The reproductive output of frogs Rana temporaria (L.) with particular reference to body size and age

Abstract

Measurements were made on 274 spawn clumps and 271 adult frogs in three consecutive years at breeding sites in the west of Ireland. Mean clutch size was 1008 ± 20 ova, mean egg diameter was 2·32 ± 0·01 mm, and mean clutch weight was 11·62 ± 0·37 g. At any particular body length, larger clutch sizes were associated with smaller egg sizes and vice versa. Clutch size, egg size and clutch weight all increased allometrically with body size. The bigger females produced more and smaller eggs and a heavier clutch, relative to their body size, than smaller ones. Egg size and clutch weight also increased allometrically with female age. Age‐specific clutch weight increased during the first two years of maturity and declined slightly thereafter. Age‐specific egg size increased with age throughout life. At any age, bigger females produced more but not larger ova, and at any length, older females contained larger but fewer eggs. Both bigger and/or older females exhibited greater variability in the reproductive parameters than smaller and/or younger ones. Laboratory mating experiments showed that egg fertility was positively correlated with absolute male length and with the relative male/female length in amplexus. The fertilizing ability of males, however, declined with mating frequency, irrespective of male length, clutch size or the time interval between successive matings. In the wild, egg fertility ranged from 24–100%, although over 90% fertility was common.

Factors affecting variation in the reproductive investment of female treefrogs, Hyla intermedia

“…The positive association between body size and egg size is commonly observed among anurans (review in Kusano and Hayashi, 2002), whereas the relationship between age and egg size shows a less consistent pattern. In some species, egg size increases with age (Gibbons and McCarthy, 1986;Berven, 1988), whereas in others, no relationships are observed after controlling for body size variation (Tejedo, 1992;Kusano and Hayashi, 2002; the present study).…”

“…In these species, size-dependent differences in fecundity may thus arise from differences in age at maturity, that is, from different tradeoffs between the expected number of reproductive episodes and the reproductive success of each episode (Shine, 1988). Furthermore, age may directly affect variation in fecundity if the proportion of resources allocated to reproduction, rather than to growth and self-maintenance, increases with age (Gibbons and McCarthy, 1986;Berven, 1988).…”

Post-mating clutch piracy in an amphibian

“…Considerable variation in the number of fertilized eggs per clutch has been reported previously for R. temporaria (5-100%) 22,23 . By experimentally rearing 25 pirated and 31 non-pirated clutches we found that under specific circumstances clutch piracy helps to increase the number of eggs fertilized per clutch (Fig.…”

Clutch size, egg survival and migration distance in the agile frog (Rana dalmatina) in a floodplain

“…In species where most individuals breed only once, such as Rana dalmatina (Guarino et al, 1995), other criteria than previous experience may prevail in migration guidance. On the other hand, despite an indeterminate growth, a positive relationship between age and body size has never been evidenced in frogs of the genus Rana (Gibbons & McCarthy, 1986 ;Augert, 1992). As a consequence, a larger body size does not suggest a previous experience of breeding migration.…”