蛛形鋼各目の類縁関係

概要

論文の詳細を見る
It is generally known that in the class Archnida the order Scorpiones are the most primitive group from the morphological view and also from the palaeontological evidence. But the interrelionships between the other orders are very obscure. Most of them appeared and seemed to have thrived in the Carboniferous Period. At that time they were already each equipped with specialized structures which can be distinguishable from each other, moreover, some primitive characters are seen independantly in a few groups. The primitive arachnids seem to have developed from the fresh- or brackish-water Merostomata or their allies and to have landed possibly in the Silurian Period. They were probably many-segmented and furnished with lung-books which were changed from the gills of the Merostomata. They were possibly nocturnal in habits, and dwelled in hollows, cavities of rocks or holes of woods, or concealed themselves under fallen leaves or under stones in the day time. During the progress of evolution, the following morphological changes seem to have gradually occurred in the arachnids; fusion of the prosoma with the opisthosoma, especially remarkable in the Acarina and Opiliones; reduction of abdominal segments; specialization of the chelicerae and pedipalpi; specialization of ambulacratory legs, reduction of abdominal appendages, centralization of nervous and circulatory systems; transition of respiratory organs, from lung-books to trachea; change of excretory system, from coxal glands to Malpighian canals. On the otherhand, the following oecological changes seem to have occurred in some arachnids; from nocturnal to diurnal habits (e. g. jumping spiders); from terrestial to arboreal nests (e.g. Araneus and spider mites); from free-living to parasitic lives (ticks and some mites): invasion to fresh-waters and sea-water (e.g. Argyroneta, Hydracarina, Desis and Halacaridae). Besides, some spiders show mimicry which is known in the higher groups in the insects such as Hymenoptera and Lepidoptera. Judging from the above data the Scorpiones are the most primitive group in the Arachnida and seem to establish a new subclass for themselves. At least, they cannot be belonged to the subclass Latigastra, because they lose the pregenital somite in the adult. In this feature they more resemble the groups of Caulogastra in which the pregenital somite diminished in size and remains sometimes as a pedicel. The three orders, Thelyphonida, Schizopeltida and Amblypygi are rather primitive groups, with segmented abdomen and lung-books, and are comparatively closely related each other among the class. The Palpigradi are also related to them but seem to be a rather degenerated group than primitive. The primitive forms of the Araneae are slightly related to the order-group just mentioned but modern forms of the Areneae are quite differentiated both in morphological and oecological points. The Solfugae are a special primitive group but with well-developed trachea. The animals seem to branch off early in the evolutionary process of the Arachnida and have been specialized separately. The Ricinulei seem somewhat correlated to the Araneae but their phylogenetic position remains unknown. The Acarina are the most modern group in the class and show various morphological diversities and wide oecological adaptations. The Opiliones indicate several similarities with the Acarina but seem to be more primitive. The Pseudoscorpiones are rather modern animals, showing oecological adaptations and having trachea, but are not so differentiated as in the two orders just referred.
日本動物分類学会の論文
1966-08-30

蛛形鋼各目の類縁関係

スポンサーリンク

概要

著者

関連論文

スポンサーリンク