Meyer and Ausich (1983) and Meyer (1985) characterized predation on living comatulids as chiefly sublethal grazing by nonspecialist fishes with damage including missing and regenerating arms, pinnules and visceral masses. Nine fish families include known comatulid predators: one species each of Lutjanidae, Ephippidae, Chaetodontidae, Labridae, Monacanthidae, Tetraodontidae and Notacanthidae; and two species each of Balistidae and Sparidae. Meyer (1985) noted that the triggerfish Balistoides conspicillum is the best documented, but only the sparid Chrysophrys auratus is known to feed on numbers of whole comatulids. He pointed out that sublethal predation pressure on tropical reef-dwelling crinoids appears to be relatively low; 47% of specimens had one or more missing or regenerating arms (chiefly <5). Semicryptic and cryptic species suffer less damage than species that perch in the open (Meyer 1985, Schneider 1988). However, Mladenov (1983) reported that 80% of Florometra serratissima specimens off Vancouver Island had one or more regenerating arms. He attributed the arm loss to the crab Oregonia gracilis and the asteroid Pycnopodia helianthioides. At least some attacks by fish may be directed at the numerous commensals resident among crinoid arms (Meyer 1985). Behavioral, morphological and visual camouflage by commensals suggests that they represent a potential food source and that their hosts provide significant shelter.

 

Possible defenses against predation include diurnal seclusion (most teleosts that feed on calcareous prey are day-active); protection of the visceral mass by semicryptic behavior, development of large spine-like oral pinnules or a dense thicket of arms and pinnules; incorporation of distasteful or toxic compounds, and crawling/swimming. (Rideout et al. 1979, Bakus 1981, Meyer & Ausich 1983, Meyer 1985). Oji and Okamoto (1994) demonstrated how the branching pattern of rays and the distribution of autotomy points (syzygies) in shallow-water comatulids (typified by Oxycomanthus japonicus) approach a theoretically ideal pattern that minimizes the effects of arm loss via predation. They contrasted this with a pattern found in deep-water isocrinids (e.g., Metacrinus rotundus) that approaches an arrangement ideal for harvesting food in a low-predation environment. In addition, comatulids display substantial regenerative powers. Meyer (1988) noted that the visceral mass of tropical Himerometra robustipinna may regenerate completely within three weeks of evisceration. Cold temperate Florometra serratissima completely regenerates 200-mm-long arms in 9 months (Mladenov, 1983). Comatulids thus exhibit a suite of features that ostensibly confer a measure of protection against predation and that apparently have contributed to their success in shallow-water following the late Mesozoic radiation of durophagous predators (Meyer & Macurda 1977, Meyer 1985, Schneider 1988, Oji & Okamoto 1994, Oji 1996).

 

[Modified from Messing (1997)]

 

References

Bakus, G.J. 1981. Chemical defense mechanisms on the Great Barrier Reef, Australia. Science 211:497-499.

Messing, C.G. 1997. Living Comatulids. Pp. 3-30 IN: Waters, J.A. & Maples, C.G. (eds.) Geobiology of Echinoderms. Paleontological Society Papers 3.

Meyer, D.L. 1985. Evolutionary implications of predation on Recent comatulid crinoids from the Great Barrier Reef. Paleobiology 11(2):154-164.

Meyer, D.L. 1988. Crinoids as renewable resources: Rapid regeneration of the visceral mass in a tropical reef-dwelling crinoid from Australia. Pp. 519-522. IN: Burke, R. D., Mladenov, P. V., Lambert, P. and Parsley, R. L. (eds.) Echinoderm Biology. Balkema, Rotterdam.

Meyer, D.L. and Macurda, D.B., Jr. 1977. Adaptive radiation of the comatulid crinoids. Paleobiology 3:74-82.

Meyer, D.L. & Ausich, W.I. 1983. Biotic interactions among Recent and among fossil crinoids. Pp. 377-427. IN: Tevesz, M. J. S. and McCall, P. L. (eds.) Biotic Interactions in Recent and Fossil Benthic Communities. Plenum, NY.

Mladenov, P.V. 1983. Rate of arm regeneration and potential causes of arm loss in the feather star Florometra serratissima (Echinodermata: Crinoidea). Canadian Journal of Zoology 61(12):2873-2879.

Oji, T. 1996. Is predation intensity reduced with increasing depth? Evidence from the west Atlantic stalked crinoid Endoxocrinus parrae (Gervais) and implications for the Mesozoic marine revolution. Paleobiology 22(3):339-351.

Oji, T. & Okamoto, T. 1994. Arm autotomy and arm branching pattern as anti-predatory adaptations in stalked and stalkless crinoids. Paleobiology 20(1):27-39.

Rideout, J.A., Smith, N.B. & Sutherland, M.D. 1979. Chemical defenses of crinoids by polyketide sulphates. Experientia 35:1273-1274.

Schneider, J.A. 1988. Frequency of arm regeneration of comatulid crinoids in relation to life habit. Pp. 531-538. IN: Burke, R. D., Mladenov, P. V., Lambert, P. and Parsley, R. L. (eds.) Echinoderm Biology. Balkema, Rotterdam.