Gonads are distinct organs in organisms with complicated reproductive systems,
and they have specific locations in the body. The gonads of crinoids, however, are
scattered in numerous genital pinnules of their arms. We studied seven species of
feather stars, Comatella maculata (Carpenter, 1888), Comatella nigra (Carpenter,
1888), Comaster multifidus (Mller, 1841), Comaster distinctus (Carpenter, 1881),
Comanthus parvicirrus (Mller, 1841), Colobometra perspinosa (Carpenter,1881) and
Himerometra magnipinna Clark, 1908 collected at Kenting, southern Taiwan in 2007.
The purpose is to explore if the distribution patterns of gonads are adaptative. With
bimonthly samplings in a year, it is discovered that the spawning seasons of the
species are not synchronized in a particular season. Three models of relationships
between maximum arm lengths and numbers of arms exist in the seven species, i.e.,
constant arm numbers, linear, and quadratic with an asymptote of arm numbers.
Therefore, the maximum arm length is more appropriate than arm number as a size
index of feather stars. Evidence of bigger mature than immature individuals is found
in Comatella maculata, Comaster distinctus and Comaster multifidus, and there is no
size difference between males and females. The gonads of feather stars are distributed
in the proximal end of arms. The proportion of arms represented by genital pinnules
within individuals were constant except in Comanthus parvicirrus where a negative
correlation was found. Except the 2 cave-dwelling species, Comatella maculata and
Comanthus parvicirrus, most regenerating arms of 5 other species had breakage
points occurred near the proximal ends of the arms. Distal breakage may regenerate
too fast to recognize. The arms obviously do not grow so fast as to limit gonad
development to the proximal ends of arms. Habitat difference may cause variation in
genital pinnule widths, but not in the number of genital pinnules as suggested by comparsions of specimens between 2 sites. The cave-dwelling Comanthus parvicirrus
has special congregated long arms, which are extended outside. Moreover, these arms
have higher probability of breakage, and smaller ranges of genital pinnules than short
arms. This phenomenon supports that the limited gonad distribution is adaptive for
reducing loss upon arm breakage.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0110109-163208 |
| Date | 10 January 2009 |
| Creators | Chen, Yi-ting |
| Contributors | Hsin-Drow Hang, Ker-yea Soong, Shyh-min Chao |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0110109-163208 |
| Rights | restricted, Copyright information available at source archive |
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