A contribution to the biology of Amphiporeia Lawrenciana in Newfoundland waters

Downer, Donovan F. (1972) A contribution to the biology of Amphiporeia Lawrenciana in Newfoundland waters. Masters thesis, Memorial University of Newfoundland.

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Abstract

In Newfoundland Amphiporeia lawrenciana is limited in its occurrence chiefly by the particle-size of the substrate and exposure of the beach. The species prefers substrate habitat in the particle size range of 125-2000 μ and it appears to recognize "home" substrate. At Salmon Cove 95% of the substrate is within the size range 125-1000 μ; at areas of greatest abundance of the animal in Newfoundland the same particle size predominates. A concentration of the species at Salmon Cove beach 25 meters from LWS during the summer months may shift seaward during the winter because of low water temperatures. A possible alternative explanation for the small numbers taken in winter samples might be that the animals burrow deeply enough into the sand to escape capture by the collection method used. Population numbers reach a peak at Salmon Cove in October when unsexable young constitute over 90% of the total; least numbers are present in January. Oogonia of the females enlarge in October and November; embryos are deposited in brood pouches in March and young are released in August. For a second brood embryos are deposited in June and released in the fall. The smaller male copulates at right angles to the body of the female and the latter assumes various reproductive hues during this season. Strong water currents created by pleopod beat aid the animal in swimming and burrowing. An efficient means of aeration of embryos in the brood pouches is provided by these water currents. The species is primarily an omnivorous filter-feeder preferring food within the particle-size range 125-250 μ but it will at times feed on large pieces of food. At Salmon Cove it eats mostly plant food. Feeding rate may be reduced during reproductive periods for females.

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