Variation in size and shape of toxin glands among cane toads from native-range and invasive populations

If optimal investment in anti-predator defences depends on predation risk, invading new regions (and thus, encountering different predators) may favour shifts in that investment. Cane toads offer an ideal system to test this prediction: expensive anti-predator toxins are stored mainly in parotoid glands whose dimensions are easy to measure, and toad invasions have changed the suites of predators they encounter. Although plasticity may influence parotoid morphology, comparisons between parents and progeny revealed that gland dimensions were highly heritable. That heritability supports the plausibility of an evolved basis to variation in gland dimensions. Measurements of 3779 adult toads show that females have larger glands than males, invasive populations have larger glands than in the native-range, and that parotoid sexual size dimorphism varies strongly among invaded areas. Geographic variation in parotoid morphology may be driven by predation risk to both adult toads and offspring (provisioned with toxins by their mother), with toxins allocated to eggs exacerbating the risk of cannibalism but reducing the risk of interspecific predation. Investment into chemical defences has evolved rapidly during the cane toad’s international diaspora, consistent with the hypothesis that organisms flexibly adjust resource allocation to anti-predator tactics in response to novel challenges.

Wolf, Canis lupus, Pup Mortality: Interspecific Predation or Non-Parental Infanticide?

A breeding male Gray Wolf, Canis lupus, equipped with a GPS collar was documented going to the den site of another Gray Wolf pack. This trip was coincident with an attack on the den of the other pack and the occurrence of a dead and partially consumed Gray Wolf pup at the same location. We present two possible explanations - interspecific predation and non-parental infanticide - to account for this observation. Because the Gray Wolf with the GPS collar and his mate were first-time breeders and were attempting to establish a territory space of their own, we speculate that, based on the available evidence, this observation most likely represents a case of non-parental infanticide that fits the predictions of the resource competition hypothesis.

Extended parental care in a hermit crab of the genus Calcinus (Anomura: Diogenidae)

The present work reports the existence of extended parental care in a hermit crab species of the genus Calcinus. The species shows a high energetic investment in egg production, only producing one to six large-sized eggs. The larval development is extremely abbreviated, with the larvae hatching at an advanced zoeal stage, a rather uncommon feature among marine and non-symbiotic decapods. The sequential moults end in a glaucothoe-type larval stage that is retained inside the female's host gastropod shell, probably in complete lecithotrophy. The high maternal reproductive investment displayed by this species is certainly maximized through the retention of juveniles until they enter a suitable gastropod shell, since it considerably reduces the chances of intra- or interspecific predation.