Effects of disc and arm loss on regeneration byMicrophiopholis gracillima (Echinodermata: Ophiuroidea) in nutrient-free seawater

Abstract

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.

Energy metabolism and regeneration impaired by seawater acidification in the infaunal brittlestar,Amphiura filiformis

“…This supports hypotheses formulated in earlier studies which suggested that regeneration in brittlestars is linked to significant energetic costs (Fielman et al, 1991;Pomory and Lawrence, 1999). In particular, the initial phase of regeneration, which is characterized by cell proliferation (Thorndyke et al, 2001;Dupont and Thorndyke, 2006), seems to require significant energetic costs that derive from aerobic metabolism.…”

“…As arms are essential organs for suspension feeding (Woodley, 1975), respiration (Ockelmann, 1978) and ventilation of the burrow (Nilsson, 1999), long-term selection pressure on A. filiformis has led to the ability to autotomize their arms in case of an attack by a predator, and to a high potential for regeneration of these lost tissues (Dupont and Thorndyke, 2006). The process itself and the physiological properties of regeneration were investigated in earlier studies, suggesting that energetic costs for the regeneration of arms are significant (Fielman et al, 1991;Pomory and Lawrence, 1999). Moreover, depending on the position of autotomy, the available energy can be used for either growth or differentiation of the regenerating arm piece (Dupont and Thorndyke, 2006).…”

Growth or differentiation? Adaptive regeneration in the brittlestarAmphiura filiformis

“…The energy costs for regenerating a new arm are likely to be significant (Salzwedel, 1974;Bowmer and Keegan, 1983;Fielman et al, 1991;Stancyk et al, 1994;Pape-Lindstrom et al, 1997;Pomory and Lawrence, 1999;Pomory and Lawrence, 2001) and this energy can be allocated to two main processes:…”

Ophionereis reticulata (Echinodermata, Ophiuroidea)

“…Regeneration acts to restore the functionality of the lost structure, however, it requires the allocation of energy and matter (POMORY & LAWRENCE, 1999). Echinoderms are well-known for their propensity to lose body parts as a result of predation, accidental injury or asexual reproduction (EMSON & WILKIE, 1980;FIELMAN et al, 1991). Ophiuroids undergo tissue loss frequently and burrowing brittle-stars present high rates of sub-lethal arm loss to numerous cropping predators, including penaeid shrimp, decapod crustaceans, pleuronectids, bothid flatfishes, and other echinoderms (BUCHANAN, 1964;EMSON & WILKIE, 1980;DUINEVELD & VAN NOORT, 1986;FIELMAN et al, 1991;BOURGOIN & GUILLOU, 1994;STEWART, 1996).…”

“…Echinoderms are well-known for their propensity to lose body parts as a result of predation, accidental injury or asexual reproduction (EMSON & WILKIE, 1980;FIELMAN et al, 1991). Ophiuroids undergo tissue loss frequently and burrowing brittle-stars present high rates of sub-lethal arm loss to numerous cropping predators, including penaeid shrimp, decapod crustaceans, pleuronectids, bothid flatfishes, and other echinoderms (BUCHANAN, 1964;EMSON & WILKIE, 1980;DUINEVELD & VAN NOORT, 1986;FIELMAN et al, 1991;BOURGOIN & GUILLOU, 1994;STEWART, 1996). Arm regeneration in populations of ophiuroids has been examined by numerous researches (SINGLETARY, 1980;DUINEVELD & VAN NOORT, 1986;O'CONNOR et al, 1983;MUNDAY, 1993;STEWART, 1996;MORGAN & JANGOUX, 2004), which observed high rates inside the populations and that regeneration scars frequently occur in the distal portion of the arms.…”