| Current Zoology(formerly Acta Zoologica Sinica), Apr. 2003, 49(2): 171 - 178 |
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| Title: | A comparison of the content and morphology of the digestive tracts of seven desert rodent species |
| Authors: | LI Jun-Sheng SONG Yan-Ling ZENG Zhi-Gao |
| Abstract: | Tract morphology among sympatric desert rodent species was examined in order to reveal if these species coexist through food resource partitioning. The field work was carried out in the summer of 2001 (July - August) in two arid deserts, one in suburban Jiayuguan city and the other in suburban Dunhuang township, both of which are in the western region of Gansu Province, China. The climate of both study areas is very dry and the maximum rainfall occurs in the summer season. The mean annual temperature was 10 ℃ and the mean annual precipitation varied from 35 mm to 45 mm during 1990-2000. Vegetation at both study areas was dominated by Tamarix remosissima, Nitraria sphaerocarpa, Haloxylon ammodendrom, Alhagi maurorum, Ephedra przewalskii, Sympegna regelii, Nitraria spp., Salsola passerina, Achnatherum splendens and Carex spp. Animals were captured with small break back traps (snapping bar). Traps were placed in a rectangular grid of five lines 10 m apart (measured) and 100 traps were laid at 5 m intervals along each line. Peanuts were used as bait. Traps were laid in the evening and checked the next morning. A total of 1 500 trapping days were conducted at each site. Captured animals were brought to the laboratory for dissection. The species of each specimen was identified, and age and sex were also determined. A total of seven species were captured, including Dipus sagitta, Allactage sibirica, Meriones meridianus, Cricetulus migratorius, C. barabensis, Mus musculus, and Ochotona erythrotis. Measurements of weight and body length were taken and the reproductive status of each specimen determined before any further examination. Digestive tracts were carefully removed and separated from adhesive and adipose tissue. The following measurements were then taken: weights of stomach, small intestine, large intestine, and caecum (all with contents); lengths of small intestine, large intestine and caecum. The contents of stomach and cheek pouches were checked and sorted as leaves, stems, flowers, roots, seeds, fruits, and insects and used to determine the food preferences of each species. The parameter of body weight was used to analyze inter specific variation in the length of the total gut and separate organs by covariance, and the weight of the separate organs and their contents by ANCOVA. Differences in relative intestine length (ratio between hind gut length to head/body length) among different species were analyzed by one way ANOVA. Analysis of stomach and cheek pouch contents showed that the seven rodents species fed on different food items. Three kinds of food preferences could be distinguished among the 7 species, i.e. herbivores, omnivores and granivores. Total digestive tract length was significantly different among the 7 species and their food preferences seemed to be an important factor in this difference. Herbivores had the longest digestive tracts, omnivores the next longest and granivores the shortest. Interspecific variation in large intestine(F5,107=15.762,P<0.01) and caecum length(F5,107= 5.024,P<0.01) was significant larger than that of the small intestine (F5,107=3.359,P<0.01). There were significant interspecific differences in stomach and caecum weight (F5,107= 6.662,P<0.01; F5,107=9.003, P<0.01, respectively). However, there were no significant difference in small and large intestine weight (F5,107= 0.851,P>0.05; F5,107=1.723, P>0.05, respectively). These results support our hypotheses that: 1) food selection patterns are different among rodent species that live in the same desert habitat, and 2) The different features of gut morphology among these species are a functional manifestation of the partitioning of food resources in the desert environment［Acta Zoologica Sinica 49(2):171-178,2003］. |
| Keywords: | Coexistence species, Rodents, Food composition, Digestive tracts morphology, Interspecific difference |
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