TY - JOUR
T1 - Re-establishment of biting mouthparts in desert-living dung beetles (Scarabaeidae: Scarabaeinae) feeding on plant litter - old structures reacquired or new ones evolved?
AU - Holter, Peter
AU - Scholtz, Clarke H.
PY - 2011/8
Y1 - 2011/8
N2 - Evolution of mouthparts in adult dung beetles (Scarabaeidae: Scarabaeinae) for eating moist, fresh dung was linked with a loss of the ability to chew. However, the desert-living genus Pachysoma, probably evolved from a wet-dung feeding, Scarabaeus-like ancestor, has switched to a diet of dry fecal pellets (of rodents or small ruminants) and plant litter that requires re-establishment of chewing. Indeed, gut contents of a litter-feeding Pachysoma species indicate efficient food comminution. Based on scanning electron microscopy, cutting and grinding mouthpart structures in six Pachysoma species, of two lineages and with different food preferences, are described and compared with homologous structures in wet-dung feeding Scarabaeus species. In Pachysoma, cutting and breaking of large food items is probably performed by a clypeal scraper, a prominent epipharyngeal tooth and large maxillary galeal hooks. Further comminution is achieved by a large, grinding area evolved on the mandibular molae. Interspecific differences and the probable function and evolution of these structures are discussed. Particularly, the unique tools for cutting/breaking are completely novel structures and not results of some reacquisition of normal biting mouthparts.
AB - Evolution of mouthparts in adult dung beetles (Scarabaeidae: Scarabaeinae) for eating moist, fresh dung was linked with a loss of the ability to chew. However, the desert-living genus Pachysoma, probably evolved from a wet-dung feeding, Scarabaeus-like ancestor, has switched to a diet of dry fecal pellets (of rodents or small ruminants) and plant litter that requires re-establishment of chewing. Indeed, gut contents of a litter-feeding Pachysoma species indicate efficient food comminution. Based on scanning electron microscopy, cutting and grinding mouthpart structures in six Pachysoma species, of two lineages and with different food preferences, are described and compared with homologous structures in wet-dung feeding Scarabaeus species. In Pachysoma, cutting and breaking of large food items is probably performed by a clypeal scraper, a prominent epipharyngeal tooth and large maxillary galeal hooks. Further comminution is achieved by a large, grinding area evolved on the mandibular molae. Interspecific differences and the probable function and evolution of these structures are discussed. Particularly, the unique tools for cutting/breaking are completely novel structures and not results of some reacquisition of normal biting mouthparts.
U2 - 10.1002/jmor.10968
DO - 10.1002/jmor.10968
M3 - Journal article
C2 - 21630319
SN - 0362-2525
VL - 272
SP - 1007
EP - 1016
JO - Journal of Morphology
JF - Journal of Morphology
IS - 8
ER -