Browsing by Author "Almada, Vítor Carvalho"
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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.
- Agonistic behaviour and control of access to hiding places in two intertidal blennies, Lipophrys pholis and Coryphoblennius galerita (Pisces: Blenniidae)Publication . Faria, Cláudia Barreiros Macedo de; Almada, Vítor CarvalhoIn this study we investigated the relationships between dominance rank and access to shelters in captive groups of Lipophrys pholis and Coryphoblennius galerita, as well as the effects of group size and shelter availability. Dominance rank was strongly correlated with size in juvenile L. pholis and with sex and size in adult C. galerita, males being dominant over females of similar size. Access to shelters was significantly correlated with dominance rank. For both species, most interactions occurred out of shelters. Direct disputes over shelters were always initiated by the dominant fish and the initiator was always the winner. The rate of aggression per fish per unit time decreased with an increase in the number of fish in L. pholis but not in C. galerita. No significant differences were found in groups differing in the number of shelters. C. galerita showed a higher rate of agonistic interactions and a higher proportion of overt aggression than L. pholis. It is suggested that one of the functions of agonistic interactions in these fishes is the control of a set of shelters, in the network of pathways used by each individual within its home range, minimising the time required to hide in case of danger.
- Agonistic behaviour and shoal composition of juvenile Diplodus sargus : First field observationsPublication . Gonçalves, Ana R.; Silva, Matheus Augusto Farias da; Vendrell, Catarina L.; Almada, Vítor CarvalhoBehavioural observations of juvenile Diplodus sargus in natural habitats were conducted to test whether agonistic interactions occur in natural circumstances and, if they do, in which context they happen. The level of aggression and the shoals composition were also compared between distinct natural habitats. Behavioural observations were also conducted in captivity, and the level of aggression was comparedwith the level recorded in natural conditions to investigate which factors may promote aggressive behaviours. The observations were performed at two sites in the Atlantic Portuguese shore: São Pedro do Estoril (38°41′N, 9°22′W) and Cabo Raso (38°42′N, 9°29′W) from early July to late August 2010 and from late July to early October 2011, respectively. In nature agonistic behaviours do occur, with a higher frequency in pools than in open areas. However, even the highest values observed in nature are significantly lower than those reported for captive conditions. Shoal composition also changed in different habitats, with more members and aggregates more compact in open areas.We suggested that the high levels of aggression observed in captive groups may be an artefact caused by very high densities in confined spaces and eventually by the accumulation of chemicals that are known to be released by stressed fish and can be detected by other conspecifics. The confinement imposed in captivity may also affect shoal composition limiting the number of members and inter-individual distances in each group.
- Agonistic behaviour and sound production in Gaidropsarus mediterraneus, (Gadidae)Publication . Almada, Vítor Carvalho; Amorim, Maria Clara Pessoa; Pereira, Eduarda; Almada, Frederico José Oliveira de; Matos, Ricardo Jorge S.C.; Godinho, RaquelAgonistic behaviour and sound production were described for captive Gaidropsarus mediterraneus, a shore-dwelling gadoid. Thump-like sounds were produced during agonistic interactions, which involved disputes over access to shelter sites.
- Alloparental behavior in the highly vocal Lusitanian toadfishPublication . Ramos, Andreia; Fonseca, Paulo Jorge; Modesto, Teresa; Almada, Vítor Carvalho; Amorim, Maria Clara PessoaIn many fish species in which males guard nests with their eggs, parental care directed to genetically unrelated offspring may arise for example from nest takeovers or cuckoldry. Lusitanian toadfish (Halobatrachus didactylus) has exclusive male parental care and face intensive nest competition during the breeding season that may lead to care of foster eggs. Males of this species use visual displays and sounds when defending their nests frequently resulting in expulsion of the intruder without escalated confrontation. In this study we intended to investigate the existence of alloparental care in Lusitanian toadfish, a behavior whose adaptive significance is still poorly understood. Fish were randomly assigned to three different treatments: parental males in nests with their eggs, parental males with foster eggs and parental males without eggs. Nests with eggs with no nest holder or with females were used as controls. We performed three territorial intrusions over periods of 15 days and observed the acoustic and visual behaviors of residents and intruders. Egg survival was tallied from nests' photographs in all groups. Circulating steroid levels were measured in the three test groups and in another set of non-manipulated males. There were no differences in acoustic and visual territorial defense behaviors among treatments. Egg survival was similar between males (parental and alloparental) and significantly higher than in nests with no nest-tender. Females presented intermediate egg survival. All groups presented similar levels of testosterone and alloparental males showed higher 11-ketotestosterone levels but within the range of levels observed in non-manipulated males. Cortisol levels were similar in all male groups suggesting that experiments did not increase fish stress. The present results suggest the existence of alloparental care in this species.
- An efficient technique for the captive breeding of an endangered freshwater fish Salaria fluviatilis (Pisces: Blenniidae), with a description of Its ontogenyPublication . Gil, Fátima; Faria, Cláudia Barreiros Macedo de; Almada, Vítor CarvalhoSalaria fluviatilis is one of the few freshwater members of the family Blenniidae and occurs around the Mediterranean Basin. This species is vulnerable or endangered in most countries where it occurs. Thus, information on its developmental biology and the establishment of methods for ex situ reproduction of highly endangered populations, to preserve them until natural habitats are restored, are much needed. A technique for the culture of this endangered species in controlled conditions is presented, together with the description of the full developmental sequence, from egg to adult. The use of the rotifer Brachionus calyciflorus at the onset of exogenous feeding proved to be an efficient way to allow larvae to reach the size when they can feed upon Artemia nauplii. Embryonic development lasted 12–14 d at 20–21 C. Newly hatched larvae measured 5.1 mm total length (TL). The mouth and anus were opened; the eyes were pigmented; there were almost no yolk; and the pectoral fins were small and unpigmented. Most larvae settled at 13.0–14.0 mm TL (27–31 d after hatching) and showed full juvenile pigmentation patterns at 27.0–28.0 mm TL (83 d after hatching). The larvae of this species showed agonistic behaviors once they began to settle.
- Analysis of conditional contingency using ACTUS2 with examples from studies of animal behaviorPublication . Estabrook, George F.; Almada, Vítor Carvalho; Robalo, Joana IsabelIn this paper we present ACTUS2, the second version of ACTUS (Analysis of Contingency Tables Using Simulation). ACTUS2 has many new features, including analysis of data in which dependencies that make some combinations of properties impossible are hypothesized. Because ACTUS2 explicitly simulates such hypotheses, it can be used without loss of accuracy to analyze small amounts of data in large tables with many zeros or very low frequencies. We illustrate these features with two studies of animal behavior: interactions of male individuals with other individuals in groups of captive, mature Triturus marmoratus pygmaeus (newts); and agonistic interactions between pairs of male juvenile Diplodus sargus (the sparid fish, white sea-bream). Both significantly frequent, and significantly infrequent, co-occurrences that had biologically meaningful interpretations were revealed.
- Androgen levels and social interactions in breeding males of the peacock blennyPublication . Oliveira, Rui Filipe; Almada, Vítor Carvalho; Gonçalves, Emanuel João; Forsgren, E.; Canário, Adelino V. M.Nest-holder male Salaria pavo have lower circulating concentrations of 11-ketotestosterone (KT) at the beginning of the breeding season than at its peak. At that peak density of nesting males was higher as were the number of visits of sneaker males to nests and of agonistic interactions between nest-holders and sneaker males. There was no difference between the two dates either in the frequency of male–male interactions or in the frequency of courtship episodes. Thus, higher plasma levels in nest-holders might be explained by a more intense sneaking pressure at the peak of the breeding season. At that peak, nest-holders had higher plasma levels of KT and a higher testosterone (T) to KT metabolization index in the gonads than did floater males. Both nest-holders and floaters had higher levels of KT and T in the testicular gland than in the testis. The levels of both androgens in the testicular gland, but not in the testis, were correlated with circulating concentrations of KT. These results suggest that the testicular gland is the major source of circulating KT in blenniids. Nest-holders had higher metabolization indexes than floaters both in the testis and in the testicular gland, which suggests that nest holding status promotes the conversion of T into KT.
- Androgenization of dominant males in a cichlid fish: Androgens mediate the social modulation of sexually dimorphic traitsPublication . Oliveira, Rui Filipe; Almada, Vítor CarvalhoWe present data on the relationship between social status and male secondary sex traits, both morphological and ethological, in Oreochromis mossambicus at the onset of sexual maturation. There is a differential expression of morphological (dorsal fin height, anal fin height, mandible width and premaxilla length) and behavioural (nuptial coloration, per cent time defending a territory, spawning pit volume, pit hovering and courtship rate) traits according to social status, with dominants presenting the highest expression of these dimorphic traits. Social status also affects the development of the genital papillae, which is considered to be a good predictor of androgen levels in cichlid fishes. The results support a causal model in which social status modulate androgen levels that in turn modulate the expression of behavioural and morphological male traits.
- Are local extinctions and recolonizations continuing at the colder limits of marine fish distributions? Halobatrachus didactylus (Bloch & Schneider, 1801), a possible candidatePublication . Robalo, Joana Isabel; Crespo, Ana Maria Azambuja Farinha da Conceição Pereira; Castilho, Rita; Francisco, Sara Martins; Amorim, Maria Clara Pessoa; Almada, Vítor CarvalhoIn this paper, we compare the populations of the Lusitanian toadfish Halobatrachus didactylus along the Portuguese shore, using a putative fragment of the mitochondrial control region and the first intron of the S7 ribosomal protein gene. This demersal species ranges from the tropical West African coast to the Iberian Peninsula and the Mediterranean, having its northern limit in the Tagus River. For the putative control region, a single haplotype occurs in all fish from Tagus and Sado (the location immediately to the south) with a clear increase in diversity to the South, peaking at Algarve (south Portugal). The data seem to point to a very recent Holocenic colonization of Tagus and Sado from the South (possibly Algarve). We suggest that even small oscillations in sea surface temperature (SST) may cause local extinctions and subsequent recolonizations in populations of thermophilic fish that are at the cold limit of their distributions.