Sex differences in resource utilization by the peacock blenny

This paper presents data on the seasonal variation of gonadosomatic, hepatosomatic and feeding indices in nesting males, females and female-like males of the blenniid fish Salaria pavo . Eviscerated condition factors, female fecundity and feeding rates are also presented. The results are consistent with the hypothesis that females maximize their feeding rates during reproduction, converting food into eggs through repeated spawning. Nesting males feed at a very low rate during the breeding season. It is argued that one major component of the reproductive costs in these males is the reduction of feeding opportunities. Female-like males present lower reproductive costs, which probably reflects the compromise between fertilizing some eggs and growing.     

The effects of resource availability on alternative mating tactics in guppies (Poecilia reticulata)

Food availability can influence the optimal allocation of timeand energy among alternative behaviors such as foraging, courting,and competing for mates. If populations differ consistentlyin food availability, selection may cause geographic divergencein allocation strategies. At the opposite extreme, a norm ofreaction may evolve such that food intake influences the allocationstrategy of individuals in the same way in all populations.Between these two extremes, food intake reaction norms may divergegenetically among populations. For example, at sites where foodis scarce, selection may strengthen the effect of food intakeon behavior, whereas at sites with abundant food, selectionmay be weak or even oppose plasticity. We tested these ideasby raising male guppies from streams differing in food availabilityin a common laboratory environment on either low or high foodlevels, and then observing them in the presence of male competitors(from the same population and diet group) and receptive females.Males from low-food-availability streams spent more time foragingthan males from high-food-availability streams, independentof food intake. Compared with males raised on the high foodlevel, males raised on the low food level spent more time foragingand were less aggressive towards other males. Courtship displayrate increased with food intake but only in males from low-foodstreams. In contrast, males from high-food streams showed greaterplasticity with respect to male-male aggression. These resultsgenerally support the resource availability/behavioral tradeoffhypothesis while also revealing a surprising degree of ontogeneticcomplexity in a relatively simple system.     

Ecological constraints on breeding system evolution: the influence of habitat on brood desertion in Kentish plover

1. One of the fundamental insights of behavioural ecology is that resources influence breeding systems. For instance, when food resources are plenty, one parent is able to care for the young on its own, so that the other parent can desert and became polygamous. We investigated this hypothesis in the context of classical polyandry when females may have several mates within a single breeding season, and parental duties are carried out largely by the male. 2. We studied a precocial wader, the Kentish plover Charadrius alexandrinus, that exhibits variable brood care such that the chicks may be raised by both parents, only by the female or, more often, only by the male. The timing of female desertion varies: some females desert their brood at hatching of the eggs and lay a clutch for a new mate, whereas other females stay with their brood until the chicks fledge. Kentish plovers are excellent organisms with which to study breeding system evolution, as some of their close relatives exhibit classical polyandry (Eurasian dotterel Eudromias morinellus, mountain plover Charadrius montanus), whereas others are polygynous (northern lapwing Vanellus vanellus). 3. Kentish plovers raised their broods in two habitats in our study site in southern Turkey: saltmarsh and lakeshore. Food intake was higher on the lakeshore than in the saltmarsh as judged from feeding behaviour of chicks and adults. As the season proceeded and the saltmarsh dried out, the broods moved toward the lakeshore. 4. As the density of plovers increased on lakeshore, the parents spent more time defending their young, and female parents stayed with their brood longer on the lakeshore. 5. We conclude that the influence of food abundance on breeding systems is more complex than currently anticipated. Abundant food resources appear to have profound implications on spatial distribution of broods, and the social interactions between broods constrain female desertion and polyandry.     

Reproductive phenology of the Azorean rock pool blenny a fish with alternative mating tactics

Both male and female Parablennius sanguinolentus parvicornis were ready to mate by the end of May. Seventy-five per cent of the 1-year-old males were mature, but only 25% of the females reached maturity at this age. In females, gonads formed an increasingly greater proportion of the total weight with age, but in males the proportion decreased. A bimodal distribution of gonadosomatic indices classes was observed in 2-year-old males (intermediate size), which reflected the lower opportunity that intermediate size males have to spend the ejaculates than have the younger and older males. The liver played an important role in the storage of energy before the reproductive season and reserves were utilized during the breeding season. Physical condition was at its lowest in July in both sexes, but in May, just before the breeding season began, large maturing females had significantly lower eviscerated condition than males. This could be due to females investing in oocyte development, while the priority for the males was to reserve their energy for the parental activities to come. In both males and females, older and bigger animals had lower hepatosomatic and body conditions than younger ones.     

Tactic-dependent plasticity in ejaculate traits in the swordtail Xiphophorus nigrensis

In species with alternative reproductive tactics, males that sneak copulations often have larger, higher quality ejaculates relative to males that defend females or nest sites. Ejaculate traits can, however, exhibit substantial phenotypic plasticity depending on a male's mating role in sperm competition, which may depend on the tactic of his competitor. We tested whether exposure to males of different tactics affected sperm number and quality in the swordtail Xipophorus nigrensis, a species with small males that sneak copulations and large males that court females. Sperm swimming speed was higher when the perceived competitor was small than when the competitor was large. Plasticity, however, was only exhibited by small males. Sperm number and viability were invariant between social environments. Our results suggest sperm quality is role-dependent and that plastic responses to the social environment can differ between male reproductive tactics.     

Evolution of alternative male morphotypes in oxyurid nematodes: a case of convergence?

Male dimorphism has been reported across different taxa and is usually expressed as the coexistence of a larger morph with exaggerated male traits and a smaller one with reduced traits. The evolution and maintenance of male dimorphism are still poorly understood for several of the species in which it has been observed. Here, we analyse male dimorphism in several species of reptile parasitic nematodes of the genus Spauligodon, in which a major male morph (exaggerated morph), which presents the traditional male morphological traits reported for this taxon, coexists with a minor morph with reduced morphological traits (i.e. reduced genital papillae) resembling more closely the males of the sister genus Skrjabinodon than Spauligodon major males. Because of the level of uncertainty in the results of ancestral state reconstruction, it is unclear if the existence of male dimorphism in this group represents independent instances of convergent evolution or an ancestral trait lost multiple times. Also, although the number of major males per host was positively correlated with the number of females, the same did not hold true for minor males, whose presence was not associated with any other ecological factor. Nevertheless, the existence of male dimorphism in Spauligodon nematodes is tentatively interpreted as resulting from alternative reproductive tactics, with differences in presence and number of individuals as indicators of differences in fitness, with the lower numbers of minor males per host likely maintained by negative frequency‐dependent selection.     

Risk taking during parental care: a test of the harm-to-offspring hypothesis

Amount of risk taking during parental care is often explainedin relation to the reproductive value of the offspring. The"harm-to-offspring hypothesis" focuses on the relative harma period of no parental care can do to the offspring. Accordingto this hypothesis, parents should take greater risks for offspringin poor condition than for offspring in good condition. We manipulatedoffspring condition in the pied flycatcher (Ficedula hypoleuca)and tested the harm-to-offspring hypothesis by exposing parentsto a predator model (a sparrowhawk, Accipiter nisus). Time elapseduntil a parent first entered the nest-box was used as a risk-takingmeasure. Parents spent significantly shorter time until first nestvisit for offspring in poor condition than for offspring ingood condition. Hence, the harm-to-offspring hypothesis wassupported.     

Steroid hormone profiles and relative body condition of calling and satellite toads: implications for proximate regulation of behavior in anurans

Males of most anuran species (frogs and toads) vocalize to attractmates. However, individuals of many vocal species may also adoptalternative noncalling "satellite" tactics. Satellite malescharacteristically remain in close proximity to calling conspecificsand attempt to intercept incoming females attracted to advertisingmales. Emerson proposed that alternation between calling andnoncalling behavior in anurans is mediated by a reciprocal interactionbetween circulating levels of corticosterone and androgens thatis driven by depletion of energy reserves during vocalization.We tested this hypothesis by examining steroid hormone profilesand the relative body condition of calling and satellite Woodhouse'stoads (Bufo woodhousii) and Great Plains toads (B. cognatus).Consistent with Emerson's hypothesis, callers had significantlyhigher circulating corticosterone levels and were in bettercondition than satellites. However, levels of testosterone anddihydrotestosterone did not differ significantly between satellitesand callers, and we found no evidence that high levels of corticosteronehad an inhibitory effect on androgen production in either species.These data thus support a relationship between corticosteronelevels and depletion of energy reserves during bouts of vocalizationbut suggest that alternation between calling and satellite behaviormay be associated with direct effects of corticosterone on brainvocal control centers. We propose a model that incorporatesrelationships among energy reserves, androgens, corticosterone,and arginine vasotocin-producing neurons in the telencephalonto explain transitions between calling and satellite tacticsin toads.     

Activity budgets of woolly spider monkeys,or muriquis (Brachyteles arachnoides)

One group of woolly spider monkeys, or muriquis (Brachyteles arachnoides), was observed from June 1983 through July 1984 at Fazenda Montes Claros, Minas Gerais, Brazil. The study subjects spent an average of 49% of their daylight time resting, 29% traveling, and 19% feeding. They shifted their diurnal schedule of activities in response to seasonal changes in temperature and rainfall. The activity budgets of adult males and females were similar. However, a comparison of three adult females in different reproductive conditions revealed that the lactating female spent a greater proportion of time feeding than did both the pregnant and nonreproductive females. Intraspecific differences in group size and diet appear to be important to understanding differences in the activity budgets of Brachyteles. Differences between locomotion patterns of woolly spider monkeys and sympatric howler monkeys may explain activity budget differences based on group size and diet.