Browsing by Author "Vieira, Maria Natividade"
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- Activity rhythms and cyclical changes of microhabitat preferences in the intertidal pipefish Nerophis lumbriciformis (Pisces: Syngnathidae)Publication . Monteiro, Nuno Miguel; Vieira, Maria Natividade; Almada, Vítor CarvalhoAs an inhabitant of the intertidal zone, Nerophis lumbriciformis predictably should show a clear rhythmic activity, with its maximum closely correlated with the high tide period, as observed in several other rocky intertidal fish species. We investigated the rhythmic activity patterns of N. lumbriciformis and analysed to what extent specific substratum preferences may be linked to water level and, ultimately, to the particular activity rhythm patterns of the fish. To determine N. lumbriciformis substratum preferences, two different experiments were conducted. The first evaluated substratum preferences from among a group of the four most common substrates found in the sample area. The second experiment evaluated the fish’s maintenance of that substratum preference, after alteration of the water level in a simulated ebb tide. From the available substrata, N. lumbriciformis displayed a clear preference for algae until the water level began to decrease. Then, the preference radically shifted from algae to boulders. N. lumbriciformis showed a clear rhythmic activity, affected by both tidal and circadian periodicity, producing asymmetrical activity peaks. Unlike the rhythms of other rocky intertidal fish species, the maximum activity peaks were not centred at the expected high tide period. The adaptive explanation for the apparently peculiar activity peaks appears to be related to the particular substratum preferences of N. lumbriciformis. The detected circatidal period seems, consequently, closely related to small migrations between substrata, whilst the observed increase in diurnal activity, independent of the tidal cycle, may be related to predatory activity, since N. lumbriciformis is a visual feeder.
- Can the limited marsupium space be a limiting factor for Syngnathus abaster with size-assortative matingPublication . Silva, K.; Vieira, Maria Natividade; Almada, Vítor Carvalho; Monteiro, Nuno Miguel1. Some syngnathid species show varying degrees of sex role reversal aside from male pregnancy, with females competing for access to mates and sometimes presenting conspicuous secondary sexual characters. Among other variables, brooding space constraints are usually considered a key element in female reproductive success, contributing strongly to the observed morphological and behavioural sexual differences. Nevertheless, a close relationship between sex role reversal and male brooding space limitation has not yet been accurately demonstrated in field studies. 2. The present work, conducted over two consecutive breeding seasons in a wild population of the sex role-reversed pipefish Syngnathus abaster , simultaneously analysed egg number and occupied space, as well as the free area in the male’s marsupium. The number of eggs that would fit in the observed unoccupied space was estimated. 3. Contrary to what would be expected, given the marked sexual dimorphism observed in the population studied, where females were larger and more colourful, male brooding space did not appear to limit female reproduction as neither large nor small individuals presented a fully occupied pouch. Interestingly, the largest unoccupied areas of marsupium were found in the larger individuals, although they received more and larger eggs. Laboratory data also showed that larger females lay larger eggs. 4. Together, these results suggest the existence of assortative mating, which may result from: (i) the reluctance of larger males (which tend not to receive small eggs usually laid by small females) to mate with lower quality females, even at the expense of a smaller number of offspring; or (ii) female– female competition, which might strongly reduce the hypothesis of a small female mating with a large male. The potential impact of temperature on reproduction and population dynamics is also discussed in the light of ongoing climatic changes.
- Contrasts in genetic structure and historical demography of marine and riverine populations of Atherina at similar geographical scalesPublication . Francisco, Sara Martins; Cabral, Henrique; Vieira, Maria Natividade; Almada, Vítor CarvalhoIn this paper, we compare the genetic structure and the historical demography of two populations of the sand smelt Atherina boyeri from the rivers Tagus and Mondego (Portugal) with two groups of samples of the closely related marine Atherina presbyter collected on the shore at comparable latitudes. A. presbyter is a pelagic marine inshore fish, while A. boyeri is typically found in coastal lagoons, estuaries and freshwaters bodies. Analysis of mtDNA control region sequences showed that the marine A. presbyter did not display signs of genetic differentiation between sites some hundreds of kilometers apart. On the contrary, A. boyeri showed clear differences between populations. The populations of A. boyeri showed a much lower genetic diversity and younger coalescence times when compared with A. presbyter. We suggest that these differences reflect the interplay between differences in ecology between the two species and the historical impact of the glaciations. While A. presbyter likely moved to the south evading the cold periods, A. boyeri probably went extinct and its populations in Western Europe are recent recolonizations from western Mediterranean refugia.
- Development and early life history behaviour of aquarium reared Syngnathus acus (Pisces: Syngnathidae)Publication . Silva, K.; Monteiro, Nuno Miguel; Almada, Vítor Carvalho; Vieira, Maria NatividadeSome notes on development and early life history behaviour of aquarium-reared Syngnathus acus are presented and compared with other syngnathid species, namely S. abaster. Implications in population dynamics and connectivity are discussed.
- Diet preference reflects the ontogenetic shift in microhabitat use in Lipophrys pholisPublication . Monteiro, Nuno Miguel; Quinteira, S. M.; Silva, K.; Vieira, Maria Natividade; Almada, Vítor CarvalhoBased on the heterogenous nature of Lipophrys pholis diet, the stage of the species’ ontogenetic development when major niche shifts occurred was identified, and the causes that force this blennid to change its feeding behaviour, vertical distribution and shelter occupation were considered. The diet analysis of the different size classes consistently showed two clusters, grouping individuals < or >8 cm total length. This shift occurred simultaneously with the onset of reproduction; it seemed to be independent of inter- and intraspecific competition and reflected a quantitative and qualitative alteration of the dietary constituents. The analysis of the diet of other sympatric intertidal blennids, Lipophrys trigloides and Coryphoblennius galerita, showed that, apart from the first developmental stages, there seemed to be no important dietary overlap. The inevitability of this niche alteration could be explained by the combination of at least two different factors: the development of the scraping capability that enabled the fish to feed on large benthic prey, together with the limited number of suitable shelters that were available in rock pools.
- Early life history of Syngnathus abasterPublication . Silva, K.; Monteiro, Nuno Miguel; Almada, Vítor Carvalho; Vieira, Maria NatividadeThe embryonic and larval development of the pipefish Syngnathus abaster is described, based on ex situ observations. The full development sequence lasted 24–32 days (at 18–19 C), which was shortened to 21 days at higher temperatures (21–22 C). Newborn juveniles, with a uniform dark brown colouration, immediately assumed a benthic spatial distribution. This vertical distribution pattern remained unchanged at least during the first 4 weeks, after the release from the marsupium. The apparent absence of a pelagic life phase might have important repercussions in terms of population connectivity given increasing fragmentation and degradation of the eelgrass habitat in the species’ range.
- Early life history of the pipe¢sh Nerophis lumbriciformis (Pisces: Syngnathidae)Publication . Monteiro, Nuno Miguel; Almada, Vítor Carvalho; Vieira, Maria NatividadeThe embryonic and larval development of the pipe¢sh Nerophis lumbriciformis is described. The full development sequence lasted 30 d (at 14-15ºC), being shortened to 25-26 d at higher temperatures (16-17ºC), and hatching occurred throughout a 2^3 d period. Unlike species of the genus Syngnathus, the newly hatched larvae presented a functional mouth apparatus and the yolk sac completely absorbed.
- Female reproductive tactics in a sex-role reversed pipefish: scanning for male quality and numberPublication . Silva, K.; Almada, Vítor Carvalho; Vieira, Maria Natividade; Monteiro, Nuno MiguelTheoretical studies predict that females should invest in current reproduction according to both the expected payoffs from mating with different-quality males and their future mating prospects. The Syngnathidae family, with its male pregnancy together with the occurrence of varying degrees of sex-role reversal, constitutes an exceptional model to study female allocation strategies. The present work tests for the influence of male availability and quality (translated into body size) on the egg allocation pattern of different-sized females of the sex role–reversed pipefish Syngnathus abaster. Besides revealing a multiple mating strategy and showing that females do not produce enough eggs to fully occupy a male’s brood pouch during the extent of a pregnancy, results reveal a complex pattern with different-sized females adopting different investment tactics. In contrast to small, less attractive females, who show a much more constant reproductive effort through the tested mating contexts, large females seem able to monitor the number and quality of available males responding accordingly by 1) laying more eggs in the presence of several large males or saving efforts for future breeding and 2) laying larger eggs in larger males while depositing smaller ones in lower quality individuals as a consequence of a serial mating process (large males first, small males later).
- Genetic structure and historical demography of the shanny Lipophrys pholis in the Portuguese coast based on mitochondrial DNA analysisPublication . Francisco, Sara Martins; Vieira, Maria Natividade; Almada, Vítor CarvalhoInexistente
- Homing behaviour and individual identification of the pipefish Nerophis lumbriciformis (Pisces; Syngnathidae): A true intertidal resident?Publication . Monteiro, Nuno Miguel; Vieira, Maria Natividade; Almada, Vítor CarvalhoSyngnathids have been the focus of growing interest due to their peculiar reproductive biology and vulnerability to environmental degradation and overcollecting. In this study, near the south limit of the species’ geographic distribution, a description of the homing behaviour of the worm pipefish, Nerophis lumbriciformis, based on the unique facial pigmentation patterns, is presented. Even though the amount of facial pigmentation was substantially higher in larger adult females, suggesting that it can be part of the secondary sexual repertoire of this sex role reversed species, this technique allowed for the positive identification of adult individuals (males and females) during at least 19 months. Recaptures showed that this pipefish shows a strong homing behaviour, with individuals being regularly captured within less than 2 m of the original identification event. The absence of horizontal migrations to adjacent areas and the observation of adults in the subtidal, together with the overall low number of recaptures (even though some individuals were cyclically resighted) highlighted the fact that the intertidal is not N. lumbriciformis’ permanent residence. This observation also demonstrates that the estimation of the population size, important for conservation purposes, based solely on intertidal data can be misleading because captured individuals are only a fraction of a larger, mainly subtidal, population.