Hydrobiologia 525: 1–100, 2004. Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands. 1 Taxonomic revision A revision of Australian river prawns, Macrobrachium (Crustacea: Decapoda: Palaemonidae) J. W. Short Queensland Centre for Biodiversity, Queensland Museum, P.O. Box 3300, South Brisbane, Queensland 4101, Australia Present address: BioAccess Australia, P.O. Box 10281, Adelaide St, Brisbane, Queensland 4000, Australia (Fax: +61-7-38869684, E-mail: [email protected]) Received 8 September 2003; in revised form 2 February 2004; accepted 9 February 2004 Key word: Crustacea, Decapoda, Palaemonidae, Macrobrachium, Australia, Taxonomy Abstract A taxonomic revision of Australian Macrobrachium identified three species new to the Australian fauna – two undescribed species and one new record, viz. M. auratum sp. nov., M. koombooloomba sp. nov., and M. mammillodactylus (Thallwitz, 1892). Eight taxa previously described by Riek (1951) are recognised as new junior subjective synonyms, viz. M. adscitum adscitum, M. atactum atactum, M. atactum ischnomorphum, M. atactum sobrinum, M. australiense crassum, M. australiense cristatum, M. australiense eupharum of M. australiense Holthuis, 1950, and M. glypticum of M. handschini Roux, 1933. Apart from an erroneous type locality for a junior subjective synonym, there were no records to confirm the presence of M. australe (Gue´rin-Me´neville, 1838) on the Australian continent. In total, 13 species of Macrobrachium are recorded from the Australian continent. Keys to male developmental stages and Australian species are provided. A revised diagnosis is given for the genus. A list of 31 atypical species which do not appear to be based on fully developed males or which require re-evaluation of their generic status is provided. Terminology applied to spines and setae is revised. Introduction River prawns of the genus Macrobrachium are a the 50 or so years since the last major revisionary conspicuous and important component of fresh- works on the group (Holthuis, 1950, 1952a). water and estuarine ecosystems throughout tropi- Typically, Macrobrachium are epigeal, epibenthic cal and warm temperate areas of the world. and largely nocturnal, although several hypogeal Although members of the genus are also com- cave species have also been described. Unlike most monly referred to as ‘freshwater’ prawns, some are related palaemonine genera, members of the genus entirely restricted to estuaries and many typically have well-developed agonistic behaviour require marine influence during larval develop- and a solitary lifestyle. ment. Many species grow to a sufficient size to be Most members of the genus are easily recog- used for human consumption. Holthuis (1980) nisable by the well developed, often elongated listed 49 species of interest to fisheries throughout second chelipeds, which in the males of many the world. The Giant River Prawn, M. rosenbergii, species may exceed the body length. Approxi- has been farmed commercially both within and mately 210 species of Macrobrachium are presently outside its natural range in localities such as Asia, recognised, with nearly half of these described in Hawaii, the Americas, and New Zealand. 2 From a taxonomic point of view, the genus is Lee (1979) re-evaluated Riek’s subspecies of one of the more challenging decapod crustacean M. australiense using morphological characters groups (Holthuis, 1950, 1952a; Chace & Bruce, and a study of F1 progeny reared in the laboratory 1993). The two main morphological features which and concluded that the differences found ‘do not have traditionally provided characters for sepa- appear to be sufficiently large or consistent enough rating species, the rostrum and the second pere- to warrant dividing the species into 4 sub-species’. iopods, are often highly variable within species Fincham (1987) described a new species, (Holthuis, 1950). The second pereiopods in par- M. bullatum, from Magela Ck and the Alligator ticular show a very high level of developmental Rivers region, N.T. He also provided a key to and sexual variation, including allometric growth Australian species based largely on the key of Riek in males. (1951). However, he also questioned the validity of Another major factor contributing to the dif- Riek’s subspecies of M. australiense, ‘the mor- ficulty of working on the genus is the influence of phological characters separating many of Riek’s social dominance on male morphology. In the subspecies were small and often involved length past it has often been assumed that all sexually ratios of pereiopod segments, which may change mature, fully grown males have developed second during development’. Furthermore, Fincham no- pereiopods. However, the importance of ted that the holotype of M. tolmerum Riek was a behavioural dominance in the morphology of non-ovigerous female rather than a male. male M. rosenbergii was demonstrated by Kuris In addition to recognised problems with the et al. (1987). Secondary sexual characters such as Riek’s classification, some of the material in the the form of the second pereiopods are most Queensland Museum collection appeared outside developed in dominant males and their develop- the range of variation recorded for Australian ment is not strictly dependent on size and age. species. This material appeared to represent three Although fully developed dominant males are new Australian records, viz., M. equidens (Dana, usually among the largest individuals, a signifi- 1852), M. idae (Heller, 1862a, b) and M. mam- cant percentage of large subordinate males with millodactylus (Thallwitz, 1892), and two unde- undeveloped or developing second pereiopods scribed species. The first two of the new records, may be present at any given locality. This is M. equidens and M. idae, have been published particularly the case where food resources are elsewhere (Bruce & Coombes, 1997; Short, 2000) limited e.g. a drying lagoon on an episodic whereas the third is reported in this paper. watercourse. The problem of correctly distin- One of the undescribed species was first guishing fully developed males when describing recognised by Kneipp (1979) in an unpublished new species was well illustrated by the taxonomy Ph.D. thesis. This species was also well represented of the Australian fauna prior to this study. A in the QM collection through field expeditions to number of nominal Australian taxa appeared to northeast Queensland during the last decade. The have been based on large subordinate males other new species was originally collected by Dr S. without fully developed chelipeds. Bunn and Mr M. Bray (Griffith University) during Taxonomic records of Macrobrachium from a limnological study for the proposed Tully-Mill- Australia date back to the early carcinological lit- stream hydroelectric scheme in 1990. A Queens- erature. The first record was by Olivier (1811) who land Museum expedition to the upper Tully River reported Palaemon ornatus (= Macrobrachium area in November 1992 yielded detailed habitat lar). Over the next 140 years the Australian fauna data and a good representative range of specimens received little attention, apart from several single including the first fully developed males. species descriptions, new records and synonyms (Heller, 1865; Ortmann, 1891; De Man, 1908; Roux, 1933; Holthuis, 1950). The first revisionary Methods and materials study of the Australian fauna was by Riek (1951). Riek’s study increased the number of known spe- A taxonomic revision of Australian Macro- cies from six (Holthuis, 1950) to ten. He also de- brachium was undertaken using external morpho- scribed six new subspecies. logical characters supplemented with biological 3 and ecological data. The study area was limited to from descriptions, diagnoses, keys, notes and the Australian continent and associated continen- illustrations of Macrobrachium in the literature. tal islands. External Australian territories such as This was refined and expanded after a detailed Christmas Island were not investigated. Extensive examination of the Macrobrachium collection in collections of preserved material housed in the the Queensland Museum and non-Australian Queensland Museum, Northern Territory Mu- Macrobrachium in several major European muse- seum of Arts and Sciences, Australian Museum, ums. A schematic drawing of a generalised Mac- Museum of Victoria and South Australian Mu- robrachium showing the main morphological seum were studied. A field collecting program in features is illustrated in Figure 1. Queensland and the Northern Territory provided Biological characters, such as habitat, life hi- additional distributional records and new infor- story, and behavioural traits were also compiled mation on behaviour, habitat ecology, and live from the literature. These were expanded and re- colouration. In total over 5000 specimens and 1000 fined during field expeditions in northern Austra- registered museum lots were examined. lia. Abbreviations used: AM, Australian Museum; Ck/s, creek, creeks; CL, postrostral carapace Delimitation of species length in mm measured from orbital margin to dorsolateral invagination of posterior margin; Species were delimited using unique character CSIRO, Commonwealth Scientific and Industrial states or character state combinations. In the case Organisation; CYPLUS, Cape York Peninsula of well-established taxa, previous diagnoses and Land Utilisation Study; diam., diameter; ERISS, known limits of variation were also used. Repro- Environmental Research Institute of the Super- ductive isolation was inferred from the