A case of mite-on-mammal ectoparasitism from Eocene Baltic amber (Acari: Prostigmata: Myobiidae and Mammalia: Erinaceomorpha)

摘要

Tetrapods are rarely recovered from fossil resins, such as amber, and fossils of parasites are even rarer. We describe the first pre-Quaternary co-occurrence of ectoparasitic mites with hairs of their mammalian hosts, preserved in life-like detail from a piece of Eocene (similar to 40 Ma) Baltic amber. The mites, representing the oldest fossils of the family Myobiidae (Acari: Prostigmata: Eleutherengona), are described as Protohylomysobia erinaceophilus Sidorchuk & Bochkov gen. et sp. nov. and belong to the generic group Amorphacarus. Recent members of this group parasitize small-sized insectivores - shrews, moles and gymnures (Mammalia: Eulipotyphla: Soricidae, Talpidae and Erinaceidae: Galericinae). The fossils indicate that the evolution of Myobiidae and their relationships with mammals were well underway by the Eocene. The hairs of the hosts are also described, and are morphologically compared with those of Recent mammals. This comparison suggests an early-derivative member from an array of mammalian groups, and provides clues to its habitus. Our data give a new perspective on a long discussion about the source of mammal hairs in Baltic amber. The combined mite, amber and hair evidence suggest a small, short- and fine-haired member of Amphilemuridae, sister family to hedgehogs, as a host for the mites and the source of at least some of the hairs preserved in Baltic amber.