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Keyword: search.filters.keyword.Charybdis feriatusSDG: search.filters.sdg.SDG 14 - Life below water

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    Effect of salinity on the embryonic development of Portunus pelagicus and Charybdis feriatus eggs
    Alba, Kristine Margaret A. (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 2003-03)
    The effect of salinity on the embryonic development of Portunus pelagicus and Charybdis feriatus was studied. The five different salinity levels used were 15 ppt, 25 ppt, 35 ppt, 45 ppt, and control (33-35 ppt) to compare their effect on the embryonic development of both species. One thousand newly spawned crab eggs were incubated in vitro in 4-L Nalgene fiberglass containers with 3-L of water at different salinity levels. Mild aeration that allows movement of eggs within the water column was provided. There were three replicates per treatment. Embryonic development of eggs (30 eggs were taken in every salinity level) was monitored daily up to hatching. The newly hatched larvae were then collected and counted. Results showed that during the incubation period, the most advanced stage of embryonic development for Portunus pelagicus was at 33-35 ppt and for Charybdis feriatus was at 35 ppt. There was normal embryonic development and hatching at 35 ppt, 45 ppt, and control (33-35 ppt) for Portunus pelagicus and at 15 ppt, 25 ppt, 35 ppt, 45 ppt, and control (33-35 ppt) for Charybdis feriatus. Eggs that were incubated at 15 ppt and 25 ppt for Portunus pelagicus died. There was normal embryonic development in both species when incubated at 45 ppt. Hatching rate for Portunus pelagicus at control (33-35 ppt) was 34.1 %, at 35 ppt was 16.1 %, and at 45 ppt was 5.8 %. Hatching rate for Charybdis feriatus at 35 ppt was 52.5 %, at control (33-35 ppt) was 21.2 %, at 45 ppt was 12.8 %, at 25 ppt was 6.7 %, and at 15 ppt was 0.3 %. To summarize, embryo of Charybdis feriatus eggs can withstand a wider range of salinity: from a low salinity of 15 ppt to a high salinity of 45 ppt, that makes them a euryhaline species. On the other hand, Portunus pelagicus cannot support embryonic development at lower salinities of 15 and 25 ppt that makes them a stenohaline species.
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    Relation of size and sex to the natural diet of the red crab Charybdis feriatus Linnaeus (Brachyura: Portunidae) from Pilar-Capiz Bays, Northern Panay
    Alabia, Irene Dolorfino (Division of Biological Sciences, College of Arts and Sciences, University of the Philippines Visayas, 2003-03)
    A total of 395 (males= 282; females=113) specimens of the red crab Charybdis feriatus were collected from Pilar-Capiz Bays from January-December 2002 and were used for the present study. Relative fullness index were computed for both sexes of different size classes. Results showed that stomachs of females were slightly fuller than that of males. Similar observation was made between juvenile and adult specimens. A total of 75 (males= 57; females= 18) gut contents were analyzed in detail. Major food items in the diet of the crabs include unidentified matter, unidentified eggs, fish, crab, and shrimp remains. Frequency of occurrence and combined visual estimation of unidentified organic matter were used for the examination. No dietary differences due to ontogenetic change were observed in the species while diet of male crabs were found to be more varied than those of females. However, frequency of occurrence of major food items in the stomachs of both sexes was comparable.