Adaptive features of life forms in Aporrectodea caliginosa

Abstract

We considered that the morphoecological differences between species of Lumbricidae have adaptive character. For our research, the amplitude and frequency of contractions of the visceral (gizzard) smooth muscles were selected. The contractive activity of the muscles was studied according to the method of isolated preparations. The greatest amplitude of contractions (86.71±3.66 per mg) was recorded in worms of mineral soils for Aporrectodea caliginosa caliginosa in which the frequency of contractions of visceral muscles was 2.46±0.58 contr/min. Apparently, in detritophages the gut muscles push the dense food mass, but their contractions are not more frequent than 2–3 times a minute. The muscles of the surface-living A. caliginosa trapezoides showed smaller amplitude, 49.58±2.56 per mg, and frequencies were 4.89±0.37 contr/min. This subspecies ingested decaying vegetative remains, which entered their intestines as loose food mass completely accessible to digestion. Earthworms inhabiting mineral soil layers have greater amplitude of gut muscle contractions than the leaf-litter species, which is probably influenced by differences in their diet. We can conclude that parameters of spontaneous contractive activity of smooth muscles of the A. caliginosa digestive tract are related to the subspecies’ life characteristics in biocenosis. These parameters are stable characteristics of the forms adapted to consumption of certain types of food resources in natural habitats.