Effect Of Male Size Research Articles

Parasites and parental care in male upland bullies (Eleotridae)

Parental care of eggs by male upland bullies Gobiomorphus breviceps was studied in the field and in the laboratory, with special emphasis on the effect of infection by trematode cysts. In the field, the proportion of old eggs in the nest affected the time taken by males to return to their nest after being chased away, but only in one year of the study. No effects of male size, male parasite load, number of eggs per nest or nest characteristics were observed. In the laboratory, heavily-infected males spent more time fanning their eggs than lightly-infected ones. Smaller males also tended to spend more time fanning than large males. Male size, parasite load and number of eggs per nest had no measurable effect on the aggressiveness of guarding males towards intruders, weight loss in males or egg incubation time. Parental investments did not vary as a function of age of the eggs. All males cannibalized some of their eggs, and there appeared to be a threshold brood size below which males consumed their entire brood. Overall, results were not consistent with those of studies on other fish species, and indicate that rules of investment in parental care may be different for fish inhabiting harsh, unpredictable environments.

Parasites and parental care in male upland bullies (Eleotridae)

Parental care of eggs by male upland bulliesGobiomorphus brevicepswas studied in the field and in the laboratory, with special emphasis on the effect of infection by trematode cysts. In the field, the proportion of old eggs in the nest affected the time taken by males to return to their nest after being chased away, but only in one year of the study. No effects of male size, male parasite load, number of eggs per nest or nest characteristics were observed. In the laboratory, heavily‐infected males spent more time fanning their eggs than lightly‐infected ones. Smaller males also tended to spend more time fanning than large males. Male size, parasite load and number of eggs per nest had no measurable effect on the aggressiveness of guarding males towards intruders, weight loss in males or egg incubation time. Parental investments did not vary as a function of age of the eggs. All males cannibalized some of their eggs, and there appeared to be a threshold brood size below which males consumed their entire brood. Overall, results were not consistent with those of studies on other fish species, and indicate that rules of investment in parental care may be different for fish inhabiting harsh, unpredictable environments.

Fertilisation success in the fly Dryomyza anilis (Dryomyzidae): effects of male size and the mating situation

Male fertilisation success in relation to male size and the mating situation (ordinary pair formation with a single, nonvirgin female vs. take overs) was examined in the fly Dryomyza anilis. In ordinary matings, large males achieved higher fertilisation success than small ones when they were the second to mate with the female. Take overs differ from ordinary pair formation in that the second male experiences intensified sperm competition. This is because in take overs the female is not able to discharge any of the sperm inseminated by the first male as she usually does before a new mating. Compared with ordinary matings, take overs reduced the fertilisation success of the second male by 8–10%, whereas that of the first male was 7–14% higher in take overs. Even though the intruder was always larger than the paired male his superior fertilisation success did not compensate for the effect of the sperm already present in the female. In D. anilis, males can increase their fertilisation success by tapping the female's external genitalia with their claspers or having several copulation bouts per mating. Thus, in a take over, the intruder could respond to the intensified sperm competition by performing more tapping sequences per copulation bout or more copulation bouts per mating. In matings observed in the wild, males performed more tapping sequences after a take over than after pair formation with a single female, although the difference was not significant. The results show that there are differences in fertilisation success between males of different size. In addition, different mating situations can result in considerable variation in the fertilisation success of an individual male. Higher fertilisation success for the first male after a take over may be significant, in particular, for the reproductive success of small males, which frequently lose their females to large males.

Fertilisation success in the fly Dryomyza anilis (Dryomyzidae): effects of male size and the mating situation

Fertilisation success in the fly Dryomyza anilis (Dryomyzidae): effects of male size and the mating situation

Evolutionary consequences of non-random mating: do large males increase offspring fitness in the anuran Bufo bufo?

The purpose of my study was to determine whether male body size, a trait known to be important to mating success, covaries with offspring performance. I tested the effects of male body size on the performance of Bufo bufo tadpoles reared at two food levels by mating large, small, and naturally-mated males to the same females. Survival of tadpoles in the high-food environment was affected by male size class, but in the opposite way to that expected. Tadpoles sired by large males had the lowest survival, and those sired by small males the highest. Neither body size at metamorphosis nor larval period were affected by male size class alone, but male size interacted with the female contribution: tadpoles sired by large males had short larval periods and large size at metamorphosis with some females,but long larval periods and small body sizes with others. Food level had a significant effect on both size at metamorphosis and larval period, and interacted with female contribution, but not male size class. This indicated that female contribution to tadpoles was dependent on food level, but that the effects of male size were not differentially expressed by tadpoles at the two food levels. My results indicate that traits with a direct effect on offspring fitness are not enhanced by large male body size, yet some males and females produced offspring with significantly better performance. I suggest that evolutionary change in this mating system is unlikely to occur through the non-random mating of males based on body size alone.

The effect of male size and operational sex ratio on male mating success in the common spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract. The effect of male size and operational sex ratio (number of adult males/number of adult males + number of females available for mating) on male mating success in the spider mite was studied both in the field and in the laboratory. Larger males defended females less intensely and for shorter periods, but had a higher probability of mating with a previously guarded female than smaller males. With increasing operational sex ratio agonistic interactions between males occurred more frequently and lasted longer. Large males guarded more selectively, i.e. spent less time guarding, than small ones. With increasing density of quiescent females (females in the final juvenile stage) all mates became more selective. Only small males guarded less selectively with increasing male bias. Females mated repeatedly. A female's first mating lasted longer on average than subsequent matings. In the absence of male-male competition, absolute mate size was positively correlated with the duration of the first mating. When males competed for females, the larger males were better able to resist attempted interference in mating than smaller males. Compared with balanced or female-biased operational sex ratios, mating interferences tended to be more common, although not significantly so, when the operational sex ratio was biased towards males. A male's chance to mate twice with a given female decreased with increasing operational sex ratio. Depending on the degree of male-male competition in a spider mite colony, the effects of male size on fighting ability, chance to mate, duration of precopulatory mate guarding and duration of mating will contribute to variation in male reproductive success in natural populations.

The effect of male size on receptivity in femaleLucilia cuprina (Diptera: Calliphoridae)

The first five matings by both large and small L. cuprinamales switched off receptivity in over 90% of females for 7 days after their initial mating. Small males were virtually unable to switch off females after five matings, whereas the fifth to tenth matings by large males rendered nearly two-thirds of females unreceptive. Mating duration of large and small males was about 11 min even after numerous matings. Given the rarity of field virgins and the temporal and spatial variability of female-required resources, larger males may enjoy greater mating success due to their ability to switch off many females in succession. Virgin males preferred to mate with nonvirgin females larger than themselves; males paired with females smaller than themselves adopted mate-rejection behavior typical of unreceptive females.

Effect of Male Size on Calling Propensity, Song Parameters, and Mating Success in Caribbean Fruit Flies, Anastrepha suspensa (Loew) (Diptera: Tephritidae)1

Sexual selection theory predicts discriminative female mate choice based on differences in male phenotype in lek-mating species. We selected large and small males of the Caribbean fruit fly, Anastrepha suspensa (Loew), and analyzed calling sounds produced by these males. Calling propensity was significantly higher and calling song pulse train interval significantly shorter in large males. In mate choice tests, 70% of mating females mated with a large male. Additionally, the power output (sound pressure level) of precopulatory songs of successfully mating males averaged 10 dB greater than that of mounting males that were rejected by females.