CYTOCHEMICAL FINE-STRUCTURE STUDY OF PHAGOTROPHY IN A PLANKTONIC FORAMINIFER, HASTIGERINA-PELAGICA (DORBIGNY)

The fate of Artemia (brine shrimp) nauplii offered as food to H. pelagica in laboratory cultures was determined using light microscopy and EM. Contact between prey and foraminiferal rhizopodia led to immediate attachment. Adhesive substance was secreted and rhizopodia invaderd crevices of the prey, penetrated the cuticle, and began disruption of prey tissue. Some tissue masses and cells were dislodged and digestion began outside the test as indicated by lysosomal enzymes surrounding partially degraded prey tissue within spaces created by surrounding rhizopodia. Dislodged prey tissue was sequestered into food vacuoles and carried into the intrashell cytoplasm where digestion occurred. The digestive enzymes were secreted by the Golgi apparatus in membrane-bound vesicles (lysosomes) which were carried throughout the cytoplasm and fused with the food vacuoles to produce digestion. The carspace or cuticle of digested prey was discarded and undigested waste material in residual vacuoles was ejected at the periphery of the rhizopodial network.