Tumidochelia uncinata (Hansen, 1913)

Esquete, Patricia & Cunha, Marina R., 2018, Additions to the Tanaidomorpha (Crustacea: Tanaidacea) from mud volcanoes and coral mounds of the Gulf of Cadiz and Horseshoe Continental Rise, Zootaxa 4377 (4), pp. 517-541 : 523-524

Tumidochelia uncinata (Hansen, 1913)

( Figs 4–5 )

Leptognathia uncinata HANSeN 1913: 83–85, PL.VIII, FIGS 4A– 4I . Tumidochelia uncinata LARSeN & ShIMOMURA 2007: 7–8.

Remarks. Tumidochelia uncinata was described by Hansen, (1913) based on specimens from the Ingolf Expedition, including a few illustrations. After comparing our specimens with the type material, we found no significant differences. Here we illustrate and describe the material from the GoC and HCR to complement previous works.

Material examined. Horseshoe Continental Rise—Mud volcanoes. M. Ivanov MV: station M86-5_329, USNEL boxcore, 0 1.03.2012, 35°44.338'N, 10°12.056'W, 4492 m depth, crater of MV; mud breccia covered by hemipelagic sediments, two neuters, dissected (DBUA0002217.01); station. M86-5_348, USNEL boxcore, 0 5.03.2012, 35°44.410'N, 10°12.179'W, 4497 m, mud breccia covered by hemipelagic sediments, one ♀, dissected (DBUA0002217.02). Tiamat MV: station M86-5_339, USNEL boxcore, 0 3.03.2012, 35°45.712'N, 10°21.248'W, 4551 m, crater of MV; mud breccia covered by hemipelagic sediments, one ♀(DBUA0002217.03). All coll. MRC.

Additional material examined: Holotype —♀ (ZMUC-CRU-8518), Ingolf expedition, station 36, Davis Strait, 61°50’N, 56°21’W, 2702 m depth. Paratype– juvenile (ZMUC-CRU-9275), Ingolf Expedition, station 103, 66°23’N, 8°52’W, 1090 m depth.

Diagnosis. (Female). Pereonites 2–4 about as long as wide. Pleotelson about as long as pleonites 3–5 together. Antenna article 4 with fusion line. Pereopod 1 merus and carpus spines not significantly longer than merus; dactylus and unguis together about half length of propodus. Uropod exopod shorter than endopod first segment.

Description of female DBUA0002217.02. Body ( Fig. 4A, B ) 6.5 times as long as broad, length 1.5 mm. Cephalothorax 1.2 times as long as broad, 0.9 times as long as first two pereonites. Pereonite 6 the shortest, about half as long as other pereonites. Pleon shorter than last two pereonites together, all pleonites alike. Pleotelson as long as three pleonites, distally tapering.

Antennule ( Fig. 4C ) article 1 1.7 times as long as broad, with one distal seta on outer margin. Article 2 1.1 times as long as broad, with one distal seta on inner margin and one distal seta on outer margin. Article 3 about as long as broad, 0.5 times as long as article 2, with one distal seta on inner margin. Article 4 twice as long as broad, 1.3 times as long as article 3, with subdistal seta and tuft of six distal setae.

Antenna ( Fig. 4D ) article 1 with one dorsodistal seta. Article 2 about as long as broad, with one dorsodistal seta. Article 3 3.8 times as long as broad, with fusion line, with two ventrodistal setae and one mediodistal seta. Article 4 0.6 times as long as article 3, with two distal setae. Article 5 minute, with two setae.

Mouthparts. Labrum ( Fig. 4E ) triangular, with setules. Left mandible ( Fig. 4F ) pars incisiva with four cusps, lacinia mobilis with four cusps; pars molaris distally with spines. Right mandible ( Fig. 4G ) pars incisiva with three cusps, without lacinia mobilis. Labium (not figured) bilobed, naked. Maxillule endite ( Fig. 4H ) with one subdistal seta and eleven distal denticulate spines; palp ( Fig. 4I ) with two distal setae. Maxilliped ( Fig. 4J ) palp article 1 naked, article 2 with three inner setae, article 3 with three inner setae, article 4 with five setae.

Cheliped ( Fig. 4K ) attached via sclerite. Basis naked, posterior border broadly rounded. Merus naked. Carpus about as long as basis, widening distally, with rounded ventrodistal shield, bearing one ventral seta. Propodus as long as carpus, extending dorsally beyond dactylus insertion, with two ventral setae; fixed finger with three inner setae next to dactylus insertion, cutting edge with three denticles and three inner setae. Dactylus with dorsal seta near insertion with carpus.

Pereopod 1 ( Fig. 5A ) basis 2.2 times as long as broad, naked. Ischium with one ventral seta. Merus 0.5 times as long as basis, 1.3 times as long as broad, with one ventrodistal seta and one ventrodistal long spine, 0.8 times as long as carpus. Carpus 0.8 times as long as merus, distally with microtrichia, with one ventrodistal and one dorsodistal serrate spines, both 0.8 times as long as carpus. Propodus 1.6 times as long as carpus, 2.8 times as long as broad, with dorsodistal spiniform apophysis, ventrally with microtrichia, ventral margin with one subdistal serrulate spine. Dactylus and unguis together 0.8 times as long as propodus; dactylus with dorsal and ventral distal spiniform processes near unguis insertion; unguis 1.5 times as long as dactylus, ventrally serrulate.

Pereopod 2 ( Fig. 5B ) basis 2.6 times as long as broad, naked. Ischium with ventral seta. Merus 0.4 times as long as basis, 1.2 times as long as broad, with ventrodistal spine, as long as carpus. Carpus about as long as merus, 1.2 times as long as broad, with one ventrodistal spine about as long as merus, one dorsodistal seta, and one mediodistal seta. Propodus 1.8 times as long as carpus, 3.8 times as long as broad, with dorsodistal spiniform apophysis, ventrally with microtrichia and one ventrodistal spine. Dactylus and unguis together 0.7 times as long as propodus, 1.3 times as long as broad.

Pereopod 3 ( Fig. 5C ) basis 1.9 times as long as broad, naked. Ischium with ventral seta. Merus 0.5 times as long as basis, 1.7 times as long as broad, with one subdistal short spine and one ventrodistal spine about as long as carpus. Carpus 0.9 times as long as merus, 1.4 times as long as broad, with one dorsodistal seta, one ventrodistal spine longer than carpus, one short ventrodistal spine, and one short mediodistal spine. Propodus 1.6 times as long as carpus, 2.8 times as long as broad, with dorsodistal spiniform process, one ventrodistal spine, distal and ventral margin with microtrichia. Dactylus and unguis together 0.7 times as long as propodus, dactylus with ventral setules, unguis 1.9 times as long as dactylus.

Pereopods 4–6 ( Fig. 5D ) alike. Basis 2.5 times as long as broad, with one ventral penicillate seta. Ischium with one ventral seta. Merus 1.5 times as long as broad, with one ventral seta and one ventral spine 0.5 times as long as carpus. Carpus 1.2 times as long as merus, 1.6 times as long as broad, distally with pair of ventral spines, one 0.7 times as long as propodus, the other shorter, and pair of dorsal spines, the same. Propodus about as long as carpus, 2.3 times as long as broad, with one dorsodistal spine (two on pereopod 6), one ventrodistal spine, and one mediodistal seta. Dactylus and unguis together about as long as propodus, dactylus with setules, unguis 0.3 times as long as dactylus.

Pleopods ( Fig. 5E ) alike, basis naked. Rami with distal plumose setae.

Uropod ( Fig. 5F ) biramous, protopod with dorsodistal spiniform process, naked. Endopod bisegmented, proximal segment 4.8 times as long as broad, with one subdistal penicillate seta, second segment as long as first, with one subdistal and three distal long setae. Exopod bisegmented, 0.6 times as long as endopod first segment, first segment 2.7 times as long as broad, naked, second segment as long as first, with one long and one short distal setae.

Remarks. The only observed difference between the material from the GoC and HCR, and the type specimens is the dorsal and ventral distal spiniform processes on dactylus of pereopod 1, which are present although less evident in the Ingolf specimens. Distribution and Ecology. This represents the first published records of the T. uncinata since its original description. The original material came from Davis Strait and the Iceland Plateau, at 2702 and 1090 m respectively. The specimens reported herein were recovered from mud breccia and overlaying hemipelagic sediments collected at HCR, at 4492–4551 m depth. Hence, the geographic distribution range of T. uncinata has been expanded to the south.

Figures

FIGURE 4. Tumidochelia uncinata. FeMALe SPecIMeN DBUA0002217.02: A, hAbITUS (DORSAL VIeW). B, hAbITUS (LATeRAL VIeW; PLeOPODS OMITTeD FOR cLARITY); C, ANTeNNULe; D, ANTeNNA; E, LAbRUM; F, LeFT MANDIbLe; G, RIGhT MANDIbLe; H, MAXILLULe eNDITe; I, MAXILLULe PALP;J, MAXILLIPeD;K, cheLIPeD OUTeR VIeW.

FIGURE 5. Tumidochelia uncinata. NeUTeR SPecIMeN DBUA0002217.01: A, PeReOPOD 1; B, PeReOPOD 2; C, PeReOPOD 3; D, PeReOPOD 5; E, PLeOPOD;F, UROPOD.