Mechanisms for substrate preference by corals

关于珊瑚对底栖生物偏好的研究很多，但几乎没有一项研究包括颗粒沉积物。另一方面，珊瑚能够清除纤毛和粘液落在它们身上的颗粒。这是一项关于选择粒型和大小的机理的研究，主要使用的动物是斑角毛壳虫和柱头毛虫。底质类型主要有滩砂和红色陆源土。在使用前，将它们筛分成不同的粒度。首先确定了斑角松的繁殖时间为5-12月，每月一次，在第一个季度满月期间。斑角拟青霉的沉降率为7.1%，双翅拟青霉的沉降率为51.7%。与平坦珊瑚选择生物处理底物的一般趋势相反，大口圆盘珊瑚选择未处理底物而不是生物处理底物。它们对海滩沙的选择性依次为：0.5 mm&gt；1 mm&gt；5 mm&gt；2 mm&gt；小于0.25 mm的海滩沙和红壤没有吸引任何浮游生物。较大颗粒的红壤也是如此。比浮萍直径小的几个颗粒聚集在一起支撑一个浮萍。珊瑚虫不能拒绝直径小于0.25毫米的红壤，这可能是因为它是气体交换的屏障。同样的原因也适用于这种大小的颗粒不能吸引菌斑沉降的问题。

Many researches were done on subustrate preference by corals, but almost none of them included particulate deposits. On the other hand, corals are capable of removing the particles falling on them by cilia and mucus. This is a study on the mechanisms of selecting the grain types and sizes.Pocillopora damicornis and Stylophora pistillata are main animals used. Beach sand and red terrestrial soil are the main types of substrates. They were sieved into different grain sizes before use.The reproduction of P.damicornis were ascertained first to take place in May-December, once a month during first quarterfull moon periods. The settling rate of P.damicornis was found to be 7.1%, whereas, that of S.pistillata 51.7%. On the contrary to general trends that coral planulae prefer biologically treated substrate, the planulae of P.damicornis orefered nontreated over treated substrate. Preference of these planulae for beach sand was in the following order : 0.5mm>1mm>5mm>2mm>calcareous plate. The beach sand and red soil of less than 0.25 mm did not attract any planulae. Red soil of larger particles did the same. A few particles smaller than the diameter of planulae aggregated to support one planula. Coral polyps were not able to reject red soil of less than 0.25 mm across, probably by acting as a barrier for gas exchange. The same reason may be applied to the inablity to attract plamulae settlement by this size particles.