FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



stages after protozoea I are based on exuviae of 

 a single surviving specimen. Trachypenaeus 

 larvae were described by Kirkegaard (1969), but 

 only the protozoea I were reared in the labora- 

 tory; later stages were isolated from preserved 

 plankton catches. The only other description of 

 Trachypenaeus is by Pearson (1939), who also 

 used a combination of plankton-caught and lab- 

 oratory-reared larvae. The present study is the 

 first description of larvae of any species of either 

 Atypopenaeus or Metapenaeopsis, based on 

 laboratory-reared specimens. 



To date, our pubHshed studies of larval prawns 

 in the Gulf of Carpentaria have dealt exclusively 

 with the genus Peyiaeus (Rothlisberg et al. 

 1983a, 1985, 1987; Rothlisberg and Jackson 

 1987). The characteristics of this genus are well 

 established and their larvae are quite distinct 

 from those of other genera (Cook 1966a). In 

 order to study other genera, we have reared 

 larvae of all six penaeid genera which are found 

 in the Gulf of Carpentaria: Metapenaeus, Meta- 

 penaeopsis, Penaeus, Atypopenaeus, Trachy- 

 penaeus, and Parapenaeopsis. For all but one 

 genus we now have a reference collection of pro- 

 tozoea I through to postlarvae; for Parapen- 

 aeopsis we have only the nauplius and protozoeal 

 stages (Rothlisberg et al. 1985). 



In assembling this key to genera of Indo-west 

 Pacific penaeid larvae, we have used both our 

 own reference material and information from 

 previously published descriptions and keys. We 

 have reUed completely on existing descriptions 

 for Macropetasma (Cockcroft 1985) and Para- 

 penaeus (Heldt 1938; Pearson 1939; Pauhnose 

 1979), genera not represented in the Gulf of Car- 

 pentaria and hence absent from our reference 

 collection. Several workers who have described 

 larvae from plankton samples claim to be able to 

 identify the genus or even the species of the 

 larvae. In the absence of supporting evidence 

 from laboratory-reared larvae we have not used 

 these descriptions in constructing our key. No 

 reliable information about Funchalia, Hetero- 

 penaeus, Penaeopsis, and Trachypenaeopsis is 

 available as they have never been reared in the 

 laboratory. 



MATERIALS AND METHODS 



Gravid female Metapenaeopsis palmensis se- 

 lected from trawl catches near Groote Eylandt in 

 the western Gulf of Carpentaria in November 

 1983 and from off Cairns, northeast Queensland, 

 in April 1985 were brought to the Cleveland 



laboratory. Gravid female Atypopenaeus for- 

 mosus were collected from commercial trawl 

 grounds in Moreton Bay, adjacent to the Cleve- 

 land laboratory, in January 1985. 



When female prawns arrived at the labora- 

 tory, one eyestalk was ablated and the prawns 

 were placed in a 90 L fiberglass aquarium with 4 

 cm of clean sand substrate. Seawater in the 

 aquarium was continually replaced at approxi- 

 mately 1 L per minute, and any eggs or larvae 

 were retained by a 90 ixm mesh screen on the 

 overflow. Prawns were fed daily on a frozen mix- 

 ture of prawn and squid. The aquarium water 

 was inspected each morning for eggs. When eggs 

 were detected they were examined microscopi- 

 cally and, if embryonic development was normal, 

 the female prawns were removed and preserved. 

 When the eggs hatched, the naupUi were si- 

 phoned off, their abundance was estimated, and 

 they were transferred into culture vessels at a 

 density of approximately 100 nauplii per liter. 



The culture vessels used were round-bot- 

 tomed, 100 mm diameter Pyrex^ tubes of 3 L 

 capacity, with aeration supphed through a nipple 

 molded into the bottom of the tube. The tubes 

 were placed in environmental cabinets that 

 enabled control of temperature (27°C) and of 

 photoperiod (12 h:12 h light:dark). On alternate 

 days, approximately 2.5 L of water were drawn 

 off from the larval cultures through a 140 jim 

 screen, and replaced with 1 \x.m filtered sea- 

 water. 



For larval food, the marine alga Tetraselmis 

 suecica was produced by batch culture in 20 L 

 glass carboys. During the log growth phase, 13 L 

 of algal culture were removed and the algal cells 

 concentrated using a modified cream separator. 

 The aerated concentrate was stored at 4°C and 

 used as stock for feeding the larvae. The stock 

 was replaced every 3-4 days. 



Twice daily, beginning at late nauplius stage 

 and continuing through to postlarva, sufficient 

 algal concentrate was added to the larval cul- 

 tures to maintain an algal cell density of approxi- 

 mately 1.5 X lO*" cells per mL. Cell density in the 

 larval cultures was estimated by fluorometry 

 based on the relationship between fluorescence 

 and cell density (P. C. Rothhsberg^). After the 

 larvae reached mysis I, freshly hatched, heat- 



' Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service. NOAA. 



-Rothlisberg, P.C, Division of Fisheries, CSIRO Marine 

 Laboratories P.O. Box 120, Cleveland, QLD 4163, Australia, 

 unpubl. data. 



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