The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 1994 11:39-51 0002G0 LEANDER PLUMOSUS SP. NOV., A NEW PALAEMONINE SHRIMP (CRUSTACEA: PALAEMONIDAE) FROM THE MALDIVE ISLANDS. A.J. BRUCE Museum and Art Gallery of the Northern Territory, P.O. Box 4646, Darwin, NT, 0801, Australia. C < iniumu abstract HtTURiM TO W-119 A new palaemonid shrimp, Leanderplumosus sp. nov., is described and illustrated on the basis of specimens collected in the Maldive Islands, but the species was first noticed on the island of Bali, Indonesia. The species is remarkable in the conspicuous development of plumose setae on the rostrum, body and antennal peduncles. A sensory mechanism on the third maxilliped is described. A key to the identification of the four known species of the genus Leander Desmarest is provided. KEYWORDS: Crustacea, Decapoda, Palaemonidae, Leander, new species, Maldive Islands, Bali, key to genus. INTRODUCTION nearly 5000 km, from the initial site of discov- ery, although the holotype of P. hurii was sepa- The author received for identification some rated by an even greater distance from the photographs of Balinese shrimps taken in 1990 paratypes, collected some two years later. by Roger Steene. Amongst these were some Carapace refers to the postorbital carapace striking pictures of a beautifully coloured shrimp length. The specimens are deposited in the col- that appeared to belong to the Palaemonidae, but lections of the Northern Territory Museum which could not be identified as any known (NTM), Darwin. genus or species. Unfortunately, no specimens were collected. A copy of the photograph was published in Indonesia in the hope that speci- SYSTEMATICS mens might be obtained (Bruce 1990) and sub- sequently in Australia by Steene (1990). Copies of the photograph were also circulated amongst Palaemonidae Rafinesque, 1815 collectors. The photograph was recognised by Palaemoninae Rafinesque, 1815 Helmut Debelius, as being of a species occurring Leander E. Desmarest, 1849 in the Maldive Islands. Through his good of- Type species: Leander tenuicornis (Say, fices, Herwarth Voigtmann, of Maayafushi, Ari 1818). Atoll, subsequently provided a single specimen, Diagnosis (from Chace and Bruce, 1993). which on examination proved to belong to the Rostrum without elevated basal crest; carapace genus Leander Desmarest and represented an with submarginal branchiostegal spine, without undescribed species. In some Leander species, the rostra of male and female are morphologi- hepatic or branchiostegal suture; fourth thoracic cally different. On request, Mr Voigtmann then sternite without slender median process; mandi- provided a second specimen of the complemen- ble with palp; ambulatory pereopods with dactyls tary sex. It is of rare occurrence for specimens of simple; endopod of male first pleopod with new species to be supplied on demand, although appendix interna. Holthuis (1981) describes a somewhat similar event with Pontonia hurii Holthuis (now Leander plumosus sp. nov. Anchiopontonia hurii (Holthuis)). It is even (Figs 1-5, 6AB, Plate 2) more remarkable when the specimens are ob- Unidentified palaemonid shrimp - Bruce, tained from a locality at such a great distance, 1990:62-63, fig. 2; Steene, 1990:285, colour fig. 39 A.J. Bruce Plate l.Leanderplumosus sp. nov. A, specimen from Maldive Islands, photograph Herwarth Voigtmann;B, C, specimen from Bali, Indonesia, photographs by Roger Steene. 40 A new palaemonid shrimp from the Maldive Islands Fig. I. Leander plumosus sp. nov.. holofype, ovigerous female, Ari Atoll, Maldive Islands. Scale divisions in millimetres. Type Material. HOLOTYPE - undissected tip. Ventral rostral margin with dense subme- ovigerous female, Ari Atoll, Maldive Islands, dian row of coarsely plumose setae from orbital coll. Herwarth Voigtmann, 1991, NTM notch to rostral tip, setae short proximally, in- Cr.008567A; PARATYPE - dissected male, creasing in length distally, projecting ventrola- NTM. Cr.008567B, same data as for holotype. terally (Fig. 2C), densely pigmented, completely Description. Small sized, slenderly built obscuring ventral rostral teeth. Supraorbital and palaemonid shrimps, each lacking one second hepatic spines absent, inferior orbital angle (Fig. pereopod (Fig. 1). 2D) produced, bluntly rounded, without medial Carapace smooth, glabrous. Rostrum very flange. Antennal spine acute, marginal, far ex- slender, elongate, slightly up-curved, extending ceeding inferior orbital angle. Branchiostegal well beyond scaphocerite, about 2.5 times cara- spine acute, subequal to antennal spine, remote pace length in male (Fig. 2B), 1.75 times in from branchiostegal margin; without female (Fig. 2A), dorsal carina feebly developed branchiostegal groove. Anterolateral angle of with acute teeth throughout length, 11 in male, branchiostegite broadly obtuse, ventral margin 12 in female. First two teeth situated on cara- setose. pace, anterior tooth distinctly posterior to level Abdomen smooth (Fig. 2F), with short longi- of orbit, posterior tooth in epigastric position, tudinal rows of short coarsely plumose setae remaining nine teeth rather irregularly distrib- scattered on tergites of second to fourth seg- uted in male, more widely spaced proximally, 10 ments. Third segment slightly posterodorsally teeth regularly spaced in female, slightly de- produced, fifth segment about 0.7 of sixth seg- creasing in size distally in both. Teeth with ment length, sixth segment 1.5 times longer small median rows of short plumose setae than deep, posterolateral angle acutely produced, anteriorly to each tooth, with scattered longer posteroventral angle produced, dorsally blunt, erect submedian plumose setae. Ventral carina with small acute ventral tooth, ventral margin feebly developed, with nine acute teeth in male, with row of short coarsely plumose setae. Pleura similar, subequal, decreasing in size slightly of first three segments broadly rounded, en- distally, uniformly distributed over distal two- larged in female, ventral margins setose, central thirds, distal tooth smaller, close to tip. Twelve portion of row with longer, coarsely plumose teeth present in female, extended over distal setae in female only. Fourth segment with nleuron four-fifths, proximal four teeth smaller, more posteriorly produced, rounded, setose, without closely spaced, distal teeth larger, increasing in coarsely plumose setae. Fifth segment with size slightly distally, distal tooth remote from pleuron posteriorly produced, acutely pointed 41 A.J. Bruce Fig.2.Leanderplumosus sp. nov. A, carapace and rostrum, lateral view, ventral rostral setae omitted;B, same, left ventral rostral setae omitted;C. anterior carapace, rostrum and antennae, dorsal;D, anterior carapace and orbital region, lateral;E, pterygostomial region and labrum,lateral;F, third to sixth abdominal segments;G, eye, dorsal;H, antennule;I, antennular peduncle; J, antenna; K, telson;L, uropod.A, female holotype.B-L, male, paratype. posteroventrally, ventral margin setose, with about 1.35 times sixth segment length, 3.0 times coarsely plumose setae posteriorly, present in longer than anterior width, tapering posteriorly, male and female. Telson (Fig. 2K) slender, lateral margins straight, convergent posteriorly. 42 A new palaemonid shrimp from the Maldive Islands Posterior margin (Fig. 5N) 0.4 of anterior width, margin, 9.0 times longer than central width, distal biconcave, with long acute median process, lamella bluntly angular, distinctly exceeding tip dorsally with transverse row of plumose setae of distolateral tooth, margins densely fringed proximally, two pairs of similar, subequal spines with long coarsely setulose setae. at 0.43 and 0.7 of telson length. Posterior mar- Ophthalmic somite without bee ocellaire, gin with lateral spines similar to dorsal spines, with small median pigment spot. Epistome with medial spines long, robust, 3.5 times lateral low rounded posteriorly convergent longitudi- spine length, 0.3 of telson length, with subme- nal ridges. Labrum (Fig. 2E) acutely produced dian pair of setulose setae, 0.38 of medial spine ventromedially, with laminar median lamella length, arising ventral to apical process. anteriorly. First and second thoracic sternites Eye (Fig. 2G) well developed, with large fused (?), forming transverse ridge with median globular cornea with dorsal accessory pigment notch; third with transverse ridge; fourth with spot, much wider than stalk, oblique, stalk short stout, transversely compressed blunt me- subcylindrical, slightly compressed, about 1.4 dian process. Fifth with rounded transverse lat- times longer than wide. eral ridges; sixth and seventh unarmed; eighth Antennular peduncle (Fig. 21) reaching to with short stout anteriorly flattened median about 0.35 of rostral length. Proximal segment process (male only). about 2.4 times longer than wide, medial margin Mandible (right) (Figs 3A, 5C) robust. Palp with long plumose setae, with minute ventrome- (Fig. 5F) slender, three-segmented, distal seg- dial tooth, lateral margin straight, anterolateral ment slender, subcylindrical, longer than com- margin (Fig. 5A) strongly acutely produced, bined length of proximal segments, with several slightly exceeding distal margin of intermediate slender simple setae distally. Molar process segment, medial margin feebly sinuous, with (Fig. 5D) stout, with four blunt teeth distally, coarsely plumose submarginal setae ventrally, without setal brushes. Incisor process (Fig. 5E) continuous with row of similar setae along lat- short, broad, with