Study of reproductive cycles and fecundity in a local population of Amphipod Gammarus sp. (Arthropoda: CRUSTACEA) in Fars Province
Gammarus (CRUSTACEA, Amphipoda), widely distributed in various geographical areas in Iran, is one of the important candidates for artificial production for using in fish food. So far, the ecology of this crustacean, its distribution map in Iran, and the probability of its production in artificial conditions has been investigated. For finding a suitable method to make its production investments beneficial, it is needed to precisely investigate reproduction cycles and growth, to find ways for reaching their maximum production. Two sub-population of G. pseudosyriacus was monthly sampled in two different stations in Arjan spring, Arjan Protected Area, Fars Province in 2006. The two stations differed mainly in their distance to the spring source and to the roadside stores and restaurants. Sex ratios, number of ovigerous females, adult females, clutch size (eggs per brood pouch), egg volume, and the population composition were counted or measured. Fecundity index (FI) and reproductive effort (RE) were calculated using these basic data. Dissolved oxygen, air and water temperature, pH, and electrical conductivity were measured in the field; calcium, magnesium, potassium, and total hardness were measured in laboratory. Station 2 showed higher water temperature, dissolved oxygen, and ionic content. The number of populations was maximum in late winter and minimum in late summer. Both populations produced fewer eggs in autumn, and there were more non-ovigerous females in autumn-winter, while more ovigerous in spring-summer. Males and females of station 1showed a higher number, however, in both stations the sex ratio by weight favored males. Both sexes showed increased weights in spring and summer months and male samples had higher weights in station 1 compared to station 2. Females of station 1 produced eggs of the twice volume, while decreasing clutch size. Both populations showed higher fecundity index in late winter and early spring, which was higher in overall in station 2. As many other Gammarus species, the two subpopulation of G. pseudosyriacus had a continuous reproduction throughout the year. Seasonal patterns of population numbers suggest that the strategy of this population is to increase number in winter and weight in summer. It was suggested that both sub-populations evaluate late-winter to early spring as more suitable, therefore do better investment to produce more offspring in this time period. On the other hand, higher fecundity index in station 2 suggests lower stability of this habitat. Individuals in this habitat expend their energy in production of more eggs to increase the chance of their offspring survival to maintain the population size in a maximum possible level. Females of sub-population 1 produced fewer eggs, but they made more investment of resources for each egg. This strategy indicates higher stability in suitable conditions of the hosting environment.
| Main Authors: | , , |
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| Format: | Report biblioteca |
| Language: | Persian |
| Published: |
Iranian Fisheries Science Research Institute
2016
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| Subjects: | Amphipod, Gammarus, Reproductive cycle, Fecundity index, Reproductive effort, |
| Online Access: | http://hdl.handle.net/1834/13730 |
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