Spatial and Temporal Variability during Periods of "Recovery" after Mass Bleaching on Western Atlantic Coral Reefs

Western Atlantic coral reefs were differentially affected bya mass bleaching (discoloration) event in 1987. We periodicallyassessed the "appearance" of zooxanthellate organisms betweenDecember 1987 and June 1988 at nine conspicuously affected sitesin the Bahamas, Florida, St. Croix, and Venezuela, using a standardizedpoint-count technique. Three to four months after the localinitiation of the event, the "bleached" state was still presentin one to three of the most abundant reef coral taxa and ina few of the less common species (n = 5 sites). "Recovery" occurredsomewhat faster at shallower depths, at least in the Bahamasand Florida. Scleractinian corals which were "prolonged bleachers"had foliaceous or massive, rather than branching, morphologies."Bleached" points disappeared from the point counts after $6to $8 months. Long-term field data on spatial and temporal variability inthe dynamics of zooxanthellate organisms would help us to understandthe ecological consequences of bleaching. More generally, weneed to distinguish anthropogenic changes in the structure andfunctioning of reef ecosystems from those which occur naturally.Point-count techniques are well suited for collaborative studiesinvolving rapid quantification of coloration states and healthin reef corals.     

The Conservation of Sea Turtles: Practices and Problems

The various techniques in common use for conservation and restorationof depleted sea turtle populations are reviewed, namely: banninginternational commerce; operating artificial hatcheries, bothin the natural beach environment and in styrofoam and othertypes of incubators; "head-starting" of hatchlings in captivity;protection of nesting females by means of beach patrols; andtranslocation of eggs or hatchlings to distant areas from whichturtles have been extirpated or to which it is desired to introducenew colonies. The difficulties of monitoring the results ofall of these techniques are discussed, and potential dangersor disadvantages of each approach are reviewed. It is concludedthat, until unequivocal data become available, turtle conservationistsshould continue to pursue common sense or logically sound restorationprograms, but should constantly re-evaluate their actions inthe light of the latest available knowledge and modify or desistfrom current approaches as necessary.     

Complete Elimination of Mitosis and DNA Synthesis in the Lens of the Hypophysectomized Frog: Effects on Cell Migration and Fiber Growth

Three weeks after hypophysectomy mitosis and DNA synthesis are absent in the lens of the leopard frog ( Rana pipiens ). By labeling germinative zone cells in their last DNA synthetic period we were able to follow them in the absence of further proliferation. By this means it has been demonstrated that migration of epithelial cells to the equator of the lens is stopped. Based on indirect measurements it seems that lens fiber formation also ceases. A correlation coefficient of 0.86 was computed between average labeling index and average distance migrated. In hypophysectomized animals the correlation coefficient between time and migration was 0.02 while in intact animals it is 0.87.     

Ultrastructure of the Eyespot and its Possible Significance in Phototaxis of Tetracystis excentrica*†

SYNOPSIS. The eyespot of the zoospore of Tetracystis excentrica (a green alga) has been studied by light and electron microscopy. In Tetracystis the eyespot consists of about 110 osmiophilic granules which form a plate in the anterior third of the cell. The granules are about 80 Å in diameter and are found in the outermost portion of the chloroplast; they commonly show hexagonal close packing and a hexagonal shape. The granules are confined positionally by the chloroplast envelope and an inner thylakoid. The plasmalemma over the eyespot is thickened and is separated from the chloroplast envelope by a 50 mμ space. The eyespot of Tetracystis is compared with others reported in the literature and the possible functional significance of these studies is discussed. The possibility that the eyespot plate in Tetracystis serves as a shading device rather than the primary photoreceptor is considered.     

Paleoenvironment of Late Mississippian fenestrate bryozoans, eastern United States

Fenestrate bryozoans in Chesterian rocks of the eastern United States are common to abundant in diverse carbonate platform lithologies but are not common in clastic deposits. Fenestella and Archimedes are the most abundant and widespread. Fenestella apparently tolerated a range of water agitation and lived on shoal margins as well as in more protected areas. Archimedes required quiet bottoms and was locally extremely abundant immediately leeward of shoals. Polypora and Septopora were less common than, but had a similar distribution to, Fenestella except that they apparently did not live on shoals. Lyroporella inhabited zones of pronounced current activity and fine quartz sand influx. Penniretepora and Ptylopora were least often encountered, restricted to fine-grained sediments deposited in protected regions.     

Microsatellites in the striped ground crickets,Allonemobius (Orthoptera: Gryllidae)

Polymorphic di‐, tri‐ and tetranucleotide repeats were examined in Allonemobius to determine whether they could serve as useful markers in studies of sperm precedence, population genetics and hybrid zone structure. Ten microsatellite DNA loci were sufficiently polymorphic to be used for paternity tests and showed no evidence of linkage disequilibrium or deviations from Hardy–Weinberg equilibrium in Allonemobius socius. Nine of 10 of these microsatellites can be amplified from three other Allonemobius species, suggesting that these markers will have widespread utility in this ground cricket genus.