Browsing by Author "Suñaz, N. A."
Hematological and histopathological changes in Oreochromis mossambicus after exposure to the molluscicides Aquatic and Brestan ER Cruz, MC de la Cruz & NA Suñaz - In RSV Pullin, T Bhukaswan, K Tonguthai & JL Maclean (Eds.), The Second International Symposium on Tilapia in Aquaculture, 16-20 March 1987, Bangkok, Thailand, 1988 - Department of Fisheries; International Center for Living Aquatic Resources ManagementDuplicate static 96-hour bioassays were conducted to determine the median lethal concentration for Oreochromis mossambicus (LC50) of two organostannous molluscicides, commonly used in fishponds: Aquatin and Brestan. O. mossambicus was more sensitive to Brestan. The acute toxicity of both Aquatin and Brestan ceased towards the end of 96 hours. The 24, 48, 72 and 96 hour LC50’s were 4.01, 3.97, 2.95 and 2.58 ppm formulated product for Aquatin and 0.35, 0.18, 0.10 and 0.09 ppm for Brestan, respectively. The computed safe concentrations for Aquatin and Brestan are 0.30 and 0.01 ppm, respectively. Exposure to lethal concentrations of Aquatin resulted in an immediate reduction in hemoglobin and hematocrit levels. Hemoglobin content was likewise lower in Brestan-exposed fish, whereas their hematocrit level was higher than that of the control fish. Histological analyses of gills, intestine, liver and kidney showed pathological changes even in sublethal levels tested. Damage became severe with increasing concentration of the pesticide. The behavior and symptoms exhibited by the fish and the physiology of hematological and histopathological changes are discussed.
Studies on the chemical control of luminous bacteria Vibrio harveyi and V. splendidus isolated from diseased Penaeus monodon larvae and rearing water MCL Baticados, CR Lavilla-Pitogo, ER Cruz-Lacierda, LD de la Peña & NA Suñaz -
Diseases of Aquatic Organisms, 1990 - Inter ResearchThe minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of 24 drugs for luminous bacteria Vibrio harveyi and V. splendidus were determined. Only chloramphenicol, sodium nifurstyrenate and the nitrofurans (furazolidone, nitrofurazone, nitrofurantoin and Prefuran) showed relatively low MICs and MBCs (<25 µg/ml-1). The bacteria showed varied responses to chloramphenicol and Prefuran and low sensitivity to oxytetracycline. Chloramphenicol, oxytetracycline and Prefuran are commonly used in shrimp hatcheries. Shrimp larvae showed high survival rates and active swimming movement after 24 h exposure to in vivo bactericidal doses of chloramphenicol, Furacin, nitrofurantoin (protozoa only), oxytetracycline (nauplius only), Prefuran (mysis only) and sodium nifurstyrenate, but the drugs caused deformities in the carapace, rostrum, and setae. Chemical control of luminous vibriosis among shrimp larvae appears limited, based on the efficacy of existing and readily available drugs, because of the possible development of resistant strains of bacteria and the limited tolerance of the shrimp larvae to the drugs.
Conference paperCR Lavilla-Pitogo, LJ Albright, MG Paner & NA Suñaz - In M Shariff, RP Subasinghe & JR Arthur (Eds.), Diseases in Asian Aquaculture I. Proceedings of the First Symposium on Diseases in Asian Aquaculture, 26-29 November 1990, Bali, Indonesia, 1992 - Asian Fisheries Society, Fish Health SectionOne of the major problems in the otherwise highly successful Penaeus monodon hatchery industry in the Philippines is the occurrence of luminescent bacterial disease due to Vibrio harveyi. The possible sources of the bacteria were investigated. Eggs within the ovaries of stage III and IV wild-caught and ablated female P. monodon harbour no bacteria. On the other hand, the midgut contents of these spawners, as well as of pond-reared juveniles, contained numerous luminescent bacteria. Plate counts of the exoskeleton from all sampled females revealed that V. harveyi is a minor component of the exoskeleton-associated flora. Scanning electron microscopy of the exoskeleton showed no significant attached populations. The bacterial loads of Chaetoceros calcitrans, a marine diatom, and Artemia salina nauplii were likewise estimated. C. calcitrans did not harbour V. harveyi at any phase of its growth. Twenty-four-hour-old A. salina appeared to have no resident V. harveyi, but its culture water contained small populations of these bacteria. These data show that the main source of the luminescent bacteria is the midgut contents of the mother, which are shed into the water almost simultaneously with the eggs during spawning.