Lysianopsis ona, Alonso, 2012

Alonso, G. M., 2012, Amphipod crustaceans (Corophiidea and Gammaridea) associated with holdfasts of Macrocystis pyrifera from the Beagle Channel (Argentina) and additional records from the Southwestern Atlantic, Journal of Natural History 46 (29 - 30), pp. 1799-1894 : 1862-1870

Lysianopsis ona sp. nov.

( Figures 27–30 )

Type material

Argentina; Beagle Channel, northern Isla Despard , 54 ◦ 52 ′ S, 68 ◦ 10 ′ W, 8–12 m depth, colls. D. Aureliano and A. Ferlito, don. G. Lovrich, 11 August 1999 : HOLOTYPE, ovig. ♀ 6 mm, MACN-In 38645a. PARATYPES, 1 ovig. ♀ 5.8 mm, MACN-In 38645b; 1 ♂ 5.3 mm, MACN-In 38645c; 1 ♂ 4.75 mm, MACN-In 38645d. Same location, same colls., 24 May 1999: 1 ovig. ♀ 6.05 mm, 1 ♀ 5.9 mm, MACN-In 38646a; 4 ♂♂ 5–5.1 mm, MACN-In 38646b. Same location, same colls., 27 May 1999: 1 ♂ 4.5 mm, MACN-In 38647a; 2 ♂♂ 4 and 4.8 mm, MACN-In 38647b. Same location, same colls., 11 August 1999: 2 ovig. ♀♀ 5.9 and 6.1 mm, 1 ♀ 6.6 mm, MACN-In 38645e; 1 ♂ 5 mm, MACN-In 38645f; 3 ♂♂ 4–5.7 mm, MACN-In 38645g; 1 ovig. ♀ 7.6 mm, MACN- In 38645h. Same location, same colls., 1 November 1999 : 1 ♂ 5.8 mm, MACN-In 38648a; 1 ♀ 6.2 mm, MACN-In 38648b. Same location, same colls., 10 November 1999: 1 ♀ 5.05 mm, MACN-In 38649a; 1 ♀ 6 mm, MACN-In 38649b; 4 ♂♂ 4.2–5.75 mm, MACN-In 38649c; 5 ♂♂ 4–5.7 mm, MACN-In 38649d; 1 ♀ 6.8 mm, MACN-In 38649e; 2 ♂♂ 5 and 5.6 mm, 1 sex indet. 3 mm, 10 February 2000, MACN-In 38650, Same location, same colls., 14 February 2000 : 1 ovig. ♀ 6 mm, MACN-In 38651a; 2 ♂♂ 4 and 5 mm, MACN-In 38651b. Same location, same colls., 2 May 2000: 1 ♀ 6 mm, MACN-In 38652a; 4 ♂♂ 4.6–5.5 mm, MACN-In 38652b; 1 ovig. ♀ 4.2 mm, 1 ♀ 5.6 mm, 2 sex indet. 2.75 and 4 mm, MACN-In 38652c; 2 ♂♂ 4 and 5 mm, MACN- In 38652d; 2 ♀♀ 6 and 6.75 mm, MACN-In 38652e; 2 ♂♂ 4 and 4.4 mm, MACN-In 38652f; 4 ♀♀ 4.8–5.8 mm, MACN-In 38652g; 6 ♂♂ 3.2–5.1 mm, MACN-In 38652h.

Material examined

See Type material specified above.

Diagnosis

Epistome: dorsal margin straight and deeply incised midway; UL: strongly produced beyond epistome, lobe apically incised. Mx1: outer plate with 11 setal teeth weakly cuspidate to multicuspidate. Gn1: sexually dimorphic. P7: basis with posterior margin convex and posterior lobe rounded. U3: peduncle short, 1.5 times as long as wide; outer ramus two-articulate. T: distal margin truncate, bearing two short apical robust setae.

Description

Holotype ovigerous female: body length 6 mm, bearing setae dorsally. Head wider than long; lateral cephalic lobe strongly produced, apically rounded; eyes large, oval, dark red in alcohol.

A1: Short, 0.2 times body length; peduncular article 1 1.3 times as long as wide, bearing few sparse plumose and simple setae on both anterior and posterior margins on distal half, distal margin with long medial setae; article 2 short, 0.3 times as long as article 1, with medium to long setae on both corners; article 3 short, 0.3 times as long as article 1, with two medium subapical setae; primary flagellum seven-articulate, with tuft of ventral aesthetascs on first five articles; accessory flagellum four-articulate, reaching end of article 5 of primary flagellum.

A2: Slender, slightly longer than article1; peduncle geniculate between articles 3 and 4; article 3 medium-length, 0.8 times as long as article 4; article 4 1.4 times as long as article 5, with groups of setae on ventral anterior surface and longer setae apically; article 5 with long medial and apical setae; flagellum seven-articulate, articles bearing long setae.

Mouthpart bundle subquadrate. Epistome separated from UL; dorsally straight and deeply incised midway.

UL: Strongly produced beyond epistome into large lobe apically incised.

Md: With protuberance lobe-like on midposterior margin, incisors large, with smooth and rounded cutting edge; lacinia mobilis long, thin, pin-like, only on left Md; accessory setal row, right with four slender setae, left with three; molar setose, with vestigial distal triturating surface; palp attached proximally to molar, article 1 very short, article 2 narrow, 1.7 times as long as article 3, with row of seven apical setae, article 3 slender, narrowing distally, with minute cuticular hairs and three apical setae.

LL: Without inner lobes, mandibular process thin and long, outer lobes setose.

Mx1: Outer plate with 11 cuspidate setal teeth, varying number of cusps from two to seven; palp large, two-articulate, with serrate apical margin, bearing one seta on distolateral corner (inner plate broken).

Mx2: Outer and inner plates slender; outer plate slightly longer and thinner than inner, with setae on apex; inner plate bearing setae on medial margin and apex.

Mxp: Inner plate elongate, subrectangular, with three apical nodular setae, oblique setal row stout, with six apical pappose setae; outer plate subovate, slightly truncate distally, naked except one submarginal medial seta; palp elongate, fourarticulate, article 2 long, more than twice as long as article 3, both with setae on distal half of inner margin, article 4 (dactylus) well developed, bearing three subterminal small setae and slender apical unguis.

Gn1: Simple; coxa large, 1.8 times as long as wide, anterior margin concave, ventral margin rounded bearing sparse submarginal facial setae, posterior margin straight; basis slender, long, 0.8 times as long as articles 3–6 combined; ischium 0.3 times as long as basis, slightly narrower than basis; merus slightly longer than ischium, with posterior margin bearing patch of small setae and long setae apically; carpus subtriangular, slightly shorter than propodus, about as wide as merus, bearing long setae on posterodistal corner and short setae on anterodistal corner; propodus elongate, subrectangular, tapering distally, posterior margin somewhat sinuous, bearing two long setae medially, six medium-length setae on distal half and four short stouter setae along medial margin; dactylus simple, bearing three subterminal setae.

Gn2: Minutely subchelate; coxa large, 2.4 times as long as wide, anterior margin somewhat expanded, posterior straight, ventral margin slightly convex; basis slender, elongate; ischium long, 0.5 times as long as basis, with apical setae on posterior corner; merus 0.9 times as long as ischium, with patch of small setae and longer apical setae on posterior margin; carpus 1.8 times as long as propodus, posterior margin broadly expanded, with short setae covering distal half, anterior margin with patch of small setae; propodus 2.1 times as long as wide, with setae along anterior margin, posterior margin with setae medially and row of many minute denticles along distal part; palm slightly obtuse; dactylus as long as palm, bearing setules.

P3: Coxa large, longer than coxae 1 and 2, 2.5 times as long as wide, anterior margin slightly convex, posterior margin somewhat excavated, ventral margin almost straight, with sparse submarginal setae; basis thin, bearing one distal seta on posterior margin; ischium with setae on posterior margin; merus broader, expanded anteromedially with lobe covering carpus proximally, bearing long setae along posterior margin, one long seta and one short seta on anterodistal corner; carpus slender, 0.8 times as long as merus, bearing four pairs of short and long setae on posterior margin; propodus slender, 1.3 times as long as carpus, subequal in length to merus, posterior margin with six setae and one distal locking seta; dactylus slender, elongate.

P4: Similar to P3 except coxa with posteroventral lobe well developed.

P5: Coxa subquadrate, anterior lobe broad; basis expanded, about as long as wide, anterior margin rounded, crenulated, bearing several short and long robust setae, posterior margin with broad and quadrangular apical lobe, then margin rounded; merus produced posterodistally, posterior margin convex with one medial seta and one apical seta, anterior margin straight, setose; carpus slender, subequal in length to merus, with posterodistal and anterodistal setae, anterior margin with medial setae; propodus 0.8 times as long as merus and carpus combined, anterior margin with two pairs of short and longer robust setae and one distal locking seta; dactylus slender, elongate.

P6: Coxa small, quadrate, with small anterior lobe; basis longer than broad, anterior margin rounded, crenellate, bearing short and longer setae, posterior margin expanded and slightly indented approximately on proximal half, then margin broadly excavated, forming large distal lobe; remaining articles as in P5.

P7: Coxa small, subrounded; basis expanded posteriorly, anterior margin nearly straight, with few short and longer robust setae, posterior margin convex, slightly crenellate, bearing one short seta in notch, distal corner rounded; remaining articles as in P6, but longer.

Gills on coxae 2–6. Oostegites attached to coxae 2–5.

Ep3: Anteroventral corner rounded, posteroventral corner produced into large rounded lobe. Urosomites dorsally smooth.

U1: Slender, elongate; peduncle 1.2 times as long as rami, with seven dorsolateral, one apicolateral, two dorsomedial and one apicomedial robust seta; inner ramus slightly shorter than outer; with one medial and two dorsolateral robust setae, outer ramus bearing four dorsolateral robust setae.

U2: Shorter than U1; peduncle slightly shorter than outer ramus, with two subdistal dorsolateral, one apicolateral, and one apicomedial robust seta; outer ramus longer than inner, bearing five dorsolateral robust setae; inner ramus with two dorsolateral robust setae, bearing constriction at 0.7 times its length.

U3: Short; peduncle 1.5 times as long as wide, slightly shorter than outer ramus, with dorsolateral flange bearing one apical robust seta and one midlateral slender seta; rami lanceolate; outer ramus two-articulate, article 1 naked, article 2 0.3 times as long as article 1 bearing one apical setule; inner ramus shorter than outer, longer than article 1, bearing one medial robust seta subdistally and one apical setule.

T: Entire, subrectangular, 1.3 times as long as wide, distal margin truncate, slightly excavated, bearing two apical robust setae and two subdistal penicillate setae.

Additional observations

Paratype ovigerous female: body length 5.8 mm.

Mx1: Inner plate slender, elongate, with two apical setae; outer plate bearing setal teeth with same arrangement as in holotype, but some setal teeth with varying number of cusps.

Paratype male: with genital papillae, body length 5.3 mm. Head, lateral cephalic lobe more produced than in female; eyes larger.

A1: Slightly more setose, with peduncular article 1 more slender, 1.6 times as long as wide; primary flagellum eight-articulate.

A2: Flagellum nine-articulate.

Gn1: Propodus longer and thinner.

U3: Peduncle 1.4 times as long as wide, with three dorsolateral and one apicolateral robust seta; inner ramus bearing one subdistal robust seta and two slender simple setae.

Etymology

Named for the indigenous people who inhabited most of Tierra del Fuego Island.

Remarks

Lysianopsis Holmes, 1903 contains six known species. Lysianopsis ona sp. nov. is grouped with species having a two-articulate outer ramus of the third uropod, with article 2 well defined, such as Lysianopsis subantarctica ( Schellenberg, 1931) , Lysianopsis ozona Lowry and Stoddart, 1997 and Lysianopsis concavus Senna, 2007 . Among the remaining taxa, article 2 is weakly defined in Lysianopsis alba Holmes, 1903 and absent in Lysianopsis hummelincki (Stephensen, 1933) and Lysianopsis adelae Winfield and Ortiz, 2009 . The new species shares with L. subantarctica the upper lip projecting well beyond the epistome and the remarkably excavated posterodistal margin of the basis of the sixth peraeopod, whereas in L. ozona the upper lip is slightly projected beyond the epistome and the posterodistal margin of the basis is not excavated. In L. concavus the basis of the sixth peraeopod is slightly excavated medially, and contrary to the new species, the apical margin of the telson is very excavated.

De Broyer et al. (2007) listed two Lysianopsis species in their catalogue: Lysianopsis subantarctica and Lysianopsis tieke Lowry and Stoddart, 1983 ; however, Lowry and Stoddart, (1997) had moved L. tieke to the genus Kakanui Lowry and Stoddart, 1983 .

Lysianopsis ona is very similar to L. subantarctica , which is the only species recorded from the Magellanic area; they share other features such as the general shape of the head, gnathopods, peraeopods, third epimeron produced with posterodistal corner rounded and telson with short apical robust setae. However, the new species can be distinguished from L. subantarctica by the following morphological features: setal rows with four and three setae on right and left mandibles, respectively, versus three on both sides; presence of lacinia mobilis only on left mandible versus on right and left mandibles; article 2 of mandibular palp with distal row of seven setae versus six setae; inner plate of first maxilla with two apical setae versus naked inner plate, and outer plate with 11 setal teeth versus 10 setal teeth; different number of setae on posterior margin of propodus of first gnathopod; posterior margin of basis of seventh peraeopod almost straight distally versus somewhat excavated; more elongate second uropod with different number of robust setae; inner ramus of third uropod overreaching article 1 versus slightly shorter inner ramus. In addition, their telson differs somewhat in shape, having the base much wider than the apex and more convex sides. A few characters such as head and first uropod could not be compared because they were neither described nor illustrated.

Lowry and Stoddart (1984) redescribed and illustrated Schellenberg’s material of L. subantarctica , but they studied only males. Lowry and Stoddart (1997), who described a new species ( L. ozona ), and diagnosed and / or redescribed L. alba , L. hummelincki and L. subantarctica , concluded that the propodus of the first gnathopod was the only secondary sexual character found in males. In the present study, males and females differed in the shape of the propodus of the first gnathopod and other subtle features such as eye size and shape of the lateral cephalic lobe.

The new species, Lysianopsis ona from the Beagle Channel, is the first species of the genus reported from holdfasts of the kelp M. pyrifera .

Figures

Figure 27. Lysianopsis ona sp. nov. Holotype, ovigerous female: (A) lateral view; (B) head; (C, D) antennae 1, 2; (E) epistome and upper lip; (F, G) right and left mandibles; (H) mandibular palp. Scale bars: a: (A) 1 mm; b: (B) 0.2 mm; c: (C–E), d: (F–H) 0.1 mm.

Figure 28. Lysianopsis ona sp. nov. Holotype, ovigerous female: (A) lower lip; (B) maxilla 1; (C) maxilla 1 outer plate; (D) maxilla 2; (E) maxilliped; (F) gnathopod 1; (G) gnathopod 1 dactylus; (H) gnathopod 2; (I) gnathopod 2 propodus. Scale bars: a: (A, B, D, E, I), d: (G) 0.1 mm; b: (C) 0.025 mm; c: (F), e: (H) 0.2 mm.

Figure 29. Lysianopsis ona sp. nov. Holotype, ovigerous female: (A–E) peraeopods 3–7. Scale bar: 0.2 mm.

Figure 30. Lysianopsis ona sp. nov. Holotype, ovigerous female: (A) epimeron 3; (B–D) uropods 1–3; (E) telson. Paratype, ovigerous female 5.8 mm: (F) maxilla 1. Paratype, male 5.3 mm: (G) gnathopod 1 propodus. Scale bars: a: (A) 0.2 mm; b: (B–G) 0.1 mm.