External fertilisation and paternal care in the paedomorphic salamander Siren intermedia Barnes, 1826 (Urodela: Sirenidae)

Parental care is widespread in the animal kingdom and enhances offspring survival. Amphibians exhibit an extraordinary diversity of care strategies, including guarding, transport and even feeding of young. Among amphibians, females are usually the carers, but here we present a case of male parental care in the aquatic salamander Siren intermedia, accompanied by records of external fertilisation. Sirenids are a phylogenetically distinct group within basal salamanders, of which the precise systematic position has long been debated. Our observations of external fertilisation and paternal care of S. intermedia lead us to conclude that apparently both internal fertilisation and maternal care evolved after the split between the more basal groups (Cryptobranchoidea and Sirenoidea) and all other salamanders (suborder Salamandroidea).