Allopontonia alastairi sp. nov., a second species of the genus Allopontonia Bruce, 1972 (Crustacea: Decapoda: Pontoniinae), from the Australian Northwest Shelf * Author Bruce, A. J. text Zootaxa 2010 2010-02-26 2372 1 33 36 https://www.biotaxa.org/Zootaxa/article/view/zootaxa.2372.1.4 journal article 10.11646/zootaxa.2372.1.4 1175-5326 5306769 Allopontonia alastairi sp. nov. ( Fig. 1 ) Material examined. Holotype male, NMV J59419 , North-western Australia , Imperieuse L 23 transect, 18°25’31”S , 120°05’55” E to 18°26’12”S , 120°06’30”E , FRV Southern Surveyor , SS 05/2007 085, 105– 103 m , beam trawl, 19 June 2007 , leg. M.F. Gomon. Diagnosis. An Allopontonia with the mobile hepatic spine small, ambulatory pereiopod dactyli simple, with bilateral distoventral fringe of divergent setae, ventral margin not serrate, propodus with single spine row, spines not distoventrally denticulate. Description. Generally closely resembling Allopontonia iaini , the only other species of the genus. Rostrum ( Fig. 1A ) damaged with distal portion missing, dorsal and ventral carinae well developed, dorsal carina with 7 similar small acute teeth, all pre-orbital, ventral border unarmed. Carapace ( Fig. 1A ) with orbit poorly defined, inferior orbital angle produced, antennal spine well developed, marginal, hepatic spine small, mobile. Antennae as in A. iaini . Cornea well developed, well pigmented, diameter about 0.2 of CL, with small accessory ocellus. Mandible, maxillula and maxilla not examined, maxillipeds as in A. iaini , exopod flagella slender with four terminal plumose setae. FIGURE 1. Allopontonia alastairi sp. nov. , holotype male, Australian Northwest Shelf, NMV J59419 : A, carapace and rostrum; B, first pereiopod; C, chela; D, same, finger tips; E, second pereiopod; F, same, chela; G, same, fingers, proximal cutting edges; H, third pereiopod; I, same, propodus; J, same, distal propodus and dactylus; K, same, distal dactylus; L, fourth pereiopod, dactylus, ventral. First pereiopod ( Fig. 1B ) robust, chela ( Fig. 1C ) about 0.42 of CL, palm oval in section, about 1.9 times longer than deep, with transverse rows of short cleaning setae proximo-ventrally, fingers ( Fig. 1D ) subequal to palm length, dactylus scaphoid with medial cutting edge, about 4.0 times longer than proximal depth, cutting edge laminar, entire, tip acute with small rounded laminar flange medially, fixed finger similar; carpus about 0.95 of palm length, 4.0 times longer than distal width, tapering proximally, with distoventral cleaning setae; merus 1.1 times longer than chela, 6.5 times longer than wide, ischium about 0.6 of chela length, 3.0 times longer than distal width, tapering proximally, ventral margin centrally with slender spiniform setae; basis about 0.25 of chela length, distoventrally produced with several simple spines; coxa with well developed distoventral process with several stouter spines. Second pereiopod ( Fig. 1E ) well developed, chela ( Fig. 1F ) about 1.08 of CL, palm smooth, oval in section, 2.4 times longer than deep, slightly swollen proximally, fingers about 0.6 of palm length, dactylus about 3.4 times longer than deep, with small hooked tip, cutting edge with stout blunt recurved tooth ( Fig. 1G ) proximally, distally laminar, entire, fixed finger similar with two small blunt teeth ( Fig. 1G ) proximally; carpus short, stout, unarmed, about 0.3 of palm length, tapering slightly proximally; merus 0.85 of palm length, 3.5 times longer than distal width, tapering slightly proximally, distolateral ventral angle slightly produced, ischium, basis and coxa without special features. Third pereiopod ( Fig. 1H ) moderately robust, dactylus ( Fig. 1J ) compressed, 4.0 times longer than deep, about 0.2 of propodus length, unguis ( Fig. 1K ) slender, curved, simple, obliquely articulated, 3.8 times longer than basal width, 0.25 of corpus length, corpus 3.5 times longer than deep, obliquely medially articulated with propodus, dorsal margin convex, ventral margin straight, simple, distoventral angle without accessory tooth, distal ventromedial and ventrolateral surfaces of corpus with numerous simple setae, most marked submarginally, forming fringe of divergent brush; propodus ( Fig. 1I ) about 0.75 of CL, 8.5 times longer than width, with pair of well developed simple distoventral spines, 13 similar ventral spines of decreasing size proximally, sparsely setose, carpus 0.33 of propodus length, merus 0.75, ischium 0.55. Fourth pereiopod ( Fig. 1L ) similar to third. Appendix masculina with 4 strong simple spines, appendix interna slightly shorter than appendix masculina. Caudal fan as in A. iaini . Etymology. The specific name is in memory of my son, Iain Alastair Bruce. Measurements. Postorbital carapace length, 2.75 mm ; total body length (approx.), 12.5 mm ; major second pereiopod chela, 3.0 mm. Systematic position. Closely resembling A. iaini but readily distinguished by the characters provided in the diagnosis. Ambulatory pereiopod dactyli simple (vs. biunguiculate), ventrally serrated in A. iaini ), with bilateral distoventral fringe of divergent setae, ventral margin of corpus not serrate (vs. serrate), propodus with single ventral spine row (vs. paired spines in A. iaini ). Host. Probably Salmacis belli Döderlein, 1902 ( Echinoidea : Temnopleuridae ), which was collected in the same trawl haul. Remarks. The single specimen is in good condition, with the mouthparts removed on the right side, mandible, maxillula and maxilla missing. Both first pereiopods but only the left second pereiopod are preserved, with the fourth left and third and part of fifth right ambulatory pereiopods. The discovery of A. alastairi indicates that the definition of the genus Allopontonia needs to be slightly revised so that species with simple ambulatory dactyli are not excluded. The probable host of A. alastairi , Salmacis belli , is a temnopleurid echinoid and is closely related to some of the hosts recorded for A. iaini , like Salmaciella and Salmacis Other hosts recorded for A. iaini are species of Asthenosoma (Echinothuriidae) and Pseudoboletiana ( Toxopneustidae ). Allopontonia iaini is one of the few pontoniine shrimps with a distribution that crosses the eastern Pacific filter bridge ( De Grave 2001 ) and has been recorded from Kenya , Zanzibar , Indonesia , Papua New Guinea , Australia ( Queensland ), New Caledonia , Marianas Islands , and Mexico . At about 100 m , A. alastairi occurs in significantly deeper waters than A. iaini . Only five pontoniine genera are known with an articulated mobile hepatic spine: Allopontonia Bruce ; Dasella Lebour ; Paranchistus Holthuis ; Patonia Mitsuhashi & Chan and Zenopontonia Bruce. Allopontonia (2 species) is associated with echinoid echinoderms, Dasella (3 species) with ascidians, Paranchistus (7 species) with bivalve molluscs and Zenopontonia (1 species) with asteroid echinoderms. The host of Patonia is unknown. Except for A.iaini , all are found only in the Indo-West Pacific. These genera are unlikely to be phylogenetically related and may be separated by the following key: 1. Rostrum compressed, with numerous dorsal teeth ....................................................................................................... 2 – Rostrum stout, with no or few dorsal teeth .................................................................................................................. 4 2. First pereiopod robust, chelae stout, fingers subspatulate, cutting edges pectinate................................ Zenopontonia – First pereiopod slender, chelae fingers not subspatulate, cutting edges entire ............................................................. 3 3. Second pereiopods similar, slender, rostral dentition 10/0, without ventral teeth, first four teeth articulated, ventral ambulatory propodi sparsely spinulate ............................................................................................................. Patonia – Second pereiopods similar, robust, rostral dentition 7–10/1, with ventral teeth, posterior dorsal teeth not articulate, ventral ambulatory propodi densely spinulate ......................................................................................... Allopontonia 4. Ambulatory dactyli with large ventral process, without micro-spinulation; dorsal telson spines large ............ Dasella – Ambulatory dactyli without large blunt ventral process, simple, or biunguiculate with acute distoventral accessory tooth, often with dense micro-spinulation; dorsal telson spines small ..................................................... Paranchistus