Wuzhishan Preliminary Investigation Of A Slow Animal Species Diversity

Tardigrades, hydrophilous micrometazoans commonly called "water bears", are generally considered to be an independent phylum. Evidence from recent molecular studies with 18S RNA has shown that tardigrades are a sister group of the arthropods. Tardigrades show bilateral symmetry with four pairs of limbs that usually terminate in claws. Mature adults average 250-500 mm. All active individuals require a film of water around the body. They could be found in permanent freshwater habitats, in sea, river or lake sediment, in littoral zone or in moist mosses. Most tardigrade species are terrestrial, occurring in moist soil and leaf litter, or among mosses, lichens, liverworts, and cushion-shaped flowering plants. Tardigrades can endure extremely low temperatures; some species have even survived absolute zero. A change in environmental conditions can induce the animal to enter a cryptobiosis, which can be anhydrobiosis, anoxybiosis, cryobiosis or osmobiosis. Cryobiosis enables tardigrades to survive freezing and thawing, and is the principal survival strategy of limno-terrestrial tardigrades living in very cold environments. The formation of tuns also plays a role in the dispersal of cryobiotes.Tardigrada fauna has been investigated on Five-Finger Mt and Mumianshan Mt, Hainan Island during March and May of 2007. Tardigrades were collected from eleven sampling sites, the height of which is from 600m to 1800m above the sea level. Ten moss samples were collected within each sampling site. Tardigrades were extracted from a total of 110 samples. All specimens were identified and counted. Species diversity at different altitude was calculated using the diversity index. The community dynamic changing regularity of Tardigrada at different altitude was studied using the Principal Component Analysis and the Similarity index. The community structure of tardigrade on Five-Finger Mt. and Taibai Mt. were compared. The research results are summarized as follows:1. 380 individual tadigrades, belonging to three orders, four families, 14 genera and 30 species including 3 new species, 7 new Chinese record species and 19 new record species for Hainan, were collected on the Five-Finger Mt and Mumianshan Mt.2. Population density and species number mainly decreased with the increase of altitude. Population density and species number at different altitude are related to the microenvironment. The higher number found on higher altitude. The one-way ANOVA showed that the altitude variation has no significant influence on the population density and species diversity. Results from Multiple comparison(LSD) showed that there were significant differences in the population density and species diversity at different altitude.3. Shannon-Wiener index decreased with the increase of altitude, while Simpson index increased with the increase of altitude. However, the one-way ANOVA showed that the altitude variation has no significant influence on Shannon-Wiener index, Pielou index and Simpson index. LSD showed that there were significant differences in the Shannon-Wiener index, Pielou index at different altitude below the medium altitude, but no significant differences above medium and high altitude. The Simpson index has no significant difference at different altitudes.4. The principal component analysis showed that the representative species of different principal component in Five-Finger Mount and Taibai Mount located at different altitude, while the representative species of same principal component located at the same altitude. These reveal that the tardigrada community varies with the change of altitude. Two principal components appear both in 2500m and 2800m in north and south slope of the Taibai Mount, which suggest that the variation of tadigrada community in Taibai Mount can represent the variation of the most tadigrada community, and the tadigrada ranging from 2500m to 2800m has the highest species richness.5. Similarity analysis showed that tardigrada communities on Five-Finger Mt has a low similarity (extremely dissimilarity and medium dissimilarity). And the similarity between south and north slope of Taibai Mt is also low, most of which is extremely dissimilarity and medium dissimilarity. We found that the afflence on tadigrada community of Five-Finger Mt is severer than on the tardigrada community of Taibai Mt, and the variation along the altitude in Taibai Mt is slower than in Five-Finger Mount.