Longiflagrum amphibium , a new estuarine apseudomorph tanaid ( Crustacea , Peracarida ) from north-western Australia

Australian tanaidacean material collected during spring 1993 and 1994 and autumn 1994 and 1995 in vicinity of Port Hedland and Oyster Island (NW Australia) included over 800 of specimens of a new species of apseudomorph, Longifl agrum amphibium sp. n. Th e species is the fi fth to be described in this genus, and it was found in the intertidal zone, as the other species have been. Th e new species is distinguished from the other members of the genus by having the shortest fl agella in the antennule and by its oval pleopod basis.


Introduction
Th e genus Longifl agrum was removed from the heterogeneous genus Apseudes Leach, 1814 by Guţu (1995) and placed in the family Parapseudidae mainly based on the lack of an apophysis on the coxa of pereopod 1.A further supporting character was the presence of a transverse dorsal row of minute setae on pleonite 1 which is borne by a few parapseudid genera, e.g.Discapseudes Băcescu and Guţu, 1975, Pseudoapseudes Guţu, 1981, Saltipedis Guţu, 1995and Ctenapseudes Bamber, Ariyananda and Silva, 1996.According to Guţu (1995Guţu ( , 1996)), Longifl agrum is characterized by the equal length of the antennule fl agella, by the presence of long setae on article 2 of antennae, at least ten articles in the antennular fl agellum, by the broadened carpus of the fi rst pereopod 1, and the wide rami of the pleopods.It currently includes fi ve species including the new one described in the present paper.Th e characters pinpointed by Guţu (1995) defi ne the genus well and can be accepted with two qualifi cations.One is the width of the pleopod rami, which can be quite narrow as in the case of L. caeruleus (Boesch, 1973); the other is that the fl agellum in the antennule can have less than ten articles (L.koyonense Angsupanich, 2004).
All fi ve Longifl agrum species occur in shallow coastal habitats such as the tidal zone, eelgrass-beds and estuaries where salinity fl uctuates in the wide range from 5 up to 34 psu (Boesch 1973;Angsupanich 2004) and they are often recorded as a frequent and abundant element of the soft-bottom ecosystem community (Boesch 1973).

Material and methods
Th e series of over 800 specimens determined as Longifl agrum amphibium sp.n. were collected four times in the Australian spring 1993 and 1994 and autumn 1994 and 1995  Th e type material is deposited in the Museum of Victoria, Melbourne, Australia.Th e terminology follows Larsen (2003) and Bamber (2005).Species included: L caeruleus (Boesch, 1973); L. estuarius (Boesch, 1973), L. koyonense (Angsupanich, 2004), L. nasutus (Nunomura, 2005) Diagnosis: Antennular fl agella with 8 articles.Antennal fl agellum with six articles, article 5 twice as long as wide.Pereopod 1 propodus as long as wide, with four spiniform setae on ventral margin that are 3-4 times as long as wide; pereopod 1 exopod with six setae on distal article.Pereopods 4-6 propodus short, 1.5 times as long as wide.Pleopod basis wide, oval, pleopod endopod twice as long as wide.

Systematics
Description of female with rudimentary oostegites: (Fig 1 A, B), body 7.4 mm long, 4.3 times as long as wide.Carapace 18% of body length, with rostrum pointed, bent down.Pereonite 1 0.4 times as long as wide, subequal to pereonite 3; pereonite 2 shorter than pereonite 1, 0.3 times as long as wide; pereonites 4 and 5 the longest, both 0.6 times as long as wide; pereonite 6 subequal to pereonite 2. Pleon 25% of total body length; pleonite-1 with dorsal row of minute setae; pleotelson as long as combined length of three pleonites.
Antennule (Fig. 2A) peduncle article 1 2.5 times as long as wide; article 2 half length of article 1, both articles with numerous simple and plumose setae; articles 3 and 4 much shorter, about 0.2 times as long as article 2; fl agella subequal, shorter than peduncle, both with eight articles and with numerous, simple setae on both fl agella; aesthetascs in number 2, 3, 2 on articles 3, 5 and 7 respectively of main fl agellum.
Antenna (Fig. 2B) peduncle article 2 with tooth-like projection and three minute plumose setae; article-3 about twice as long as wide, with six long setae on inner margin; articles 3 and 4 subequal, both as long as wide; article 5 twice as long as wide.Flagellum with six articles.Peduncle articles 3-5 and fl agellum fi rst article with long setae on inner margin.Squama with 14 simple setae.
Mouthparts.Left mandible (Fig. 2C) incisor with four spiniform setae; lacinia mobilis as big as incisor with four spiniform setae; setiferous lobe with one simple and fi ve long, distally bifurcated/trifurcated setae; molar (Fig. 2C') wide, with some serrated spiniform setae on edge and with row of fi ne spiniform setae on crushing surface.
Maxilla (Fig. 2E) outer lobe of moveable endite with two setae subdistally and row of serrated setae distally; inner lobe with about ten serrate setae; outer lobe of fi xed Labium (Fig. 2D) lobe with minute setation on inner margin and four spines on outer margin.
Palp with numerous, long, minute setae on both margins and three simple setae distally.Maxilliped (Fig. 2G) basis as long as wide, naked; palp article1 with one small distal, seta on outer margin and three simple, long setae on inner margin; article2 about twice as long as wide, with four long setae distally on outer margin and numerous short and long setae on inner margin; article 3 with three simple setae distally on outer margin and numerous simple setae on inner margin; article 4 with numerous simple setae along inner and distal margin and at middle.Endite (Fig. 2G') with fi ve long setae, and six short spiniform setae distally; inner margin with seven setae and four coupling-hooks.
Cheliped (Fig. 2H) basis narrow proximally, about 1.5 times as long as merus, with two simple setae and spiniform seta ventrally and bunch of fi ve simple setae distoventrally; merus about 0.4 times as long as carpus, with two groups of simple setae ventrally; carpus elongate, 3.5 times as long as wide, with numerous simple setae proximally, ventrally and distally, dorsal margin with row of three (four) setae; propodus subequal in length to dactylus and unguis combined, with one seta dorsally and numerous inner and outer setae near dactylus and ventrally; fi xed fi nger with row of minute spines and serrate setae (Fig. 2H'); dactylus with three simple setae dorsally.Exopod 3 articled, distal article with four feather setae.
Pereopod 1 (Fig. 3A) coxa present, basis wide, narrowed proximally, 3.5 times as long as wide, with spiniform seta and two long setae distoventrally; ischium with fi ve simple setae distoventrally; merus wide, 1.2 times as long as wide with spiniform seta distoventrally and one distodorsally and numerous simple setae on distal half of ventral margin and in mesial row; carpus half as long as wide (expanded dorsal part), with two spiniform setae distoventrally and spiniform seta distodorsally and numerous simple setae on both margins; propodus 1.2 times as long as wide, with four stout spiniform setae ventrally and two spiniform setae distodorsally, which are three to four times as long as wide, and with numerous simple setae on both margin; dactylus and unguis 0.6 times as long as propodus, with one minute seta ventrally.Exopod with three articles, distal article with six plumose setae.
Pereopod 2 (Fig. 3B) coxa naked; basis elongate twice as long as wide, with three simple setae distoventrally (one longer, two shorter); ischium about 0.6 times as long as merus, with three long, and one short simple seta; merus about 0.7 times as long as carpus, with eight simple setae ventrally and group of fi ve simple setae at middle; carpus 1.2 times as long as propodus, with three spiniform setae distoventrally (one small) and numerous simple setae describe the diagonal row; propodus with row of three spiniform and six simple setae ventrally and two spiniform and six simple setae dorsally; dactylus and unguis about as long as propodus, unguis 0.2 times as long as dactylus.
Pereopod 3 (Fig. 3C) similar to pereopod 2, but merus additionally with spiniform seta ventrally, and carpus with seven spiniform setae distoventrally and distodorsally.Pereopod 4 (Fig. 3D) basis elongate, subequal in length to ischium, merus and carpus combined, about twice long as wide, with one simple setae distoventrally, three middorsal and one midventral plumose setae; ischium 0.4 times as long as merus, naked; merus 0.7 times as long as carpus, with eight simple setae and two spiniform setae ventrally; carpus 1.5 times as long as propodus, with eight simple and seven spiniform setae ventrally; propodus with one plumose setae dorsally, four simple setae distally and row of short, serrated setae along distal margin; dactylus about 2.5 times as long as unguis.
Pereopod 5 (Fig. 3E) basis elongate, subequal in length to ischium, merus and carpus combined, about twice as long as wide, with two middorsal and one midventral plumose setae; ischium 0.3 times as long as merus, with fi ve short simple setae; merus 0.8 times as long as carpus, with seven simple and three spiniform setae distoventrally; carpus 1.2 times as long as propodus with six simple and fi ve spiniform setae distoventrally and one spiniform seta distodorsally; propodus subequal in length to merus, with plumose seta dorsally, three simple and two spiniform setae ventrally, three simple and two spiniform setae distally; dactylus and unguis combined about as long as propodus.
Pereopod 6 (Fig. 3F) basis elongate, subequal in length to ischium, merus and carpus combined, about twice as long as wide, with seven simple setae ventrally and row of numerous simple setae running from dorsally to middle part of article; ischium triangular, with four simple setae distoventrally; merus 0.6 times as long as carpus, with one simple seta ventrally, two simple and two spiniform setae distoventrally; carpus 1.7 times as long as propodus, with six simple and seven spiniform setae ventrally, three long, simple setae distoproximally; propodus with one plumose seta dorsally and row of numerous, short serrate setae along distal and distoventral margin, one spiniform seta midventrally and four simple setae distally; dactylus and unguis combined little longer than propodus.
Pleopods (Fig. 3G) in fi ve pairs, all similar, basal article 1.8 times as long as wide, with numerous plumose setae along both margins; exopod with numerous plumose setae along outer and distal and innerdistal margin and three setae distoproximally; endopod with numerous simple setae along all margins and one short, feather seta on inner margin.Exopod 0.8 as long as endopod.
Uropod (Fig. 3H) basal article with one small spine and one simple seta.Endopod with 29 articles and sparse short simple and plumose setae.Exopod with fi ve articles, 0.2 times as long as endopod.
Male.Similar to female except for chelipeds (Fig. 2I), which are much robust, especially carpus less than twice as long as wide; fi xed fi nger with additional large tooth near dactylus insertion.Antennule similar to female.
Remarks.Of the fi ve species now in the genus Longifl agrum, L. amphibium sp.n. has the shortest antennular fl agella, with only eight-articles.Th e Pacifi c species, L. caeruleus, L. estuarius and L. nasutus have more than ten articles in both fl agella (16/15, 14/12 and 15/11, respectively), while the Indonesian L. koyonense has eight to nine in the inner fl agellum and 12-13 in the outer one.A trend in reduction in the number of antennal fl agellum articles can be noticed as well, with eleven articles in L. caeruleus, nine in L. estuarius, seven in both L. koyonense and L. nasutus and only six in L. amphibium.
L. amphibium has wide (almost oval) bases of the pleopods.Th is article is usually narrow and rectangular or at least square in the other species.
Apart from the shape of the pleopod bases and the articulation of the antennule and antenna, L. amphibium is most similar to L. koyonense, although that species has a sparsely setose dorsal side to the cheliped carpus and more ( 14) setae in the squama.Also L. koyonense has a relatively short (1.5 times as long as wide) fi fth article in the antennal peduncle, which is twice as long as wide in all other species except for L. caeruleus in which this article is only as long as wide.
Males of Longifl agrum are recognizable by the shape of the chela.Th e new species is the only one without a proximal spiniform seta on the ventral margin of the cheliped dactylus.Th is structure is very prominent in L. koyonense, L. nasustus, L. estuarius, and small, but clear in L. caeruleus.
Distribution.Th e species is known only from the type locality (Port Hedland, NW Australia), from the tidal depth.