Paracallisoma alberti Chevreux, 1903

Horton, Tammy & Thurston, Michael H., 2015, A revision of the genus Paracallisoma Chevreux, 1903 (Crustacea: Amphipoda: Scopelocheiridae: Paracallisominae) with a redescription of the type species of the genus Paracallisoma and the description of two new genera and two new species from the Atlantic Ocean, Zootaxa 3995 (1), pp. 91-132 : 94-101

Paracallisoma alberti Chevreux, 1903

Figs 1–5

Paracallisoma alberti Chevreux 1903: 84 , figs 2, 3.— Stebbing 1906: 719.— Chevreux 1935: 39, pl. 1, fig. 3, pl. 9, fig. 2, pl. 16, fig. 5 (in part).—Birstein & Vinogradov 1955: 223, 279 (in part).— Schellenberg 1955: 191 (in part).— J.L. Barnard 1958: 97 (list).— Belloc 1960: 4.—Birstein & Vinogradov 1960: 176, fig. 5, 233, fig. 33 (in part).—Andres 1977: 60— Desbruyères, Geistdorfer, Ingram, Khripoudoff & Lagardère 1985: 236, fig. 1, 237.— Thurston 1990: 262 (in part, part = P. idioxenos ).— Barnard & Karaman 1991: 511 (in part).— Palerud & Vader 1991: 41 (in part).— Lopes, Marques & Bellan-Santini 1993: 209, table 1.— Dauvin & Bellan-Santini 2002: 316 (table 1).— Horton 2006: 20, table 2.— Horton, Thurston & Duffy 2013: 355, table 2.

Not Paracallisoma alberti .— Schellenberg 1926a: 258, fig. 11.—Birstein & Vinogradov 1962: 34.— Lowry & Bullock 1976: 102.— De Broyer & Jażdżewski 1993: 73. (= Paracallisoma sp. De Broyer, Lowry, Jażdżewski & Robert 2007).

Not Paracallisoma alberti . — Lampitt, Merrett, & Thurston 1983: 76, table 1(= P. idioxenos ). — Thurston 1990: 266. (part = P. idioxenos , part = P. alberti s.s.).

Not Paracallisoma alberti .— Birstein & Vinogradov 1958: 228.—Birstein & Vinogradov 1960: 176, fig. 5, 233, fig. 33.— Gurjanova 1962: 309, fig. 102.— Nagata 1963: 1.—Birstein & Vinogradov 1970: table 1, table 3.— Hatch 1983: 194, 195, table 3.— Nysewander 1983: 328, table 7.— Hatch 2013: 275 (= P. coecum ).

Not Paracallisoma alberti .—Birstein & Vinogradov 1964: 161; Not Paracallisoma aff. alberti .—Treude, Janßen, Queisser & Witte 2002: 1284, table 2. (= Paracallisoma sp.).

Type material. Syntypes— one female, 13mm, Princesse-Alice station 532, 26–27 June 1895, 37°52'N 24°42.75'W, trap on seafloor, 2178 m; three females, Princesse-Alice station 730, 3–5 August 1896, 37°58'N 26°13.25'W, trap on seafloor, muddy sand, 2660 m; five males, nine females, Princesse-Alice station 792, 29 June– 1 July 1897, 32°32.16'N 17°04.42'W, trap on seafloor, blackish grey ooze to fine sand, 2480 m. All syntypes are held at the Musée Océanographique Monaco. The co-ordinates given here are those reported in Chevreux (1935) rather than in the original publication ( Chevreux 1903), which used the Paris, not the Greenwich meridian for calculating longitude. The syntypes were not examined as part of this study but are figured in Kilgallen & Lowry (2015).

Material examined. Faroe-Shetland Channel. Station 57060#1, 11–13 August 2002, 61°39.16' N, 01º13.97' W, DEMAR, 1611m, one adult female 14.5 mm (dissected carcass and four slides ( NHMUK 2015. 2825)), seven adult males, three juveniles ( NHMUK 2015. 2827–2836).

Cape Verde Basin. Station 53509#3, 3 September 1995, 29°13.07'N 43°08.50'W to 29°17.49'N 43°06.14'W, RMT8M-3, 2880– 3025 m (227–407 m above bottom), one specimen.

Mid Atlantic Ridge. Station 54106#2, 21 August 1997, 37°07.5'N 32°22.0'W to 37°04.5'N 32°22.0'W, RMT8- 2, 2542– 2619 m. Station JC011/079, 5 August 2007, 53°56.44'N 36°11.56'W, DEMAR, 2564 m, four specimens. Station JC011/098, 9–11 August 2007, 54°04.08’N 34°09.43'W, DEMAR, 2500 m, 23 specimens. JC011/114, 12– 13 August 2007, 54°02.31'N 34°09.60'W, DEMAR, 2453 m, five specimens. Station JC037/013, 8–10 August 2009, 49°02.00'N 27°43.44'W, AMPHITRAP, 2501 m, 59 specimens. Station JC037/052, 25–27 August 2009, 53°59.32'N 36°08.12'W, AMPHITRAP, 2570 m, 14 specimens. Station JC037/060, 27–30 August 2009, 53°58.46'N 36°06.12'W, AMPHITRAP, 2340 m, six specimens. Station JC037/076, 31 August–1 September 2009, 53°58.94'N 34°02.94'W, AMPHITRAP, 2552 m, eight specimens. Station JC048/008, 2–6 June 2010, 53°59.32'N 36°08.07'W, AMPHITRAP, 2628 m, eight specimens. Station JC048/020, 8–9 June 2010, 54°03.95'N 34°09.12'W, AMPHITRAP, 2505 m, eight specimens. Station JC048/032, 16–19 June 2010, 48°47.34'N 28°38.45'W, AMPHITRAP, 2448 m, 1886 specimens. Station JC048/046, 23–26 June, 49°02.01'N, 27°43.44'W, AMPHITRAP, 2507 m, 784 specimens.

Iberian Basin, Sedlo Seamount. Station 56319#1, (Meteor cruise M60/1, operation #696) 23 November 2003, 40º11.43'N, 26º33.99'W, DEMAR, 2655 m, 24 specimens. Station 56354#1, (Meteor cruise M60/1, operation #735), 29 November 2003, 39º50.17'N, 26º17.82'W, DEMAR, 2876 m, twelve specimens.

Norwegian Sea. Midnatssol Exploration Well, Station TL/ 280807 /010#2, 28 August 2007, 64°09.93'N 05°16.75'E, ROV-deployed trap, 928 m, 19 specimens. Haklang Exploration Well, Station TL/ 171008 /031#1, 17 October 2008, 67°02.81'N 07°03.53'E, ROV-deployed trap, 1248 m, one specimen.

Description. Based on adult female, 14.5 mm, Faroe-Shetland Channel, Station 57060#1, 1611 m.

Head exposed, deeper than long, lateral cephalic lobe large, narrow, subacute; rostrum absent; eyes pigmented, lacking ommatidia, pigment lost in alcohol. Antenna 1 short, length 0.1 x body; peduncular article 1 short, length 0.73 x breadth, without posterodistal spine or lobe; peduncular article 2 short, 0.25 x article 1; peduncular article 3 short, 0.25 x article 1; flagellum seven-articulate, without posterodistal setae, calceoli absent; accessory flagellum long, 0.6 x primary flagellum, 3-articulate, article 1 long, 4.0 x article 2, forming partial cap over callynophore. Antenna 2: length 1.5 x antenna 1; peduncle without brush setae; peduncular article 1 greatly enlarged, not covering article 2; weakly geniculate between peduncular articles 3–4, article 3 short, 0.5 x article 4; peduncular articles 4 and 5 not enlarged; flagellum well-developed, 21 articulate, calceoli absent.

Mouthpart bundle subquadrate. Epistome and upper lip, interantennal carina notched proximally; epistome produced, rounded, dominant; upper lip slightly produced and rounded. Mandible incisors symmetrical, large, with convex margins, left and right accessory setal rows with simple robust setae; left lacinia mobilis a smooth stemmed, distally asymmetrically expanded blade; molar an acute conical structure, mandibular palp attached midway; article 1 short, length 0.65 x breadth, without setae; article 2 slender, length 4.2 x breadth, with 17 distolateral A2-setae; article 3 slender, blade-like, with 14 D3 setae along distal two thirds of the margin, and three E3 setae. Maxilla 1 inner plate triangular, with ten pappose setae; outer plate setal teeth, outer row with ST1-7 large, slender, ST1 bifurcate apically, ST2 four-cuspidate, ST3 three-cuspidate, ST4-5 five-cuspidate, ST6-7 sixcuspidate, inner row with STA-D slender, STA one-cuspidate, STB three-cuspidate, STC four-cuspidate, STD three-cuspidate distally; palp large, two-articulate, article 1 short, article 2 with six terminal robust setae, robust flag seta and one subterminal seta; Maxilla 2 inner plate broad, tapering distally, with 18 pappose setae in subparallel medial setal row, with terminal robust setae; outer plate slightly longer than inner with apicomedial dentate and plumose setae. Maxilliped inner plate large, subrectangular, slightly emarginate distally with three apical nodular setae, oblique facial setal row strong with 15 pappose setae reaching apical margin, two marginal pappose setae; outer plate medium size, subrectangular with eleven apical plumose setae, with eight small nodular setae medially and two longer robust setae on the distomedial corner; palp large, 4-articulate, article 2 broad, length 2.2 x breadth, 1.8 x article 3; article 3 long, slender, length 2.2 x breadth; dactylus well-developed, with one subterminal seta, unguis present.

Gnathopod 1 simple; coxa large, as long as coxa 2, subquadrate; basis long, slender, length 3.4 x breadth, anterior margin smooth, with simple setae; ischium long, length 1.7 x breadth, anterior margin smooth with one seta posterodistally; merus, posterior margin with a few simple setae distally; carpus subrectangular, long, length 3 x breadth, subequal to propodus; propodus large, margins subparallel, posterior margin with a few groups of simple, slender setae, apex with numerous distally pappose robust setae; dactylus, anterior margin shrouded in pappose setae, posterior margin with one small tooth. Gnathopod 2 subchelate; coxa large, subequal in size to coxa 3; ischium, length 3.0 x breadth; carpus long, length 3.0 x breadth, posterior margin straight; propodus subtriangular, expanded distally, length twice breadth, posterior margin with five groups of slender robust setae, apically with row of distally plumose setae decreasing in size towards palm; palm acute, with very slightly concave serrate margin; dactylus inserted close to anterodistal corner of propodus, curved strongly and reaching only halfway across palm, palm corner with tooth. Pereopod 3 coxa large, subrectangular; basis robust, sinuous and slightly expanded distally; merus slightly expanded anteriorly; propodus posterior margin with six robust setae and two distal locking setae; dactylus short, curved. Pereopod 4 as pereopod 3 except coxa wider than deep with welldeveloped but narrow posterior lobe, ventral and posterior margins confluent, width 1.3 x depth, apex narrowly rounded; propodus posterior margin with six robust setae, five simple setae and one pair of distal locking robust setae. Pereopod 5 coxa posteriorly lobate with a lateral ridge, 14–15 simple setae along posterodistal margin; basis weakly expanded proximally, widening distally with strong posterodistal lobe extending to 0.3 x length of merus, posterior margin concave with four short robust setae, posterodistal lobe anterior margin with two robust seta distally; merus slightly expanded posteriorly with robust setae on both posterior and anterior margins; propodus long, length 5.2 x breadth, anterior margin with one single and five pairs of robust setae and one pair of distal locking setae, posterior margin with five long slender simple setae; dactylus slender, curved. Pereopod 6 coxa small, weakly lobate posteriorly; basis anterior margin smooth, slightly convex with four short robust setae anterodistally, posteroproximal margin expanded rounded, forming lobe with six simple setae on margin, posterior margin slightly concave with four short simple marginal setae, rounded posterodistal lobe extending beyond ischium; merus weakly expanded posteriorly; propodus long, length 5.7 x breadth, anterior margin with eleven pairs/single robust setae and one pair of distal locking setae, posterior margin with 14 long slender simple setae; dactylus slender, curved. Pereopod 7 coxa small, postero-lobate with four simple slender setae on posteroventral margin and twelve simple setae on anterior margin; basis anterior margin straight with five short robust setae distally, proximal posterior margin expanded, convex with nine short simple setae along margin, excavate posterodistally with a round posterodistal lobe extending beyond ischium; merus weakly expanded posteriorly; propodus long, length 4.7 x breadth, anterior margin with five groups of robust setae, and one pair of distal locking setae, posterior margin with five long slender simple setae; dactylus long, slender, slightly curved.

Pleonites 1–3 dorsally smooth. Epimeron 1 anterior margin straight, posteriorly rounded with minute tooth. Epimeron 2 anterior margin sinuous, rounded; posterior margin convex, posteroventral corner with small tooth. Epimeron 3 posteroventral corner produced, subrectangular, ventral margin with seven robust setae.

Gills on pereopods 2–7. Brood plates on pereopods 2–5.

Urosomite 1 concave anteriorly with a rounded smooth boss posteriorly. Uropod 1 peduncle long, 1.2 x inner ramus, with one apicolateral robust seta, one apicomedial robust seta, and nine dorsomedial setae; rami subequal; inner ramus, with one medial robust seta, and a microsetose lateral margin; outer ramus, with two lateral robust setae and a microsetose medial margin. Uropod 2 peduncle long, as long as inner ramus, with one apicolateral robust seta, one apicomedial robust seta, five dorsomedial setae, and six dorsolateral robust setae; inner ramus, length 1.2 x outer ramus, with four medial robust setae and four lateral robust setae; outer ramus, with three lateral robust setae and a microsetose medial margin. Uropod 3 peduncle short, length 0.6 x inner ramus, with two apicolateral robust setae, one apicomedial robust seta and two simple setae, and five slender simple medial setae; inner ramus, with four medial robust setae and twelve medial slender plumose setae; outer ramus, two-articulate, article 2 short (0.41 x article 1), with a microsetose medial margin; article 1 with four medial robust setae and three slender plumose setae, and three lateral robust setae.

Telson weakly tapering, length 1.8 x breadth, cleft 67%, with four robust setae per lobe, distal margins incised with subapical notch and one small immersed seta per lobe

Sexual dimorphism. Male antenna twice as long as antenna 1, 23-articulate, with brush setae, stronger callynophore with more profuse aesthetascs, calceoli present on both antennae.

Remarks. Paracallisoma alberti , the type species of the genus is redescribed here in full using new material. These specimens indicate that the species has eyes ( Fig. 5 ). In common with many other deep-sea lysianassoids, the eyes show no macroscopic structure and the red pigment found is highly labile in alcohol ( Thurston 1974; Thurston & Bett 1993; Horton & Thurston 2014).

It should be noted that there is an ontogenetic change, with the gnathopod 2 dactyl: palm ratio, which decreases with increasing body length.

Separation of this Atlantic species from the Pacific species Paracallisoma coecum ( Holmes, 1908) has been discussed in the literature. Schellenberg, (1926a) placed the Pacific species P. coecum ( Holmes, 1908) in synonymy with P. al b er t i ( Chevreux, 1903). This view was followed by Birstein & Vinogradov (1955, 1958, 1960, 1962, 1964, 1970) and Gurjanova (1962) although the latter did note several differences between her Bering Sea specimens and the drawings of Chevreux (1903). Hurley (1963) and Barnard (1964) retained P. coecum as a distinct species pending a re-examination of Atlantic material. The description of Paracallisoma platepistomum Andres, 1977 , a species closely related to P. coecum made it clear, even without further Atlantic material, that the two species were distinct. Examination of material of both species and the description of new species of Paracallisoma have allowed us not only to distinguish easily between the two species, but warranted the erection of a new genus for the more slender and largely pelagic ‘paracallisomas’.

Depth range. 928–3025 m. The species has been captured in mid-water nets at least 200 m above the sea floor (this study).

Distribution. P. alberti is known from the North East Atlantic in the Madeiran and Iberian Basins at depths of 2178–2660 m ( Chevreux 1903), the Porcupine Seabight ( Lampitt et al. 1983), the Bay of Biscay ( Chevreux 1935; Desbruyères et al. 1985), the Faroe-Shetland Channel at 1396–1661 m ( Horton 2006) and the Mid-Atlantic Ridge at 2340–2628 m (Horton et al. 2013).

Figures

FIGURE 5. Paracallisoma alberti Chevreux, 1903. Adult female, Sedlo Seamount, Azores, 2655 m; fresh specimen, showing ocular patches.