Rudolphia macrodactylus, Grosso, Luis E. & Peralta, Marcela, 2009

Grosso, Luis E. & Peralta, Marcela, 2009, A new Paraleptamphopidae (Crustacea Amphipoda) in the burrow of Virilastacus rucapihuelensis (Parastacidae) and surrounding peat bogs. Rudolphia macrodactylus n. gen., n. sp. from southern South America, Zootaxa 2243, pp. 40-52 : 42-48

Rudolphia macrodactylus n. sp.

( Figs. 1–5)

Material studied. Holotype male 5.34 mm. Allotype female 5.8 mm ( Fig. 1 a), Paratype female 6.1 mm.

Type locality: Rucapihuel, Prov. Osorno- X Región Chile. 40 º 35 ’S 73 º 34 ’W. In the water within burrows of Virilastacus rucapihuelensis , at 10 cm depth, 02/09/ 2002, Francisco Retamal and Erich Rudolph col.. Specimens deposited in the collection at Fundación Miguel Lillo (= FML), Argentina ( Holotype FML 0 0 980, Allotype FML 0 0 981, Paratype FML 00982 ).

Additional material: 7 males, same date, collector, habitat and locality as type material ( FML 00983 ); 15 females, 16 males and 8 inmatures, from the water of a peat bog located 10 m from the type habitat, same collectors ( FML 00984 ); 5 males and 4 females, from swampy terrain, same data as type material, E. Rudolph col. ( FML 00985 ); 1 male, 1 female and 1 inmature, from a peat bog, same data as type material, E. Rudolph col. ( FML 00986 ).

Description of male Holotype: Body colorless, not very slender. Dorsum without conspicuous setae. Head subquadrate, anterior margin sinuous. Eyes reduced. Antennae very elongated. Gn 1 shorter and more robust than second one. Pleonites deeper than peraeonites, coxal plates 1–4 deeper than 5 –7. Pleonites with posteroventral angles acute and ventral margin naked. Urosomites free and shallower than the peraeonites. Telson excavated.

A 1 ( Fig. 1 b; c), as long as body. Second article of peduncle as long as 3 / 4 of length of article 1 and twice as length of article 3. Outer flagellum with 29 articles, inner flagellum scale shaped with two terminal setae ( Fig. 1 c). First article of peduncle with strong, simple and plumose setae on distal inner surface, and 8 short stout aligned setae plus a pair of medial long, stout and plumose setae inserted behind the row on outer surface. Second article with similar setation as the article 1 and a dorsal medial groove holding a calceolus and two simple setae. Third article with two calceoli-setae complex groups, one dorsomedial with two setae, the other dorsodistal with three setae. Each outer flagellum article with 2–3 distal groups of simple setae, a dorsodistal calceolus on the 12 first articles, some of them with aesthetascs, the 17 distal articles with setae and every two articles with an aesthetasc, always smaller than calceoli. Calceolus morphology ( Fig. 5 a; b) of gammarid structural type ( Lincoln & Hurley, 1981), of the simplest configuration: distal element conformed by 23–26 overlapping transverse plates; proximal element concave and low-cut on inner margin to the distal element; receptacle, bulla and stalk clearly configured.

A 2 ( Fig. 1 d) nearly half of body length. Peduncle: articles 4–5 of equal length, both with terminal setae and a group of 2–3 setae halfway on ventral margin. Flagellum with 16 articles, all of them with dorso- and ventrodistal groups of setae and calceoli on articles 1–10, decreasing in size.

Labrum ( Fig. 1 c) oval with scarce short setae on anterior margin.

Right mandible (=Md) ( Fig. 1 f) pars incisiva with 6 teeth, 4 short and blunt, 2 stout; lacinia mobilis strong, bicuspidate, with small denticles and one row of fine setae; diastema with 5 serrated setae; pars molaris elevated with oblong triturative surface, one half ridged and incompletely surrounded by denticles; palp triarticulated, medial segment longer than the others, with row of 4 large plumose setae on ventromedial margin, pointed terminal segment with 10 similar setae on ventral margin, a similar seta near articulation. Left Md ( Fig. 1 g) similar to right one, but with 6 serrate setae on diastema and 4 teeth on lacinia mobilis.

Labium ( Fig. 1 h) outer lobes convergent with acute mandibular lobes, inner lobes depressed.

Mx 1 asymmetrical. Right Mx 1 ( Fig. 2 a) inner lobe short, distal border oblique with 8 terminal plumose setae; external lobe with 12 setae, internal one pectinate, remaining denticulate. Palp uniform width, basal segment one third of distal segment length with 7 setae on tip: 5 stout and 2 slender; 2 thin setae near tip. Left Mx 1 ( Fig. 2 b) similar to right one, but with 10 setae on external lobe and 6 slender setae on tip of palp.

Mx 2 ( Fig. 2 c–d) inner lobe elliptic, scarcely shorter than external lobe, ventral surface crossed by oblique row of 9 long plumose setae, 5 fine setae along medial margin, with 3 rows of apical plumose or pectinate setae, one dorsal row of 4 setae, one terminal row of 8 setae and a ventral row of 14 setae. External lobe with 2 rows of pectinate setae, one dorsal with 7 setae and the other of 8 setae.

Maxilliped (=Mxp) ( Fig. 2 e) internal lobe reaching half of external one, with a row of 8 setae on internal surface, with 3 apical robust stout spines alternating with 3 fine pappose setae and a pair of fine external pappose setae. External lobe with 7 blunt setae on internal margin intercalated with 4 fine bifid setae, 4 apical serrate setae. Palp 4 -articulated, with abundant setation on internal border, article 1 with 1 seta, article 2 with 25–26 plumodenticulate setae on entire internal border, 6–7 most proximal setae in a simple row and the remaining in a double row, article 3 with internal margin lobulated with 9 bifid plumodenticulated setae, internal face with 4 ( 3 aligned) bifid plumodenticulate setae. External margin with two groups of setae ( 4 – 3), an external one with 2 setae, 1 long simple and 1 bifid, and bipectinate; distal group with 4 bifid bipectinate setae, with small area with microsetae on distal angle. Dactylus small with a fine claw and 5 denticulate setae, external margin with microsetae.

Coxal plates ( Fig. 1 a): 1–4 deeper than wide with 4–5 spinules on ventral margin, plate 4 posteriorly excavated, plate 5 bilobate, plates 6 and 7 smaller, unilobate. Plates 3–7 with coxal gills, coxal gills 3 –5, 7 bilobate, coxal gills 6 elliptic. Sternal gills absent.

Gn 1 ( Fig. 2 f) coxal plate: posterior margin with only 1 seta bigger than the spinules of ventral margin; basis with 5 long setae on external face and 4 on internal one and 1 distoventral seta; ischium triangular with 1 distoventral seta; merus quadrangular with a rugose post-ventral lobe and 5 long bifid plumose setae; carpus with rugose posteroventral lobe, two groups of bifid plumose setae: proximally with 5 setae, distal with 7 setae and 3 similar setae on internal face; propodus mitten-like, palmar border flanked on both sides by 5–6 denticulated setae, with 3 bifid strong setae on palmar angle; 6 long setae on distodorsal angle, a group of 3 similar setae and oblique row of 3 setae on internal surface; posterior margin with 2 groups of 4 bipectinate setae. Palmar index ( Ruffo, 1973) = 1.81.

Gn 2 ( Fig. 2 g): slender and longer than Gn 1 with similar spination, although propodus with rugose lobe and merus without them. Palmar index = 2.39.

Peraeopods ( Fig. 3 a–f): P 3 and P 4 similar, with 4–6 long setae on anterior and posterior margins of basis. P 5 –P 7 increasing in length. Dactyls unusually long.

Pleopods ( Fig. 4 a–d) peduncles with 2 hooked retinacula, biramous, rami 10–12 - segmented; peduncle of Pl 1 with row of 4 fine setae. Pl 2 with dimorphism consisting of modifications of 3 last setae of slightly wider exopodite ( Fig. 4 c) with oblique segmentation.

Uropods ( Fig. 4 e–g) biramous, rami uniarticulate, exopodites 1–2 scarcely shorter than endopodites, Ur 3 rami of equal length. Ur 1 peduncle longer than rami, with internal row of 4 setae, rami with 3–4 internal setae.

Ur 2 resembling Ur 1 but much shorter. Ur 3 subequal in length of Ur 2, peduncle shorter than rami, with two internal setae; rami of equal length, acuminated, with 4–5 pairs of setae, each one with a bifid shorter seta and a plumose seta inserted in a fossette.

Telson ( Fig. 4 h): cleft halfway with two lateral pairs of plumose setae, and a long bipectinate seta on each lobule, 4–5 tiny bifid setae on posterior half surface.

Description of Paratype female: Similar to male but with the following differences: A 1 and A 2 longer, without calceoli, A 1 with 34 articles ( 29 in male) and A 2 with 18 articles ( 16 in male), inner lobe of Mx 1 with 10 terminal plumose setae ( 8 in male), exopodite Pl 2 without modifications in the last 3 setae. Mature females with oostegites foliaceous with simple setae ( Fig. 3 f) on peraeonites 2–4 and oostegite oval without setae on 5.

Both female specimens ( 5.8 mm and 6.1 mm) bigger than males (mean 4.74 mm).

Etymology: Rudolphia macrodactylus refers to the collector surname Erich Rudolph and the unusually length of the pereopods dactyls.

Remarks. Family status

Bousfield ( 1983: 273) provided a diagnosis of the Paraleptamphopus family group and included them within Eusiroidea. This author listed thirteen characters, only two of which differ from those of Rudolphia n. gen.: large inferior antennal sinus and plate-like coxal gills. Fenwick ( 2006) described a new genus, Ringanui , with two species, R. koonuiroa and R. toonuiiti , from South Island, New Zealand, and included them within Paraleptamphopidae .

Cladistic analysis. The result of the cladistic analysis was one most parsimonious tree ( Fig. 6) with a score of 83.