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Studies On the Larval Development of Brachyura Ii. Development of Philyra Scabri Uscula (Fabricius) and Ixa Cylindrus (Fabricius) of the Family Leucosiidae

Rajabai, K.G.
Crustaceana 1960 v.1 no.1 pp. 1-8
Crustacea, color, crabs, egg membranes, eggs, larvae, larval development, life history, pigmentation, plankton, sand, India
STUDIES ON THE LARVAL DEVELOPMENT OF BRACHYURA II. DEVELOPMENT OF PHILYRA SCABRI USCULA (FABRICIUS) AND IXA CYLINDRUS (FABRICIUS) OF THE FAMILY LEUCOSIIDAE BY Miss K. G. RAJABAI Department of Zoology, Sri Venkateswara University, Tirupati, India INTRODUCTION In the family Leucosiidae, the development of only two species of the genus Philyra has been studied so far (Aikawa, 1929; Menon, 1937). Aikawa (1929) described the first larval stage of P. pi.runa De Haan, 1841, from specimens hatch- ed in the laboratory. Menon (1937) described the life history of (Fabricius, 1798) from the various stages collected from the plankton. From the observations based on the larvae actually hatched out in the laboratory, it is seen that the larvae described by Menon (1937) possibly belong to another species of Philyra. The megalopa described by Menon (1937) also seems to be that of an- other species. In the genus Ixa no work has been done so far on the development. The definition of the larval stages is the same as used in an earlier account (RajaBai, 1959). A. EARLY ZOEAL STAGES AND MEGALOPA OF Philyra scabritlscttla (FABRICIUS) (Figs. 1-16). Material. During low tide on the 23rd December 1951, a berried Philyra briu.rculd of carapace length 11 mm and breadth 10.6 mm was caught while it was attempting to sink into the wet sand at Scandal Point, Visakhapatnam. Sub- sequently several other berried crabs of the same species were collected and the eggs hatched in the laboratory. Observations. A number of P. fcabi-iuscula with early egg stages were collect- ed, the eggs were ellipsoidal or spherical and always of orange hue. The ellipsoidal eggs measured 366 fL on the major axis and 283 f-L on the minor axis. The spherical ones measured 300 > in diameter. It is evident that the ellipsoidal shape is due to pressure on them for those on the outer sides are all perfectly spherical. The eggs were at the time of collection in an advanced stage of development and were dark in colour owing to the development of black pigmentation in the larvae which can easily be seen through the transparent egg membranes. Just at