Metatanais spinipropodus Morales-Núñez, Pelleteri & Heard, 2016, sp. nov.
Creators: name: Morales-Núñez, Andrés G.
name: Pelleteri, Sara
name: Heard, Richard W.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Tanaidacea
Paratanaidae
Metatanais
Metatanais spinipropodus

description: Metatanais spinipropodus sp. nov.
Figs. 1−5, 6 A, 7A.
Material examined. Holotype— sub-adult ♂ (?), length about 1.65 mm, (BPBM S16458), Station (Stn) 1, North Channel (21º 30' 22.1"N; 157º 50' 57.1"W), Kāneʻohe Bay, O'ahu, Hawaii, depth 1 to 6 m, 17 Nov 1999.
Other material— one non-ovigerous ♀ (dissected), length about 2.0 mm, Stn 3, Hakipu’u Reef (21º 30' 3.9"N; 157º 50' 25.7"W), depth 1.5 to 5 m, 17 Nov 1999; one non-ovigerous ♀, length 1.6 mm. Stn 9, Channel Marker 12 (21º 27' 35.2" N; 157º 49' 22.1"W), depth 1.5 to 5 m, 19 Nov 1999; one subadult ♀ (partially dissected). Stn 1, Kawaihae Reef (20º 01' 55.5"N; 155º 50' 9.4"W), Hawaii (Big Island), depth 4 to 9 m.
Diagnosis. Cheliped with merus having simple setae on mid-ventral margin; base of fixed finger with welldeveloped, chisel-like, spiniform seta extending nearly to sub-distal margin; dactylus with stout inner spiniform seta proximally. Pereopod-1 propodus having anterior margin with sub-distal well-developed seta extending past distal margin of article. Pleopods present in male, absent in female.
Etymology. From the Latin prefix spini = referring to chisel-like, spiniform seta on the inner face of fixed finger + propodus.
Type locality. North Channel, Kāneʻohe Bay (21º 30' 22.1"N; 157º 50' 57.1"W), O'ahu, Hawaii.
Distribution. Hawaii, presently only known with certainty from the type locality.
Description. Sub-adult male, holotype.
Body (Figs. 1 A −B, 6A): Cylindrical, robust and stout, length about 1.60 mm, about 4.6 times width.
Cephalothorax (Fig. 1 A −B): About 20% of TL, with length slightly longer than pereonites 1 and 2 combined. Eye-lobes subacute, ocular lobes bearing pigmented eyes.
Pereon (Fig. 1 A): About 55% of TL, pereonites 1 and 6 each with length about 2/3 as long as pereonites-2; pereonites 2−5 about equal in length, pereonite-1 with simple seta on each dorsal lateral margin; pereonites 2−3 about equal length and width, nearly 2.3 times as wide as long; pereonites 4−5 longer than pereonites 2−3; pereonite-5 longest, length about 1.5 times as long as pereonite-1; all pereonites wider than long.
Pleon (Fig. 1 A): About 20% of TL, swollen, shorter than pereonites 4‒6 combined, all pleonites about same width and length, 4.4 times as broad as long.
Pleotelson (Figs. 1 A −B, 6A): About 5% of TL, prominent rounded posteriorly, sub-equal in length to last three pleonites combined, with two stiff setae on the dorsal margin; margins of anal plate appearing to form mid-ventral keel under terminal lobe of telson.
Antennule (Fig. 2 A): Just over half length of the cephalothorax. Article-1 massive, inflated, about 2.2 times as long as wide, with two stiff setae of unequal length on lateral margin (1 middle and 1 sub-distal), two clusters of three and four sensory-setae on lateral ventral margin (1 middle and 1 sub-distal), distoventral margin with short spiniform seta. Article-2 about 1.1 times as wide as long with stiff small seta on mid-lateral margin. Article-3 about twice as long as width, with three thick setae of varying lengths, and single thick aesthetasc.
Antenna (Fig. 2 B): Article-1 reduced, asetose, wider than long. Article-2 about 1.2 times as long as wide, with small spiniform seta on distodorsal margin. Article-3 slightly wider than long, with small spiniform seta on dorsodistal margin. Article-4 about 1.6 times as long as width, with three (one sub-distal and two distal) sensorysetae on dorsal margin. Article-5 about 1.6 times as long as width, with long simple seta on distoventral margin. Article-6 cap-article, with four long stiff setae of unequal lengths.
Mouthparts: Labrum (Fig. 2 C): Broadly rounded and finely setose. Mandibles (Fig. 2 D −E): Left: incisor entire; lacinia mobilis similar to incisor, apparently smooth (Fig. 2 D). Right: incisor with bifid tip and crenulated upper margin (Fig. 2 E). Molar process robust, with ridged, grinding surface (Fig. 2 D −E). Labium (Fig. 2 F): Bilobed, lobes equal, finely setose distally. Maxillule (Fig. 2 G): Endite with eight distal spiniform setae, outerdistal margin with simple setae; palp bearing two long terminal seta. Maxilla (Fig. 2 H): Smooth, subrectangular.
Maxilliped (Fig. 3 A): Basis deeply cleft, unfused, asetose. Endite broad, deeply cleft, unfused, inner sub-distal margin with long, stout stiff seta; outer and medial distal margins serrate. Palp: Article-1 with simple seta on outer margin. Article-2 with three (one short and curved, and two long) setulose setae on sub-distal inner margin. Article- 3 with four setulose setae on middle inner margin. Article-4 with five setulose setae distally, and one simple seta on sub-distal outer margin.
Epignath (not recovered).
Cheliped (Fig. 3 B −D): Coxal sclerite sub-quadrate, massive, reaching posterior margin of cephalothorax, strongly overlapping basis anterior mass; basis with posterior lobe much smaller than anterior mass, apparently asetose. Merus triangular, with simple seta on mid-ventral margin. Carpus about 1.2 times as long as wide, with one simple seta on dorsoproximal margin; ventral margin with small robust spiniform seta. Propodus about 1.2 times as long as wide, with small robust spiniform seta on 2/3 of ventral margin, palm with inner face having “comb row” of five to eleven, short, stout setae on sub-anterodistal margin (five in the holotype); fixed finger with dorsal margin having two simple setae on outer incisive margin and small robust spiniform seta, and strongly developed, chisel-like, spiniform seta near sub-distal inner margin (Fig. 3 D). Dactylus and unguis nearly 2/3 length of propodus, dactylus with stout spiniform seta on inner margin proximally.
Pereopod-1 (Fig. 4 A): Coxa with simple seta. Basis slender, 4.2 times as long as wide. Ischium wider than long, with single simple ventral seta. Merus about 1.9 times as long as wide, with one small distoventral spiniform seta. Carpus about 2.3 times as long as wide, with three small stout spiniform setae and simple seta distally. Propodus, four times as long as width, with spiniform seta on sub-distal dorsal margin. Dactylus and unguis combined slightly longer than half-length of propodus, unguis longer than dactylus.
Pereopod-2 (Fig. 4 B): Coxa with simple seta. Basis slender, 4.8 times as long as wide. Ischium wider than long, with single simple ventral seta. Merus about 1.8 times as long as wide, with two small distoventral spiniform setae. Carpus about 2.4 times as long as wide, with three small stout spiniform setae and simple seta distally.
Propodus about 4.6 times as long as wide, with small spiniform seta on sub-distal lateral margin. Dactylus and unguis combined slightly longer than half-length of propodus, unguis longer than dactylus.
Pereopod-3 (Fig. 4 C): Similar to pereopod-2 but shorter. Merus with one small distoventral spiniform seta.
Pereopod-4 (Fig. 4 D): Coxa asetose. Basis slender, 3.3 times as long as wide with two sensory-setae on subproximal and middle dorsal margin. Ischium wider than long, with single simple ventral seta. Merus about 1.2 times as long as wide, with two robust spiniform setae on distoventral margin. Carpus about 2.2 times as long as wide, distally with one stiff seta and four spiniform setae. Propodus about 3.8 times as long as wide, with one spiniform seta on sub-distal dorsodistal margin and two spiniform setae on sub-distal ventral margin. Dactylus and unguis combined longer than half-length of propodus, unguis shorter than dactylus.
Pereopod-5 (Fig. 4 E): Similar to pereopod-4 but longer. Basis with one sensory-seta on sub-proximal dorsal margin. Carpus with two stiff setae.
Pereopod-6 (Fig. 4 F): Similar to pereopod-5, except carpus with one stiff seta. Propodus with three pectinate spiniform setae on distodorsal margin.
Pleopods (Fig. 4 G): Hard to see, five similar, uniramous. Basal article about1.5 times as long as wide, asetose. Ramus longer than basal article, twice as long as broad, with stiff setae.
Uropod (Fig. 4 H): Basal article wider than long, uniramous, uniarticulate. Endopod article with two sensorysetae and four long stiff setae on distal margin.
Adult male: Unknown.
Non-ovigerous female: Similar to male but larger and without pleopods. Body (Fig. 5): Cylindrical, robust and stout, length about 2.1 mm, about 4.4 times width.
Cephalothorax (Fig. 5): About 20% of TL, with length nearly as long as pereonites 1−3 combined. Eye-lobes subacute, ocular lobes bearing pigmented eyes.
Pereon (Fig. 5): About 50% of TL, pereonites 1 and 6 slightly shorter than pereonites 2−5, pereonite-1 with simple seta on each dorsal lateral margin, with simple seta (no illustrated) on each lateral margin; pereonites 2−3 about equal length and width, nearly three times as wide as long; pereonites 4−5 longer than pereonites 1, 2−3 and 6; pereonite-5 length about 1.7 times longer than pereonite-1; all pereonites wider than long.
Pleon (Fig. 5): About 25% of TL, swollen, shorter than pereonites 4‒6 combined, all about same width and length.
Pleotelson (Fig. 5): About 5% of TL, prominent rounded posteriorly, sub-equal in length to last three pleonites combined, with two stiff setae on the dorsal margin; margins of anal plate appearing to form mid-ventral keel under terminal lobe of telson.
Cheliped (not illustrated): palm with inner face having “comb row” of five (left) to six (right.), stout setae on antero sub-distal margin, respectively.
Remarks. Metatanais spinipropodus sp. nov. is distinguished by its chela having the inner face of the fixed finger bearing a strongly developed, chisel-like, spiniform seta. This stout seta is absent on the three other congeners, M. bipunctatus, M. cylindricus, and M. progenitor. Further, the long, stout seta on maxillipedal endite of M. spinipropodus emanates from the inner sub-distal margin, not from the distal margin as in the other three species.
The number of setae (comb row) on the inner face of propodus appears to be an unreliable (at least in this species) character because this number varies from five to eight in females and five to eleven in males through the specimens available for this study.
Metatanais spinipropodus co-occurred with two other tanaidomorphan species, Leptochelia dubia sensu Miller (Miller 1940), and Aparatanais hawaiensis sp. nov.
description: Published as part of Morales-Núñez, Andrés G., Pelleteri, Sara & Heard, Richard W., 2016, Two new paratanaid Tanaidacea (Crustacea: Malacostraca: Peracarida) from the Hawaiian Islands, with illustrated taxonomic keys, pp. 467-492 in Zootaxa 4150 (4) on pages 468-477, DOI: 10.11646/zootaxa.4150.4.5, http://zenodo.org/record/272108