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Cannibalism is a behaviour exhibited across amphibian life history stages; however, there are few records that involve cannibalism between siblings. Here, we describe observations of recently hatched tadpoles of the frog Philoria pughi consuming sibling embryos with delayed or failed development. Our observations indicate that additional nutrition is obtained from the ingested embryos, despite tadpoles of species of Philoria being capable of endotrophic development. This discovery should be considered when establishing captive breeding colonies for Philoria species and needs further investigation in wild populations.
In marsupials there have been several studies on oocyte maturation and sperm–egg interactions at the time of fertilisation, but controversy exists as to when and how some of the processes occur. Here we present a summary of relevant data from a species of dasyurid marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata). The findings show that in oocytes of developing ovarian follicles cortical granules are produced with many of the granules sometimes initially congregating around the cytoplasmic vacuoles before migrating to the proximity of the oocyte cell membrane. During fertilisation the spermatozoon binds to the zona pellucida that surrounds the oocyte with its tail lying parallel to the long axis of the head. As the spermatozoon passes through the zona pellucida it is surrounded by the zona matrix and, when entering the egg cytoplasm, a localised area of elevated ooplasm occurs around the spermatozoon. Also, unlike a recent claim to the contrary, the head of the spermatozoon travels a considerable distance into the egg cytoplasm before chromatin decondensation occurs, an event that probably minimises the chances of chromatin disruption by the sperm tail at the time of its incorporation.
Morphological and molecular studies have consistently suggested that Sminthopsis, as currently defined, is rendered paraphyletic by the kultarr (Antechinomys laniger). They have also suggested a sister relationship between the kultarr and the long-tailed dunnart. Based on DNA sequence data from multiple mitochondrial and nuclear gene loci we reassign the long-tailed dunnart (formerly Sminthopsis longicaudata) to Antechinomys. Although there is good evidence of genetic structure within the kultarr (A. laniger), it does not correspond to the two currently recognised subspecies, viz A. laniger laniger and A. l. spenceri. We conclude that Antechinomys consists of two species, A. laniger and A. longicaudatus, consistent with morphology. We suggest that the observed genetic and morphological variation within A. laniger merits a more thorough investigation of more samples from across its range to resolve the taxonomy.
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