カニ類,ベンケイガニ亜科9種の後期発生の比較
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概要
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1) The larval development of the subfamily Sesarminae, the land crabs, has been studied from the first zoea to megalopa, using the following four species as materials : Sesarma (Sesarma) intermedia, Sesarma (Parasesarma) erythrodactyla, Sesarma (Chiromantes) bidens and Cyclograpsus intermedius. 2) In order to clarify the specific differences of the larvae in this subfamily, several comparisons have been made among these four species as well as with other five species, the developments of which were reported in one of the auther's previous papers (1974) : Sesarma (Parasesarma) picta, Sesarma (Holometopus) haematocheir, Sesarma (Holometopus) dehaani, Helice tridens tridens and Chasmagnathus canvexus. 3) The number of zoea stages comprised in entire course of development differs according to genera, this being four in S. (H.) dehaani, S. (P.) picta, S. (P.) erythrodactyla, S. (C.) bidens, Chasmagnathus convexus and five in the others. 4) Of the characters which are constant through all the stages of zoea, the followings are found common to all the examined species of the subfamily: (a) The arrangement of setae on some of the limbs: the endopod of the maxilla I, 4.1(5)-1; the protopod of the maxillipede I, 3.3.2.2(10); the same of the maxillipede II, 1.1.1.1(4); the endopod of the maxillipede II, 3.3(6)-1-0; (b) The maxillipede I has a chromatophore on the protopod. (c) The telson belongs to A_0-type. 5) Of the characters which are constant through all the zoea stages, the followings are different according to genera. (a) The lateral spines of carapace which are present in Helice and Chasmagnathus are absent from Sesarma and Cyclograpsus. (b) The arrangement of setae on the endopod of the maxilla II is 3.2(5) in Sesarma, whereas 2.2(4) in the others. (c) In Cyclograpsus, the protopod of the maxillipede II has chromatophores which are absent in the others. (d) Helice and Chasmagnathus carry lateral spines on the pleomere IV, but Sesarma and Cyclograpsus are lacking in these. 6) Of the characters which undergo changes as the development progresses, the following are common to all the species examined : (a) Judging from the first stage of the development, the endopod rudiment of the antenna II, pereiopods and pleopods are more or less uniform in their growth rate through all the species. (b) In the zoea stage II, a plumose seta appears on the basis of the maxilla I on outer side to persist through subsequent stages. (c) The maxilla II has a feebly bifurcate basis, and the setae are arranged as 4.5(9) in the first two stages. (d) The maxillipede I has setae as 4.1(5)-2-1-2-2 on the endopod in the first two stages. (e) Natatory setae on expods of the maxillipedes I and II increase in their number after a formula : 2×(S+1), where S is the ordinal number of stages. (f) The articulation of the telson becomes distinct in the zoea III. (g) The endopod rudiment of antenna I becomes distinct in the final stage of zoea in Helice, Chasmagnathus, and Cyclograpsus, but it does not exist even in this stage in Sesarma. (h) In the scaphognathite of the maxilla II of Sesarma, the plumose, setae increase with the stages as follows : zoea I, 4.1(5), zoea II, 5.3(8), and zoea III, 7.4(11). (i) Only in Sesarma, the telson is armed with six setae between the caudal furcae through all the stages. 7) Features of megalopa common to all the nine species of Sesarminae are as follows: (a) The maxillipede II has one outer seta on the exopod segment I. (b) The maxillipede III has one seta on the exopod segment I. (c) The pleopod IV lacks plumose setae on the coxa. (d) The uropod which bears one seta on the coxa lacks endopod in all the members of Sesarminae. 8) Generic differences in the characters of megalopa are as follows : In Sesarma, the antenna I lacks the endopod, the mandibular palp bears four setae in the distal segment, the maxillipede I carries three plumose setae on the proximal exopod segment along the outer border, and the uropod is furnished with six plumose setae on the lateral margin of the exopod. In the other genera, the antenna I has an endopod, and the mandibular palp, exoped of the maxillipede I and exopod of the uropod have setae in eight, two and ten respectively.
- 日本甲殻類学会の論文