Filter-feeding Animals Research Articles

Relation of the Phytoplankton to Turbulence and Nutrient Renewal in Casco Bay, Maine

A diatomaceous phytoplankton remains at fairly high densities, 102−5 × 103 cells/cm4, from the end of winter to the end of summer in Casco Bay. During spring the algal populations deplete the nutrient content of the water, particularly nitrate, except in the deep water at the entrances to the bay. Here appreciable quantities of nitrate persist into midsummer. These may be carried inward by influxes of deep water and then maybe mixed upward to support the continued growth of diatoms, although the change from the spring diatoms belonging to the genera Thalassiosira and Chaetoceros to the summer dominant Skeletonema costatum is considered to depend on temperature and light changes. The high concentrations of Skeletonema, often exceeding 103 cells/cm3, are shown to be enough for the maintenance and growth of several filter-feeding animals.

Filter-feeding mechanisms in some brachiopods from New Zealand

Summary All major types of lophophore in branehiopods, except the ptyeholophe, are represented among the growth stages of the five species described here. The basic ciliary mechanisms are uniform, and similar to those known in other species. The mantle cavity is always divided by the lophophore into inhalant and exhalant chambers with separate apertures; but the arrangement may change radically during ontogeny with the increasing complexity of the lophophore, which is attributed to a dimensional relation between food-collecting capacity and metabolic requirements. The limited variety of lophophoral arrangements is taken to reflect an inherent limitation imposed by the basic structure and function of lophophores. The feeding mechanisms are compared briefly with those of other filter-feeding animals.

SOME ECOLOGICAL RELATIONSHIPS BETWEEN PHYTO- AND ZOOPLANKTON

1. Several planktonic algae from the brines of the sea water evaporation ponds were fed to the brine shrimp Artemia. They were found to differ in their nutritive value to this filter-feeding animal. One of these algae, Stichococcus sp., could not be utilized by the animal as a food source.2. Controlled experiments of the effect of filter-feeding Artemia and Tigriopus on a mixed population of two unicellular algae indicate that the animals are capable of acting as differential grazers; The heavy bloom of Stichococcus in the evaporation ponds could be due to the effect of preferential digestion of competing algae by grazing animals.