Eiconaxius dongshaensis, Poore & Dworschak, 2018

Poore, Gary C. B. & Dworschak, Peter C., 2018, The Eiconaxius cristagalli species complex (Decapoda, Axiidea, Axiidae), Memoirs of Museum Victoria 77, pp. 105-120 : 108-111

Eiconaxius dongshaensis sp. nov.

(http://zoobank.org/urn:lsid:zoobank.org:act:7A965426-D789-

4C02-8B8C-4A3A84C17E3B)

Figures 3 , 4a, b

Eiconaxius indicus . – Sakai and Ohta, 2005: 73–77, figs 3–5. –

Tsang et al., 2008: 363, fig. 2.

Material examined. Holotype. South China Sea, off Pratas Islands, S of Hong Kong, 20°50.9'N, 117°27.17'E, 730– 720 m (stn CD320), NTOU A01439 (female, 10.0 mm).

Paratype. Collected with holotype, NTOU A01440 (female, 9.4 mm) .

Diagnosis. Rostrum 1.5–2.0 times as long as wide; with ventral tooth. Median carina erect, with clear dentition; sublateral gastric carinae present, diverging widely from base of median carina; lateral gastric carina not running from rostrum, commencing level with confluence of submedian carinae. Major cheliped, palm wider distally than at midpoint, upper margin denticulate; lateral and mesial faces of palm tuberculate near base of fingers; distolateral margin with 2 teeth at base of dactylus, lobe and keyhole-shaped notch in gape; fixed finger about half as long as upper margin of palm, cutting edge with basal notch, blade-like proximal half, and distal concavity; dactylus cutting edge with basal molar-like tooth, notch and straight beyond. Minor cheliped, palm upper margin as long as greatest width; distolateral margin with prominent triangular tooth at base of dactylus (bifid); lateral and mesial faces tuberculate near base of fingers.

Description. Carapace smooth. Rostrum 0.18 carapace length, concave dorsally, tapering evenly to acute tip, twice as long as wide at base, with 6 teeth on lateral margins, depressed below level of median carina, not continuous with lateral carinae, with ventral tooth. Lateral gastric carina unarmed, reaching anteriorly to base of median carina. Submedian gastric carina smooth, together curved and converging on median carina. Median gastric carina prominent, erect, reaching two-thirds along rostrum, with c. 13 uneven sharp teeth.

Pleuron 1 posteroventrally rounded; pleuron 2 truncate, posteroventrally acute; pleura 3 and 4 truncate, posteroventrally subacute; pleuron 5 rounded, all 5 pleura without anteroventral tooth; pleuron 6 with acute posteroventral angle; pleonite 6 dorsal posterior margin denticulate.

Eyestalk, 0.4 length of rostrum; cornea white. Antennular peduncle reaching to midpoint of antennal article 4; article 1 unarmed. Antennal peduncle article 1 unarmed; article 2 with upper-distal elongate triangular blade, reaching two-thirds along article 4; scaphocerite a vertical blade, reaching just beyond end of article 4; article 3 lower margin with distomesial tooth; article 5 about half length of article 4.

Maxilliped 3 basis with mesial spine; ischium unarmed; crista dentata of about 16 small similar teeth; merus and carpus unarmed; exopod with flagellum reaching to base of merus.

Major cheliped merus lower margin with c. 8 irregular teeth, upper margin with 2 minute blunt teeth; carpus lower margin with 1 distal tooth; propodus upper margin carinate, obscurely dentate, angled distally, length 0.9 greatest height, lower margin smooth, lateral face tuberculate near base of fixed finger, mesial face with few tubercles near base of fixed finger; fixed finger 0.6 times as long as upper palm, cutting edge shallowly concave over proximal two-thirds, denticulate beyond, with longitudinal mesial ridge; distolateral margin of palm with 2 teeth at base of dactylus, lobe and keyhole-shaped notch in gape; distomesial margin of palm with 2 teeth at base of dactylus; dactylus distally curved, upper margin carinate, cutting edge with basal tooth, straight beyond.

Minor cheliped shorter and more slender than major, palm 0.8 times height of major palm; merus lower margin with 8 sharp teeth, increasing in size distally; carpus lower margin with 1 distal tooth; propodus dilating, upper margin carinate, weakly denticulate, as long as greatest height, lower margin smooth, lateral and mesial faces tuberculate near base of fixed finger; fixed finger 1.25 times as long as upper palm, cutting edge dentate, with longitudinal mesial and lateral ridges; distolateral margin of palm oblique, with prominent bifid triangular tooth in gape; distomesial margin of palm oblique, with 2 triangular teeth in gape; dactylus distally curved, upper margin carinate, cutting edge smooth.

Pereopod 2 ischium lower margin unarmed; merus lower margin unarmed; carpus 0.8 length of propodus upper margin; propodus upper margin 2.5 times as long as dactylus. Pereopod 3 merus unarmed; propodus 3.3 times as long as dactylus, with 7 rows of spiniform setae, of 2–4 setae; dactylus spatulate, with 10 spiniform setae along oblique margin, plus unguis, 4 facial spiniform setae. Pereopod 4 similar to pereopod 3; propodus 3.5 times as long as dactylus, with 7 rows of spiniform setae, of 1–3 setae; dactylus spatulate, with 8 spiniform setae along oblique margin, plus unguis, and 2 facial spiniform setae. Pereopod 5 dactylus spatulate, with 8 spiniform setae along oblique margin, plus unguis, with 1 facial spiniform seta.

Uropodal endopod 1.9 times as long as wide, oval, anterior-distal margin with c. 20 evenly-spaced teeth, without longitudinal ridge. Uropodal exopod 1.7 times as long as wide, oval, anterior margin with many small irregular teeth over most of length, without longitudinal rib.

Telson 1.35 times as long as wide, widest at midlength, then tapering to rounded posterolateral angles, lateral margin upturned, denticulate, distal margin evenly curved, with posteromedian spine; dorsal face smooth, concave.

Etymology. dongshaensis , from Dongsha, the Chinese name of the Pratas Islands near the type locality.

Distribution. Sulu Sea, Philippines, 688–2019 m ( Sakai and Ohta, 2005); Pratas Is., South China Sea, 720–730 m ( Tsang et al., 2008).

Remarks. Sakai and Ohta (2005) illustrated the habitus, tailfan and chelipeds of this species as Eiconaxius indicus based on nine specimens of both sexes from the Sulu Sea. Their figures can by-and-large be reconciled with those published here. The chelipeds are similar but the palmar distolateral and mesiolateral armature is simpler in their figures than in the types. Sakai and Ohta (2005) showed tubercles on the lateral face of the palm of the major cheliped in fig. 3 but not in fig. 5, and did not note the easily overlooked subrostral tooth.

Eiconaxius dongshaensis is the only species in this group with a rostral ventral tooth. This tooth and the small keyhole-shaped notch in the gape of the cheliped are like no other species.

Figures

Figure 3. Eiconaxius dongshaensis sp. nov. Holotype, NTOU A01439 (female, 10.0 mm) – a, carapace, pleon, lateral. b, anterior carapace, antenna, lateral. c, anterior carapace, antennule, antenna, dorsal. d, pleomere 6, telson, right uropod. e, f, right major cheliped, lateral and mesial. g, h, left minor cheliped, lateral and mesial. i, maxilliped 3. j, pereopod 2. k, l, left pereopod 3, detail of dactylus. m, n, left pereopod 4, detail of dactylus. o, p, left pereopod 5, detail of dactylus. Scale = 2 mm (except b, c, l, n, p).

Figure 4. Eiconaxius dongshaensis sp. nov., holotype, NTOU A01439 (female, 10.0 mm) – a, habitus, in vivo. b, habitus in host sponge (photos, Tin-Yam Chan). Eiconaxius gololobovi sp. nov., unspecified specimen – c, habitus, in vivo (photo, David Shale).