| Simocephalus himalayensis microdus was collected in June 1990 from a perpetually clear water pool in the experimental tree farm of Northeast Forestry University in Haerbin, Heilongjiang Province. The samples was reared at 5 - 30°C, and fed with Scenedesmus obliqnus at density of 4×105 cell/ml. It was found that Simocephalus himalayensis microdus has 4 pre-adult instars and 15 - 18 adult instars. The female keep living for at most about 48.7±8.92 days at 20°C, and the males for about 28 days at 15°C. The female needs about one minute (the male about 30 - 40 seconds) to get rid of the old carapace. Population parameters regarding growth, longevity and population increase were recorded throughout their life-span.
1. The growth of body-length (lt, in mm) in relation to age (t, in day) can be described as lt=3.334–2.7345e-0.1117t.
2. Temperature is a most important factor influencing the growth speed. In certain range of temperature, the growth speed directly proportional to the temperature, higher temperature shortens the time for the development to maturity. The relationship between the age at maturity and water temperature of 10 - 30°C, for female is: h=8072t-1.313 (r=0.985, P＜0.01); for male, for temperature of 5 - 25°C is: h=1074t-0.855 (r=0.9844, P＜0.01). (Fig.3)
3. The mean longevity of individuals was estimated to be 48.7±8.92 days or 18±2.11 instars. The relationship between instar (x) and age (t) is given approximately as t=0.07169x2+1.3808x-1.7361 for female and t=0.0425x2+2.534x-1.86 for male. (Fig.4)
4. The life expectancy and specific fecundity table of Simocephalus himalayensis microdus are given in Tab.1. The innate capacity for increase (rm) as computed from the tables is 0.4076 per female per day; the net reproduction rate (R0) is 359.298 per generation and the mean length of a generation (T) is 14.4 days. (Tab.1)
5. In a population originated from 10 individuals, the population growth curve of Simocephalus himalayensis microdus may be expressed as: y=3625/[1+e(3.848–0.164t)], in which y denotes total individuals and t, days. (Fig.5) |
