Glauconema bermudense Small, 1986
Glauconema bermudense: living trophont, after Small et al., 1986
Taxonomic Characterization: The trophont stage of Glauconema bermudense possesses a set of preoral polykinetids that gently curve anteriorwards between kinety 1 and n, and the first and second oral polykinetids merge together at their respective posterior and anterior margins so that they form an inverted and tapered comma-shaped organellar complex. The oral dikenetid is curved posteriorly around the cytostome. In the living cell, the anterior end is slightly twisted to the right with its cytostome and immediately surrounding oral area tucked into a medially located inpocket. The somatic kinetome is composed of 15-16 bipolar kineties in which kinety 1 is clearly sigmoid and the others on the ventral surface are less skewed. In the anterior 1/2 of the cell, slightly anterior to the level of the cytostome is situated a 10 cubic micron globular macronucleus with a 2 cubic micron nested on its anterior surface. A cytoproct has been observed to expulse particulate wastes situated between kineties 1 and n. A single contractile vacuole has also been observed in the posterior end of the cell to the right of the cytoproct region.
Tomite cells differ from the tomonts by their diminutive site (18-26 microns long by 12-20 microns wide). The oral apparatus is situated mid ventrally and is much reduced, Four sets of barren paired kinetosome kinetids comprise the oral dikinetid c segment. In all stained specimens, the cytostome is retained along with a connected internal "preparatory" food vacuole (Small et al., 1986).
Glauconema bermudense: living tomite, after Small et al., 1986
Ecological Classification: Stygobitic
Size: Total cell length 64-56 microns, width 24-28 microns.
Number of Species in Genus: Three
Species Range: Known from Green Bay, Church, Wonderland and Tucker's Town Caves in Bermuda.
Closest Related Species: Glauconema bermudense is related to G. trihymene from the Atlantic coast off Virginia and G. pacificum from subtidal sand along the Pacific coast off California. G. bermudense is much larger than either of its congeners, has slightly fewer kineties and has a greater degree of posterior kinetal skew (Small et al., 1986).
Habitat: Anchialine limestone caves
Ecology: Specimens of Glauconema bermudense were collected in the interior of caves, but not in the entrances or in open waters. The species was found at various depths and salinities in several caves in Bermuda. The organisms were collected from the mucoid surfaces of a dead fish found in the interior of Green Bay Cave, and cultures of the species were prepared. The species was also recovered from fish-baited traps in other caves in Bermuda (Small et al., 1986).
Life History: This ciliate undergoes a tomont to tomite morphogenetic transformation when well fed and in light. When cultured tomites were placed darkness with freshly bacterized canned tuna fish revert to the trophont morphotype. These transformations may allow the ciliate to survive in sediments in very low numbers in a very reduced state of metabolic activity as tomites. In the presence of an introduced food source such as a dead fish, the ciliates then transform to feed and grow to become tomonts. Tomite transformation could then occur, with some of the tomites surviving until the next opportunistic feeding event occurs (Small et al., 1986).
Evolutionary Origins: Since G. bermudense is only found in the inner parts of anchialine caves and has morphogenetic adaptations to this environment, it is considered to be a true protistan stygobite, the first record of such an occurrence for marine ciliate protists (Small et al., 1986).
Contributor: Eugene B. Small, University of Maryland, College Park, MD
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