Philocheras gardenensis, Han & Keesing, 2018

Han, Qingxi & Keesing, John K., 2018, A new species of Philocheras (Decapoda: Caridea: Crangonidae) from Western Australia, with a key to all species of this genus worldwide, Zootaxa 4382 (1), pp. 175-184 : 176-179

1. Philocheras gardenensis sp. nov.

( Figs 1–2 )

Type material. Garden Island , Western Australia, coll.: M. van de Cliff, date: 00/00/1996, substrate: seagrasses and sand, 1 ovig. female holotype CL 5.5 mm, WAM reg. no. C23447 ; 1 ovig. female paratype CL= 5.3 mm, WAM reg. no. C72670.

Etymology. Named after the sampling location, Garden Island, which lies off the south-west coast of Western Australia.

Description. Body stout, strongly depressed dorsoventrally ( Fig. 1 ). Rostrum short, with slight convex end in dorsal view, approximate 0.13 times as long as postorbital carapace length, directed straightly forward, reaching only to middle of cornea of eyes; dorsal surface shallowly concave; lateral margin unsetose proximally; ventral surface carinate medially.

Carapace approximately as long as broad, without setae; faint transverse groove posterior to rostral base; dorsal midline carinate with a distinct and continuous middorsal carina; extending from the middorsal tooth to almost the posterior end of the carapace, middorsal tooth (epigastric tooth) large and sharp, direct anteriorly, situated 0.20 of carapace.

Hepatic spine absent, but a epigastric carina present behind the orbital margin, extending from nearly the same level of epigastric tooth; antennal spine small but acute, followed by a long and sinuous carina, extending nearly to the posterior end of carapace; branchiostegal spine large and acute, reaching beyond dorsodistal margin of antennal basicerite, and also a conspicuous carina run behind it, extending posteriorly beyond the middle of the carapace.

Pleon widest at the first somite, becoming narrowest at fifth somite; first four pleonal somites devoid of middorsal carina and sculpture; fifth somite with an inconspicuous median carina dorsally; sixth pleonal somite devoid of sculpture or carina, about 1.5 times as long as fifth somite; posterolateral process terminating in acute tooth; posteroventral angle blunt; telson ( Fig. 2H ) 1.5 times longer than sixth somite, terminating in small, triangular and acute projection, however, only one left in the holotype specimen; dorsal surface with shallow median sulcus, lacking dorsolateral spines and dorsolateral carina; first to fifth pleonal sternites without median tooth.

Antennular peduncle failing to reach the midlength of antennal scale; first segment longer than distal 2 segments combined; distolateral angle produced into a slender process; second segment about as long as wide, with slightly produced distolateral angle; third segment much narrower than the second segment; lateral flagellum moderately slender, overreaching distal margin of antennal scale by about one fourth, composed of approximately 19 articles (basal article occupying about 0.3 length); mesial flagellum much shorter than lateral flagellum, failing to reach distal margin of antennal scale, composed of 9 articles (basal article occupying about 0.3 of the total length). Antennal scale subovate, lateral margin unarmed and nearly straight; distolateral tooth extending beyond straight distal margin of lamella.

Third maxilliped consisting of 4 segments, flattened dorsoventrally, overreaching the distal margin of antennal scale ( Fig. 2A ); ultimate segment approximate 1.3 times longer than penultimate segment (carpus), moderately narrow, tapering distally, lacking row of long spines on both lateral margin, but covered with long stiff setae; penultimate segment (carpus) with short to long setae on ventral and lateral margin; antepenultimate segment (merus, ischium and basis fused segment) weakly sinuous in dorsal view; ventral surface distally with 3 spinules; exopodal peduncle extending about middle of antepenultimate segment, ischio-merus fused with basis, tapering distally, bearing well-developed flagellum.

First pereopod ( Fig. 2B ) stout, slightly overreaching distal margin of antennal scale; palm about 2.7 times longer than wide; cutting edge strongly oblique, with submarginal row of thick and short setae dorsally; pollex fixed, long and straight; dactylus strongly curved, about half length of palm; carpus short, with an acute distoventral tooth on lateral margin and cluster of grooming setae on mesial surface; merus compressed, especially proximally, with a strong and acute submarginal tooth; exopod absent.

Second pereopod ( Fig. 2C ) just reaching distal margin of carpus of anteriorly extended first pereopod, chelate; dactylus 1.8 times as long as palm, with unguis; chela 0.82 times as long as carpus, with two rows of long stiff setae on dorsal and ventral margins; carpus 0.50 length of merus, with long setae on each dorsal and ventral margins; merus and ischium with row of long setae on dorsal and ventral margins; ischium slightly shorter than merus.

Third pereopod ( Fig. 2D ) very slender, failing to reach the distal margin of antennal scale; dactylus 0.46 times as long as propodus, terminating in acute tip; carpus elongate, about 1.5 times longer than distal two segments combined; merus slight longer than ischium.

Fourth pereopod ( Fig. 2E ) moderately stout, overreaching distal margin of antennal scale by length of dactylus; dactylus 0.40 length of propodus, slender and slightly curved, terminating in thin unguis; as propodus; propodus noticeably compressed laterally, with sharply edged dorsal margin and concave lateral surface; carpus 0.78 length of propodus, rounded, without marginal setae; distal four segment, with the exception of short setae present on lateral margin propodus, devoid of marginal setae; ischium with long setae on dorsal and ventral surfaces; merus about 0.81 times longer than ischium.

Fifth pereopod ( Fig. 2F ) stronger than fourth pereopod, slightly overreaching distal margin of antennal scale; dactylus 0.35 length of propodus, almost straight; short setae present on lateral margin propodus; carpus 0.74 length of propodus, devoid of setae; merus almost as long as propodus, devoid of setae; ischium about 0.50 times as long as merus, with sparse long setae on dorsal surface.

Pleopods ( Fig. 2G ) each with relatively stout protopods; endopod of first pleopod about 0.30 length of exopod, tapering distally; second to fifth pleopods becoming shorter posteriorly, lacking appendix interna; protopod of uropod relatively narrow and slender; endopod of uropod approximately as long as exopod, overreaching tip of telson, about 0.20 length of the endopod or exopod; exopod with its lateral margin almost straight, posterior margin slightly round.

Type locality. Garden Island , Western Australia.

Distribution. So far only known from the type locality in Garden Island, Western Australia; depth unknown.

Coloration in life. Not recorded.

Remarks. Philocheras gardenensis sp. nov. closely resembles P. fasciatus (Risso, 1816) , which was recorded from British Islands to Canary Islands, and the Mediterranean, sharing the following characteristic in common: 1) antennal scale not denticulate or armed on outer margin, and lateral margin straight; 2) first four pleonal somites dorsally smooth; 3) carapace with only one middorsal tooth and no lateral teeth (Kemp, 1910).

The new species differs from Philocheras fasciatus by the following characters: 1) middorsal carina is longer, almost extending to the posterior end of the carapace, whereas in Philocheras fasciatus , the middorsal carina is much shorter, about 0.45 times as long as the carapace length; 2) there is no lobe-like folds on either side of the middle line of the, whereas in Philocheras fasciatus , two lobe-like folds are present on either side of the middle line of the carapace; 3) a well-defined carina runs backward from the branchiostegal spine, about 0.5 length of the carapace, whereas in Philocheras fasciatus , this carina is absent; 4) scaphocerite with distolateral tooth extending beyond rounded distal lamella, whereas in Philocheras fasciatus , distolateral tooth of antennal scale fails to overreach the rounded distal lamella.

With the addition of the new species, there are 58 known species or subspecies in the genus Philocheras Stebbing, 1900 . The species may be distinguished by the key given below in this paper following the description of Philocheras obliquus ( Fulton & Grant, 1902) . This key is partly combined and modified from Kemp (1911), Kemp (1916), De Man (1920), Crosnier & Forest (1973); Chace (1984), Komai (2008) and Taylor (2010). Komai (2008) also provided a checklist for the genus Philocheras , and related references are also included for each species. The geographic distribution is also indicated for possible use in identification. The following abbreviations are used in the key, WA: Western Australia; SA: South Australia; Vic.: Victoria; QLD: Queensland; Tas.: Tasmania; NSW: New South Wales; NT: North Territory.

Figures

FIGURE 1. Philocheras gardenensis sp. nov., holotype ovigerous female, CL 5.5 mm, WAM C23447, Western Australia: A, entire animal in dorsal view; B, entire animal in lateral view.

FIGURE 2. Philocheras gardenensis sp. nov., holotype ovigerous female, CL 5.5 mm, WAM C23447, Western Australia: A, left third maxilliped, dorsal view, setae on exopod omitted; B, right first pereopod, ventral view; C, right second pereopod, lateral view; D, right third pereopod, lateral view; E, left fourth pereopod, ventral view; F, left fifth pereopod, ventral view; G, right second pleopod, ventral view; H, telson, dorsal view.Scales=1 mm.