Ka. Hammond et Ba. Wunder, EFFECT OF COLD TEMPERATURES ON THE MORPHOLOGY OF GASTROINTESTINAL TRACTS OF 2 MICROTINE RODENTS, Journal of mammalogy, 76(1), 1995, pp. 232-239
Microtus ochrogaster and Dicrostanyx groenlandicus are closely related
species that share many life-history characteristics, but have differ
ent food habits; D. groenlandicus primarily eats dicots, such as everg
reen and deciduous shrubs, while M. ochregaster primarily eats forbs a
nd grasses. We compared the size of gastrointestinal tracts of these t
wo species acclimated to either 5 or 23 degrees C. In both species, an
imals acclimated to cold ambient temperatures (5 degrees C) had longer
gastrointestinal tracts than did those acclimated to warmer temperatu
res (23 degrees C). In addition, animals acclimated to colder temperat
ures also carried a greater mass of digesta in their gastrointestinal
tracts. Only in M. ochrogaster did the wet mass of the tract increase
in response to cold-temperature acclimation. In general, D. groenlandi
cus had larger and heavier tracts than did M. ochrogaster. The small i
ntestine and cecum increased in size at cold temperatures, but this in
crease occurred differently in each species. The differences we observ
ed can be attributed to differences in the additional food eaten by ea
ch species in the cold.