ZOOLOGISCHE MEDEDELINGEN

Transcription

1 WvVVuvS. j_.6 CRUSTACEA LIBRARY SMITHSONIAN INST REl'UKN TO W-119 ZOOLOGISCHE MEDEDELINGEN UITGEGEVEN DOOR HET RIJKSMUSEUM VAN NATUURLIJKE HISTORIE TE LEIDEN (MINISTERIE VAN CULTUUR, RECREATIE EN MAATSCHAPPELIJK WERK) Deel 55 n augustus 1980 A NEW GAVERNICOLOUS FRESHWATER CRAB FROM NEW GUINEA (CRUSTACEA DEC APOD A) by L. B. HOLTHUIS Rijksmuseum van Natuurlijke Histrie, Leiden, Netherlands With i text-figure and i plate Thrugh the kindness f Mr. Philip Chapman f Culfrd, Bury St. Edmunds, Sufflk, it as made pssible fr me t examine a male and a female f a species f caverniclus crab frm the Western Highlands f Papua Ne Guinea, cllected there by Mr. N. Plumley. The species prved t be ne t science and its descriptin is given bel. A recent revisin f the Ne Guinea freshater crabs (Btt, 1974) listed 13 certain and 3 dubius species frm the island. These 13 species belng t 3 genera (Ruxana Btt, 1969: 5 species; Geelvinkia Btt, 1974: 3 species; and Hlthuisana Btt, 1969: 5 species). The first t genera and the nminate subgenus f the third are cnfined t Ne Guinea. All three genera belng t the family Sundathelphusidae Btt, The ne species is placed here in the genus (and subgenus) Hlthuisana; H. subcnvexa (Rux). it prves t be clsest t Nne f the knn species f Ne Guinea freshater crabs has ever been reprted frm caves and nne shs any adaptatin t subterranean life. The find f the present trglbitic species therefre is f special interest, and I am mst grateful t Mr. Chapman fr this material. The draing f pi. 1 is made by Mr. W. C. G. Gertenaar, staff artist f the Rijksmuseum van Natuurlijke Histrie. Hlthuisana alba ne species (text-fig. 1; pi. 1) Askembutem Cave, Wk Askembu near Tabubil, West Sepik District, Papua Ne Guinea; in pls n a ledge at the bttm f the secnd vertical pitch; Octber 1978; leg. N. Plumley, n $ hltype, 1 9 paratype. Descriptin f hltype male. The carapace is high and distinctly cnvex in a lngitudinal directin: the anterir part is curved dn. Transversely

2 316 ZOOLOGISCHE MEDEDELINGEN 55 (1980) surface f the eyestalk is remarkable by the presence f granules, pits and shrt hairs. The antennulae fld transversely and the t fssae are separated by a thin sharply edged all, hich extends frm the tip f the frntal triangle t the middle f the anterir margin f the epistme. The epistme is deeply sunken in the middle, shing a deep and rather ide transverse grve, hich anterirly is brdered by the ridge-like elevated anterir margin, hich is straight and transverse. The psterir margin f the epistme cnsists f three parts: a median triangular ridge-like elevatin pinting backard, and t lateral transverse ridges; the three parts are separated by deep incisins. The lateral ends f the epistme sh sme elevatins and pits. The antennal peduncle frms the inner margin f the rbit, and the flagellum enters the rbit. The subrbital regin is smth, and, apart frm a fe scattered granules shs n rnamentatin. The distal segment f the mandibular palp is deeply bifurcate and f the Gecarcinucid type. The third maxillipeds fill the entire ral field, except fr the efferent penings hich are semicircular. The uter angle f the merus is rectangularly runded. The merus is 3/4 as lng as ide and is abut half as lng as the ischium; it shs n grve. The ischium has a lngitudinal grve slightly t the inside f its median line. The peduncle f the expd is expsed, but the multi-articulated flagellum is hidden. The chelipeds f the male are unequal; the right is the larger. Its fingers are smehat lnger than the palm and end in a sharp tip hich is hrnclured; the tips are crssing. The cutting edges f the fingers are slightly gaping prximally and carry distinct, but nt very large teeth ver their entire length. The teeth f the dactylus and thse f the distal part f the cutting edge f the fixed finger are rughly alternatingly smaller and larger. The prximal five teeth f the fixed finger all are as large as, r slightly larger than, the largest f the ther teeth. Bth fingers are finely granular and sh indistinct lngitudinal grves. The palm is slightly lnger than high and smehat sllen; it carries neither carinae nr spines, but shs sme scattered very small tubercles hich smetimes frm indistinct transverse rs; there is n tubercle r selling near the base f the fingers. The carpus is shrt and cnical ith a large triangular tth n the inner surface; behind this large tth there is a smaller t-tpped tth. The merus bears sme granules and has the upper margin and the uter ler margin indistinctly serrate; n spines are present n any f the margins. The left first pereipd is mre slender and smaller than the right. The fingers are distinctly lnger than the palm, they are slender and clse ver

3 r > * ^Zm ' v ; " a / Hlthuisana alba ne species, hltype $ in drsal vie. W. C. G. Gertenaar del. \ f y s, 11 / N 3 r i i r in n K W

4 IIOLTHUIS, A NEW CAVERNICOEOUS CRAP. 317 their entire length. The cutting edges are tthed ver their full length, larger and smaller teeth are irregularly alternating. The palm is lnger than high. The ther segments are similar t thse f the larger cheliped, but slenderer. The length f the chela is greater than the idth f the carapace. The r alking legs are slender, but nt excessively s. The secnd pereipd is abut as lng as the first. The dactylus is slender and shs fur lngitudinal ridges hich carry spines; the spines f the upper ridges are distinctly shrter than thse f the ler ridges. The prpdus is as lng as r slightly shrter than the dactylus, it bears a faint lngitudinal ridge n either surface. The ler margin f the prpdus bears t lngitudinal rs f abut 5 spines. The carpus measures abut 3/4 f the length f the prpdus. The merus is abut tice as lng as the carpus and abut 4 times as lng as ide; the upper margin is irregularly serrate and des sh a cncavity just befre the anterir end, but it bears n subdistal tth. The secnd leg is the shrtest alking leg, the fifth being slightly lnger. The third and furth legs are practically f equal length, and are distinctly lnger than the ther legs. The prprtins f the varius segments f the alking legs are practically the same, as is als the spinatin. The dactylus f the fifth leg, hever, has the spines lnger, especially thse f the distal part f the upper margin, hich are as lng as the ventral spines. The spines n the prpdus f legs 3 t 5 are smaller than thse f the secnd leg. The merus f the third pereipd is slightly shrter than the carapace (abut 7/8). The thracic sternum f the male is smth ith scattered pits; a shrt transverse grve is present just befre the tip f the appressed abdmen. The male abdmen is smehat T-shaped. The first segment is very shrt and ide, ith a median transverse carina. The secnd segment is abut tice as lng as the first and slightly ider, it tuches the cxae f the fifth pereipds. It, and the flling segments, d nt sh any carina at all. The third segment at its base is smehat ider than the secnd and narrs anterirly, being trapezid in shape; the psterir margin is abut 1.3 times as ide as the anterir. The segment is slightly lnger than the secnd and abut 6 times as ide (at the base) as lng. The furth segment is abut as lng as the third and als narrs anterirly, its basal idth being abut 1.3 times the distal idth. The fifth segment is smehat lnger than the furth and narrs slightly less strngly anterirly; its lateral margins are very slightly cncave. The sixth segment is the lngest f the abdminal segments, being abut 1.5 times as lng as the fifth; it hardly at all narrs distally and its lateral margins are straight and practically parallel. The telsn is as lng as the sixth segment; it is triangular ith a bradly runded tp, being slightly shrter than ide.

5 318 ZOOLOGISCHE MEDEDELINGEN 55 (1980) The first male gnpd is rbust, straight, ith the tp curved smehat utard. The distal t segments are firmly fused and the brder beteen them is indistinct. The distal segment ccupies less than 1/4 f the ttal length f the gnpd; it ends in a crneus tubifrm brad and truncate tip. The gnpd shs a deep grve n the inner surface fr the receptin f the secnd gnpd. The secnd gnpd is lnger than the first, it is slender and straight. It ends in a thin, narrly val lbe hich reaches beynd the pening f the duct. The distal segment is mre than half as lng as the preceding, and mre slender. The prximal segment idens at the base. Female. The female resembles the male in abut all respects. The chelipeds, althugh unequal, are relatively smaller and mre slender than thse f the male. The larger cheliped f the female (als the right in this specimen) resembles the smaller cheliped f the male. The carpus f this larger cheliped has the tth behind the large inner tth f the carpus quite sharp and distinct, flled by t l teeth. In the smaller female cheliped there are three rather small teeth behind the larger tth f the carpus. The female abdmen is very ide and reaches practically t the cxae f the secnd t fifth pereipds. The segments becme gradually lnger distally; the first t the fifth becme gradually ider, the abdmen being idest at the line separating the 4th and 5th segments. The sixth segment and the telsn tgether frm almst a semicircle. The female penings n the sternite f the third pereipd are large and almst circular. Size. The carapace f the male is 21 mm lng and 26 mm ide; in the female these measurements are 22 mm and 27 mm respectively. Types. The male is the hltype, the female the paratype. They frm part f the cllectin f the Rijksmuseum van Natuurlijke Histrie, Leiden under ns. Crust. D (hltype), and (paratype). Clur. The clur f the preserved specimens is unifrmly yellish hite, ithut any trace f pigment. In life the animals are hitish transparent. Remarks. The shape f the distal segment f the mandibular palp shs clearly that the present species belngs in Btt's (1970: 22) Parathelphusidea hich mre crrectly shuld be named Gecarcinucidea (see Hlthuis, 1979: 25). The presence f a distinct frntal triangle makes that it shuld be assigned either t the Parathelphusidae r the Sundathelphusidae as defined by Btt (1970: 62, 95). The shape f the frntal triangle f the present species agrees better ith the descriptin f that rgan in the Parathelphusidae as given by Btt (1970: 95) than ith the ne f Sunda-

6 HOLTHUIS, A NEW CAVERNICOLOUS CRAB 319 thelphusidae (Btt, 1970: 62), hile als the first gnpd shs much resemblance t that f sme Parathelphusids. Hever, the absence f an epibranchial tth and f anterlateral teeth, and a cmparisn ith specimens f the genus Hlthuisana shs that the Ne Guinea cave crab shuld be placed amng the Sundathelphusidae and in the latter genus. Hlthuisana is ne f the three genera f Ne Guinea freshater crabs, all three belng t the family Sundathelphusidae. Btt (1974) revised these genera (Ruxana Btt, 1969, Geelvinkia Btt, 1974, and Hlthuisana Btt, 1969) in his mngraphic treatment f the Ne Guinea freshater crabs. The facts that in the ne species the first male gnpd is curved utard, evenly narred distally and des nt have the last segment distinctly separated frm the preceding, hile the frntal triangle has a distinct upper margin, that it is a species f Hlthuisana sh as defined by Btt; it differs in these characters frm the ther t genera. Amng the species f Hlthuisana, H. alba resembles clsest H. subcnvexa (Rux, 1927), but it differs by having the upper surface f the carapace rughened by tubercles and ridges, by the narrer frntal triangle, hich is nly abut half as ide as the frnt, the mre slender legs, the lack f a subdistal tth n the upper margin f the merus f the alking legs, the uncnstricted distal part f the male abdmen and the mre rbust first male gnpd. In its hite clur and the reduced eyes H. alba differs frm all species f knn at present. As just mentined Hlthuisana Gecarcinucidea alba is the first hite caverniclus species f Gecarcinucidea t becme knn, it is furthermre the secnd species f hite and blind cave crab t be fund in the Ind-West Pacific regin, utside that regin nly fur mre trglbitic crabs are knn. The five species f freshater crabs that by the lss f sight, by the hite clur and slender legs prve t have becme fully adapted t life in subterranean aters are fur species f Pseudthelphusidea (Trichdactylus mensabak Cttarelli & Argan, 1977, and Typhlpseudthelphusa mcini Rija, 1953, bth frm Mexic, and T. juberthiei Delamare Debutteville, 1976, and T. mitchelli Delamare Debutteville, 1976, bth frm Guatemala), and ne species f Ptamidea (Cerberusa caeca Hlthuis, 1979, frm nrthern Saraak, Brne). The present species thus brings the ttal number f true trglbitic species amng the freshater crabs up t 6. REFERENCES BOTT, R., Flusskrabben aus Asien unci ihre Klassifikatin (Crustacea, Decapda). Senckenbergiana bil., 50: , Die Siissasserkrabben vn Eurpa, Asien, Australien und ihre Stammesgeschichte. Eine Revisin der Ptamidea und der Parathelphusidea. (Crustacea, Decapda). Abh. Senckenberg. naturf. Ges., 526: 1-338, 1 map, text-figs. 1-8, pis

7 ZOOLOGISCHE MEDEDELINGEN 55 (1980) BOTT, R., Die Siissasserkrabben vn Neu Guinea. Zl. Verhand. Leiden, 136: 1-36, text-figs. 1-14, pis HOLTHUIS, L. B., Caverniclus and terrestrial decapd Crustacea frm nrthern Saraak, Brne. Zl. Verhand. Leiden, 171 : 1-47, text-figs. 1-9, pis. 1-8.