Morphometric variations of giant tiger prawn (Penaeus monodon) under different spatiotemporal conditions in the waters of Taiwan
Date Issued
2007
Date
2007
Author(s)
Lan, Chung-Wen
DOI
zh-TW
Abstract
Giant tiger prawn (Penaeus monodon) was one of the important species for aquaculture in Taiwan. Although artificial propagation for giant tiger prawn has been developed successfully, the natural population of broodstock is essential for sustaining the genetic diversity of prawn in aquaculture. In recent years, the characters of broodstock are getting worse, and the cultured prawn infected diseases frequently. Therefore, studies on genetic diversity for natural populations of giant tiger prawn are cruicial for aquaculture. We collected the prawn samples from I-lan and Tungkung that were trawled from the Northeast and Southwest waters around Taiwan, respectively. A total of 321 prawn samples, including 187 male and 134 female, were obtained during March 2004 to March 2005. To explore the differences in morphology of prawn populations between two hydrographic areas, we selected thirteen landmarks from both lateral and dorsal side of prawns for further analysis.
The results of classics morphometric analysis show no significant difference between sexes of giant tiger prawn in the relationship between body weight and carapace length and the relationship between total length and carapace length. The results of geometric morphometric analysis show significant difference between winter groups of Southwest and Northeast populations of giant tiger prawn. The variation s of morphology could be response to the genetic divergences between populations and/or environmental effects between different geographic distribution. The seasonal populations of giant tiger prawn in the Southwest Taiwan can be divided into three cohorts based on the morphometric analysis. They are winter cohort, spring cohort and summer-autumn cohort. This result suggests that the morphometric variations among seasonal cohorts of prawn could be detected and treated as the variations within population. These variations result in the seasonal polymorphism for intra-population of prawn. However, the misidentification rates are 39.77~17.58 based on the discriminant function analysis. This suggests that the polymorphism for intra-population is smaller than the polymorphism for inter-population. Thus, it is reasonable to suggest that the Northeast and Southwest populations of giant tiger prawn in Taiwan are two stocks.
The results of this study show that the body size for populations of giant tiger prawn is sexual dimorphism, i.e. female larger than male. There is no suitable character can be applied to determine the age of giant tiger prawn till now. Therefore, it cannot be concluded that the difference in body size between sexes of giant tiger prawn is the result of allometric growth or selective mortalities caused by other factors. However, the isometric growth in morphology between male and female prawns is evident. Thus, the spatial difference of giant tiger prawns should not be affected by the condition of sexual dimorphism.
Subjects
草蝦
標徵點
幾何形態分析
Penaeus monodon
landmark
geometric morphometric analysis
Type
thesis
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