Temporal Variation in Populations of the Brittlestars Hemipholis Elongata (Say, 1825) and Microphiopholis Atra (Stimpson, 1852) (Echinodermata: Ophiuroidea) in Eastern Mississippi Sound
Dense populations of two species of infaunal brittlestars, Hemipholis elongata (Say, 1825) and Microphiopholis atra (Simpson, 1852) have been known to persist in dense concentrations, in the north central Gulf of Mexico for the past 30 years. Despite this, little is known about the population dynamics of these organisms. Therefore, I investigated the seasonality of these two species from April, 1986 through August, 1987 in eastern Mississippi Sound, an estuarine environment in the north central Gulf of Mexico. Mean density of M. atra peaked during its recruitment period in October, 1986 and August, 1987 (109 and 112 individuals˙m−2 respectively), with juveniles comprising 80% of the population at those times. Survivorship of the 1986 recruitment class of juveniles was estimated to be low (approximately 3-4%). H. elongata also had its highest mean densities (48 individual˙m−2) associated with its recruitment period, May through August, but the highest monthly density was observed in March 1987 (54 individuals˙m−2). Survivorship for recruits of this species from 1986 was also estimated to be low (approximately 3%). While recruit andjuvenile densities of M. atra varied significantly between 1986 and 1987 the total densities (adult + immature individuals) did not. In contrast, neither total, juvenile or recruits of H. elongata differed over the same periods. These results indicate that although recruitment appears to affect the seasonality of these brittlestars it does not appear to play role in their annual variability.
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Document Type: Research Article
Publication date: 1991-05-01
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