Fuegiphoxus Barnard & Barnard, 1980

Chiesa, Ignacio L. & Alonso, Gloria M., 2011, Redescription and generic assignment of Fuegiphoxus uncinatus (Chevreux, 1912) (Crustacea, Amphipoda, Phoxocephalidae), Zoosystema 33 (2), pp. 219-233 : 221-230

Genus Fuegiphoxus Barnard & Barnard, 1980

TYPE SPECIES. — Parharpinia fuegiensis Schellenberg, 1931 by original designation.

DIAGNOSIS EMENDED FROM BARNARD & BARNARD (1980) AND BARNARD & KARAMAN (1991)

Rostrum unconstricted, fully developed. Eyes present. Antenna 1, peduncular article 2 short, ventral setae confined apically, moderately spread. Antenna 2, peduncular article 1 not ensiform; facial robust setae on article 4 in three or more rows, with some setae thick and some setae thin;

article 5 shorter and rather narrower than article 4. Mandibles, right incisor with three teeth; right lacinia mobilis bifid, flabellate, left lacinia mobilis with four teeth; molar not triturative, small, bearing three robust setae, one of those elongate and serrate; palpar hump small, article 1 of mandibular palp short to elongate, article 2 without outer setae, apex of article 3 oblique. Maxilla 1, inner plate with four setae, outer plate with 10 or 11 robust setae; palp biarticulate. Maxilliped, inner plate with one or two thick apical robust setae; apex of palp article 3 not strongly protuberant; dactyl elongate, apical nail distinct, medium to short length.

Gnathopods medium, dissimilar, gnathopod 2 weakly enlarged; carpus of gnathopod 1 of medium length and free, of gnathopod 2 short to elongate (only in F. abjectus is elongate), and subcryptic to cryptic; propodus of gnathopods 1 and 2 ovatorectangular and elongate, poorly setose anteriorly, palms oblique. Pereopods 3 and 4, carpus without posteroproximal seta; propodus with thin and thick armaments, midapical setae absent. Pereopod 5 basis of broad form, not tapering distally. Pereopods 5 and 6, merus and carpus narrow to medium, basis not setose posteriorly. Pereopod 7, basis naked ventrally, without facial setae; ischium not enlarged.

Epimera 1-2 (not described for F. uncinatus ) without long facial brushes or posterior setae; epimeron 3 posteroventral corner rounded, subquadrate or with a hook, bearing two or more ventral setae. Urosomite 1 (not described for F. uncinatus ) bearing or lacking lateral setae and with or without ventral setae. Urosomite 3 posterodorsally rounded. Uropod 1, peduncle elongate, without inter-ramal robust seta and major displaced robust seta; with dorsolateral setae confined apically or widely spread, medial setae widely spread. Uropod 2, peduncle strongly setose dorsally. Uropods 1 and 2, apicolateral corners of peduncles with faint comb (not described for F. uncinatus ); rami not continuously setose to apex, without subapical nails, with immersed apical nails. Uropod 3, rami longer than peduncle, outer ramus article 2 bearing two medium to long apical setae. Telson, each lobe with two or three apical robust setae plus setule on each lobe.

REMARKS

To allocate the species Fuegiphoxus uncinatus properly, we have expanded the diagnosis of Fuegiphoxus given by Barnard & Barnard (1980) and Barnard & Karaman (1991) adding the following morphological character states: inner plate of maxilliped bearing one (original diagnosis) or two thick apical robust setae; carpus of gnathopod 2 subcryptic to cryptic (original diagnoses); epimeron 3 posteroventral corner rounded or with hook, and telson bearing two (original diagnoses) or three apical robust setae.

COMPARISONS AMONG FUEGIPHOXUS

AND RELATED GENERA

Fuegiphoxus shares some morphological characters with Eyakia , such as enlarged robust seta of the mandibular molar, inner plate of maxilla 1 bearing four apical setae, more than two rows of facial robust setae on peduncular article 4 of antenna 2, carpus of gnathopod 2 short, and apical nails on uropods 1 and 2 immersed.On the contrary, Eyakia presents antenna 1 peduncular article 2 of medium length with ventral setae widely spread, propodus of pereopods 3 and 4 with only thick armaments, basis of pereopod 5 tapering distally, peduncle of uropod 2 with numerous long setae, and epimeron 3 with facial setae.

Fuegiphoxus shares with Linca the enlarged robust seta of the molar and the absence of midapical seta on propodus of pereopods 3 and 4, but Linca differs in the elongate peduncular article 2 of antenna 1 with setae placed midventrally and spread, and in the palms of gnathopods 1 and 2 subtransverse.

Fuegiphoxus shares with Paraphoxus the short peduncular article 2 of antenna 1, the ventral setae confined apically on this article, and the carpus of gnathopod 2 almost cryptic. Both genera can be distinguished because Fuegiphoxus has an enlarged robust seta on the mandibular molar, more than one strong setal facial row on article 4 of antenna 2, and four setae on the inner plate of maxilla 1, instead of two.

The genera Wildus and Elpeddo appear to be similar to Fuegiphoxus , but they can be separated by many differences, mainly the absence of an enlarged robust seta on the mandibular molar and the presence of the major apicomedial displaced robust seta on the peduncle of uropod 1 (see Barnard & Barnard 1980 and Discussion).

Fuegiphoxus uncinatus ( Chevreux, 1912) ( Figs 1-4 )

Pontharpinia uncinata Chevreux, 1912: 211 ; 1913: 82, 100-104, figs 10-12. — Thurston 1974: app. C. — Barnard & Drummond 1978: 32, 146.

Paraphoxus uncinatus – Barnard 1958a: 146 (by implication); 1960: 186, 195, 283. — Lowry & Bullock 1976: 128.

Paraphoxus uncinata – Barnard 1958b: 118.

Fuegiphoxus ? uncinatus – Barnard & Barnard 1980: 867. — Alonso de Pina et al. 2008: 2 , 11, 12, 33 (considered Rauschert’s unpublished records).

? Fuegiphoxus uncinatus – De Broyer & Jażdżewski 1993: 83.

Fuegiphoxus ? uncinata – Barnard & Barnard 1990: 50. — Barnard & Karaman 1991: 610.

Fuegiphoxus uncinatus – Wakabara et al. 1990: 2, 5, 7. — De Broyer et al. 2007: 188, 189.

MATERIAL EXAMINED. — Palmer Archipelago. Neumayer Channel (Roosen Channel), Port Lockroy, 64°49’S, 63°30’W, 60-70 m, deuxième expédition antarctique française 1908-1910, gear dredge, 1 ovigerous ♀, holotype (MNHN-Am7551).

DISTRIBUTION Magellan region : Straits of Magellan, Paso Ancho, 53°3.6’S, 70°32.8’W, 88 m ; Straits of Magellan , Voces Bay, 53°42.6’S, 70°57.5’W, 51 m ; Brecknock Channel , Sidney Island, 54°45.5’S, 71°44.4’W, 33 m ; Beagle Channel , Garibaldi Sound, 54°51’S, 69°55.7’W, 30 m ; Beagle Channel , Port Williams, 54°53.8’S, 67°34.5’W, 35 m ; Paso Goree, 55°18.6’S, 67°08.5’W, 42 m. South Shetland Islands, 62°00.3’S, 59°14.9’W, 130 m ; South Shetland Islands 62°58’07’’S, 57°08’01”W, 88 m. Palmer Archipelago, Neumayer Channel (Roosen Channel), Port Lockroy, 64°49’S, 63°30’W, 60-70 m. Weddell Sea, Cape Norvegia, 71°23.10’S, 14°19.70’W, 628 m. Depth range: 30-628 m. (See Alonso de Pina et al. 2008 [considered Rauschert’s unpublished records]) .

A

DIAGNOSIS

Eyes large.Flagellum of antenna 1 without aesthetascs. Facial robust setae formula on article 4 of antenna 2 = 3-5-1. Mandible, palp article 1 short, left incisor broad with two teeth on the ends and undulations on the middle. Maxilliped, inner plate with two thick apical robust setae, palp article 4 with medium apical nail. Gnathopod 2 carpus short, subquadrate, subcryptic, posterior margin shorter. Pereopod 5, basis with posterior margin crenellate. Pereopod 7, basis strongly expanded posteroventrally, almost reaching apex of carpus, dactylus slender, 0.7 times as long as propodus. Epimeron 3, posteroventral corner with a moderate acute hook, ventral margin with four setae. Uropod 1 with seven basofacial to ventral slender setae. Uropod 3 elongate.Telson with three apical robust setae of different length.

REDESCRIPTION

Antenna 1 ( Fig. 1A ), peduncular article 1 almost 1.1 times as long as wide, about 2 times as wide as peduncular article 2, ventral margin with three setules, two medium simple, and two somewhat longer penicillate setae ( Chevreux 1913 described four ciliate [sic] setae), produced dorsal apex bearing two medium setae; peduncular article 2 short, about 0.6 times as long as peduncular article 1, ventrally with distal cycle of 10 setae: four long and three medium subfacial setae, and three long marginal setae, dorsally with two apical and four subapical setae, and medially with three apical setae. Primary flagellum with 11 articles, about 0.85 times as long as peduncle, without aesthetascs; accessory flagellum with eight articles; both flagella bearing dorsal and ventral short setae in all articles.

Antenna 2 ( Fig. 1B ) not ensiform. Peduncular article 3 with two setules; peduncular article 4 much wider than peduncle article 5, dorsal margin with two proximal setae, three distal setae: two simple and one penicillate, and medial notch bearing four setae, ventral margin with about six groups of two to three medium to long setae (some penicillate), four very long ventrodistal setae, and one ventrodistal long robust seta placed subfacially; facial robust setae formula = 3-5-1; peduncular article 5, 0.72 times as long as peduncular article 4, facial robust setae formula = 3-2, dorsal margin bearing four thin and short setae medially, and three short setae (one penicillate) distally, ventral margin with three notches, each with a short seta (one penicillate), ventrodistal corner bearing three long setae and two somewhat shorter subfacial setae. Flagellum about 0.95 times as long as articles 4 and 5 combined, with 11 articles bearing dorsal and ventral short setae.

Mandibles ( Fig. 1C, D ), right incisor broad, with three teeth, middle tooth largest; left incisor broad with two teeth on the ends and undulations on the middle; right lacinia mobilis bifid, flabellate, proximal branch simple, much longer than the distal, middle part minutely denticulate; left lacinia mobilis with four teeth, middle teeth rounded; right rakers six ( Chevreux 1913 described them as five spines), left rakers seven; molars composed of bulbous protrusions, not triturative, bearing three robust setae, one of them larger and weakly serrate; palp opposite to molar with weak palpar hump, article 1 short, naked, article 2 elongate, about 7 times as long as wide, bearing eight short to medium facial setae (these setae appear as inner in Chevreux 1913 drawing), article 3 about 0.7 times as long as article 2, with two basofacial setae, apex feebly oblique (better observed and drawn by Chevreux 1913) with six medium to long slender setae.

Maxilla 1 ( Fig. 2A ), inner plate large, broad, bearing two medium apicolateral plumose setae, two apical simple setae (one short and one medium), and one short facial simple seta ( Chevreux 1913 described four ciliate [sic] setae); outer plate with 11 robust setae, the three distal most ones specially thick and large, four long and thinner, and four medium, thinner and bidentate; palp biarticulate (not drawn in Chevreux 1913, see Discussion), longer than outer plate, article 2 with three apical setae, five medial setae and five submarginal setae.

Maxilla 2 ( Fig. 2B ), inner plate shorter than outer plate, both subequally broad and setose; outer plate with five apicolateral medium simple setae; inner plate medial margin with a row of three long plumose setae and four medium plumose setae.

Maxilliped ( Fig.2C ),inner plate short, rectangular, with two thick apical robust setae, five medium to long apicofacial plumose setae and nine medium setae: six plumose and three simple; outer plate small, subtriangular, scarcely overlapping article 1, with 11 medial robust setae slightly serrate, and four apical setae: three long and serrate, and one thick and short; palp 4-articulate, stout, article 1 naked; article 2 strong, 1.6 times longer than article 3, with two apicolateral medium setae and medial margin strongly setose; article 3 suboval, 1.45 times longer than broad, with two subapicolateral setae, four medium to long apical setae, nine medium facial setae, and medial margin very setose; article 4 thin, slightly longer than article 3, with medium apical nail bearing one inner setule.

Coxae 1-3 ( Figs 2D ; 3A, B ) subrectangular, moderately expanded distally, anterior margin slightly convex, posterior straight. Main ventral setae of coxae 1-4 = 14-13-11-14; ventral margin almost straight, anteroventral margin with weak notch bearing one very short setule. Coxa 4 ( Fig. 3C ) large, subquadrate, anterior and posterior margins almost parallel, anterior margin slightly convex, posterior margin almost straight, posterodorsal corner very rounded, posterodorsal margin short, excavate; width/length ratio 100:115.

Gnathopods 1 and 2 ( Figs 2D ; 3A ) of moderate size, dissimilar; gnathopod 2 slightly larger than 1. Coxa 1, 1.8 times longer than wide; coxa 2 twice longer than wide. Gnathopods 1 and 2, basis elongate, longer than broad, with 11 long posterior setae each, zero-three short posterior setae, and with a tuft of medium to long simple setae on posterodistal angles; merus subtriangular with posterodistal setae; width ratios of merus-carpus-propodus = 21:25:32 and 23:25:39, length ratios = 22:42:65 and 23:29:68. Gnathopod 1 ( Fig. 2D ) carpus free, elongate, subrectangular, posterior margin slightly convex. Gnathopod 2 ( Fig. 3A ) carpus short, subquadrate, subcryptic, posterior margin shorter than anterior margin, almost straight. Gnathopods 1 and 2, propodus ovatorectangular, naked anteriorly, and with small setae posteriorly; palms strongly oblique, palmar humps large (principally in gnathopod 2), with one robust seta each.

Pereopods 3 and 4 ( Fig. 3B, C ) similar in shape, except by coxae, pereopod 4 slightly stouter than 3; basis with 14 and 11 long posterior setae respectively and a tuft of medium to long simple setae on posterodistal angles; merus very stout with an- terodistal lobe somewhat produced over following article; propodus thinner than carpus; facial seta on merus five and five, on carpus five and two; main spine of carpus extending along 55% and 56% of propodus; carpus without proximoposterior robust seta; propodus robust setal formula = 4+5 and 4+5, some setae especially long; length ratios of merus, carpus and propodus 58:30:44 and 65:30:46; dactylus 0.5 times longer than propodus, acclivities on inner margin not observed, anterior margins with midfacial small plumose setule.

Pereopod 6 not seen (it was described by Chevreux 1913, see bellow).

Coxae 5 and 7, posteroventral margins naked. Pereopods 5 and 7 ( Fig. 3D ; 4A ) width ratios of basis, merus, carpus and propodus of pereopod 5 = 63:34:30:14, of pereopod 7 = 125:22:20:11; length ratios of pereopod 5 = 95:35:41:45, of pereopod 7 = 145:22:32:42. Pereopod 5 ( Fig. 3D ), basis subrectangular, facially naked, with long ridge, anterior margin expanded, strongly convex, posterior margin slightly concave, crenellate; merus almost facially naked; carpus bearing very sparse facial robust setae rows; dactylus without acclivity.Pereopod 7 ( Fig.4A ), basis strongly expanded posteroventrally, almost reaching apex of carpus, facially naked, with long ridge, posterior margin with about nine serrations; comb and digital processes of medial apex of propodus could not be observed. Pereopods 5 and 7, dactylus slender, 0.6 times and 0.7 times as long as propodus respectively, without acclivities, facial plumose setule (not observed in pereopod 5) placed proximally.

Gills, oostegites, pleopods and epimera were not found mounted on the slides.

Uropods 1 and 2 ( Fig. 4B, C ), rami with fused immersed apical nail, inner ramus shorter than outer. Comb on apicolateral corners of peduncles not observed.

Uropod 1 ( Fig. 4B ), peduncle elongate, about 2.8 times longer than broad, bearing seven dorsolateral slender to wider robust setae, three apicolateral shorter robust setae, and seven basofacial to ventral slender setae; rami shorter than peduncle, inner ramus bearing one dorsomedial robust seta, outer ramus with three dorsomedial robust setae.

Uropod 2 ( Fig. 4C ), peduncle stout, 2.4 times longer than broad, with 11 dorsolateral robust setae ( Chevreux 1913 described 14 setae), the three proximal ones the longest, and one subapicolateral robust seta; rami shorter than peduncle, outer ramus with two dorsomedial robust setae, inner ramus naked.

Uropod 3 ( Fig. 4D ), peduncle 1.2 times longer than broad, bearing seven ventral robust setae, one subapical medial robust seta, and dorsally with one shorter seta. Rami unequal in length; inner ramus extending 98% on article 1 of outer ramus, apex carrying two long plumose setae, lateral and medial margins with six (three broken) and four (one broken) plumose setae respectively; outer ramus, medial margin with seven plumose setae (some broken), lateral margin with four acclivities, setal formula = 1-1-1-2-2, article 2 of outer ramus short, 10% of article 1, bearing two apical medium plumose setae.

Telson ( Fig. 4E ) large, 1.2 times longer than broad, cleft 72% of total length, each apex wide, rounded, subtruncate, acclivities shallow, with three apical robust setae of different length, and one slender plumose seta (only seen on right apex); each lobe bearing two midlateral plumose setules of different length (on left side only seen one setule).

MORPHOLOGICAL CHARACTERS

DESCRIBED BY CHEVREUX

The following morphological characters could not be observed on the type material deposited in the MNHN, although they were described by Chevreux (1912, 1913).

Ovigerous female, 6 mm length, body laterally strongly compressed. Head slightly longer than the three first segments of pereon. Rostrum unconstricted, extending beyond the middle of peduncular article 2 of antenna 1. Eyes large, reniform, with many ocelli. Antenna 1 somewhat longer than head. Antenna 2 a little longer than antenna 1. Mandibular palp thin and long, twice as long as mandible. Maxilla 1, palp with a strong thickening near the base, not clearly distinguished, suggests two articles (see Discussion). Maxilla 2, inner plate with a row of 10 setae in medial margin. Coxae 1-4 longer than the corresponding segments of the pereon. Pereopod 5, basis with posterior margin crenellate, posterior margin of carpus with five distal plumose setae. Pereopod 6 longer than pereopods 3-5 and 7, basis longer than wide, posterior margin smooth, anterior margin with long setae, some of them plumose; ischium bearing plumose setae; merus and carpus less stout than those of preceding pereopods; propodus subequal in length to carpus. Epimeron 3, posteroventral corner with a moderate acute hook, ventral margin with four setae.

REMARKS

Barnard & Barnard (1980) had pointed out that some character states of Fuegiphoxus uncinatus needed to be confirmed. We were able to observe and describe the following morphological characters: antenna 2 peduncular article 4 facial robust setae formula = 3-5-1; right lacinia mobilis bifid, flabellate, left lacinia mobilis with four teeth; mandibular palp, article 2 elongate, bearing eight short to medium facial setae, article 3 about 0.7 times as long as article 2, with two basofacial setae, apex feebly oblique with six slender setae; maxilliped, inner plate with two thick apical robust setae, five medium to long apicofacial plumose setae and nine medial setae, outer plate with 11 medial robust setae slightly serrate, and four apical setae, article 4 of palp thin, with medium apical nail, bearing one inner setule; uropods 1 and 2, peduncles bearing three apicolateral robust setae and one subapicolateral robust seta respectively, both inner and outer rami with fused immersed apical nails.

Unfortunately, the setal formulas of epimera 1 and 2, and urosomite 1, that Barnard & Barnard (1980) also recommended checking, were not possible to observe on the dissected type material (see Discussion).

Fuegiphoxus uncinatus is easily distinguished from the other species of the genus by the shape of epimeron 3 with a slight acute hook on the posteroventral corner (see Chevreux 1913); the facial robust setae formula on article 4 of second antenna = 3-5-1; the mandible left incisor broad with two teeth on the ends and undulations on the middle; the inner plate on maxilliped with two thick apical robust setae; the pereopod 7 with basis strongly expanded posteroventrally, almost reaching apex of carpus, and with the dactylus slender 0.7 times as long as propodus; and the telson bearing three apical robust setae of different length.

In addition, Fuegiphoxus uncinatus differs from both F. fuegiensis and F. inutilus in: flagellum of antenna 1 without aesthetascs, mandible palp article 1 short, and epimeron 3 ventral margin bearing four setae.

The absence of the male in the Fuegiphoxus uncinatus material makes difficult the comparison with F. abjectus , which is only known from a male; however, some features present in F. abjectus are very different from those observed in F. uncinatus , such as the small, diffuse or absent eyes, the specially setose propodus of pereopods 3 and 4, the epimeron 3 subquadrate posteroventrally, the somewhat larger gnathopod 2, and the elongate carpus of gnathopod 2.

Figures

FIG. 1. — Fuegiphoxus uncinatus (Chevreux, 1912), holotype ovigerous ♀ (MNHN-Am7551): A, antenna 1; B, antenna 2; C, right mandible; D, left mandible. Scale bars: A-C, 0.5 mm; D, 0.1 mm.

FIG. 2.— Fuegiphoxus uncinatus (Chevreux,1912),holotype ovigerous female (MNHN-Am7551):A, maxilla 1; B, maxilla 2; C, maxilliped; D, gnathopod 1. Scale bars: A, B, 0.2 mm; C, 0.3 mm; D, 1 mm.

FIG. 3. — Fuegiphoxus uncinatus (Chevreux, 1912), holotype ovigerous female (MNHN-Am7551): A, gnathopod 2; B, pereopod 3; C, pereopod 4; D, pereopod 5. Scale bar: 1 mm.

FIG. 4.— Fuegiphoxus uncinatus (Chevreux,1912),holotype ovigerous female (MNHN-Am7551):A, pereopod 7;B, uropod 1; C, uropod 2; D, uropod 3; E, telson. Scale bars: A, 1 mm; B-D, 0.5 mm; E, 0.2 mm.