sex steroids were measured by radioimmunoassay in the blood plasma of specimens caught off the Madeira Archipelago and mainland Portugal to link this species migratory path with its reproductive cycle. Furthermore, a pilot study using Mozambique tilapia (Oreochromis mossambicus) was designed to evaluate the effect of sample freshness on steroid levels because black scabbardfish blood was collected at separate times after specimens were caught. The changes in T and 11-KT concentrations between the time of blood extraction and the time after preservation did not statistically differ among the different methods applied. Therefore, measured black scabbardfish steroid concentrations were directly used in the subsequent data analyses. In females, E2 and in T concentrations peaked at a late stage of vitellogenesis. E2 concentration was significantly different between females caught off each area. Clustering E2 and T concentrations from all developing females resulted in the separation of two distinct groups, independently of their geographical area. In males, T and 11-KT were not significantly different between maturity stages. The hepatosomatic index of males caught off mainland Portugal was relatively high. This may reflect a mechanism for storing energy that will later be consumed during migration to the spawning grounds. The trend of sex steroids concentrations throughout the sexual maturation of the species is consistent with the morphological indicators and shows evidence of the reproductive and migratory pattern hypothesised for the black scabbardfish in NE Atlantic.