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    Histomorphological study of the gonads of Pholas orientalis
    Beluso, Michelle O. (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 1994-04)
    A total of five "diwal", Pholas orientalis, two of which wore obtained from Hinigaran, Neg. Occ. on January 1995 and three from Lanas, Barotac Nuevo on February 1994, were examined for the histomorphological study of the gonads of the species. Among the five samples, two were males and three were females. No hermaphrodites were encountered. Macroscopical examination showed that the gonads were diffused in the visceral mass extending from the anterior to the posterior part of the animal. The gonads were arborescent in form and creamy in color. No external sexual differences were observed. Histological examination showed that male and female gonads were scattered in the visceral mass and concentrate most around the stomach. Male and female gonads consist of follicles which were lobular and embedded in the connective tissues. Three sexual maturity stages were observed among the five specimens, which are the late active, ripe, and partially spent stages. During the late active stages in both male arid female gonads, developing gametes (spermatocytes and young oocytes, respectively) are attached to the follicular wall with maturing gametes lying free in the follicular lumen. At the ripe stage, male gonads showed mature sperms free in the follicle lumen with sperm tails radiating into the center of the lumen. In females, ripe oocytes are free in the follicle lumen with some maturing oocytes still attached to the folli- cular wall by a slender stalk. Partially spent stage was observed only in females. Spent gonads showed spaces in ovarian follicles due to loss of ova through spawning (1938). Since there is a growing demand for "diwal", interest on this species had picked up lately. One of the earliest studies on P. orientalis was the study on the "diwal" fishery in Neg. Occ. conducted by Ablan (1938). The larval biology and mariculture of the angelwing clam, Cyrtopleura cos- tata, were studied by Gustafson, et al. (1991) and investigations into spawning and hatchery technique for P. orientalis are underway (Gustafson, et al., 1991). Studies on the biology of P. orientalis are few and in fact no literature regarding reproductive biology of the species was obtained. Thus, this study was carried out with the following objectives: (1) to determine the location of the gonads in the visceral mass of P. orientalis, (2) to describe the histomorphology of the gonads, and (3) to differentiate the gonadal conditions histologically
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    Influence of lunar cycle and tidal fluctuation of gonadal maturity of green mussel (Pema viridis) in Inner Malampaya Sound, Taytay, Palawan
    Baldevieso, Adzel Adrian G. (University of the Philippines Visayas, 2018-07)
    This study aims to identify the ideal period of harvesting cultured green mussel (Perna viridis) in order to attain larger flesh to shell ratio in inner Malampaya Sound, Taytay, Palawan by investigating the gonadal maturity in relationship to lunar cycle, tides, physicochemical and water productivity parameters. Twenty green mussel samples undergo histological analysis of gonad and 50 samples were measured for body indices weekly from October 2017 to March 2018. Results showed that the body and gonad indices have significant positive correlation with slight higher values during the first quarter weeks, and during a day before the low low tides. The peak of spawning was recorded during October. After which, partial spawning was observed and starts during the weeks of full moon until new moon with a duration of 1-3 week. Thus, the gonadal development/maturity of green mussel in the study is influenced by lunar cycle and tidal fluctuations. Among the water parameters monitored, salinity, pH, and temperature have a significant difference in the monthly, and lunar weeks levels. Furthermore, the drop in salinity might trigger the peak spawning. Diatoms (91%) dominate the plankton composition in the sampling area followed by small percentage of dinoflagellates (4%), zooplankton (2%), and cyanobacteria (2%) and ciliates (1%). The genus Coscinodiscus has the highest percentage (97.73%) among the diatom genera, this species could be one of the major algal diet of green mussels in the area. On the other hand, there was no significant correlation between the gonad index and body indices to the physicochemical parameters and water productivity parameters. Based on body indices and gonad index values, the ideal period to harvest green mussel is during the first quarter weeks. One out of 540 samples was found to be hermaphrodite.