19 resultados para Ciona-intestinalis Metamorphosis


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Stages of development of P. placenta from the straight-hinge veliger to the adult are described. Mature larvae metamorphose at lengths from 220-230 m. Larvae probably attach byssally to the water surface at metamorphosis and remain in the plankton for some time before finally settling on the mud bottom.

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Following brief descriptions of the various phases in the natural life history of the milkfish (Chanos chanos), namely adults, eggs and embryos, larvae, fry and metamorphosis, juveniles and sub-adults, a summary is provided of the life history, providing also a schematic diagram.

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"Mukene"Rastrineobola argentea occurs in lakes Victoria, Kyoga, Nabugabo and the Victoria Nile. On lakes Victoria and Kyoga the commercial fishery is well developed. While some fishing occurs at isolated places on the Victoria Nile, the species is yet to be exploited on lake Nabugabo although the potential exists. Experimental fishing (light fishing and beach seining) was conducted on Lake Nabugabo based at the Lake Nabugabo Holiday and Conference Center. Specimens obtained were analyzed for biological and fisheries parameters. Mukene on Lake Nabugabo still grows to a large adult size compared to the Lake Victoria populations. Size at first maturity at 42mmSL is close to that observed on Lake Victoria. Peak breeding occurred between August and January. Unlike on Lake Victoria, R.argentea in Lake Nabugabo is not infested by the cestode Ligula intestinalis that is common in these fishes. Catch rates of 9.8 kg/lamp/hr by the lampara net on this lake compare favorably with many parts of Lake Victoria and on Lake Kyoga where a commercial fishery exists. The amount of by-catch species in the catches however is high and does not therefore favour the establishment of the fishery on this lake. Human exploitation of mukene on Lake Nabugabo would also affect the Nile perch fishery which depends on the species as a source of food.

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This is one of the largest species of angelfish reaching almost 20 inches (50cm) in length. As an adult it has a violet blue body with a large yellow blotch on the side that some say resembles the continent of Africa. As a juvenile it is similar in appearance (and easily confused with) other young Pomacanthus, especially the Blue-ring Angelfish P. annularis. But as its color pattern begins to metamorphosis, the sub-adult begins to look very much like the Arabian Angelfish P. asfur. It will have a similar looking vertical yellow bar on its body, but lack the bright yellow tailfin of the Arabian Angel. Its yellow marking develops as a characteristic "yellowband", finally becoming more prominent and blotch-like as the fish ages. Hence this fish is also known by a number of descriptive common names including Yellowbar Angelfish, Half Moon Angelfish, Map Angelfish, Yellow-Band Angelfish, Yellow-blotch Angelfish, Blue-moon Angelfish, and more.