| Fiddler crabs are important ocean crustacean species. They live in the habitats such as mangroves, mud flat and estuary, distribute from Hainan island in the south to Shandong province in the north in China. And they are among the common crab species in China. Fiddler crabs are ecological engineer in mangroves. Their feeding and burrowing behavior can accelerate the biogeography circulate of Carbon and Nitrogen, improve the production of vegetation in the mangroves. Not only do the behavior of fiddler crabs can indicate the water quality, their activities can also improve the water quality by accelerating the degradation of organics. As fiddler crabs are sensitive to the change of water quality, they are biological indicator to the water quality. Additionally, the community structure (e.g. density, sex ratio) of fiddler crabs can also reflect the environmental stability. Although fiddler crabs are of great important to the local ecosystems, especially to the mangroves, little research is related to the fiddler crabs in the mainland of China. Leading to the neglect of fiddler crabs, thus the knowledge of mangrove is biased, and little information about the status of fiddler crabs and their impacts on the mangrove ecosystems in China is known. Therefore, to the disadvantage of the protection and ecological restoration of mangroves in China.Then, I chose three sites (No.2tidal creek, No.3tidal creek, Fengtang river dock) in Futian Nature Mangrove Reserve as the sampling sites, studied11behavior, feeding rate, sex ratio, handedness of Uca arcuata which is the native dominant species and their relationship to the environmental factors. The study of behavior was achieved by random selected a fiddler crab, observing and recording the time it spends on each behavior during5min, then transform the time to time ratio.1measured the feeding rate by random selected a fiddler crab which was feeding, counting the number of feeding motions in30S, the result was doubled to get the feeding rate. I took a scan of fiddler crabs activity on the surface to record the sex ratio and handedness of Uca arcuata. The observation was operated on the rainless weather, and began after the tide retreated or before the tide flood the sampling site. Before observation, the sex, handedness, observation time, site and tidal were recorded. The results are as follows:1. Altogether673fiddler crabs were sampled for the behavior in Futian mangrove. The average time a Uca arcuata allocated to each behavior various, with feeding (42.27%), feeding while walking(26.99%), standing(10.58%), in burrow(6.60%), walking(4.09%), aggression and defense(2.93%), burrowing(2.88%), waving(1.51%), mating(0.98%), grooming(0.95%), sexual interaction(0.23%). In5min, the count of behavior category vary from1to8, and the average count is3.36. Habitat has remarkable impact on6kind of behavior,4for time (months),3for sex and1for handedness and tide. As the main activity of Uca arcuata is feeding which is limited by the food (e.g. algae, microorganism), and the food is influenced by temperature and nutrition. Therefore, habitat (nutrition status) and months (temperature variation) have the greatest effects on the behavior of Uca arcuata. The sexual has influence on the behavior is mainly because the male fiddler crabs have an enlarged cheliped, they can only feed with the smaller cheliped while the female can feed with two small chelipeds. Meantime, the differences between males and females leading to the differences in the energy investigated to the behavior such as sexual and social behavior.2. Altogether519fiddler crabs were sampled for the feeding rate in Futian mangrove. The average feeding rate is50.44feeding motions per minute, with the fastest is148feeding motions per min and the lowest is16feeding motions per min. Females feed faster than males. The fiddler crabs in No.2tidal creek feed faster than the fiddler crabs in No.3tidal creek, and the fiddler crabs in No.3tidal creek feed faster than the fiddler crabs in Fengtang river dock. The influence of temporal variation, tidal and handedness are not remarkable. The feeding rate of fiddler crabs is mainly influenced by the food quality and quantity. With the higher food quality and more food quantity, the lower feeding rate and the higher ratio of feeding time to foraging time. As the females have two small feeding chelipeds while the males only have one feeding cheliped, the females feed extremely faster than the males.3. The sex ratio (male/female) and handedness (right handedness/left handedness) of Uca arcuata have been sampled for30times. The sex ratio is1.20, with the lowest is0.36and the highest is2.78. The handedness is0.99, with the lowest is0.41and the highest is1.56. The temporal variation, habitat and their interaction have remarkable effect on the sex ratio. However, their impact on the handedness were not remarkable. The results of sex ratio and handedness of Uca arcuata in Futian mangrove are resemble to previous research.4. The feeding rate and behavior characteristic of Uca arcuata can reflect the water quality of the habitat, i.e. the heavier pollution status, the less time Uca arcuata spend on foraging, the higher ratio of feeding time to foraging time, the lower feeding rate and the more time Uca arcuata spend on the burrowing behavior.5. The behavior of Uca arcuata were more complicated than anticipated. According to the results and related research paper, I suggested adding2behavior category:探洞行为and feeding while walking and waving. Because during the research period, the frequency of the two behavior were high, the duration time were long, they have impact on other fiddler crabs, and they are common (can be found on other species), thus, enable them to be independent behavior category. As the sexual behavior was less common, I suggested integrated the sexual behavior and mating behavior to be the reproduce behavior. |
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