Microhabitat segregation in three rocky intertidal fish species in Portugal: does it reflect interspecific competition?

Recruits of Lipophrys pholis , Coryphoblennius galerita and Gobius cobitis spend the low tide under water in pools, and in the case of G. cobitis also in channels. The pools used by the two blenniids show greater similarity than those used by G. cobitis. Larger juveniles and adults of C. galerita continue to use the same type of pools, which are temporarily abandoned by the males during the breeding season when they use emersed holes and crevices as nests. The much faster growing L. pholis and G. cobitis leave the pools in their first autumn, when they are c. 7 cm long. Whereas G. cobitis >7 cm move to channels and large upper pools, with a smooth substratum, sand and boulders, L. pholis begin to use emersed crevices where they spend low tide often in large groups. When L. pholis or C. galerita were added or removed selectively from pools, their numbers returned to pre-experimental levels after 2 weeks, suggesting that, although intraspecific competition may be strong, interspecific competition was unlikely to explain these results fully.     

Effects of temperature on the food processing of three species of seaweed-eating fishes from European coastal waters

Food consumption, gut transit times and assimilation efficiencies of the temperate fishes Lipophrys pholis and Parablennius sanguinolentus (Blenniidae) and Gobius cobitis (Gobiidae. when fed the green alga Ulva lactuca were determined at four temperatures in the laboratory. Food consumption increased and gut transit times decreased with increase in temperature in all three species. Assimilation efficiencies for algal carbon and nitrogen did not vary with temperature in G. cobitis . Carbon but not nitrogen assimilation efficiency varied with temperature in P. sanguinolentus , and both carbon and nitrogen assimilation efficiencies changed broadly with temperature in L. pholis , the most omnivorous of the three fishes. Assimilation efficiencies of all three species were generally within the previously reported ranges for herbivorous marine fishes. These species are thus clearly capable of extracting energy from algal food sources.     

Sexing blennies using genital papilla morphology or ano-genital distance

Information on the genital morphology of male and female Lipophrys pholis is provided, as well as for two other sympatric blenniid species, Coryphoblennius galerita and Lipophrys trigloides. The use of non-invasive sex determination procedures described may be extremely useful not only for ecological studies but also as a proxy for the detection of environmental exposure to endocrine disruptive chemicals, given that blennies have been proposed as potential sentinel species for chemical contamination.     

Morphological evidence for the biological role of caniniform teeth in combtooth blennies (Blenniidae, Teleostei)

Combtooth blennies have recurved, fang-like caniniform teeth at the rear end of a single row of incisiform teeth. The lengths and positions of these canines were measured in the lower jaws of males of 14 species of Mediterranean Blenniidae. In four species, lower jaw canines were measured in males and females, while in one species, the upper jaw canines of both sexes were also measured. Relative (to body length) canine length in males tends to be significantly greater (10–40%) than in females. There are significant interspecific differences in relative canine length, with smaller species tending to have relatively larger teeth. No significant correlation was obtained between canine length and importance of animal prey in the diet, nor with 'hole fit' of males, which may be related with the intensity of paternal care. We suggest that canines in combtooth blennies are predominately used for predator deterrence and agonistic interactions.     

Diet of combtooth blennies (Blenniidae) in Kochi and Okinawa,Japan

Combtooth blennies (Blenniidae) have a wide array of diets, including coral polyps, fish scales/mucus/rays, and detritus. However, there is limited knowledge about the diet of some species. We described the diet of 30 blenny species from subtidal, intertidal, or supralittoral habitats in Kochi (warm temperate) and Okinawa (tropical), Japan. Cluster analysis of dietary overlap grouped blennies into seven feeding groups: omnivores, herbivores, detritivores, molluscivores, corallivores, worm-like invertebrate feeders, and fish mucus/scale/ray feeders. The largest cluster, detritivores, contained 17 blenny species from all habitat zones and both climate zones. Our findings suggest that closely related species fill similar feeding niches and detritus is an important component of many blenny diets.     

A comparison of circatidal rhythmicity and entrainment by hydrostatic pressure cycles in the rock goby, Gobius paganellus L. and the shanny, Lipophrys pholis (L.)

The intertidal teleosts Gobius paganellus and Lipophrys pholis show endogenous circatidal activity rhythms when recorded in constant conditions. Under these conditions, the rhythm of L. pholis is the more precise which may indicate stronger coupling between underlying circalunadian oscillators in this species. In G. pagunellus the inter-oscillator coupling may be weaker and this could enable a more subtle interpretation of tidal fluctuations than in L. pholis . The oscillators may, however, be fundamentally different in the two species; circalunadian in G. paganellus and circatidal in L. pholis .
When exposed to hydrostatic pressure cycles of tidal frequency both species responded pre- dominantly to increasing pressure, which suggests that in the wild they are likely to be most active on the rising tide. Hydrostatic pressure cycles are confirmed as a zeitgeber for both species by the successful entrainment of some individuals. The lack of entrainment of others impIies that additional zeitgebers are required for complete entrainment.     

Parental care in the rocky intertidal: a case study of adaptation and exaptation in Mediterranean and Atlantic blennies

Summary The main features of the behavioural ecology of rocky intertidal species are compared both within families — though concentrated on blennies — and between habitats. It is suggested that, at the behavioural level, the reduction of vertical and swimming elements in the male sexual and agonistic displays of Blennioidei may constitute an adaptation to typical intertidal conditions, especially in those species that inhabit areas exposed to strong wave action. The other aspect which is discussed is the prevalence of parental care in rocky intertidal fishes. In these fishes parental care is much more frequent than for marine fishes as a whole. Taken alone, this could also suggest that guarding evolved as an adaptation during the process of colonization of these habitats. The hypothesis proposed in this paper is that guarding was already present in the ancestors of the resident species, at least in the majority of cases. Many differences in interhabitat studies may express the action of the environment, not as an agent of natural selection, but as a filter, which prevented some groups from invading a given habitat and, at the same time, made colonization easier for other groups. When a number of taxa that colonized a given habitat display clear similarities in their behaviour and their biology, adaptation is not necessarily demonstrated. There is evidence in the literature to support the hypothesis that those traits were already present in the ancestors of the rocky intertidal resident fishes, thus being best viewed as exaptations.     

Agonistic behaviour and control of access to hiding places in two intertidal blennies, Lipophrys pholis and Coryphoblennius galerita (Pisces: Blenniidae)

In 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. Received in revised form: 29 January 2001 Electronic Publication     

SPATIAL DYNAMICS OF A HIMANTHALIA ELONGATA (FUCALES, PHAEOPHYTA) POPULATION

In dense monospecific stands of plants intraspecific competition usually results in self-thinning, the concurrent increase in biomass and decrease in density over time. Self-thinning may also result in a change in the spatial pattern of individuals, but so far the spatial dynamics of marine plants has not been investigated. The brown alga Himanthalia elongata ( L.) S. F. Gray forms dense monospecific stands on many northern temperate rocky shores, and various attributes (including its simple form) facilitated the study of the spatial dynamics of this species .
The spatial pattern of settling zygotes was examined in the laboratory. In the absence of water movement, substratum heterogeneity, and a point source, zygotes usually settled in clumps rather than randomly. Within the clumps zygotes appeared to be regularly distributed at a scale similar to the size of the zygotes themselves. Furthermore, the clumps themselves seemed to be regularly distributed. On the shore, well-established stands of "button-stage" Himanthalia populations were examined during a period of extensive growth and self-thinning. Individual plants were initially highly regular in spatial pattern but became less so over time. The pattern of plants dying during self-thinning was also highly regular and probably reflected existing spatial regularity. However, using a hypothesis of mortality as a random event, I found that smaller plants had a less than average survival potential, while larger plants had a greater than average chance. A consideration of the spatial pattern of plants alive at the end of the study revealed regularity at a scale of 2–7 mm but a random spatial pattern at larger scales, which might indicate a small sphere of influence of competing individuals. The best predictor of mean nearest neighbor distances in the populations was mean plant diameter .     

Use of cues by Lipophrys pholis L. (Teleostei, Blenniidae) in learning the position of a refuge

The ability of Lipophrys pholis to remember the position of a refuge was tested in an artificial habitat under the influence of different visual clues. L. pholis learned the position of the refuge in the presence of a clue consisting only of a small black screen. They responded to this clue by moving towards it and pressing themselves up against it. Lego towers and a white screen clue did not provoke such a response. In a further experiment L. pholis continued to respond to the black screen in this way when the screen was moved to another location further from the refuge. After 12 days L. pholis learned to use the black screen in its new position as an indirect clue and navigate to the refuge directly without first approaching the black screen. These results suggested that when placed in a novel habitat the immediate reaction of L. pholis is to move quickly towards the first dark area they see but, with experience, they can use the position of large objects around them to navigate quickly and efficiently to a refuge.     

Extreme dentition does not prevent diet and tooth diversification within combtooth blennies (Ovalentaria: Blenniidae)

The dentition of fishes can be quite striking and is often correlated with a specific diet. Combtooth blennies have long incisiform oral teeth, unlike most actinopterygians. It has been suggested that the long tooth morphology is an adaptation for detritivory, but given the diversity of diets (detritus, coral polyps, polychaetes, and pieces of other fishes), are blenny teeth indeed monomorphic? Or does tooth variation associated with diet still exist at this extreme? To explore tooth and diet diversification, we used a new phylogenetic hypothesis of Blenniidae, measured tooth shape, number, and mode of attachment, and quantified blenniid diet. The ancestral diet of blennies contained detritus and diversified into many different diets, including almost exclusively detritivory. Our results reveal a dental cline that may be constrained by tooth shape, but has not prevented diet diversification. Ancestral state reconstruction of tooth morphologies suggests that the ancestor of blennies had many unattached teeth and featured transitions to fewer attached teeth, with several transitions back to attached or unattached teeth. The dentition of blenniids is not monotypic; rather it is diverse and small changes in tooth shape are accompanied by changes in size, number, attachment, and often diet.     

Predators,Parasites and Heterospecific Aggregations in Chrysomeline Larvae

Gregariousness is a common feature in aposematic insect prey and offers the additional benefit of enhancing the effectiveness of their toxic defences. Aggregations of the aposematic larvae of two species of leaf beetles, Paropsis atomaria and Paropsisterna variicollis, occur together on the same Eucalyptus trees over spring and summer. Conventionally, the colouration of these larvae is thought to provide aposematic protection against vertebrate predators, but supporting evidence is limited. We determine whether environmental preferences contribute to the heterospecific aggregations, and the potential costs for larvae of living in heterospecific aggregations. We surveyed natural aggregations of the larvae of both species in the field and recorded environmental variables of these aggregations. This revealed that heterospecific aggregations occurred more commonly at higher leaf temperatures, and in less visually conspicuous locations. Paropsis atomaria larvae were twice as likely to be found in heterospecific aggregations than Pa. variicollis. Next, we manipulated larval aggregations in the field to investigate the survival and gregarious behaviour of larvae in heterospecific aggregations. The gregarious behaviour of both species of larvae did not differ between heterospecific and monospecific aggregations. Further, the survival of larvae did not significantly differ between heterospecific and monospecific aggregations. We suggest that the preference for P. atomaria larvae to aggregate with Pa. variicollis at higher leaf temperature results in the observed heterospecific aggregations, with a potential benefit of lowerer parasitoidism rates for P. atomaria.     

Genetic divergence in the Atlantic-Mediterranean Montagu's blenny, Coryphoblennius galerita (Linnaeus 1758) revealed by molecular and morphological characters

Coryphoblennius galerita is a small intertidal fish with a wide distribution and limited dispersal ability, occurring in the northeastern Atlantic and Mediterranean. In this study, we examined Atlantic and Mediterranean populations of C. galerita to assess levels of genetic divergence across populations and to elucidate historical and contemporary factors underlying the distribution of the genetic variability. We analyse three mitochondrial and one nuclear marker and 18 morphological measurements. The combined dataset clearly supports the existence of two groups of C. galerita: one in the Mediterranean and another in the northeastern Atlantic. The latter group is subdivided in two subgroups: Azores and the remaining northeastern Atlantic locations. Divergence between the Atlantic and the Mediterranean can be the result of historical isolation between the populations of the two basins during the Pleistocene glaciations. Present-day barriers such as the Gibraltar Strait or the 'Almeria-Oran jet' are also suggested as responsible for this isolation. Our results show no signs of local extinctions during the Pleistocene glaciations, namely at the Azores, and contrast with the biogeographical pattern that has been observed for Atlantic-Mediterranean warm-water species, in which two groups of populations exist, one including the Mediterranean and the Atlantic coast of western Europe, and another encompassing the western tropical coast of Africa and the Atlantic islands of the Azores, Madeira and Canaries. Species like C. galerita that tolerate cooler waters, may have persisted during the Pleistocene glaciations in moderately affected locations, thus being able to accumulate genetic differences in the more isolated locations such as the Azores and the Mediterranean. This study is one of the first to combine morphological and molecular markers (mitochondrial and nuclear) with variable rates of molecular evolution to the study of the relationships of the Atlantic and Mediterranean populations of a cool-water species.     

Agonistic Support in Juvenile Japanese Macaques: Cognitive and Functional Implications

Agonistic support is generally considered a classical example of altruistic behaviour. It plays a critical role in the process of rank acquisition. This study investigates agonistic coalitions involving juvenile Japanese macaques (Macaca fuscata) living in a large captive group. Kinship was a good predictor of agonistic support received by juvenile macaques. Kinship also had a significant, though weaker, influence on agonistic support given by juvenile macaques. The latter was strongly influenced by the prospective rank of the individual against which the coalition was directed, i.e. by the rank relationship between the target of the coalition and the juvenile’s mother. Juvenile macaques intervened aggressively more against prospectively subordinate individuals than against prospectively dominant individuals. These results imply agonistic support is not necessarily altruistic, and support the hypothesis that primates may understand the rank relationship that exist among their group mates, i.e. that they are aware of third‐party social relationships. They also suggest that selective pressures associated with the process of rank acquisition may have favoured the evolution of higher cognitive abilities.     

Serial agonistic attacks by greylag goose families, Anser anser, against the same opponent

It is known from primates that alliance partners may support each other's interests in competition with others, for example, through repeated agonistic attacks against a particular individual. We examined serial aggressive interactions between greylag goose families and other flock members. We found that repeated attacks towards the same individual were common and that up to five serial attacks by family members followed an initial attack. Family size did not affect the frequency of such serial attacks. Juvenile geese evidently benefited most from active social support through serial attacks. About 60% of the juveniles' lost primary interactions were subsequently reversed by another family member. This may be one of the reasons why juveniles rank higher in the social hierarchy than would be expected from their age and size alone. Losses in serial attacks predominantly occurred against other, presumably higher-ranking, family geese and ganders. We propose three major functions/consequences of serial attacks. Analogous to primates, serial attacks in greylag geese may serve to reinforce a losing experience of an opponent defeated in a preceding attack. On the side of the winning family, serial attacks may reinforce the experience of winning. Both winning and losing experiences are linked with physiological consequences in higher vertebrates, affecting the future social performance of winners or losers. Finally, serial attacks may signal the agonistic potential of a family to other flock members. This is supported by heart rate data, which indicate that greylags are competent to interpret third-party relationships.     

Biochemical and hormonal correlates of dominance and social behavior in all-male groups of squirrel monkeys (Saimiri sciureus)

This study examined the relationship between dominance rank and several physiological and behavioral measures in stable, captive, all-male squirrel monkey groups. Four groups, each containing three males, were observed for 12 weeks during the breeding season. Relative dominance ranking among males in each group was based on the direction of agonistic behaviors displayed. For each subject, whole blood serotonin (WBS), plasma testosterone (T), and cortisol (C) were sampled 4 to 6 times over the course of the study. Samples were separated by 1- to 2-week intervals. Each group had a stable linear dominance hierarchy. WBS had small intraanimal variance and was positively related to dominance rank. In contrast, T and C were highly variable within subjects and were unrelated to dominance rank. Among alpha males, concentrations of T and C were positively correlated, and WBS and C were negatively correlated. The effect of dominance rank on the relationship between within-animal fluctuations in WBS, T, and C and behavior was also assessed. In dominant, but not subordinate subjects, intraanimal fluctuations in WBS correlated with agonistic behavior initiated, and fluctuations in C and T correlated with huddling. In beta and gamma males, C was related to agonism received, and in gamma males to food stealing received. Dominance status also affected endocrine response to the stress of capture but not the rate of sneezing. Sneezing was positively correlated with T concentrations irrespective of dominance rank. These results extend the association between WBS and dominance rank previously reported in Old World monkeys to a New World monkey species, support previous suggestions that mean T and C titers are not reflective of dominance rank in well-established groups, and indicate that dominance rank affects adrenocortical response to the stress associated with capture and anesthesia.     

Male rank and reproductive activity in Savanna baboons

Access to sexually receptive baboon females has been linked to male dominance rank. An intensive 19-month field study of mate choice and mate competition among savanna baboons was undertaken in order to elucidate those factors influencing mating success. During this study, male agonistic rank was not correlated with male mating success among adult males. However, the inclusion of adolescent males into the analysis yielded significant correlations between rank and mating success. Examination of prior fieldwork revealed that no baboon field study has conclusively demonstrated a significant correlation between male rank and reproduction among adult males. Most studies reporting a correlation between male rank and reproduction have included subadult males in the analysis. It is concluded that male rank is an unreliable predictor of male reproductive activity among adult male baboons. A low agonistic rank need not reduce male mating success because adult male baboons utilize a variety of reproductive tactics in gaining access to consort females.     

Body Size and the Maintenance of Reproductive Isolation in Stickleback,Genus Gasterosteus

The blackspotted stickleback Gasterosteus wheatlandi and the widely studied threespine stickleback G. aculeatus are sympatric throughout the former’s range and share many aspects of life history and reproductive behaviour. These two species differ significantly in size, with G. wheatlandi of both sexes measured at approximately 60% of the standard length of their G. aculeatus counterparts. This study concentrated on G. wheatlandi courtship behaviour and investigated its role in the maintenance of reproductive isolation with G. aculeatus. Specifically, the roles that (1) female body size plays in influencing male courtship preferences and (2) male body size and behaviour play in female courtship preferences were investigated through dummy and live conspecific and heterospecific stimulus presentations. Male G. wheatlandi courtship preferences are consistent with previously described patterns for G. aculeatus. Males of both species preferentially approach and court the larger of two simultaneously presented live or dummy females. Thus, the smaller G. wheatlandi males are indiscriminate with respect to assortative mate choice; not only preferring to approach and court more fecund conspecific females but, more significantly, G. aculeatus‐sized females. In contrast, females of both species demonstrate strong assortative courtship preferences. When presented with pairs of flask‐enclosed males, females of both species preferentially orient and court the conspecific male over the heterospecific. Similarly, when presented with a conspecific male and a heterospecific male presented singly, females prefer to enter the nest of the conspecific. Systematic analysis of the interactions between these pairs of fish (one male, one female) demonstrates that the breakdown of courtship in heterospecific courtship occurs late in the courtship sequence when the widely differing forms of male leading behaviour results in drastically differing female responses. I suggest that, as previously described in G. aculeatus, the supernormality effect plays a significant role in mediating adaptive mate choice behaviour in G. wheatlandi. However, the added element of a larger sympatric species introduces a possible cost in time and energy devoted to courting heterospecific, and sympatric, females that the larger G. aculeatus do not likely incur. There is substantial evidence from many sympatric G. aculeatus species pairs that there is assortative mate choice based on size and/or courtship behaviour. Courtship trials suggest a more pervasive role for females in assortative mate choice. Whether it is male body size per se, or in combination with behaviour, morphology or other cues, is unresolved in the present study.     

On the spatial distribution, feeding and reproduction of the vermetid gastropod Dendropoma maximum

D. maximum is a dominant species of outer reef flats in the Red Sea, reaching densities of about 22/m² and biomass of 15.8 g dry tissue/m². A few individuals attached to loose rocks are found inside the breaker zone but they may have been dislodged by heavy seas from the outer reef flat. D. maximum feeds from a mucus net which is spread by wave action over the substratum. Hauling the net occurs at approximately 13 minute intervals throughout the 24 hours and lasts about two minutes. Neighbours with overlapping nets stimulate each other to haul and reduce feeding efficiency. The net is grasped by a pair of lateral jaws, tugged free of the substratum by rotation of the body and ingested by a zipper-like action of the lateral and marginal radula teeth. The robust, central and lateral teeth become worn, possibly while channelling out the substratum to accommodate new shell. Defaecation occurs about 2.4 times an hour, amounting to 10450 kcal/m²/y. Females may brood simultaneously at least 11 egg capsules at various stages of development, which are suspended by stalks from the roof of the shell and pass through a dorsal slit in the mantle. Each capsule contains–500 embryos which develop into larvae with simple, coiled shells 0.33 mm in diameter. There is no planktonic phase. Adult shells amount to 2.5 kg/m² on the outer reef flat, while dead shells are often occupied by blennies. Although D. maximum is not a specialized filter feeder, the highly developed ciliary mechanisms suggest that filtering may be an auxiliary feeding method.