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Vol. 36 No. 2, 1997
Regeneration and Potential Functional Differentiation of Arms in the Brittlestar, Ophiocoma scolopendrina (Lamarck) (Echinodermata: Ophiuroidea)
Keryea Soong1,*, Yen Shen1, Shu-Hsien Tseng1 and Chang-Po Chen2
1Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan 804, R.O.C. E-mail: keryea@mail.nsysu.edu.tw
2Institute of Zoology, Academia Sinica, Taipei, Taiwan 115, R.O.C.
Keryea Soong, Yen Shen, Shu-Hsien Tseng and Chang-Po Chen (1997) Regeneration and potential functional differentiation of arms in the brittlestar, Ophiocoma scolopendrina (Lamarck) (Echinodermata: Ophiuroidea). Zoological Studies 36(2): 90-97. Arm breakage and regeneration in the brittlestar, Ophiocoma scolopendrina
(Lamarck), were surveyed in southern Taiwan from July 1991 to April
1992. A total of 618 individuals were examined, revealing that in 56%
of individuals, or 19% of arms, were undergoing the process of
regeneration. Breakage occurred mainly at the distal 1/3 of the arm.
The number of individuals with 3 or more regenerating arms exceeded
that of expectation from a binomial distribution, suggesting that
individual arm breakage might be dependent on the status of the other
arms. The arms, according to their position relative to the
madreporite, have different probabilities of being protruded, and they
also have dif· ferent probabilities of breakage in the field. The arms
most frequently protruded tend to be the most frequently injured. This
phenomenon suggests that functions of arms may have differentiated
despite the similar mor• phology of the various arms in the brittlestar.
Laboratory experimental results indicate that the rate of regeneration
per broken arm averages 0.4 mm/day, whether 1 or 3 arms were injured.
Arm position, relative to the madreporite, however, made no difference
in regeneration rates when all 5 arms were cut. Nevertheless, when 3
adjacent arms were severed, the center arm regenerated faster than the
2 side arms; this did not happen when the 3 injured arms were not all
adjacent. The faster regeneration of the center arm may provide the
advantage of restoring arm functions sooner.
Key words: Brittlestar, Regeneration.
*Correspondence:
Institute of Marine Biology, National Sun Yat-sen University,
Kaohsiung, Taiwan 804, R.O.C. E-mail: keryea@mail.nsysu.edu.tw
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