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Abstract. Respiration in Holothuria tubulosa was investigated in individuals from the Posidonia oceanica meadow off Lacco Ameno (Ischia Island, Italy). Respiratory rates increase with increasing body weight and increasing sea water temperature. Oxygen consumption of an average individual (7g dw body wall) ranges from 0.409 (14 °C) to 1.300 (26 °C) mg O2 · h-1 . Data on population density, mean size of individuals, and annual sea water temperature variations allow an assessment of holothuroid production. Values of 45.65 and 13.75 kJ · m-2 · y-1 were calculated for shallow (3 to 10 m) and deep (25 to 33 m) areas of the Posidonia meadow, respectively. Holothuroid production shows a bathymetric pattern similar to primary production of the Posidonia -epiphytes complex and the production of Posidonia litter. 相似文献
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Abstract. The synaptid holothuroid Leptosynapta inhaerens has the ability to expel unwanted particles that enter its body cavity. Intracoelomic particles ( viz. experimentally injected carmine particles) are trapped either by a coelom-produced mucoid net or by specialized organs (the vibratile urnae) that occur in bands in some interradial areas. Whatever the trapping method, particles are incorporated into dense mucoid masses that move towards the posterior part of the body cavity, in the vicinity of the rectum. These aggregates then cross the rectal wall through rectal pores, mix with the faeces, and are eventually incorporated into the wall of the synaptid burrow. Clearance of foreign particles requires 2 to 3 days. The coelom-cleaning system of synaptids appears to be the most effective within the class Holothuroidea , being well designed for endofaunal organisms whose walls are delicate and easily rupture. 相似文献
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Abstract. Holothuria tubulosa individuals were sampled regularly at three different depths (6, 19, and 33m) over a 20-month period in a Posidonia oceanica meadow off Ischia Island (Italy). Biometrical analysis demonstrated that holothuroids have a well-marked size-related distribution according to depth, with the smallest individuals in the shallowest part of the meadow and the large ones in its deepest part. The observed distributions reflect the ability of H. tubulosa to grow more efficiently in areas of low water turbulence where Posidonia shoots are scattered and detrital food is more easily accessible. Recruitment takes place in the shallow meadow, and holothuroids with high reproductive potential only occur in the deep meadow. Small holothuroids (shallow individuals of similar sizes) may be either juveniles or sexually mature individuals; environmental constraints apparently restrict the growth of individuals and their gonads. There is a progressive downward migration of growing individuals when the whole population is considered, although at the level of the individual the migration occurs randomly. Accordingly, the size of a sexually mature individual is more a function of its past history in the meadow than of its real age. 相似文献
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