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Form, function, and embryonic migration in large gelatinous egg masses of arenicolid worms
Author(s) -
Strathmann Richard R.
Publication year - 2000
Publication title -
invertebrate biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.486
H-Index - 42
eISSN - 1744-7410
pISSN - 1077-8306
DOI - 10.1111/j.1744-7410.2000.tb00018.x
Subject(s) - intertidal zone , biology , photosynthesis , oxygen , respiration , embryo , botany , biophysics , ecology , anatomy , fishery , chemistry , organic chemistry
. Attachment and gas exchange are design problems for the spheroidal egg masses that annelids and molluscs tether in sediments. At an intertidal site in Bodega Harbor, a high proportion of masses of arenicolid worms became detached, but they were not stranded higher than attached masses, and the embryos developed to advanced stages. The large masses, weighing 100–200 g, challenge predictions on limiting size for oxygen supply by diffusion. The estimated concentrations of embryos and thickness of the embryo layer exceed the limits predicted by a simple model for oxygen supply by diffusion from the surrounding water, but several features may enhance oxygen supply to embryos. (1) There is an internal cavity. Distal tears in the gel layer admit pulses of water into the center, thus adding an inner surface for gas exchange. (2) The motile embryos aggregate near the outer and sometimes inner surfaces of the gel layer. Embryos migrate in the gel toward regions of greater oxygen concentration. (3) Pennate diatoms colonize the masses, coating the surfaces and penetrating into the gelatinous matrix. Photosynthesis can exceed respiration when a mass is in the light. The pH in gel changes diurnally from a low of ∼7 to as much as 9.5, indicating an excess of respiration over photosynthesis at night and at least sometimes an excess of photosynthesis over respiration by day.