Size-frequency distribution of living populations and dead shell assemblages in a marine intertidal sand snail Umbonium (Suchium) moniliferum (Lamarck), and their palaeoecological significance
Abstract Size-frequency distribution of living and dead shell samples of Umbonium (Suchium) moniliferum (Lamarck) in a small inlet in Tsuyazaki, Northern Kyushu, West Japan, have been analysed monthly to obtain quantitative data on the growth of a population, production of dead shells and post-mortem modification of the primary size-frequency distribution of the shell assemblage. Size-specific survivorship curves reflect the population structure well and, therefore, give an idea about the size-frequency of dead shells. The size-frequency distribution of dead shells from various locations in the present study usually shows the unmodified primary patterns. However, it tends to be modified owing to size-selective transportation by currents and, especially, by two pagrid species of hermit crabs. As an example of palaeoecological application, the size-frequency distribution of the fossil shell assemblage of U. (S.) moniliferum from the Holocene shell bed in Fukuoka City, Northern Kyushu was compared with data from the living population. The result shows that the primary patterns of the size-frequency distribution have been modified significantly before final burial in the case of the fossil shell assemblage. This was probably caused by the size-selective transportation of dead shells by hermit crabs.