Investment in sensory structures, testis size, and wing coloration in males of a diurnal moth species: trade-offs or correlated growth?

For dioecious animals, reproductive success typically involves an exchange between the sexes of signals that provide information about mate location and quality. Typically, the elaborate, secondary sexual ornaments of males signal their quality, while females may signal their location and receptivity. In theory, the receptor structures that receive the latter signals may also become elaborate or enlarged in a way that ultimately functions to enhance mating success through improved mate location. The large, elaborate antennae of many male moths are one such sensory structure, and eye size may also be important in diurnal moths. Investment in these traits may be costly, resulting in trade-offs among different traits associated with mate location. For polyandrous species, such trade-offs may also include traits associated with paternity success, such as larger testes. Conversely, we would not expect this to be the case for monandrous species, where sperm competition is unlikely. We investigated these ideas by evaluating the relationship between investment in sensory structures (antennae, eye), testis, and a putative warning signal (orange hindwing patch) in field-caught males of the monandrous diurnal painted apple moth Teia anartoides (Lepidoptera: Lymantriidae) in southeastern Australia. As predicted for a monandrous species, we found no evidence that male moths with larger sensory structures had reduced investment in testis size. However, contrary to expectation, investment in sensory structures was correlated: males with relatively larger antennae also had relatively larger eyes. Intriguingly, also, the size of male orange hindwing patches was positively correlated with testis size.

Testing the interactive effects of carotenoids and polyunsaturated fatty acids on ejaculate traits in the guppy Poecilia reticulata (Pisces: Poeciliidae)

Using the polyandrous livebearing guppy Poecilia reticulata, this study revealed no main effects of carotenoids in the diet on ejaculate traits, but significant main effects of polyunsaturated fatty acids (PUFAs) on sperm viability and weak but significant interacting effects of both nutrients on sperm length. Collectively, these findings not only add evidence that PUFAs are critical determinants of sperm quality, but also provide tentative evidence that for some traits these effects may be moderated by carotenoid intake.

The mothematics of female pheromone signaling: strategies for aging virgins

Although females rarely experience strong mate limitation, delays or lifelong problems of mate acquisition are detrimental to female fitness. In systems where males search for females via pheromone plumes, it is often difficult to assess whether female signaling is costly. Direct costs include the energetics of pheromone production and attention from unwanted eavesdroppers, such as parasites, parasitoids, and predators. Suboptimal outcomes are also possible from too many or too few mating events or near-simultaneous arrival of males who make unwanted mating attempts (even if successfully thwarted). We show that, in theory, even small costs can lead to a scenario where young females signal less intensely (lower pheromone concentration and/or shorter time spent signaling) and increase signaling effort only as they age and gather evidence (while still virgin) on whether sperm limitation threatens their reproductive success. Our synthesis of the empirical data available on Lepidoptera supports this prediction for one frequently reported component of signaling-time spent calling (often reported as the time of onset of calling at night)-but not for another, pheromone titer. This difference is explicable under the plausible but currently untested assumption that signaling earlier than other females each night is a more reliable way of increasing the probability of acquiring at least one mate than producing a more concentrated pheromone plume.