Paragathotanais crateris, Esquete & Cunha, 2018

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 : 519-523

Paragathotanais crateris sp. nov.

( Figs. 2–3 )

Material examined. Holotype—³ ( MNCN 20.04/11444), cruise M86-5, station M86-5_369, USNEL boxcore, HCR, Abzu MV, 0 8.03.2012, 35°45.045'N, 10°19.018'W, 4550 m depth crater of MV; mud breccia covered by hemipelagic sediments.

Allotype— neuter (MNCN 20.04/11445), cruise M86-5, station M86-5_329, USNEL boxcore, HCR, M. Ivanov MV, 0 1.03.2012, 35°44.338'N, 10°12.056'W, 4492 m depth, crater of MV; mud breccia covered by hemipelagic sediments. All coll. MRC.

Further paratypes —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, one ♂, one ♀ (DBUA0002216.01); station. M86-5_388, USNEL boxcore, 11.03.2012, 35°44.327'N, 10°11.965'W, 4485 m, crater of MV; mud breccia covered by hemipelagic sediments, one ♀, three neuters (DBUA0002216.02); station M86-5_407, USNEL boxcore, 14.03.2012, 35°44.342'N, 10°12.056'W, 4507 m, crater of MV, mud breccia, one neuter dissected, one ³ dissected (DBUA0002216.03). All coll. MRC.

Etymology. From the Latin noun crateris –crater, as all specimens were found within the crater of mud volcanoes; noun in apposition

Diagnosis. Cephalothorax about as long as pereonites 1–2 together. Antenna article 3 without seta. Maxilliped basis without setae, endite with two tubercles. Pereopods 4–6 dactylus with two distal spines. Uropod endopod more than twice as long as basis.

Description of male DBUA0002216.01A. Body ( Fig. 2B ) slender, 8.4 times longer than broad, length 4.2 mm. Cephalothorax about as long as pereonites 1–2 together, 1.7 times as long as broad. Pereon 0.6 times as long as body; pereonite 1 0.9 times as long as broad, pereonites 2 and 3 about as long as broad, pereonites 4 and 5 1.3 times as long as broad, pereonite 6 1.1 times as long as broad. Pleonites ( Fig. 2C ) all similar, pleonite 6 with pair of marginal setae. Pleotelson ( Fig. 2C ) distally tapering, with distal pair of setae.

Antennule ( Fig. 2D ) article 1 2.3 times as long as broad, with one simple and three penicillate setae on outer margin. Article 2 0.9 times as long as broad, outer margin distal corner with one simple and two penicillate setae, inner margin distal corner with one simple seta. Article 3 0.8 times as long as broad, inner margin distal corner with one simple and one penicillate setae. Article 4 0.9 times as long as broad, with distal tuft of seven simple setae.

Antenna ( Fig. 2E ) basal article fused to cephalothorax. Article 2 with one dorsodistal seta. Article 3 about as long as broad, naked. Article 4 1.3 times as long as two preceding articles, distally with two penicillate and one simple setae. Article 5 0.3 times as long as article 4, distally narrowing. Terminal article minute with two setae, one longer.

Mouthparts. Labrum ( Fig. 3A ) semicircular, with setules. Left mandible ( Fig. 3B ) pars incisiva with subdistal and distal lobes, lacinia mobilis spiniform with blunt tip; pars molaris distally tapering with setules. Right mandible ( Fig. 3B ) as left but without lacinia mobilis, pars incisiva distally crenulated. Maxillule ( Fig. 3C ) endite with eight distal spines, palp not recovered.

Maxilliped ( Fig. 3A ) endites with distal pair of tubercles; palp article 1 naked, article 2 with three inner setae, article 3 with two inner setae, article 4 with one subdistal and five distal setae.

Cheliped ( Fig. 3D ) attached via pseudocoxa. Basis 0.7 times as long as broad, naked. Merus naked. Carpus 2.4 times as long as broad, with ventral seta. Chela about as long as carpus, fixed finger with three setae near cutting edge and one ventral seta; dactylus naked.

Pereopod 1 ( Fig. 3E ) coxa with seta. Basis 5.7 times as long as broad, naked. Ischium with ventral seta. Merus 0.3 times as long as basis, with one ventrodistal seta. Carpus 1.4 times as long as merus, with one ventrodistal seta and one dorsodistal seta 0.6 times as long as propodus. Propodus 1.1 times as long as carpus, ventral margin with subdistal spine, dorsal margin with spiniform apophysis. Dactylus and unguis together as long as carpus, unguis about as long as dactylus.

Pereopod 2 ( Fig. 3F ) basis narrower proximally, naked. Ischium with ventral seta. Merus 0.8 times as long as basis, ventrodistal margin with one short and one long seta. Carpus 1.3 times as long as merus, distally with three long setae and one short seta. Propodus 1.1 times as long as carpus, ventral margin with one subdistal spine, dorsal margin with spiniform apophysis. Dactylus and unguis together about as long as propodus, unguis about as long as dactylus.

Pereopod 3 ( Fig. 3G ) coxa with seta. Basis proximal half narrower, with dorsal penicillate seta. Ischium with ventral seta. Merus 0.4 times as long as basis, with ventrodistal seta, 0.8 times as long as carpus. Carpus 1.3 times as long as merus, with two ventrodistal and one dorsodistal setae. Propodus 1.3 times as long as carpus, distally with microtrichia, with dorsal apophysis and ventral subdistal short spine. Dactylus and unguis together about as long as propodus, unguis about as long as dactylus.

Pereopod 4 ( Fig. 3H ) basis proximal half narrower, with one ventral penicillate seta. Ischium naked. Merus 0.3 times as long as basis, with pair of ventral setae. Carpus 1.1 times as long as merus, with three distal setae and one dorsodistal seta. Propodus 1.1 times as long as carpus, with three distal setae and dorsodistal spiniform apophysis. Dactylus and unguis together 1.2 times as long as propodus, dactylus with two distal spines about 0.5 times as long as unguis.

Pereopods 5 ( Fig. 3I ) and 6 similar to pereopod 4, but ischium with one seta, carpus with three setae only, propodus with four distal setae.

Pleopods ( Fig. 3J ) alike. Basis naked. Rami with row of distal setae only.

Uropod ( Fig. 3K ) Exopod slightly marked, with very long seta. Endopod 2.6 times as long as broad, with one medial penicillate seta, distally with one penicillate and four simple setae.

Distinctions of neuter MNCN 20.04/11445. Antennule ( Fig. 2F ) more slender and with fewer setae than in male. Article 1 2.9 times as long as broad, naked. Article 2 0.3 times as long as article 1, about as long as broad, with one distal seta. Article 3 0.8 times as long as article 2, 1.2 times as long as broad, with two distal setae. Article 4 1.2 times as long as article 3, 2.2 times as long as broad, with four distal setae. Pleopods absent.

Remarks. Paragathotanais vikingus Bird, 2010 from waters off Southeast Iceland is very similar to the newly described species in having a pair of marginal setae on pleonite 6, pereopods 4–6 dactylus with two equal distal spines, uropod with slightly marked exopod process; however, differs from P. crateris sp. nov. in having a more slender antennule on males, antenna article 2 without seta, mandibular pars molaris with no setules, maxilliped basis with setae, endite with setae instead of tubercles, chela fixed finger with three low teeth, and pereopods 4–6 carpus with row of spinules and dactylus with setules.

The presence of two distal spines on dactylus on pereopods 4–6 is a character shared with P. triunguisus Larsen & Bird, 2013 from Antarctic waters; this species differs from P. crateris in the presence of ventral spines on cheliped dactylus and pereopods 1–3 merus and carpus with very short setae. An undescribed, partially illustrated species from the Gulf of Mexico, Paragathotanais sp. A (see Larsen 2005), presents dorsal and ventral spines on dactylus of pereopods 4–6, but the cephalothorax is only 1.3 times as long as broad, and all pereonites are as long as broad or shorter.

Paragathotanais spinosus Larsen, 2005 from the Gulf of Mexico differs from P. crateris in having a proportionally shorter antennule, maxilliped endite without tubercles, cheliped basis proportionally shorter, pereopods 4–6 with one long distal spine and two more proximal, smaller spines and shorter uropod endopod

Paragathotanais gracilis Bird & Holdich, 1988 from the Northeast Atlantic has a similar labrum and a slender cheliped carpus, but differs from P. crateris in having only one distal spine on dactylus of pereopods 4–6 and accessory subdistal spines. Furthermore, it presents an antenna article 2 with spinules, maxilliped endites with processes and spinules but no tubercles, and cheliped dactylus with one seta.

Paragathotanais nanus Bird & Holdich, 1988 and Paragathotanais robustus Bird & Holdich, 1988 , also from the Northeast Atlantic have not spines on pereopods 4–6 dactyli. Both species also differ from P. crateris in having the female antennule article 2 distinctively longer than article 3, maxilliped endites with setae instead of tubercles, and cheliped carpus as long as broad, inter alia.

Paragathotanais insolitus Guerrero?Kommritz, 2003, from the Angola Basin shares with the new species the presence of paired tubercles on maxilliped endites and slender cheliped carpus, but is different from P. crateris in having pereopods 4–6 dactyli without spines, and uropod protopod as long as endopod, with tubercle.

Distribution and Ecology. Paragathotanais crateris was recovered from mud breccia and the overlaying hemipelagic sediments in two mud volcanoes of the Horseshoe Continental Rise: Abzu and Ivanov (4485–4507 m depth).

Figures

FIGURE 2. Paragathotanais crateris sp. nov. FeMALe PARATYPe DBUA0002216.01A: A, hAbITUS (DORSAL VIeW); C, PLeON AND PLeOTeLSON(VeNTRAL VIeW);F, ANTeNNULe;G, ANTeNNA.HOLOTYPe MALe MNCN20.04/11444:B, hAbITUS (LATeRAL VIeW);D, ANTeNNULe; E, ANTeNNA.

FIGURE3. Paragathotanaiscrateris sp. nov. PARATYPeDBUA0002216.03A:A, LAbRUM ANDMAXILLIPeD;B, LeFT MANDIbLe pars incisiva OF RIGhT MANDIbLe; C, MAXILLULe; D, CheLIPeD. DBUA0002216.03: E, PeReOPOD 1; F, PeReOPOD 2; G, PeReOPOD 3; H, PeReOPOD 4; I, PeReOPOD 5; J, PLeOPOD;K, UROPOD.