TY - JOUR
T1 - Elongated hindguts in desert-living dung beetles (Scarabaeidae: Scarabaeinae) feeding on dry dung pellets or plant litter
AU - Holter, Peter
AU - Scholtz, Clarke H.
PY - 2013/6
Y1 - 2013/6
N2 - Most adult dung beetles (Scarabaeidae: Scarabaeinae) feed on fresh, wet dung of larger herbivorous or omnivorous mammals. As refractory plant fragments are selected out before ingestion, the food is presumed easily digestible. However, members of the desert-living scarabaeine genus Pachysoma (probably evolved from an ancestor closely related to the wet-dung feeding genus Scarabaeus) select dry dung pellets and/or plant litter. Thus, they ingest a much higher proportion of structural plant material, which nevertheless appears to be digested rather efficiently. This study investigates morphological modifications of the gut for this digestion in adults of eight Pachysoma species, both pellet and litter feeders. To ascertain hypothesized ancestral conditions, four fresh-dung feeding Scarabaeus species were also examined. The latter have the usual dung beetle gut consisting of a long, simple midgut, followed by an equally simple, much shorter hindgut of the same width. Lengths of midguts (M) and hindguts (H) divided by body length (B) for comparison between species of different size are: 4.9-6.3 (M/B) and 0.7-0.8 (H/B), which is normal for dung feeders. In Pachysoma, lengths are 6.3-6.5 (M/B) and 1.0-1.4 (H/B) in pellet feeders, and 4.4-5.0 (M/B) and 2.0-2.5 (H/B) for litter feeders. Hindguts are still morphologically undifferentiated and of midgut width, but clearly longer, particularly in litter feeders. Presumably, plant fragments in the food are digested, at least partly, in the hindgut. If so, the morphological adaptation is unusual: simple elongation rather than the expansion of part of the hindgut, as found in several other plant- or detritus-feeding scarabaeids.
AB - Most adult dung beetles (Scarabaeidae: Scarabaeinae) feed on fresh, wet dung of larger herbivorous or omnivorous mammals. As refractory plant fragments are selected out before ingestion, the food is presumed easily digestible. However, members of the desert-living scarabaeine genus Pachysoma (probably evolved from an ancestor closely related to the wet-dung feeding genus Scarabaeus) select dry dung pellets and/or plant litter. Thus, they ingest a much higher proportion of structural plant material, which nevertheless appears to be digested rather efficiently. This study investigates morphological modifications of the gut for this digestion in adults of eight Pachysoma species, both pellet and litter feeders. To ascertain hypothesized ancestral conditions, four fresh-dung feeding Scarabaeus species were also examined. The latter have the usual dung beetle gut consisting of a long, simple midgut, followed by an equally simple, much shorter hindgut of the same width. Lengths of midguts (M) and hindguts (H) divided by body length (B) for comparison between species of different size are: 4.9-6.3 (M/B) and 0.7-0.8 (H/B), which is normal for dung feeders. In Pachysoma, lengths are 6.3-6.5 (M/B) and 1.0-1.4 (H/B) in pellet feeders, and 4.4-5.0 (M/B) and 2.0-2.5 (H/B) for litter feeders. Hindguts are still morphologically undifferentiated and of midgut width, but clearly longer, particularly in litter feeders. Presumably, plant fragments in the food are digested, at least partly, in the hindgut. If so, the morphological adaptation is unusual: simple elongation rather than the expansion of part of the hindgut, as found in several other plant- or detritus-feeding scarabaeids.
U2 - 10.1002/jmor.20123
DO - 10.1002/jmor.20123
M3 - Journal article
C2 - 23450631
SN - 0362-2525
VL - 274
SP - 657
EP - 662
JO - Journal of Morphology
JF - Journal of Morphology
IS - 6
ER -