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Journal Articles - UP - MSI

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Author: search.filters.author.Cabaitan, Patrick C.Scientific name: search.filters.scientificname.Tridacna crocea

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    Reproductive consequences of thermal stress-induced bleaching in the giant clam Tridacna crocea
    Sayco, Sherry Lyn G.; Alabort Pomares, Ana; Cabaitan, Patrick C.; Kurihara, Haruko (Elsevier, 2024-01)
    Reproduction is a fundamental process necessary for maintaining a population. However, reproductive processes are sensitive to thermal stress which can cause bleaching in reef organisms such as corals and giant clams. Here we examined the phototrophic and physiological performances, particularly the reproductive processes, in Tridacna crocea during bleaching and recovery periods. Giant clam individuals were induced to bleach at heated treatment (32-33 °C) for 16 days and allowed to recover at 28-29 °C for 35 days. The control giant clams were kept at 28-29 °C. Heated giant clams showed lower phototrophic performances (Fv/Fm and photosynthesis), but their respiration and survival were similar to control giant clams. The gonadosomatic index (GSI) was lower, and the proportion of regressive eggs (i.e., eggs that are no longer viable) was higher in heated than in control giant clams. However, heated giant clams were able to maintain their egg size. In addition, T. crocea showed recovery of phototrophic potential and color of mantle but not of their reproductive output after a month of recovery. Our results indicate that bleaching reduces the reproductive output in giant clams by disrupting their gametogenesis, such as through egg resorption, but giant clams showed potential reproductive strategy, through maintenance of their egg size, to ensure the quality of their offspring. Furthermore, one month of recovery is not sufficient to restore the normal reproductive processes in T. crocea, which may delay their population recovery after a bleaching disturbance.
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    Declining population of giant clams (Cardiidae:Tridacninae) in Palawan, Philippines
    Dolorosa, Roger G.; Mecha, Niño Jess Mar F.; Bano, Jemima D.; Ecube, Krizia Meryl A.; Villanueva, Elmer G.; Cabaitan, Patrick C. (FapUNIFESP (SciELO), 2024)
    For more than two decades, the Philippine government has protected the giant clams (Bivalvia: Cardiidae: Tridacninae) from exploitation and trade. However, there still is lack of information on the impact of these protective measures in conserving the species richness and density, especially in Palawan, the country’s last stronghold of these reef-associated bivalves. Hence, to assess the species richness and density of giant clams in Palawan, we conducted 57 photo-transect surveys in six sites covering 12,325 m 2. Out of these transect, 15 measured 5 × 25 m and the rest measured 5 × 50 m. For historical trends in the population of giant clams in Palawan, we used six published papers obtained from online platforms, 13 reports, and five undergraduate theses archived in local libraries. Information derived from recent field surveys indicated high variations in species richness (2 to 5 species) and densities (0.1 to > 3.6 ind.100 m -2). Historical data starting from 1984, including recent fieldwork, indicated very low densities and a declining trend. The current status suggests that giant clam populations’ viability and the reefs’ health are threatened. Effective mechanisms are needed to safeguard and enhance the remaining giant clam populations.
    This paper is an output of the research project: Evaluating the status of giant clams in Palawan (QMSR–MRRD–MEC-314-1543) with funding support from the Department of Science and Technology-Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (DOST-PCAARRD). We wish to thank the different Local Government Units (LGUs), the WWF-Philippines and our friends: S. F. Conales Jr., L. Ardines Jr., C. Maquiso, R. V. Ravina Jr., S. D. Villalva, J. A. Matillano, J. Genilan, N. Dieron, M. F. J. M. Oquendo, and B. A. Bonares, for their assistance during field surveys. We are also grateful for the comments and suggestions of the anonymous reviewers.