Propephonte duangitensis Gheerardyn and Fiers

Gheerardyn, Hendrik, Fiers, Frank, Vincx, Magda & Troch, Marleen De, 2006, Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs, Zootaxa 1327, pp. 41-62 : 51-58

Propephonte duangitensis Gheerardyn and Fiers gen. n., sp. n.

Type locality.—Western Pacific Ocean, Papua New Guinea, Madang Province, Hansa Bay (Duangit Reef) (4°10’S, 144°53’E), coral sand and coral rubble from the east side, water depth 40– 46 m.

Material.— Holotype Ψ dissected on 1 slide ( COP 1940); allotype ♂ dissected on 1 slide ( COP 1941); paratypes are 1 Ψ dissected on 3 slides ( COP 4726a–c) and 1 ♂ preserved in 75% alcohol ( COP 1942); all collected 28 May 1979 by J. Pierret.

Etymology.—The specific name duangitensis refers to the type locality of this species.

Description of female

Total body length 326–350 µm (measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalothorax: 88 µm.

Rostrum ( Fig. 6 E) strongly prominent and triangular; fused to cephalothorax; rather narrow, with slightly concave margins; tip small, slightly bifid; with pair of sensilla anteriorly; dorsal surface pitted.

Habitus ( Fig. 5 A–B). Body fusiform prehensile, slightly depressed. Cephalothorax with parallel margins, only tapering in anterior quarter. Free prosomites and first urosomite as wide as cephalothorax; second to fourth urosomites expanded ventrolaterally. Urosome gently tapering towards the anal somite. Posterolateral angles of cephalothorax lobate. Pleural areas of free prosomites well developed and rounded, bearing spinules along margin. Second and third urosomite fused to form genital double­somite. Genital doublesomite with transverse serrate surface ridge dorsally and laterally, indicating original segmentation; fused ventrally.

Integument of cephalothorax pitted; regularly ornamented with small sensilla. Pleurotergites of prosomites and urosomites, and dorsal surface of anal somite and caudal rami entirely pitted. Rows of closely arranged pits transforming into rows of small denticles. Posterodorsal margin of cephalothorax smooth; of the free somites serrate. Posterodorsal margins of cephalothorax and free somites (except penultimate urosomite) bearing a number of small sensilla. Anal operculum well developed and slightly protruding backwardly; flanked by 2 sensilla; with serrate margin.

Ventral surface (Fig. 9A) of the genital double­somite striated anteriorly, smooth posteriorly. Ventral surface of following 2 urosomites smooth; of anal somite pitted. Posteroventral margins of genital double­somite and following urosomites bearing a row of spinules.

Caudal rami (9A–B) almost twice as long as wide; cylindrical; surface of the caudal rami without processes. Ventral surface and outer margin of the caudal rami spinulose. Inner margin slightly tapering towards the distal margin and bearing strong spinules. Seta I, II and III inserted in distal third of outer margin. Seta IV and V not fused. Seta VII inserted in the distal third.

Antennule ( Fig. 6 A) 6­segmented; majority of setae long and slender. Segment 1–3 pitted dorsally, smooth ventrally. Segment 4–6 smooth. Segment 1 elongate, almost 2.5 times as long as wide; dorsally with blunt process on the proximal half; outer margin bears blunt thorn proximally. Segment 2 with large, posteriorly directed hook along outer margin. Inner margin of first to third segment and outer margin of third to sixth segment with spinules. Armature formula: 1­[1 pinnate], 2­[7 + 1 pinnate], 3­[7], 4­[1 + (1 + ae)], 5­[1], 6­[9 + acrothek]. Apical acrothek consisting of a small aesthetasc fused basally to 2 setae.

Antenna ( Fig. 6 B). Allobasis with 1 short, unipinnate abexopodal seta, inserted in distal half. Exopod 1­segmented and small, but well developed; bearing 3 sub­equal setae apically, and 1 bipinnate, slender and slightly longer seta sub­apically. Endopod with 2 rows of spinules and 2 sub­apical frills; with following armature: subapically 2 spines (one is unipinnate) and a small, slender seta, apically 2 claw­like spines, 3 geniculate setae (the outermost pinnate) and 1 slender seta.

Mandible ( Fig. 6 F). Biting edge formed by several blunt teeth and a seta. Palp uniramous; endopod and exopod represented by 3 and 1 smooth seta(e), respectively. Medial seta plumose.

Maxillule ( Fig. 6 G). Praecoxal arthrite bearing a spinular row on the posterior surface; apically with 6 setae/spines; with 1 small, obliquely positioned seta along the outer and 2 slender setae along the inner margin. Coxal endite with 1 seta and 1 curved spine. Basal endite with 2 setae and 1 curved spine. Endopod obsolete, represented by 3 setae. Exopod 1­segmented with 2 apical setae.

Maxilla ( Fig. 6 H). Syncoxa with 2 endites; with a spinular row along the inner and along the outer margin. Praecoxal endite absent. Proximal coxal endite with 1 strong, pinnate spine and 2 slender, naked setae. Distal coxal endite with 1 curved spine and 1 slender seta. Allobasis drawn out into strong, slightly curved, distally pinnate claw; bearing 2 setae. Endopod obsolete, represented by 2 setae (one of which is very short).

Maxilliped ( Fig. 6 I). Syncoxa with spinular row along the outer margin and some spinules proximally; apically bearing pinnate seta and small seta next to it. Basis with slightly convex outer margin. Endopod clawshaped, unarmed, with short, naked seta at base.

P1 ( Fig. 7 A). Coxa and basis cylindrical, each about as long as broad; with several spinular rows. Basis with slender, plumose outer seta; inner unipinnate seta arising on anterior surface. Exopod 2­segmented, outer margins and anterior surfaces with spinules. Exp­1 with a strongly armed outer spine; exp­2 with 3 naked outer setae and 2 geniculate apical setae. Enp­1 about 2.5 times as long as exp; enp­2 with a strong, smooth claw and 1 minute, naked accessory seta.

P2–P4 ( Fig. 7 B–7G). Setal formulae in table 1. Exopods 3­segmented and endopods 2­ segmented. Prae­coxae small and triangular; devoid of integumental structures. Coxae and bases with spinules along the outer margin. Outer margin of basis with long, plumose (P2) or long, naked (P3–P4) seta. Proportional lengths of the endopods rather short; reaching to middle of exp­ 2 in P2, to the distal margin of exp­ 1 in P3 and to middle of exp­ 1 in P4. Outer spine of exp­1 of P3 and outer exopodal spines of P4 ornamented with slender, long spinules. Segments of endopods and exopods with pattern of spinules as figured.

P5 ( Fig. 8 C) with separate exopod and baseoendopod; the margins bearing long, slender spinules or stout, short spinules. Anterior surface furnished with rows of spinules. Proximal setae of endopodal lobe unipinnate; sub­apical and apical seta plumose. Baseoendopod reaching to middle of exopod. Exopod ovate shape; about 2 times as long as wide; bearing 5 plumose setae distally.

P6 vestiges (Fig. 9A) each bearing 1 small, naked seta. Copulatory pore minute, situated in middle of anterior somite.

Description of male

Total body length 309–350 µm (measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalothorax: 80 µm.

Habitus ( Fig. 5 C). More slender than female; especially with respect to the urosome. Second and third urosomite fully separated. Ventrolateral extensions of second to fourth urosomite are absent. Ventral surface of third urosomite with 2 rows of long spinules; anterior one along the entire surface, posterior one with a large gap in the middle (Fig. 9C).

Antennule ( Fig. 6 C–D) 8­segmented; sub­chirocer. Segment 1 and 2 as in female. Armature formula: 1­[1], 2­[8 + 1 pinnate], 3­[6], 4­[2], 5­[9 (?) + (1 + ae)], 6­[0], 7­[1], 8­ [8 + acrothek]. Apical acrothek consisting of a small aesthetasc fused basally to 2 setae.

Antenna, mouthparts and P1 as in female.

Swimming legs P2–P4 as in female ( Fig. 8 A–B), except enp­2 of P4 has lost the inner seta.

P5 ( Fig. 8 D) pair of legs medially fused. Endopodal lobe of P5 obsolete; bearing 1 pinnate seta. Exopodite oblong; bearing 5 setae and a row of spinules along the outer margin.

P6 vestiges (Fig. 9C) asymmetrical; 1 vestige functional; 1 vestige fused to somite; outer distal corner with 1 pinnate inner and 1 naked outer seta, each on small pedestal.

Variability.—The female holotype has a left P2 enp ( Fig. 7 D) with only one apical seta, a right P2 exp­2 ( Fig. 7 C) without an inner seta and a left P3 enp ( Fig. 7 F) with a very small second segment, bearing only one seta. The allotype bears only two setae on the right endopod of P3, which contrasts with the other paratypes and the left endopod of the same specimen.

Known range.—To date, P. duangitensis is known from the type locality only.

Figures

FIGURE 5. Propephonte duangitensis sp. n. (Ψ, COP 4726). A, habitus, dorsal; B, habitus, lateral. C (ɗ, COP 1942), habitus, dorsal.

FIGURE 6. Propephonte duangitensis sp. n. A – B, E – I (Ψ, COP 1940); C – D (ɗ, COP 1941). A, antennule, ventral; B, antenna; C, antennule (armature of segments 3 – 5 omitted), dorsal; D, antennule (segments 3 – 5), ventral; E, rostrum; F, mandible; G, maxillule; H, maxilla; I, maxilliped.

FIGURE 7. Propephonte duangitensis sp. n. (Ψ, COP 1940). A, P 1, anterior; B, left P 2 exp­ 2 and exp­ 3, anterior; C, right P 2, anterior; D, left P 2 enp, anterior; E, right P 3, posterior; F, left P 3 enp, posterior; G, left P 4, anterior.

FIGURE 8. Propephonte duangitensis sp. n. A – B, D (ɗ, COP 1941); C (Ψ, COP 1940). A, P 3, anterior; B, P 4, posterior; C, P 5, anterior; D, P 5, anterior.