Ensayara gappai, 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 : 1853-1861

Ensayara gappai sp. nov.

( Figures 23–26 )

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: HOLOTYPE, ovig. ♀ 4.8 mm, 1 November 1999, MACN-In 38634a. PARATYPES, 1 ♀ 4.7 mm, 11 August 1999, MACN-In 38635a; 2 ovig. ♀♀ 3.98 and 4.5 mm, 24 May 1999, MACN-In 38636; 2 ♀♀ 4 and 4.25 mm, 27 May 1999, MACN-In 38637. Same location, same colls., 5 August 1999: 2 ♀♀ 3.5 and 4 mm, MACN-In 38638a; 2 ♀♀ 4.15 and 4.35 mm, MACN-In 38638b; 2 ovig. ♀♀ 4.1 and 4.7 mm, 2 ♀♀ 3.95 mm, 10 August 1999, MACN In 38639. Same location, same colls., 11 August 1999: 2 ♀♀ 4.05 and 4.5 mm, MACN-In 38635b; 2 ovig. ♀♀ 4.3 and 4.85 mm, MACN In 38635c; 7 ♀♀ 4–4.75 mm, MACN In 38635d. Same location, same colls., 1 November 1999: 2 ♀♀ 3.9 mm, MACN-In 38634b; 2 ovig. ♀♀ 3.7 and 4.25 mm, 1 ♀ 4 mm, MACN-In 38634c; 1 ovig. ♀ 3.9 mm, MACN-In 38634d; 1 ovig. ♀ 4.5 mm, 1 ♀ 4.1 mm, 1 sex indet. 4 mm, MACN-In 38634e. Same location, same colls., 10 November 1999: 2 ♀♀ 3.65 and 4.2 mm, 2 sex indet. 3.1 and 3.3 mm, MACN-In 38640a; 1 sex indet. (damaged), MACN-In 38640b. Same location, same colls., 10 February 2000: 1 ovig. ♀ (damaged), MACN-In 38641a; 2 ♀♀ 4.05 and 5.15 mm, MACN-In 38641b; 5 ♀♀ 3.9–4.75 mm, MACN-In 38641c; 2 ♀♀ 4.2 and 4.8 mm, MACN-In 38641d; 1 ♀ 4.1 mm, 1 sex indet. 4 mm, MACN-In 38641e; 2 sex indet. 3–3.6 mm, MACN-In 38641f. Same location, same colls., 14 February 2000: 4 sex indet. 2.45–3.15 mm, MACN-In 38642a; 1 ovig. ♀ 4 mm, MACN-In 38642b; 1 ♀ 3.4 mm, MACN-In 38642c. Same location, same colls., 2 May 2000: 1 ovig. ♀ 4.3 mm, 2 ♀♀ 4 and 4.6 mm, MACN-In 38643a; 2 ovig. ♀♀ 4.15 and 4.35 mm, 4 ♀♀ 4.2–4.75 mm, MACN-In 38643b; 1 ovig. ♀ 4.65 mm, 6 ♀♀ 4–4.8 mm, MACN- In 38643c; 1 sex indet. 2.75 mm, MACN-In 38643d; 1 ovig. ♀ 3.95 mm,. 2 ♀♀ 4 and 4.1 mm, MACN-In 38643e. Same location, same colls., 29 May 2000: 2 ♀♀ 4.05 and 4.75 mm, 2 sex indet. 3.3 and 3.95 mm, MACN-In 38644a; 1 ovig. ♀ 3.8 mm, 3 ♀♀ 3.7–4.05 mm, 1 sex indet. 3.6 mm, MACN-In 38644b; 2 ♀♀ 4.1 and 4.2 mm, MACN-In 38644c .

Material examined

See Type material specified above.

Diagnosis

Lateral cephalic lobe stubby. Eyes large, reddish. A1: peduncular articles 1–3 well defined; primary flagellum with seven articles. A2: flagellum with four articles. Mandibular palp, article 3 covered with minute hairs, bearing four setae on obliquely truncate apex and four setae on posterior margin. Mx1: palp biarticulate. Mxp: article 4 claviform, bearing apical unguis. Coxae 1–4 subrectangular, increasingly elongate, overlapping. Coxa 1, ventral margin convex, with two tiny submarginal setae. Coxae 2–4, ventral margin with sparse submarginal setae and numerous long marginal setae. Coxae 1–3 with ventrodistal notch bearing simple seta. Coxa 4 without corner seta, excavated and produced posteroventrally. P3: propodus palm forming right angle with posterior margin. P6: basis posteriorly lobate, with posterior margin somewhat excavated medially, weakly crenulated, with small setae inserted in notches. P7: basis posteriorly lobate, posterior margin convex medially and straight distally, entire margin crenellate, ventrally indented, with one seta on each notch. U1 and U2: inner ramus with one middorsal robust seta.

Description

Holotype ovigerous female: body length 4.8 mm. Head with lateral cephalic lobe stubby. Eyes large, ovoid, reddish in alcohol.

A1 and A2: Very short, subequal in length. A1: peduncle with three well-defined articles, article 3 small but distinct; primary flagellum 0.5 times as long as peduncle, with seven articles; accessory flagellum bearing four articles.

A2: Peduncular article 5 0.7 times as long as article 4; flagellum about 0.6 times as long as peduncular article 5, with four articles.

UL and epistome each produced separately, epistome blunt and weakly dominant in projection.

Md: Incisors broad, convex, with smooth cutting edge, weakly tooth at opposite corners; lacinia mobilis absent; accessory setal rows each with two small simple setae; molars subconical, minutely ridged, fringed with hair; palp three-articulate, attached proximal to molar, article 1 0.3 times and article 3 0.4 times as long as article 2, respectively, article 2 greatly elongate, with one apical and two subapical posterolateral setae, article 3 covered with minute hairs, bearing four setae on obliquely truncate apex and four setae on posterior margin.

LL: Outer lobes separate, lacking cones; inner lobes fused forming broad truncate line.

Mx1: Inner plate, small lobe bearing one apical short seta; outer plate with 10 terminal setal teeth moderately serrate, six long and four short, medial margin of plate hairy; palp biarticulate, with four terminal stout setae and one thin seta.

Mx2: Inner plate shorter than outer bearing four apical setae, inner margin with proximal hairs; outer plate with three strong setae and numerous thinner setae.

Mxp: Inner plate short, with three small apicofacial setae and three weak nodular setae on apex, almost fully fused; outer plate large, bearing several slightly produced tubercles on medial margin; palp four-articulate, article 3 with apical hairs, article 4 claviform, bearing apical unguis.

Coxae 1–4 subrectangular, increasingly elongate, overlapping. Coxa 1, ventral margin convex, with two tiny submarginal setae. Coxae 2–4, ventral margin with sparse submarginal setae and numerous medium marginal setae. Coxae 1–3 with ventrodistal notch bearing simple seta. Coxa 4 without corner seta, excavated and produced posteroventrally.

Gn1: Short, simple; basis about one-third as long as whole appendage; ischium swollen, posterior margin about half as long as basis, finely setose distally; merus small, with pubescence posteriorly; carpus short, with posterior margin finely setose, bearing two long and three short distal setae on posterior and anterior corners, respectively; propodus elongate, styliform, 0.8 times as long as basis, with few sparse medium setae on posterior margin and many shorter setae on proximal half of anterior margin; dactylus stout, inner margin bearing one small seta subdistally.

Gn2: Slender, chelate; ischium elongate, slightly more than half as long as basis; carpus much longer than propodus, both finely setose; propodus subquadrate, posterior margin with row of minute denticles and produced distally; dactylus small but distinct.

P3: Subchelate; carpus wide, produced anterodistally; propodus attached to distal projection of carpus, enlarged, subrectangular, width 0.7 times length, palm transverse, lined with row of facial tooth-like structures, posterodistal corner defined by two robust setae; dactylus fitting entire palm.

P4: Linear, as in gammarideans.

P5: Coxa subquadrate, slightly broader than long, bilobate; basis as long as broad, posterior margin straight, with few short setae, distally lobate, anterior margin rounded, with few short robust setae, finely setose on distal half; merus expanded posterodistally, distal lobe subrounded with few robust setae, anterior margin bearing fine setae and few short robust setae.

P6: Coxa smaller than coxa 5, rectangular, anterior lobe small; basis longer than broad, posteriorly lobate, anterior margin convex, posterior margin somewhat excavated medially, weakly crenulated, with small setae inserted in notches; merus expanded posteromedially, distal lobe subacute, anterior margin with sparse hairs, both margins with few short robust setae.

P7: Coxa smaller than in preceding appendage; basis longer than broad, larger than in P6, posteriorly lobate, anterior margin smoothly rounded and posterior convex medially and straight distally, entire margin crenellated, with one seta on each notch.

Gills sac-like, attached to coxae 2–6. Two large eggs present, but oostegites not observed.

Pl1: Peduncle stout, subrectangular, 0.6 times as long as rami, with two straight locking spines; outer and inner rami with 10 and nine articles, respectively. Ep1–Ep3: rectangular, bare, and gradually increasing in size. Ep3: posteriorly produced, forming an angle of about 45 ◦, posterodistal corner rounded.

U1: Extended somewhat beyond U2; peduncle longer than rami, with six dorsolateral robust setae, one apicolateral and one apicomedial robust seta; outer ramus slightly longer than inner bearing three dorsal robust setae; inner ramus with one middorsal robust seta.

U2: Shorter than U1, extending beyond U3; peduncle as long as rami, with two dorsolateral, one apicolateral and one apicomedial robust setae; outer ramus slightly longer than inner, bearing three dorsal robust setae; inner ramus with one middorsal robust seta.

U3: Short; peduncle as long as outer ramus, produced ventrodistally, bearing one subapical seta, one distal seta and one apical robust seta; outer ramus two-articulate, article 1 extended apicomedially, bearing two ventrodistal robust setae, article 2 prominent, almost half length of article 1, with one minute seta on apex; inner ramus as long as article 1, bearing one minute seta on acute apex.

T: Entire, short, subtriangular, slightly longer than broad, with one pair of midlateral penicillate setae and one subapical simple seta on one side.

Additional observations

Paratype females: oostegites absent, vestigial or at different developmental stages. In mature females, oostegites on coxae 2–6, and on coxae 2–4 and 6 represented by long tiny lobe and on coxa 5 (figure) bud-shaped.

T: With one pair of midlateral penicillate setae and two subapical simple setae on each side.

Genital papillae not observed.

Etymology

Named for Juan J. López Gappa, biologist at the MACN, in recognition of his generosity with optical equipment.

Remarks

The eleven known species assigned to Ensayara J.L. Barnard, 1964 are very similar to each other, being distinguished basically by slight morphological characters, or more usually, by their combination.

Ensayara gappai , the first species described from the Magellanic area, is characterized by the subchelate third peraeopod with the propodus palm forming a right angle with the posterior margin, in contrast to the other species whose palm is oblique. It can also be separated from the other taxa by a set of combined features.

The new species has in common with Ensayara dentaria Hirayama, 1985 the four long simple setae on the posterior margin of article 3 of the mandibular palp, but they differ, among other features, in that the latter species has a toothed posterior margin of the basis of the first gnathopod, a character not found in the remaining species. It shares with Ensayara entrichoma Gable and Lazo-Wassem, 1990 and Ensayara microphthalma Ledoyer, 1986 a row of dense setae on the ventral margin of coxae 2–4, though coxa 1 of the former species is also setose; Ensayara kermadecensis Kilgallen, 2009 has fifth and sixth coxae of very different shape. Another character used to distinguish species of Ensayara is the presence or absence of a simple apical seta on the inner lobe of maxilla 1; many species share with E. gappai the presence of a single distal seta on the inner lobe, whereas E. entrichoma , Ensayara ramonella J.L. Barnard, 1964 and Ensayara jumanae J.L. Barnard and Thomas, 1990 have a naked inner lobe. The posteroventral corner of the propodus palm of the third peraeopod usually bears a large robust seta and a smaller robust seta, except in E. ramonella and E. entrichoma from Bermuda; however, Lowry and Stoddart (1997) reported two robust setae for specimens of the latter species from the eastern Gulf of Mexico. The new species has large and reddish eyes with many ommatidia, whereas Ensayara carpinei Bellan- Santini, 1974 has white eyes with few ommatidia and E. microphthalma has small eyes; Ensayara ursus Kilgallen, 2009 apparently lacks eyes; according to the available information, other species possess black or dark eyes. It has been observed that the number of robust setae on the first and second uropods is intraspecifically constant, whereas it varies among some of the known species; hence, E. gappai has a middorsal robust seta on the inner rami of the first and second uropods with as in E. carpinei , Ensayara iara Lowry and Stoddart, 1983 , E. dentaria and Ensayara angustipes Ledoyer, 1978 , instead of inner rami without any robust seta as in E. jumanae , E. ramonella , E. entrichoma and E. microphthalma . The number of robust setae on the peduncle of the first and second uropods is similar in both E. gappai and E. iara , but they differ in the setosity on the outer rami, with the new species possessing a higher number of dorsal robust setae. This feature also discriminates the new species from the other species. With respect to Ensayara bifurcata Horton, 2008 , its description was based on a juvenile where the most distinct morphological character is the uniarticulate and bifurcate outer ramus of the third uropod, which is biarticulate in the remaining species.

J.L. Barnard (1964) has pointed out that the modified propodus of the third peraeopod observed only in the lysianassoid genera Ensayara and Endevoura Chilton, 1921 is probably associated with an inquilinous habit. This suggestion was subsequently supported by studies (e.g. Gable and Lazo-Wasem, 1990) providing ecological information on the environments where the specimens had been collected. The occurrence of E. gappai sp. nov. in holdfasts of the kelp M. pyrifera confirms that Ensayara includes inquiline species.

Figures

Figure 23. Ensayara gappai sp. nov. Holotype, ovigerous female: (A) lateral view; (B) head; (C, D) antennae 1, 2; (E) upper lip; (F, G) right and left mandibles; (H) mandibular palp. Scale bars: a: (A) 1 mm; b: (B) 0.2 mm; c: (C, D), d: (E–H) 0.1 mm.

Figure 24. Ensayara gappai sp. nov. Holotype, ovigerous female: (A) lower lip; (B, C) maxillae 1, 2; (D) maxilliped; (E) maxilliped outer plate; (F) gnathopod 1; (G) gnathopod 1 dactylus. Scale bars: a: (A–E, G) 0.1 mm; b: (F) 0.2 mm.

Figure 25. Ensayara gappai sp. nov. Holotype, ovigerous female: (A) gnathopod 2; (B) gnathopod 2 propodus; (C) peraeopod 3; (D) peraeopod 3 propodus; (E, F) peraeopods 4, 5. Scale bars: a: (A, C, F), c: (E) 0.2 mm; b: (B, D) 0.1 mm.

Figure 26. Ensayara gappai sp. nov. Holotype, ovigerous female: (A, B) peraeopods 6, 7; (C) pleopod 1; (D-F) uropods 1–3. Paratype, female 4.7 mm: (G) coxa 5; (H) telson. Paratype, female 4.7mm: (I) telson. Scale bars: a: (A, B, H) 0.2 mm; b: (C–F), c: (G, I) 0.1 mm.