Reproduction corals

The gorgonian coral Plexaura homomalla is a source of prostaglandin A2. This compound can be converted to medically useful prostaglandins that regulate mammalian reproduction, blood pressure, and digestion. 

Sarcophyton species contain diterpenes up to 10% of their dry weight, and this large quantity of secondary metabolites plays an important role in the survival of Octo-corals with defensive, competitive, reproductive, and possibly pheromonal functions. Soft corals lacking physical defense thus seem to be protected from predation by the presence of diterpene toxins in their tissue. Nearly 25 species of this genus occurring in different seawaters have been examined chemically so far, and more than 80 cembranoid diterpenes have been isolated from the Sarcophyton genus since the 1970s. 

Figure 21.2 Nutrient availability changes the relationship between tnicroalgal symbionts and coral hosts (adapted from Dubinsky and Stambler, 1996 Furnas, 2003). Under low nutrient conditions zooxanthellae translocate photosynthate to corals for growth, calcification and reproduction. Under higher nutrients, zooxanthellae increase in abundance and keep more of the photosynthate for themselves translocating less to host coral for metabolic needs.

Elevated nutrients (ammonium, nitrate and phosphate) may derive from multiple sources (see above) and can directly affect both adult coral colonies as well as reproduction and recruitment of larvae in a number of ways (Fabricius, 2005). 

Certainly the idea of equilibrium has been applied to populations of a particular species generally. Some species exhibit sequential hermaphroditism. In these species, such as many species of coral reef fishes, sex change is a normal anatomical process. Clownfish, wrasses, moray eels, gobies and other fish species are known to change sex, including reproductive functions. A school of clownfish is always built into a hierarchy with a female fish at the top (Figure 17.6). When she dies. 

Exposure to crude oil induces numerous effects on the reproductive system of a host of invertebrate species. Renzoni (1975) showed that the spermatozoa of molluscs were highly sensitive to various crude oils, thereby depressing the rate of successful fertilization and increasing the frequency of developmental abnormalities. Similarly, Barry and Yevich (1975) reported that exposure of the mollusc Mya arenaria to crude oil resulted in the development of neoplastic lesions in gonadal tissue, as well as in the kidney, urinary pores, heart, and epibranchial chamber. Comparable lesions have been found in the reproductive tissue and mucous secretory cells of the coral Manicina areolata (Peters etaL, 1981). 

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