Microphiopholis gracillima can autotomize and then regenerate the autotomized central disc, including integument, gut, and gonads. Experiments were carried out to determine the relative importance of internal nutrient reserve translocation and exogenous nutrient uptake during the regeneration process. Approximately 60% of the dry body weight of M. gracillima is organic material. Intact animals held for three weeks in natural seawater did not change significantly in weight, caloric content, or relative concentration of protein, carbohydrates, or lipids. Intact animals held for three weeks in artificial seawater devoid of nutrients lost weight and caloric content. The rate of loss was rapid initially, but slowed after about eight days. Animals regenerated in natural seawater lost weight initially, then regained the lost weight. Animals regenerated in artificial seawater lost weight constantly and at a higher rate than either the artificial seawater control or natural seawater regenerated animals. All weight losses were attributable to significant changes in the protein and carbohydrate fractions of the organic body component. The lipid fraction and ash components did not change significantly in any treatment. M. gracillima appears to be adapted to regenerate the lost disk rapidly, even under conditions of food deprivation.

Restoration of seagrass beds has been suggested as a method to correct declining vegetation cover in shallow waters. Secondary production of the polychaete Kinbergonuphis simoni was used to evaluate faunal equivalency of newly restored (2-yr-old) seagrass beds to beds that are mature (at least 17 yr old) in an embayment in Tampa Bay, Florida. Information on density of polychaetes, size structure, reproductive characteristics, and production (growth increment summation method) was collected from May 1989 to February 1991 from individuals within monthly sediment cores from both planted and natural seagrass beds. Additionally, total macroinfauna were sampled every 3 mo at the same sites. Deposit-feeding polychaetes were the dominant macroinfaunal taxa in all seagrass beds examined. Three polychaete species, including Kinbergonuphis simoni, displayed significantly enhanced abundances in planted compared to natural seagrass beds. Population abundance and size class distribution of Kinbergonuphis within planted sites displayed more rapid and consistent population increases after populations disappeared in winter 1989 than that recorded for natural sites. Production values of planted areas over 22 mo were an order of magnitude higher than that recorded in natural areas. Higher production values resulted principally from rapid recovery of populations in planted areas in contrast to natural beds, which did not display such resiliency. Biomass allocation to reproduction did not vary among individuals from natural and planted beds, but more total individuals were participating in reproductive events in planted areas. Results of this study suggest that in addition to abundance of some frequently encountered deposit-feeders, functional characteristics of a common polychaete from seagrass beds vary with age of bed. Moreover, the link between faunal functional equivalency and vegetational cover remains obscure.

Abstract. Individual Microphiopholis gracillima (Stimpson) were collected in February 1987 from an intertidal mudflat in the North Inlet Estuary near Georgetown, South Carolina, USA, and allowed to regenerate for 10 or 20 d in nutrient-free seawater after having different amounts of disc and/or arm tissue removed. In the absence of external nutrients, the pattern of regeneration was affected by both the quantity and type of tissue lost, and changed over time. Depending upon which tissues were lost, M. gracillima allocated stored materials to disc and/or arm regeneration until a gut and three complete arms were achieved. This "minimal functional configuration" allows the brittlestar to construct its respiration and feeding burrows and digest whatever food it captures. In the absence of external nutrients, M. gracillima slowed the rate of regeneration once this state was reached, subsequently using nutrients for maintenance metabolism only. Brittlestars which suffer frequent sublethal tissue loss in nature have regeneration patterns that result from a complex interplay between time, quantity and quality of tissue lost, available nutrients and risk of future damage or mortality.

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