Keraia ricardae, Willen & Dittmar, 2009

Willen, Elke & Dittmar, Janine, 2009, A new genus of Pseudomesochrinae Willen, 1996 (Copepoda, Harpacticoida, Pseudotachidiidae) from the Guinea Basin *, Zootaxa 2096 (1), pp. 287-298 : 288-296

Keraia ricardae gen. nov., sp. nov.

( Figures 1–6 )

Holotype: Keraia ricardae gen. nov., sp. nov.: 1 female specimen collected during the DIVA 2 campaign (M63/2) of RV Meteor to the Eastern Atlantic from 24.1.– 30.3. 2005 using a multicorer at station 59 in the Guinea Basin ( 0°0.0'S, 2°25.1'W; depth: 5063 m), sampled on 15.03.2005.

Other examined material: Keraia sp. : 1 female specimen collected during the DIVA 1 campaign of the RV Meteor M 48/1 to the Angola Basin from 06.7.–08.8. 2000 using a multicorer at station 346 ( 16°17.00'S, 005°27.00'E; depth: 5388 m), sampled on 27.7.2000 ; 1 female specimen collected during the DIVA 1 campaign of the RV Meteor M 48/1 to the Angola Basin from 06.7.–08.8. 2000 using a multicorer at station 346 ( 16° 17.005'S, 005° 26.989' E, depth 5432 m), sampled on 27.7.2000 ; 3 copepodid specimens from the DIVA 2 expedition (RV Meteor cruise M63/2):

Cape Basin: 28° 6.7' S, 7° 20.8' E, 5035 m depth

Guinea Basin II: 0° 50.1' N, 5° 35.0' W, 5138 m depth

Guinea Basin I: 0° 0.1' S, 2° 25.1' W, 5197 m depth

Etymology. The genus name is Greek and means “antenna”, referring to the modified antenna, which characterises the genus. The species is named after the mother of the junior author, Ricarda Dittmar.

Genus diagnosis. Pseudomesochrinae. Rostrum with 4 sensilla, antennule 5-segmented, with outer projections on first segment, antenna with 2-segmented exp, exp1 enlarged, exp2 with large, modified terminal seta, one of which developed as a “rat-tail” seta, P1 with elongate exp1, outer spines of exp1 and exp2 seta-like, terminal and outer spines of P1 exp3 developed as long “rat-tail” setae; setation of P1 enp2 consists of slender outer seta, longer middle “rat-tail” seta and 1 shorter inner seta; P2–P4 endopods 2-segmented, inner terminal setae on enp2 shortened, P2–P4 exopods 3-segmented, P5 of characteristic shape: benp narrow and elongate, expodal part only slightly prominent.

Setal formula (after Lang 1948):

	Exp	Enp
P2–P4	1-1-2, 2, 3	1-2, 2, 1

Type species: Keraia tamara ( Smirnov, 1946) . Other species: Keraia longiseta ( Vasconcelos, George & Santos 2008) .

Description of female ( holotype). Body length 890 µm, furcal rami length 150 µm.

Rostrum (figure 1A). Demarcated from cephalothorax, slightly broader than long, rounded, with one pair of sensilla apically and one subapically.

Body (figures 1A; 2A, B) with distinct separation between prosome and urosome. Cephalothorax longer than broad, cylindrical, cephalic shield with sensilla. Posterior margin of each body somite (excluding penultimate somite) with sensilla, frill of prosomal somites with reticular texture, frill of urosomal somites smooth with serrated margin. Urosomal somites with dorsolateral spinule rows, genital double-somite (free somites 5 and 6) ventrally separated by cuticular ridge, dorsally not completely fused, genital field as in figure 2B; P6 with 1 elongate slender outer seta and 2 minute inner setae. Anal somite completely divided with two dorsal sensilla, anal operculum absent, pseudoperculum present (figure 1A). Furcal rami (figures 1A; 2A, B) approximately 5 times longer than broad, furcal seta I absent, II very small, III inserting near apical margin, displaced slightly proximad, outer edge developed as a large pore, IV and V well developed, distal parts shaped as “rat-tail” setae, VI inserting on apical margin, juxtaposed to IV and V, VII subterminally on dorsal surface.

Antennule (figure 3C) with 5 segments. Armature: damaged; segment I with 1 large and 1 small process on outer distal edge.

Antenna (figure 3A). Allobasis medially with a long abexopodal pinnate seta; exp 2-segmented, exp1 longer and broader than exp2, with 2 marginal setae, exp2 bent off perpendicularly to exp1, with 1 outer pinnate seta and 2 elongated and enlarged claws terminally, enp with subapical spinule row, subapical armature consisting of 3 setae; apically with 7 setae: 1 slender naked spine, 4 geniculate setae of “rat-tail” shape, the outermost of which is fused basally with a long slender seta, and one additional small naked seta on outer edge.

Mandible (figure 4B, C, D). Gnathobase slender with 4 larger and several smaller, finer, pointed and rounded teeth, fringed with spinule row, inner edge with 1 large, tapering pinnate seta, basis with 4 setae; enp longer than exp, with 3 lateral and 6 terminal setae; exp shorter, with 4 lateral and 2 terminal setae.

Maxillule (figure 1B). Arthrite of praecoxa with 7 apical spines and 2 pinnate setae, 1 small and naked seta posteriorly, 2 juxtaposed setae on anterior surface; coxal endite with 6 setae; basis with uni-lobed endite bearing 6 setae; exp and enp cylindrical, with 3 setae each.

Maxilla (figure 4A). Syncoxa with 3 endites; proximal endite bilobed, proximal lobe with 1 large pinnate spine and apical row of spinules, distal lobe with 1 pinnate spine and 1 small seta, middle and distal endites each with 3 large pinnate setae, on distal endite one of which of claw-like shape; basal endite with 1 pinnate claw fused to basis, accompanied by 1 slender naked seta on posterior and 2 setae on anterior side; enp 1- segmented, bearing 2 + 2 setae.

Maxilliped (figure 3B). Syncoxa short and broad, shorter than basis, with spinule row and 1 slender naked seta on distal margin; basis compact, bearing 1 naked seta near distal edge as well as several strong spinules on inner margin; enp with claw, accompanied by 2 naked setae and armed with a few large spinules.

P1 (figure 4E). Basis with small inner and elongate pinnate outer seta; terminal margin, base of spines without spinule rows. Exp 3-segmented, outer and terminal margins of exp1 and exp2 with spinules; exp1 elongated, much longer than exp2 and exp3, exp1 with 1 outer pinnate spine, exp2 with small inner seta and outer spine modified as a “rat-tail” seta; exp3 with 2 terminal and 2 outer “rat-tail” setae, the latter of which is slightly displaced distally; enp two-segmented with spinules along outer and distal margins, enp1 shorter than enp2, with 1 inner pinnate seta; enp2 with 1 inner pinnate seta and terminally with long and slender pinnate outer seta, longer middle “rat-tail” seta and shorter inner terminal pinnate seta.

P2–P4 (figures 5A, B; 6A). Exopodites three-segmented, endopodites two-segmented with inner terminal seta on enp2 shortened. Coxae of almost rectangular shape, with spinule rows on surface, terminal and outer margins. Basis of P2–P4 each with slender outer seta, and spinule rows on distal margin and at base of outer setae.

Setal formulae (after Lang 1948):

P5 (figure 6B). Pair of legs not fused medially, rami fused to single plate, baseoendopodal part with a slender, long seta located at proximal outer edge, endopodal lobe narrow and elongated, with 4 terminal pinnate setae, exopodal part represented by a small projection bearing 1 shorter outer and 1 longer terminal seta.

Male unknown.

Figures

FIGURE 1. Keraia ricardae gen. nov., sp. nov. A, habitus, dorsal, scale bar = 100 µm; B, Mxl, scale bar = 25 µm.

FIGURE 2. Keraia ricardae gen. nov., sp. nov. A, habitus lateral, scale bar = 100 µm; B, urosome ventral, scale bar = 50 µm.

FIGURE 3. Keraia ricardae gen. nov., sp. nov. A, antenna, scale bar = 25 µm; B, maxilliped, scale bar = 12.5 µm; C, antennule, scale bar = 50 µm.

FIGURE 4. Keraia ricardae gen. nov., sp. nov. A, Mx, scale bar = 25 µm; B, mandible gnathobase, scale bar = 25 µm; C, mandible exopodite, scale bar = 25 µm; D, mandible endopodite, scale bar = 25 µm; E, P1, scale bar = 25 µm.

FIGURE 5. Keraia ricardae gen. nov., sp. nov. A, P3; B, P2; scale bars = 25 µm.

FIGURE 6. Keraia ricardae gen. nov., sp. nov. A, P4, scale bar = 25 µm; B, P5, scale bar = 25 µm.

Setal formula (after Lang 1948 ):

Setal formulae (after Lang 1948 ):