共生多毛類、特にウロコムシ科(POLYNOIDAE)について

抄録

Many species of polynoids have been famous for the "conrnensal" habit among Polychaeta. The author can count 274 species of cornmensal (or may be commensal) Polychaeta in 34 different families in literature, and 40% of them in polynoids. They are classified into three ranks. Rank A is for the Polychaetes almost always foufhd in commensal condition with hosts. Rank B is for the species not only frequently found in commensal but also in free living condition. Rank C is for the species almost free living, bur sometimes in commensal. The polychactes of strong tendency toward commensal life (A+B=t) are 154 species, and the species of the family Poiynoidae are half of them (72 species).
Many groups of marine organisms are well known as involving of many commensal or parasitic species. But almost all the groups are classified as the differentiated or modified situation rather than the primitive one in each higher taxa. Polynoidae is said to one of the most primitive families in Polychaeta, and it is the largest family in Polychaeta. This is he most peculiar point of Polynoidae comparing with other commensal groups. But commensal condition of Polynoe dae is rather similar to that of the shrimps of the family Alpheidae.
The setal modifications for comtneusal life in polynoids may be three characters. 1) Basal cusp in neurosetae, 2) Hook-shaped neurosetae to anterior parapodia, 3) short, stout neurosetae with reduced teeth on their free margin. Many genera known to contain commensal species, are applicable to some of three characters mentioned above, but some genera dissatisfy any of those. In opposition, two genera, weberia Horst 1915 and Paraholoepidella Pettibone 1965 never rerorded commensalism, satisfy the third character, therefore, these two genera my be commensas. Adaptive color patterns are also conspicuous in many species. Ventral lamellae aid unusual development of ventral cirri are also characteristic in some commensal species.
Poiynoid comensals can be divided into two types, lodging type and clinging type. The former is for the species living in tubes or burrows of polychaetes, holothurians and other marine organisms. The latter is for the species clinging on the body surface of echinoderms, alcyonarians, etc. Polynoids of the subfamily Lepidonotinae prefer to lodging type, and that of the subfamily harmat;loinae to clinging type. Therefore, the range of host types are different between two subfamilies. The species in Lepidonotinae frequently prefer to sedentary polychaetes as theirr hosts, the other hand the species in Harmothoinae usually prefer to echinoderms and anthozoans.
It seers reasonable that morphological and color adaptive changes for commensal life are necessary for the clingings rather than the lodgings. Therefore, Hamothoinae has more adaptive modifications in setal morphology or ventral structures than Lepidonotinae.Furthermore, the former has more genera consisted of only commensal species than the latter.