Report of Gammarus parthicus in the east of Iran (South Khorasan, Birjand) along with the frequency distribution of body length and the relationship between the number of eggs and different parts of the body

The goal of this study was to investigate in Gammarus parthicus, body length frequency distribution (male, female) and relationship between clutch size and different body parts (head, pereon, pleon). Sampling from a Qanat in 2019 was done in Birjand city (Spring, Summer, Autumn and Winter). Totally, 252 gammaruses were catched. In each sampling, one hour was attempted to catch gammaruses by a hand sieve with one mm mesh size. To measure, a stereo microscope and millimeter paper were used and the samples were photographed. With a petri dish and the plastic talc (placed over the samples) gammaruses were photographed lively. Length was measured from the beginning of the head (Rostrum) to the end of tail (Telson). In addition, head, back and tail length were measured separately. Image-J software was used to analyze the resulted images. The mean total length of males and females gammaruses in four seasons were (Mean± SE) (15.75±1.21) and (12.93±1.43) respectively. Sex ratios differed according to the seasons. The total body length was obtained as a model of the explanatory variables including head length, tail length and season. The most sex ration in spring (1.39) and the lowest one in winter (0.31) were observed respectively. The total body length was obtained as a model of the explanatory variables including head length, tail length and season. The number of eggs (clutch size) per fertilized female was obtained by tearing the bag of eggs. The number of eggs was counted in a sample of gammaruses after 10 days keeping in the climate room. The climate room was used to simulate the reproduction conditions. The number of eggs was obtained as a model of head length and tail length. The report of Gammarus in the east of Iran and the influence of season in life cycle of the Gammarus.