Zeuxoides troncosoi Esquete & Bamber

Esquete, Patricia, Bamber, Roger & Aldea, Cristian, 2012, On some shallow-water Tanaidomorpha (Crustacea: Peracarida: Tanaidacea) of Chilean fjords, with description of a new species of Zeuxoides Sieg, 1980, Zootaxa 3257, pp. 38-55 : 39-45

publication ID	https://doi.org/ 10.5281/zenodo.208970
DOI	https://doi.org/10.5281/zenodo.5658956
persistent identifier	https://treatment.plazi.org/id/DE4D87DF-FFB1-FFF1-D3D2-E4E8A288FD3E
treatment provided by	Plazi
scientific name	Zeuxoides troncosoi Esquete & Bamber
status

Treatment

Order TANAIDACEA Dana, 1849 View in CoL

Suborder TANAIDOMORPHA Sieg, 1980 Superfamily TANAOIDEA Dana, 1849 Family TANAIDAE Dana, 1849 Subfamily Pancolinae Sieg, 1980 Tribe Anatanaini Sieg, 1980

Genus Zeuxoides Sieg, 1980

Zeuxoides troncosoi Esquete & Bamber , sp. nov. Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4

Material examined. Holotype: preparatory female ( MNCN 20.04/8663), and 1 neuter (paratype, MNCN 20.04/ 8664), 49º36.27ʹS 75º23.52ʹW, rocks with the kelp Macrocystis pyrifera , 5–15 m depth, 19 March 2010; Allotype: male ( MNCN 20.04/8665), 49º51.06ʹS 75º15.30ʹW, rocks with Macrocystis pyrifera , 5–15 m depth, 18 March 2010; 1 neuter (paratype, C-MNHN-11858), 49º11.45ʹS 75º23.51ʹW, rocks with Macrocystis pyrifera , 5–15 m, 19 March 2010. All coll. R. Barría, E. Newcombe, M. Hune and T. Césped.

Diagnosis. Zeuxoides with purple dorsal pigmentation. Antennular articles 2 and 3 together longer than half of the length of the first article; terminal article very short, bearing very long setae and three aesthetascs in females, nine aesthetascs in males; left mandible with triangular lacinia mobilis, right mandible with lacinia mobilis reduced to a small spine; chelae fixed finger cutting edge curved in female, bearing a proximal protuberance in males; pereopod 1 coxal spur pronounced, bearing three setae; pereopods 2 and 4 to 6 carpus with two rows of six compound spines; pereopod 3 carpus with three ventral and one dorsodistal compound spines; pleopods 1–2 basis with single inner and six outer plumose setae; pleopod 3 basis with four outer setae; uropods of seven segments including basis, terminal segment minute, bearing long setae.

Description of female. Holotype total length: 3.8 mm. Body ( Fig. 1 View FIGURE 1 A) elongated, 4.7 times as long as broad. Dorsally with purple mottling on cephalon, pereonites and pleonites (also on chelipeds and antennules); cephalothorax slightly longer than pereonites 1-3 together, subrectangular, lateral margins convex, eyes present, pigmented. Pereonite 1 shortest; pereonites 2, 3 and 6 about twice as long as pereonite 1, pereonite 4 longest, nearly three times as long as pereonite 1; (all pereonites respectively 6.8, 3, 2.4, 1.5, 1.6 and 1.8 times as broad as long). Pleon of five free pleonites, pleonites 1-3 subequal, about 2.5 times as broad as long, pleonites 2-3 with tufts of dorsolateral plumose setae; pleonites 4 and 5 shorter and narrower, about seven times as broad as long, without pleopods. Pleotelson ( Fig. 1 View FIGURE 1 B) semicircular, 1.8 times as broad as long, bearing one pair of simple and one penicillate setae laterodistally on each side, and one pair of terminal, longer setae.

Antennule ( Fig. 1 View FIGURE 1 C) first article twice as long as broad, with medial penicillate setae and long distal setae (longer than the three remaining segments together); second and third articles subequal in length, together 0.8 times as long as the first, bearing distal setae; terminal article very short, bearing very long setae (some as long as the antennule) and 3 aesthetascs.

Antenna ( Fig. 1 View FIGURE 1 D) first article about as long as broad, naked; second article 1.2 times as long as broad, dorsal margin rugose, naked; third article 1.2 times as broad as long, dorsal margin rugose, bearing distal penicillate setae; fourth article 1.3 times as long as broad, bearing long distal setae and one ventrodistal penicillate seta; fifth article 2.2 times as long as broad, about as long as preceding article, with one medial seta, ventrodistal penicillate seta and five distal setae; sixth article 1/3 as long as the preceding article, about as long as broad, with two distal setae; distal article small, cap shaped, bearing long, distal setae (some as long as the antenna).

Labrum ( Fig. 2 View FIGURE 2 A) simple, setulose. Left mandible ( Fig. 2 View FIGURE 2 C) with lacinia mobilis triangular, tooth shaped, incisor crenulated, molar ( Fig. 2 View FIGURE 2 D) triturative. Right mandible ( Fig. 2 View FIGURE 2 B) with lacinia mobilis reduced to a small spine. Labium ( Fig. 2 View FIGURE 2 E) inner lobe finely setose in distal half, distal-most setules slightly longer, outer lobe margin setulose, palp present, setose. Maxillule ( Fig. 2 View FIGURE 2 F) with microtrichia, outer margin serrated, with seven distal denticulated spines, central spine thinnest, and four subdistal setae; palp ( Fig. 2 View FIGURE 2 G) with seven plumose distal setae. Maxilla simple. Maxilliped ( Fig. 2 View FIGURE 2 I) basis with microtrichia; palp first article with one outer distal seta, second article with one outer seta, an inner row of seven setae and two setulose spines on inner distal corner, third article with regular inner row of filtering setae, fourth article elongated, three times as long as wide, with row of filtering setae on distal margin. Endite ( Fig. 2 View FIGURE 2 J) outer margin with fine denticles, distal margin with fine setae and two setulose spines. Epignath ( Fig. 2 View FIGURE 2 H) typical of genus, elongate with distal spine and finely setose margin.

Cheliped ( Fig. 3 View FIGURE 3 A, B) basis 1.4 times as long as broad, naked; merus with tuft of three ventral setae; carpus subtriangular, 1.7 times as long as broad, with tufts of ventrodistal and dorsodistal setae; chela 2.3 times as long as broad; fixed finger with row of six ventral setae, cutting edge slightly curved, with row of setae, and one seta close to insertion of the dactylus; cutting edge of dactylus with row of fine spines, claw 1/5 of total length of dactylus.

First pereopod ( Fig. 3 View FIGURE 3 C) coxa with pronounced blunt apophysis bearing two distal and two subdistal setae, but no denticulation; basis 4.2 times as long as broad, with two proximal ventral setae and one dorsodistal seta; merus 0.3 times as long as basis, 1.5 times as long as broad, naked; carpus 1.3 times as long as carpus, with one lateroventral subdistal seta; propodus 1.7 times as long as carpus, straightening distally, with medial seta and subdistal setae; dactylus 0.6 times length of carpus, with one proximal seta, unguis about twice length of dactylus.

Second pereopod ( Fig. 3 View FIGURE 3 D) basis 5.4 times as long as broad, with medial penicillate and simple setae, and ventrodistal tuft of setae; merus 1.6 times as long as broad, with tufts of ventrodistal and dorsodistal seta, and one compound, ventral spine; carpus half length of merus, with dorsodistal and ventrodistal setae, and row of 6 marginal compound spines; propodus 1.5 times as long as carpus, with one dorsal penicillate seta, four ventral setae; dactylus 0.7 times as long as propodus, bearing one small seta, unguis slender.

Third pereopod ( Fig. 3 View FIGURE 3 E) similar in proportions to second pereopod; basis bearing dorsal and ventral medial penicillate setae, and tuft of ventrodistal setae; merus ventral margin rugose distally, bearing tuft of ventrodistal setae and one tooth-like spine; carpus ventral margin rugose, bearing two ventrodistal compound spines and one dorsodistal compound spine; propodus bearing row of ventral simple setae and one long, dorsodistal seta; dactylus with slender unguis.

Fourth pereopod ( Fig. 3 View FIGURE 3 F) with oostegite; basis cylindrical, 1.8 times as long as broad, with distal setae; merus 0.4 times as long as basis, twice as long as broad, with distal setae; carpus subequal in length with merus, with two confluent ventral margins, bearing two rows of compound spines distally; propodus longer than carpus, ventral margin rugose, bearing ventral setae and one dorsodistal, long seta; dactylus and unguis fused into claw, curved, with lateral spine combs.

Fifth pereopod ( Fig. 3 View FIGURE 3 G) similar to the fourth, but bearing two ventrodistal spines on merus, and one penicillate seta dorsally on propodus.

Sixth pereopod ( Fig. 3 View FIGURE 3 H) similar to the fifth, with a ventrodistal row of leaf-like spines along the propodus.

Pleopods of pleonites 1 and 2 ( Fig. 3 View FIGURE 3 I) basis with single inner and six outer plumose setae; exopod with 33 to 35 plumose setae along outer edge; endopod with four inner plumose setae, outer edge distally with shorter, stout, spine. Third pleopod with four outer basis setae.

Uropod ( Fig. 3 View FIGURE 3 J) of seven segments including basis, all segments bearing long distal setae, distal segment less than 1/6 length of penultimate segment, bearing very long distal setae.

Male. Generally similar to female, slightly more robust. Body length of allotype ( Fig. 4 View FIGURE 4 A) 4.1 mm. Cephalothorax almost triangular in dorsal view. Antennule with nine aesthetascs. Cheliped ( Fig. 4 View FIGURE 4 B) larger in proportion than that of female, robust; carpus 1.2 times as long as broad; chela 2.3 times as long as broad, cutting edge of fixed finger with proximal protuberance; cutting edge of dactylus bearing small spines proximally. Coxal spur of pereopod 1 more robust than that of the female ( Fig. 4 View FIGURE 4 C).

Juvenile. Body length: 1.9–2.3 mm. No significant differences from female observed, other than size and setation of pleopods: pleopods of pleonites 1 and 2 basis with single inner and five outer plumose setae; endopod with two inner plumose setae. Pleopod 3 basis with three outer plumose setae, inner margin naked; endopod with two inner plumose setae.

Etymology: We are pleased to name the new species after Dr. J.S. Troncoso, eminent malacologist and enthusiastic professor, who transmits to his students his love for marine life.

Remarks: The only species of Zeuxoides recorded previously for South America was Zeuxoides ohlini (Stebbing, 1914) , found in the Falkland Islands and Tierra de Fuego ( Sieg, 1980a, partly based on his assuming Monod’s [1926] “ Tanais sp ( litoralis ?)” was Z. ohlini ). Zeuxoides troncosoi sp. nov. can be distinguished from that species in the greater reduction in the mandibles of Z. troncosoi , (which have no spines, in comparison to the spine on the left mandible in Z. ohlini , and a simpler lacinia mobilis on the right mandible), the relatively shorter segments of the antennules, in having pereonites 4 and 5 more than half as long as wide (less than half as long as wide in Z. ohlini ), and the lower number of setae of the basis of the pleopods (four or six in Z. troncosoi , eight or nine in Z. ohlini ), although the possibility of this last feature being size-related cannot be ruled out, Sieg’s (1980) material of Z. ohlini being some 25% larger than the Z. troncosoi types.

The reduction and structure of the lacinia mobilis, and the absence of a setal row on both mandibles in Zeuxoides troncosoi is only shared by the Australian species Zeuxoides mawbeyi Edgar, 2008 , and the New Zealand species Zeuxoides rimuwhero Bird, 2008 . The main differences with the former are the number or terminal spines on the maxillule (six in Z. mawbeyi , seven in Z. troncosoi ), the cutting edge of the fixed finger of the male chela (proximally convex in Z. mawbeyi ) and the number of segments of the uropods (six in Z. mawbeyi ) (see Edgar, 2008). Z. troncosoi is closest to Z. rimuwhero , although the left lacinia mobilis is rectangular, and broader in that species than in Z. troncosoi . Furthermore, these species differ in the number of aesthetascs (six in the female and eight in the male of Z. rimuwhero , three and nine respectively in Z. troncosoi ), the cutting edges of the fingers of the chela (which are straight in both sexes of Z. rimwhero , distinctly curved in the present species), the number of carpal spines (pereopods 2 and 3 have eleven and nine in Z. rimuwhero as compared to six and three in Z. troncosoi ), and the setation of the pleopods (fewer in Z. troncosoi ) (see Bird, 2008).