The evolutionary paleobiological study on the predation scars on the valves of reef ostracodes

本研究的主要目的是明确琉球群岛浅水介形类瓣膜上的捕食伤痕形态群(包括活体和化石)与介形类生态的关系。根据捕食伤痕的形态，将其分为抛物线型、圆柱型和不规则形孔。介形类具有捕食伤痕，包括沙底居民、泥质海底居民和以海洋植物为食的居民。在最近的珊瑚礁介形类中，植生物种占主导地位，它们身上有捕食的伤痕。肉食性原生动物和其他腹足类一直被认为是产生抛物线孔、圆柱孔和部分不规则形孔的原因。但是，肉食性腹足类只生活在沙质或泥泞的海底，因此，攻击植生介形类的捕食者仍有待调查。不规则形状的孔经常通过在孔周围的阀门外表面上刮擦和溶解而伴随着疤痕。这些证据可能表明，这些不规则形状的洞不仅包括钻孔，还包括通过切割或穿孔形成的捕食伤痕。在一些介形虫阀门中也发现了溶液孔。溶洞可能是由于消化溶液或无序溶液造成的。作者将特定物种的介形虫与其预期的选择性捕食者放在一个水箱的同一容器中饲养，并试图识别捕食者以产生捕食疤痕，但失败了。值得注意的是，在未来的试验中，容器中的水应该保持良好的状态，捕食者的“候选”应该考虑到与捕食有关的附属物的结构。

The main purpose of this study is to clear the relationships between the morphological groups of predation scars on the valves of the shallow-water ostracodes from the Ryukyu Islands, including both living and fossil, and the ecology of the ostracodes.The predation scars, which are the holes penetrating through ostracode valves, are grouped into the parabolic, cylindrical and irregular-shaped holes based on their morphology. The ostracodes bearing predation scars concist of the sandy bottom inhabitants, muddy bottom inhabitants and dwellers living on sea plants. The phytal species prevail in the recent reef ostracodes bearing predation scars. The carnivorous naticids and other gastropods have been considered to produce the drillholes such as the parabolic, cylindrical holes and part of the irregular-shaped holes. But, the carnivorous gastropods live only on sandy or muddy bottoms, and therefore, the predators attacking the phytal ostracodes remain to be inquired. The irregular-shaped holes frequently accompany the scars by scratching, scraping and solution on the outer valve surfaces around the holes. These evidences might suggest that the irregular-shaped holes include not only drillholes, but also the predation scars by cutting or piercing. Solution holes are also found in some ostracode valves. The solution holes can be due to digestive-solution or inorgamic solution.The author reared some ostracodes of a particular species with its expected selective predators in the same container in a water tank, and tried to identify the predator to produce the predation scars, but failed. It is notable for the future trials that the water in the container should be kept in a good condition, and the 'candidates' of predators should be selected in consideration of the structures of appendages relevant to predation.