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UPV Theses and Dissertations

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    Reproductive biology of coconut crab Birgus latro (LINNAEUS 1767) from Antique, Western Visayas, Philippines
    Alberca, Pavi Jewime O. (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 2016-06)
    The coconut crabs Birgus latro continue to decline globally and are now considered as an endangered species. In order to prevent further depletion of the species, much effort must be placed on implementing municipal ordinances such as seasonal closures and minimum legal size limits. This study aimed to monitor the breeding cycle of the Birgus latro from the islands of Sibolon and Maniquin. Antique. Philippines using macroscopic and microscopic techniques. A minimum of ten crabs were collected every month for six months (Aug. 2015 - Jan. 2016). The crab samples were examined based on the morphological and histological appearance of the gonads. The body weight, thoracic length (TL). cephalothoracic length, carapace width, pleonal expansion, gonad weight and hepatopancreas weight were measured. The gonadosomatic index (GSI), hepatosomatic index (HSI). pleonal expansion index (PEI) and gonad index (GI) were calculated. The results revealed two stages of development for both the male and female B. latro. The testicular stages were a) maturing stage - creamy white with the presence of spermatogonia, spermatids and spermatozoa; b) mature stage - creamy white and larger with the presence of the spermatozoa only. The ovarian stages were a) maturing stage - light yellow with the presence of oogonia, endogenous and exogenous vitellogenic oocytes and follicle cells: b) mature stage - reddish brown and larger with the presence of the fully mature oocytes. The smallest sexually mature crab for the male was 28 mm TL and for the female was 32 mm TL. The mature testes were observed all throughout sampling period, while the mature ovaries were only in August, September and October. The occurrence of the male B. latro was higher than the females. In males, the GSI and GI were directly proportional to the developmental stages. The HSI was inversely proportional. while the PEI showed no relationship. In females, the GSI. HSI. PEI and GI showed a direct relationship with the stages of development.
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    Some aspects of the reproductive biology of the telescope snail Telescopium telescopium (Linne) in milkfish ponds
    Arboleda, Ianthe Anfone (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 1999-04)
    Telescopium telescopium, a mudsnail locally known as “bagungon” , is important since at high densities it may become a pest in fish aquaculture ponds. Knowledge of its reproductive biology is necessary in order to properly manage this resource. Thus, this study aimed to 1) describe histologically the different gonadal stages of T. telescopium, 2) determine the reproductive cycle and spawning peaks of the species based on the gonadosomatic index (GSI), and 3) determine the size at sexual maturity of the species in the milkfish ponds. Monthly samples were collected from May 1997 to March 1998 (except for September 1997) from brackishwater milkfish ponds. Shell length and GSI for each snail was measured. The gonads were processed histologically after all sampling activities were concluded. Histological examination showed the following gonadal stages: immature, developing (male and female), ripe (male and female), spawning ( female), and redeveloping ( female). The GSI profile showed no marked fluctuations, indicating partial and continuous spawning. However, the mean monthly GSI values may have been greatly affected by the harvesting of the snails done in the milkfish ponds and the presence of immature gonads with weights that could not be determined using the available balance (weights<0.01 g). The smallest observed mature male had a shell length of 43.32 mm, and the smallest observed mature female had a shell length of 36.42 mm.