Distribution pattern, population structure, and growth of Septifer bilocularis (Bivalvia: Mytilidae) on reefs of Southern Vietnam
ABSTRACT The features of the spatial distribution, size and age structure of populations, and growth of the bivalve mollusk Septifer bilocularis (Linnaeus, 1758) were investigated for the first time in the waters of Vietnam. It is shown that in the subtidal area, on
reefs well protected from wave effects, S. bilocularis occupies a corallogenous substrate constructed of dead branchy colonies of Acropora and Porites and forms settlements there with a population density and biomass exceeding those in populations located along the open coast
and developing on massive coral colonies of the genera Porites, Favia, and Favites. The extensive accumulation of sediments in the inner part of Vanphong Bay (Khanh Hoa Province) correlated with a decrease
in the size and age ranges for populations of S. bilocularis. It is found that in places with regularly active hydrodynamics the mollusks grew somewhat more slowly and formed a more
convex shell than on reefs protected from surf. The longevity of S. bilocularis estimated both from the greatest observed age and from the growth equation of Bertalanffy was somewhat greater in the former
case compared with the latter one, but in general did not exceed 11 years for both cases. The results of the studies are discussed
from the position of morphophysiological adaptations of sessile bivalve mollusks to life in contrasting environmental conditions
of the upper subtidal zone.
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ABSTRACT: The byssal apparatus appears during post-larval life when its secretion permits brief attachment during metamorphosis when the animal assumes the form which fits it for life in the adult habitat.The byssus persists for continued temporary attachment in animals which may lose it in adult life, e.g. Mya arenaria, or in which it becomes an organ of permanent fixation, e.g. Mytilus edulis, Pododesmus macroschisma and Tridacna croceaJournal of the Marine Biological Association of the UK 01/1962; 42(01):113 - 125. · 1.02 Impact Factor
- Journal of Experimental Zoology 05/2005; 90(1):1 - 30.
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ABSTRACT: Exposed rocky shores in Hong Kong are dominated at mid-tidal levels by a broad band of the mytilid Septifer virgatus. A 48-month study of a population inhabiting the shores at Cape d'Aguilar has been undertaken. The species matures at a shell length of 15 mm, about one year after recruitment. Septifer virgatus is dioecious with a slight, but insignificant, female bias overall. There is, however, a significant juvenile male bias. Generally, most adult individuals remain mature year round, although spawning is limited to two periods in spring (February to March) and autumn (September to December) with subsequent recruitment into the adult population. The species lives for 4–5 years, although older individuals, possibly up to 12 years of age and with a maximum recorded shell length of 65 mm, occur as solitary individuals lower down the shore. Mortality in winter mainly affects newly recruited juveniles. A heavy mortality of adults in summer is thought to be related to high rock temperatures at midday ( 50°C), concurrent with low spring tides.The life-history tactics and sexual strategy of Septifer virgatus can be correlated with seasonal changes in hydrography. There are a number of similarities with other local mytilids, notably the dioecious condition and the bimodal pattern of spawning and recruitment. Such similarities are discussed in relation to the habitats occupied by these species.Journal of Zoology 02/1995; 235(3):485 - 500. · 2.04 Impact Factor