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← Theoretical 2

Q89 — Amplexus and Sperm Competition in Newts

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Mating Systems & Sexual Selection

During the breeding season, Notophthalmus viridescens newts form groups. A mature female produces pheromones, and has a full abdomen of eggs and actively seeks a mate. Males also secrete pheromones, exhibit coloured spots, display courtship behavior in the form of wiggling movements, and compete specifically for larger females. During amplexus, the male clasps the female’s body with his hind limbs for up to three hours (Figure 1), during which time he exhibits various behaviors, such as cheek rubbing, tail vibration and forelimb rubbing. Rival males could occasionally try to dislodge the mating male during amplexus. Following amplexus, the male deposits his sperm packet on the bottom of the pond. Females use their cloacas to collect the sperm packets. Rival males can also release sperm packets close to the mating pair and these could be collected by the female as well. Fertilized eggs are laid over the following few weeks.

Photograph of two Notophthalmus viridescens newts in amplexus, the male clasped on top of the female. Figure 1. Amplexus of Notophthalmus viridescens newts: the male is on top.

Using the information above, determine which of the statements are true or which are false.

A. Male-male contests can occur both through the competition over larger-bodied females and during amplexus.
B. A male uses both olfactory and tactile cues to both attract the female and also stimulate her during amplexus.
C. Females actively seek larger-bodied males to ensure their own reproductive success.
D. There are apparently no mechanisms for sperm competition to occur in this newt species.
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)