Sexual Reproduction

Records of sexual reproduction in corallimorpharia are not common in the scientific literature. Most deal only with observa-

tions of the presence of gonads or gametes in collected specimens (e .g. den Hartog, 1980, 1987; Dunn and Hamner, 1980). Only two studies have investigated sexual reproduction in coralfimorphar-ians, Holts and Beauchamp's 1993 paper on Corynactis califor-nica and Chen et al.1 s 1995a paper on Rhodactis indosinensis.

Corynactis californica has been shown to be gonochoristic (i.e. they have separate sexes) but many of the colonies are either one sex or the other. It takes approximately five months to develop either eggs or sperm, and spawning takes place in late winter (Holts and Beauchamp, 1993). Rhodactis indosinensis differs from C. californica in several ways. The eggs are much larger (> 500 um vs. 120-140 um), there are separate sexes within colonies (smaller males on the periphery, larger females in the center), oogenesis takes nine months and spermatogenesis takes three to four months, and spawning takes place from May to June (Chen et al., 1995a). The ovaries of Rhodactis were either deep blue, dark red, or pale green coloured, grape-like structures, while mature sperm bundles appeared as elongated white spirals. During non-spawning periods the egg bundles appear as small white spheres.

In a separate study, Chen et al (1995b) found that within colonies of Rhodactis, there were definite size and sex differences. Those towards the center were much larger and were all female, while those on the outside tended to be smaller and male. In several anemone species size is dependent on environmental conditions and size is linked to sex (in Chen et al. 1995b). It was speculated that environmental conditions on the edges were less favourable than in the middle due to greater exposure to air, hence less energy was available for egg production, while the less energetically demanding sperm could still be easily produced. When small individuals were transplanted to the center they grew in size and became female. Female polyps transplanted to the edges became smaller and some became male. This provided evidence that a polyp's relative position within a colony was more important in determining size and sex, than is age (Chen et al 1995b). These first tantalizing observations indicate that corallimorpharian reproductive biology may offer new insights into reproduction in anthozoans as a whole.

The COMPLETE guide to Aquariums

The COMPLETE guide to Aquariums

The word aquarium originates from the ancient Latin language, aqua meaning water and the suffix rium meaning place or building. Aquariums are beautiful and look good anywhere! Home aquariums are becoming more and more popular, it is a hobby that many people are flocking too and fish shops are on the rise. Fish are generally easy to keep although do they need quite a bit of attention. Puppies and kittens were the typical pet but now fish are becoming more and more frequent in house holds. In recent years fish shops have noticed a great increase in the rise of people wanting to purchase aquariums and fish, the boom has been great for local shops as the fish industry hasnt been such a great industry before now.

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