Female parent-offspring phenotypic data on color morph frequencies in the red-backed salamander, Plethodon cinereus, were obtained from two Virginia localities (164 broods from Greene County and 97 broods from Giles County). The color morph data indicate that the striped morph is genetically dominant in Giles County and recessive in Greene County. It is suggested that epistatic interaction of t...

Caspian brown trout (Salmo trutta caspius) is one of the economically valuable species in the Caspian Sea. Artificial propagation and production of larvae are the main problems in the early culture of this species. The purpose of this paper is to study the effect of reproductive performance of female broods on opposition reproduction efficiency in Caspian brown trout in the breeding season of 2...

1. Offspring sex ratio may be an unpredictable component of life history that might select for behavioural plasticity in parental care. If the parents do not have such plasticity and the two sexes of offspring differ in size, individuals in a brood or litter biased towards the larger sex offspring may suffer from food shortage. Sibling sex ratio could also affect the young through asymmetric se...

In species with biparental care, sexual conflict occurs because the benefit of care depends on the total amount of care provided by the two parents while the cost of care depends on each parent's own contribution. Asynchronous hatching may play a role in mediating the resolution of this conflict over parental care. The sexual conflict hypothesis for the evolution of asynchronous hatching sugges...

Heterosaccus lunatus parasitizes the portunid crab, Charybdis callianassa in Moreton Bay, Australia. With the host crabs maintained at 22.5 degrees C this sacculinid rhizocephalan released larval broods every 6-7 days. During July-August 1996 and particularly August 1999 such broods showed the change-over from male only larvae in the early broods to females only in the later broods. As the host...

In species with bi-parental care, individuals must partition energy between parental effort and mating effort. Typically, female songbirds invest more than males in reproductive activities such as egg-laying and incubation, but males invest more in secondary sexual traits used in attracting mates. Animals that breed more than once within a season must also allocate time and energy between first...

Female birds incorporate in the yolks of their eggs significant concentrations of a number of different androgens. Yolk androgen has been shown to positively affect several fitness components at the embryo, nestling and juvenile stages. Previous experiments have shown that females lay eggs with higher androgen concentrations when they are paired with highly ornamented males. This pattern sugges...

Investment in present vs. future reproduction is a life-history trade-off faced by many animals. Because males generally pay a higher cost from lost mating opportunities than females, males are expected to react more strongly to changes in brood value. We examined the effect of an experimental brood reduction on male desertion in the substrate-brooding biparental cichlid Aequidens coeruleopunct...

Polyembryony is a unique mode of development in which multiple genetically identical embryos develop from a single egg. In some polyembryonic species a proportion of the embryos develop into soldier larvae, which attack competitors in the host. We studied the development of the polyembryonic wasp Copidosoma koehleri in its host Phthorimaea opercullela. We dissected hosts parasitized by either v...

Experimental synchronization of onset of incubation was employed in laboratory held zebra finches Taeniopygia guttata to study whether differential resource allocation and possible bias of offspring sex in subsequent eggs in the laying order could mitigate the effects of hatching asynchrony. We found that egg mass increased with laying order, but offspring sex was not related to laying order. A...