A Comparative Study of Some Larval Stages of Penaeus monodon and Penaeus merguiensis (Crustacea : Decapoda) from Indonesia

Abstract

The nauplius VI, protozoea II and mysis II of Penaeus monodon and P. merguiensis from Indonesian waters have been described and illustrated. The similarities and the differences between the two species have been observed. The comparison between the present study and that by previous authors have been made. Setation on endopod of maxilliped I and maxilliped II of protozoea and mysis stages as specific characters for identification is suggested. Two species of economically important penaeid prawns, Penaeus merguiensis De Man, 1888, and, P. monodon Fabricius, 1798, are among the many penaeids found in Indonesian waters. Although it is well known that their larvae occur in the coastal waters and are often mixed together (Noor-Hamid, 1976), accurate identification of their wild larvae is now possible only for post-larvae and juveniles, and identification at earlier stages is not yet succeeded. Larval stages of these species have already been described by some authors based upon materials from India (Silas et al., 1978) and the Philippines (Motoh, 1979; Motoh & Buri, 1979). Their information is available for identification of these larvae in Indonesian waters to certain extent, but some problems, which are probably related to difference of material andjor accuracy in observation, must be cleared before it is applied to Indonesian materials. In the present paper, larval stages of these two species, especially nauplius VI, protozoea II and mysis II, are described and compared on the basis of specimens reared in the laboratory, paying special attention to the type and number of setae on the appendages. Larvae of two species of penaeid prawns, Penaeus monodon and P. merguiensis, reared from eggs spawned in the laboratory were received from the Brackishwater Aquaculture Development Centre, Jepara. The larvae were preserved in 10% formalin and were used for morphological observation. Dissection of appendages was performed in 10% glycerin and drawings were made with Projectina, a micro photographic and drawing instrument. For each larval stage of the two species, 10 specimens were randomly taken for measurements with a micrometer eyepiece. The identification of substages is based on that used by Motoh (1979). Body lengths of nauplii were measured along the midline from apical to caudal margins, exclud-