Morphological modifications caused by Sacculina polygenea in Hemigrapsus sanguineus (De Haan) (Brachyura: Grapsidae)

概要

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The morphological modifications caused by Sacculina polygenea in the grapsid crab Hemigrapsus sanguineus were examined. Parasitized males carrying externa were divided into seven stages of feminization by the degree of reduction of the first and second pleopods and the appearance of biramous pleopods on the third to fifth abdominal segments. All males examined retained first pleopods and most of them were Stage I or II. The development of femaletype biramous pleopods rarely occurs. Only 10.1% crabs were in advanced stages of feminization. Enlargement of the abdomen and reduction of chela height in parasitized males were pro nounced in small males and less so in larger males. Modification caused by the rhizocephalan parasite likely proceeds from when the host is young and small.