Ringanui koonuiroa, Fenwick, Graham D., 2006

Fenwick, Graham D., 2006, Ringanui, a new genus of stygobitic amphipod from New Zealand (Amphipoda: Gammaridea: Paraleptamphopidae), Zootaxa 1148, pp. 1-25 : 5-14

Ringanui koonuiroa n. sp.

( Figs 1–5 )

Calliope subterranea .— Chilton, 1882b: 177 –179, pl. 9, figs 1–10 (part, male only).

Material examined

Holotype: adult ɗ, 4.3 mm, NMNZ CR.10013 (wet, and 5 slides), Templeton, Canterbury 43º33.11´S, 172º26.38´E, coll. L. Sinton, 2 Sept 1982, taken in net from Well 10, 20 m deep. Paratypes: adult Ψ, 4.2 mm, NMNZ CR.10014 (wet and 6 slides), Templeton, Canterbury, 43º33.11´S, 172º26.38´E, coll. L. Sinton, 2 Sept 1982, taken in net from Well 10, 20 m deep. Templeton, Canterbury: 1 Ψ 4.1 mm long, 1 ɗ, 4.0 mm, 1 juvenile, 2.8 mm, NMNZ CR.10016, coll. G.D. Fenwick, 28 Jan 1986, from net sample in Well 10, 24 m depth; 2 females, 3.3, 5.2 mm, 1 ɗ, 3.6 mm long, 8 indet., 1.8–4.4 mm long, NMNZ CR.10015, coll. G.D. Fenwick, 12 Oct 1985, net sample, Well 10; 1 ɗ, NIWA 3441, P­1429 (wet), coll. G.D. Fenwick, 1 July 1986, among cages in Well 4; 1 Ψ, 5.0 mm, 2 males, 2.8, 4.0 mm, 1 indet., 2.8 mm long, AM P.68198 (wet), coll. G.D. Fenwick, 20 Dec 2001, net sample from Well 2, 18 m depth; Temuka (Gresham’s well), Canterbury, New Zealand (44º 14.5´S, 171º 17.9´E): 1 Ψ, NIWA 3442, P­1430 (wet), coll. M. Scarsbrook, 15 Sept 1998.

Additional material: Templeton, Canterbury, New Zealand: 1 Ψ, coll. G.D. Fenwick, 22 July 1998, in net from Well 10, 20 m depth [ NIWA GW 6­2]; 1 Ψ, coll. L. Sinton, 22 Sept 1982, taken in net from Well 3, 18 m depth [ NIWA GW 7­1]; 1 Ψ, 1 ɗ, coll. L. Sinton, 20 Sept 1982, taken in net from Well 1, 18 m depth [ NIWA GW 10­1]; 1 indet., coll. G.D. Fenwick, 10 Feb 1999, net sample from Well 8 [ NIWA GW 91­6]; 1 ɗ, coll. G.D. Fenwick, 3 Feb 1999, net samples from wells upstream of disposal site, c. 20 m depth [ NIWA GW 55­7]; 2 indet., coll. M. Scarsbrook, 12 May 2000, in Well 4, 20 m depth [ NIWA GW 267­4]; 1 Ψ, coll. M. Scarsbrook, 1 May 2000, in Well 11, 23 m depth [ NIWA GW 268­1]; Burnham, Canterbury, New Zealand: 1 ɗ, coll. L. Sinton, 5 Aug 1982, in net samples from Well 11, c. 20 m depth [ NIWA GW 19­3]; Orari, Canterbury, New Zealand (44º07.7´S, 171º20.0´E): 1 ɗ, NZAC Ph 115­b, coll. G. Kuschel & J. McBurney, 22 March 1973, pumped from open well, 4.8 m deep, water temperate 13º C.

Diagnosis

Small in size (<5.0 mm long); maxilla 1 inner plate with 4 large, plumose SS medially; maxilla 2 outer plate with few (<5) setules distolaterally; maxilliped outer plate extending well beyond distal end of palp article 1 and beyond midpoint of article 2; maxilliped palp article 1 lateral margin naked, article 2 lateral margin with 1 slender seta distolaterally, article 4 with 2 setules laterally and none medially; gnathopod 1 coxa 1 as long as wide, anterior margin straight, broadly rounded distally; gnathopod 1 article 6 posterior margin evenly convex, largest defining RS more than half as long as dactyl and longer than article 6 width; gnathopod 2 article 6 shorter than gnathopod 1 article 6, gnathopod 2 palm defined by 3–4 short RS; pereopod 5 coxa posterior lobe larger than anterior lobe; pereopod 6 coxa anterior lobe obsolescent; pereopods 6–7 article 2 with broad, evenly rounded lobe posterodistally; pereopods 5–7 dactyl posterior margins naked; pleopod rami subequal, of 7–9 articles; uropods 1–2 peduncles lacking RS laterally, outer rami conspicuously shorter than inner; uropod 3 peduncle subequal in length to rami; telson tapering distally, lobes subacute.

Description (holotype)

Head and body colourless or unpigmented. Head with well developed rostrum; lateral cephalic lobes well developed, rounded; eyes absent. Pereonites dorsally smooth, naked; pleon dorsally naked; urosome dorsally naked.

Antenna 1 calceoli present on peduncle articles 2–3, and on proximal flagellum articles; peduncle 1–1.1 x flagellum length; article 1 1.3 x length of article 2; article 3 0.4 x length of article 2; accessory flagellum minute, shorter than primary flagellum article 1, 1­ articulate. Antenna 2 1 x as long as antenna 1; article 4 0.9– 1 x length of 5; flagellum 1 x length of peduncle articles 4–5; calceoli present on flagellum.

Upper lip entire, broadly rounded. Mandible palp attached adjacent to molar, article 1 distinctly longer than wide, article 3 moderately curved, falciform, 0.8 x length of article 2, palp setal formula: 4 D2­setae, 6 D3­setae, 5 E3­setae; molar well developed, distinct triturating surface; incisor large, 7 strong cusps; lacinia mobilis well developed, toothed; strongly asymmetrical. Lower lip inner lobes lacking; outer lobes with dense fine setules. Maxilla 1 palp extending beyond outer plate RS, article 2 2.5 x longer than wide, widened distally, 4 RS distally, 1 SS laterodistally; outer plate subrectangular, slightly longer than wide, distal margin transverse, bearing 10 dentate RS, outer margin naked, inner margin lacking SS, some setules; inner plate about half as long as outer, ovate, 1.4 x longer than wide, medial setae only, 4 plumose SS inserted submedially. Maxilla 2 outer plate length 2–2.1 x width, lateral margin with setules grouped distally, distal margin oblique, armed with 10 large SS, medial margin naked; inner plate 1.7 x longer than wide, distal margin narrowly rounded, discontinuous with medial margin, bearing 7 simple SS,>20 marginal setules, and 3 plumose SS submarginally. Maxilliped inner plate distally subrectangular, 2 x longer than wide, extending to 0.5 of outer plate, distal margin armed with 2 RS and 4 SS, medial margin with 1 SS; outer plate reaching midpoint of palp article 2, outer margin broadly convex, mediodistal corner rounded, 1.6 x longer than wide, with a row of 4 RS, decreasing in length medially, changing to 1 simple RS medially, inner margin continuous with distal margin, with 1 SS and 2–3 RS; palp article 1 with 0 distolateral SS, 0 SS mediodistally, article 2 1.4 x longer than 1, moderately setose medially, 1 SS distolaterally, 0 setae along lateral margin, article 3 0.9 x length of article 2, 2 x longer than wide, article 4 inserted subterminally, 0.4 x length of article 3 (excluding distal nail or spine), 2 x longer than basal width, medial margin straight, with 1 SS, outer margin bearing 1 SS, nail present, 0.7 x article length.

Coxal gills present on pereonites 2–6 or 7, pediculate, ovate, thick, opaque; surface unridged. Accessory coxal gills absent. Sternal gills absent. Gnathopod 1 coxa widened distally, distal width 1.4 x proximal width, 0.9 x deeper than long, extending to 0.4 x length of article 2, anterior margin straight, anterodistal corner rounded, with marginal SS anteroventrally only, submarginal SS lacking; article 2 3.1 x longer than wide, markedly constricted proximally; article 3 0.2 x length of 2; article 4 1.4 x length of 3; article 5 short, 0.4 x length of article 2, subrectangular, 1 x as long as wide, with posterior lobe completely separating articles 4 and 6, anterodistal margin with 0 SS, posterodistal margin with 6 SS; article 6 very large, subovate, narrowed distally, 1.3 x length of article 2, 3.5 x length of article 5, 1.7–1.8 x longer than wide, posterior margin (proximal to palm) 0.15 x length of article length, naked; palm strongly oblique, 30 degrees to article 6 axis, convex, not excavate, irregular, palm defined by 3 RS, simple, longest defining spine 0.5 x article 6 length; dactyl slender, unconstricted, moderately curved, as long as palm, anterior margin lacking ornamentation, posterior margin evenly concave, with 0 posterior cusps or setules, 0 facial SS subterminally, lacking comb­like ridges, tip simple, pointed. Gnathopod 2 subchelate, moderately developed, almost as long as, and as stout as gnathopod 1; coxa rounded, narrowed distally, distal width 0.7 x proximal width, anterodistal corner rounded, anterior margin convex, with marginal SS ventrally only, submarginal setae lacking; article 2 3.5 x longer than wide; article 3 normal length, 0.3 x length of 2, 0.6 x length of article 5; article 4 1.1 x length of 3; article 5 medium length, 0.6 x length of article 2, subtriangular, 1.8 x as long as wide, anteriodistal corner with 0 SS, with 15–20 SS posteriodistally; article 6 moderately developed, subovate, narrowed distally, 0.8 x length of article 2, 1.3 x length of article 5, 1.6 x longer than wide, posterior margin proximal to palm 0.3–0.4 x article length; palm oblique, 30 degrees to article axis, sinuous, not excavate, irregular, posterodistally unproduced, defined by 3 bifid RS, largest 0.05 x length of article 6; dactyl slender, moderately curved, tip simple, blunt, as long as palm, anterior margin lacking ornamentation, posterior margin evenly concave, with 0 setules or cusps, lacking any fine comb­like rows.

Pereopod 3 coxa distally subquadrate, length (depth) 1.7 x width; article 2 linear, 1 x as long as coxa, 4 SS posteriorly; article 3 0.2 x as long as article 2; article 4 0.5 x length of article 2, produced anterodistally; article 5 0.7 x length of article 4; articles 4–6 sparsely setose; article 6 1.3 x length of article 5, 1 RS, and 3 SS along posterior margin, 0 RS, and 2 SS anteriorly; dactyl slender, slightly curved, 0.4 x length of article 6, posterior margin simple, tip simple. Pereopod 4 coxa subovate, as deep as coxa 3, 1.9 x depth of coxa 5, extending to 0.6 x length of article 2, 1.3 x deeper than wide, distal margin rounded, posterior margin concave, moderately excavate; articles 2–7 similar to pereopod 3 in proportions and setation of articles. Pereopod 5 coxa 1.8–1.9 x wider than deep, anterior lobe as deep as posterior, posterior lobe as broad as anterior lobe, posterior lobe with sparse SS; article 2 inflated, 1.6–1.7 x longer than wide, tapering distally, posterior margin rounded, with sparse coarse teeth, posteriodistally produced into short, broadly rounded lobe, anterior margin with few slender and RS; article 4 0.5 x length of article 2, posterodistally produced to overhang article 5, for about 0.1–0.2 of its length; article 5 1–1.1 x as long as article 4; article 6 1.5–1.6 x length of article 5; articles 4–6 with sparse RS; dactyl posterior margin with 2 fine setules. Pereopods 6–7 similar to pereopod 5 in article shape and setation; successively longer. Pereopod 6 coxa posterior lobe reaching to about 0.3 of article 2, with 1 SS and 0 RS; article 2 expanded, width 0.7 x length, subovate, tapered distally, anterior margin with few RS, posterior margin rounded, serrate, with several SS, posterodistally produced to overhang article 3 for about 0.6 of its length, lobe broadly rounded. Pereopod 7 coxa lacking anterior lobe, posterior lobe with 1 SS and 0 RS; article 2 expanded, width 0.7 x length, subovate or subquadrate, tapered distally, anterior margin with few RS, posterior margin rounded, serrate, with several SS, posterodistally produced to overhang article 3 for about 0.5–0.6 of its length, lobe broadly rounded.

Epimeron 1 ventral margin naked; posterior margin weakly convex, naked; posterodistal corner subquadrate; naked. Epimeron 2 ventral margin naked; posterior margin straight, naked. Epimeron 3 ventral margin naked; posterior margin convex, naked; posteroventral corner quadrate; lacking any cusps or teeth. Pleopods biramous, stout, rami multi­articulate, strongly setose. Pleopod 1 peduncle 2 x longer than wide, with pair of coupling hooks only; inner ramus with 7–8 articles, article 1 2.6 x longer than wide, 2 simple SS medially, plus pair of distal plumose SS; outer ramus with 7 articles, article 1 1.8–1.9 x longer than wide, 1 plumose SS medially, lacking setae laterally other than distal plumose pair, outer ramus 0.8–0.9 x as long as inner, pleopods 2–3 similar in structure and size to pleopod 1. Pleopod 2 outer ramus 8 articulate, 1 x as long as inner; inner ramus with 7–8 articles. Pleopod 3 outer ramus 8 articulate, 0.9 x as long as inner; inner ramus with 9 articles.

Uropod 1 reaching to distal end of uropod 3 rami; peduncle lacking RS posteroventrally between rami, with 2 RS mediodorsally, 1 RS dorsolaterally, terminal dorsolateral RS larger than others; inner ramus 0.7 x length of peduncle, with 0 RS laterally, 3 medially, and 4 distally; outer ramus 0.7–0.8 x length of inner, with 2 RS laterally, 3 medially, and 2 distal RS. Uropod 2 exceeding distal end of uropod 3 peduncle; peduncle slender, 3.4 x longer than wide, lacking RS posteroventrally between rami, with 3 RS mediodorsally, 1 RS dorsolaterally, terminal dorsolateral RS absent; inner ramus 0.8 x length of peduncle, with 0 RS laterally, 2 medially, and 2 distally; outer ramus 0.7 x length of inner, with 2 RS laterally, 0 medially, and 2 distal RS. Uropod 3 extending as far as uropods 1–2, biramous, rami subequal; peduncle slender, 1.6 x longer than wide, with 3 RS mediodorsally, 0 RS dorsolaterally, terminal dorsolateral RS absent; inner ramus 1 x length of outer ramus, uniarticulate, with 1 RS laterally, and 2 medially, terminally slender, 2 subterminal SS and, 0 RS terminally; outer ramus 1.1 x length of peduncle, uniarticulate, with 2 RS laterally and 2 medially, terminally slender, naked; lateral and medial RS on both rami accompanied by long, plumose SS; rami tips naked and heavily scleritised.

Telson subrectangular, tapered, lateral margins straight, 0.9 x as long as wide, emarginate, 0.25 of its length, lobes distally obtuse, with 1 setule, terminally on each lobe, and 0 SS laterally; thin, laminar in lateral view.

Female: The only notable difference between the female and the holotype male was the presence of oostegites on coxae 2–5. These oostegites were fleshy and opaque, extending as far as the distal end of pereopods’ second articles, broadly subtriangular to subovate in shape, and naked except for a few (0–5) very short SS spaced around their margins.

Va r i a t i o n

Examination of other specimens showed that gills tend to vary in size between individuals, perhaps due to differences in fixation and preservation of specimens, extending to the distal ends of pereopod second articles in many specimens. The telson also varies slightly in its length relative to width, appearing slightly more elongate than in the holotype in some specimens. Note that article 3 of the mandibular palp is invariably strongly tapered and strongly curved like that of R. toonuiiti described and illustrated below; the illustration of the holotype’s palp article 3 shows it in an oblique perspective.

Etymology

The name koonuiroa is derived from Maori koonui (thumb) and roa (long) and refers to the very large robust seta defining the proximal end of the gnathopod 1 palm, which is characteristic of this species.

Distribution

Canterbury: Templeton, Burnham, Temuka, Orari.

Remarks

Chilton’s 1882b male differed appreciably from the 1894 male in the morphology of both gnathopods, suggesting the possibility of two species. However, most specimens with long­spined first gnathopods were smaller than those with the 1894­ type of gnathopod 1 (Fig. 6) and the two forms were often found in the same collection, suggesting that they might be juvenile and adult, as Chilton (1894) appeared to believe. Evidence from the material on hand enabled this to be investigated more carefully. First, specimens with the greatly enlarged gnathopod 1 palmar defining spine (robust seta) included both females with oostegites and males, and their body lengths overlapped with amphipods with the other gnathopod 1 type (i.e., the larger R. toonuiiti ) (Fig. 6). Second, there was no evidence of a transitional form of gnathopod 1 (i.e. the large spine was consistently about as long as article 6 was wide). Third, the collection included one gravid female with long­spined first gnathopods. Fourth, the only other gravid female in the entire collection had short­spined gnathopods and her brood comprised three juveniles, all with first gnathopods very similar to their mother’s (see below). For these reasons, two species are clearly warranted.

Figures

FIGURE 1. Ringanui koonuiroa holotype ♂, 4.3 mm long: whole animal (top), antenna 1 and antenna 2.

FIGURE 2. Ringanui koonuiroa holotype ♂, 4.3 mm long: mouthparts.

FIGURE 3. Ringanui koonuiroa holotype ♂, 4.3 mm long: gnathopods 1, 2.

FIGURE 4. Ringanui koonuiroa holotype ♂, 4.3 mm long: pereopods 3 – 7.

FIGURE 5. Ringanui koonuiroa holotype ♂, 4.3 mm long: pleopods 1 – 3, uropods 1 – 3, telson.