Rayllianassa huonensis, Poore, 2023

Poore, Gary C. B., 2023, New records, one new genus and 21 new species of Callianassidae (Crustacea, Axiidea) from the Indo-West Pacific, Memoirs of Museum Victoria 82, pp. 167-255 : 233-235

Rayllianassa huonensis sp. nov.

http://zoobank.org/urn:lsid:zoobank.org:act:F4FE461E-177A-

4750-A156-A08643400AC9

Figures 44 , 45

Material examined. Holotype. Papua New Guinea, Huon Gulf, SE of Lae, 07° 27' S, 147° 31' E, 462–495 m (BIOPAPUA stn CP3636), MNHN IU-2011-6054 # (ovigerous female, 3.1 mm).

Diagnosis. Antennular peduncle about as long as antennal peduncle. Major cheliped merus with simple proximal tooth and carinate along most of lower margin; carpus and merus upper margins carinate; palm upper margin with narrow rounded keel, without tubercles and ridges on distal mesial and lateral margins at the base of fingers; dactylus with blade along cutting edge, apex simple. Pereopod 3 propodus oval, widest proximally. Uropodal exopod widest near midpoint, 1.6 times as long as wide.

Description of holotype. Carapace dorsally flat in lateral view, 0.8 length of pleomeres 1–2 combined; orbital margin oblique; anterolateral angle blunt; subanterolateral margin horizontal; anterior margin of branchiostegite convex; cervical groove deeply incised, across 0.8 length of carapace, almost reaching linea thalassinica. Pleomere 1 tergite without transverse groove. Pleomere 1.7 times as long as pleomere 1. Pleomere 6 about as long as wide.

Eyestalk 1.4 times as long as wide, with dorsal face close to rostrum, with sharp ventrolateral margin, anterolateral margin oblique, anteromedial angle triangular, acute in dorsal view, upturned, reaching distal margin of antennular peduncle article 1. Cornea densely pigmented, small, not filling anterior half of eyestalk.

Antennular peduncle about as long as antennal peduncle; article 1 visible in dorsal view; article 3 longer than articles 1 and 2 combined; articles 2 and 3 with longitudinal ventral row of long setae. Antennal peduncle article 5 as long as article 4; scaphocerite minute, oval.

Maxilliped 3 ischium almost parallel-sided, 1.3 times as long as wide, crista dentata consisting of row of about 13 teeth, contiguous distally; merus about two thirds as long as ischium measured along outer margin, about 1.4 times as wide as long, wider than ischium, with mesiodistal margin produced as convex lobe beyond base of carpus; carpus about as long as merus outer margin; propodus ovoid-tapering, 1.8 times as long as wide; dactylus digitiform, 0.8 length of propodus.

Major cheliped massive, carpus-palm upper margin 0.9 carapace length. Ischium expanding distally, upper margin almost straight, unarmed; lower margin with row of 4 similar spines. Merus little shorter than ischium, 1.5 times as long as wide (tooth excluded), ovate; upper margin convex, unarmed, carinate; lower margin with proximal angled spine, carinate over distal three quarters. Carpus 0.65 as long as wide; upper and lower margins carinate. Propodus upper margin 1.7 times as long as carpus; palm widest at midpoint, wider than carpus, as long as wide; upper margin convex, with narrow rounded keel; lateral surface smooth, convex; mesial surface convex, distolateral margin with tubercle near base of fixed finger; lower margin carinate, with row of setae extending onto fixed finger; fixed finger half as long as palm, distally directed; cutting edge lateral, blade-like, ending in step two thirds along. Dactylus as long as fixed finger, hooked distally, with acute tip; upper margin ridged, with tufts of long setae; lateral surface with few tufts of long setae along cutting edge; cutting edge unarmed.

Minor cheliped unknown.

Pereopod 2 merus lower margin almost straight, 2.5 times as long as wide; carpus about 1.8 times as long as wide; chela subtriangular; palm about 1.7 times as wide as upper margin; dactylus 2.2 times as long as palm upper margin. Pereopod 3 merus 2.5 times as long as wide; carpus subtriangular, 1.7 times as long as wide; propodus oval, upper margin as long as greatest width, lower margin rounded over proximal half, distal half sinusoidal, marginal setae with 2 clear gaps along distal half, with 1 slender spiniform seta subdistally; dactylus about 0.6 length of propodus upper margin. Pereopod 4 propodus about 3.8 times as long as wide. Pereopod 5 chelate.

Pleopods of female 1, 2 typical. Pleopods 3–5 biramous, endopod 2.3 times as long as wide; appendix interna slender, rod-like, projecting well beyond mesial margin of endopod.

Uropod endopod and exopod overreaching posterior margin of telson. Endopod oval-tapering, widest at midpoint, about 1.6 times as long as wide; upper surface with 1 long proximal spiniform setae on dorsal rib; anterior margin almost straight ending in small tooth; anterodistal margin with 2 short spiniform setae; distal margin convex, with fringe of setae; posterior margin setose. Exopod widest near midpoint, 1.6 times as long as wide, exceeding endopod by one third its length; anterior margin almost straight; all margins with numerous slender setae, with more than 10 blade-like setae on posterior margin indistinguishably merged with distal margin; dorsal plate apparent near distal margin as row of about 7 stiff setae.

Telson trapezoidal, as wide as long, broadest at anterior fifth, narrowing posteriorly; greatest width 1.4 times posterior width; posterolateral angle each with 2 spiniform setae; posterior margin medially excavate, with median tooth; dorsal surface with few medial setae including pair of spiniform setae.

Etymology. From the Gulf of Huon, Papua New Guinea.

Distribution. Solomon Sea ( Papua New Guinea); 462– 495 m.

Remarks. Rayllianassa huonensis shares with R. bifida sp. nov. a proximal spine on the merus of the major cheliped but lacks the strong cheliped carina and bifid cheliped dactylus seen in this species. The new species is also genetically and morphologically close to Rayllianassa sp. (see below).

Figures

Figure 44. Rayllianassa huonensis sp. nov. Papua New Guinea. MNHN IU-2011-6054 (holotype ovigerous female, 3.1 mm: a, eyestalks, carapace, pleon, telson, uropod (dorsal); b, eyestalk, carapace, pleomeres 1, 2 (lateral); c, d, antennular, antennal peduncles, eyestalk, anterior carapace (lateral, dorsal); e, telson, right uropod; f, major cheliped (right, mesial); g, major cheliped distal palm, fingers (lateral); h, carpus–dactylus (upper). Scale bars = 1 mm.

Figure 45. Rayllianassa huonensis sp. nov. Papua New Guinea. MNHN IU-2011-6054 (holotype ovigerous female, 3.1 mm: a, b, maxilliped 3 (mesial, lateral views); c–f, pereopods 2–5; g, pereopod 3 propodus, dactylus, h, pleopod 3 (with detail of appendix interna. Scale bars = 1 mm.