Scottolana geei, Mu & Huys, 2004

Mu, Fang-Hong & Huys, Rony, 2004, Canuellidae (Copepoda, Harpacticoida) from the Bohai Sea, China, Journal of Natural History 38 (1), pp. 1-36 : 3-18

Scottolana geei n. sp.

(figures 1–12)

Material examined

H  : adult X dissected on 18 slides (NHM reg. no. 2002.230). P    : one W dissected on 18 slides and three WW preserved in alcohol (NHM reg. nos 2002.231–234).

Description

Female (holotype) (figures 1–6, 7A, 8, 9). Body length: 880 m m. Body (figure 1A, B) robust, comprising cephalosome, five pedigerous somites and three-segmented urosome. Urosome consisting of genital double-somite and two postgenital somites. Cephalic shield increasing in width posteriorly; thoracic and abdominal somites both gradually tapering posteriorly. Body covered with pattern of minute pimples and spinules varying in size and shape (not illustrated in figure 1 but comparable to those in S. bulbifera : figure 23A). P1-bearing somite separated from the cephalosome but concealed by cephalic shield in dorsal aspect (figure 1B). Original segmentation of genital double-somite marked by discontinuous internal chitinous rib laterally (figures 1A, B, 2A). Intersomitic membranes well developed; hyaline frills smooth (figures 1A, B, 2A). Anal operculum weakly developed (figures 1A, 7B). Anus terminal.

Rostrum (figures 1A, 2E) very large, about three-quarters length of cephalic shield; bell-shaped, with distal third tapering abruptly; with two tiny lateral sensillae.

Antennule (figure 3) three-segmented. First segment largest, showing three incomplete sutures around posterior margin but no functional articulations; proximal part with setular tuft and spinule row ventrally; with 29 pinnate or spinulose setae/spines (four bi-articulate at base) and two aesthetascs. Middle segment short, with three pinnate and one plumose setae. Distal segment with three long plumose setae apically, a plumose seta posteriorly and five naked plus five pinnate setae around anterior margin.

Antenna (figure 4A–C) comprising coxo-basis, two-segmented endopod and ninesegmented exopod. Coxo-basis relatively short, produced into cylindrical pedestal supporting exopod; with setular patches on anterior surface. Endopod with two setae on proximal segment, one of them minute and smooth; distal segment with incomplete transverse membranous insert indicating original segmentation; with four lateral and seven apical setae, six of them pinnate, the other one short and smooth. Exopod with nine distinct segments; segments 1–3 and 7–8 each with plumose seta; segments 4–6 each with pinnate seta; terminal segment minute, U-shaped and partly concealed in segment 8, with three setae.

Mandible (figure 5A): gnathobase with row of six strong teeth superimposed on second row of smaller teeth; dorsal corner with one tripinnate spine; with additional spinules around gnathobasal teeth and dorsal margin. Basis with two pinnate setae and three rows of small spinules. Endopod two-segmented; enp-1 with three pinnate setae; enp-2 with six pinnate and two plumose setae. Exopod without complete segment boundaries but showing indications of ancestral four-segmented condition with probable setal formula [2, 1, 1, 2]; all setae plumose; setular row present on ancestral segment 2.

Maxillule (figure 6A): praecoxa and coxa partly fused. Praecoxal arthrite with nine spines and two setae around distal margin and two tube-setae on anterior surface; posterior surface with two rows of spinules. Coxa with epipodite represented by two plumose setae; endite cylindrical, with two smooth and three pinnate setae, anterior surface with one row of spinules. Basis with closely set endites, proximal endite with four pinnate setae, distal endite with one smooth and three pinnate setae; with row of spinules on posterior surface. Exopod large, foliaceous; with five smooth setae on inner margin, six plumose setae around distal margin and one small, pinnate seta on outer margin; inner edge with a row of fine setules. Endopod two-segmented; enp-1 with five pinnate setae laterally; enp-2 with six setae, outer four plumose, inner two pinnate.

Maxilla (figure 5B) comprising praecoxa, coxa, allobasis and three-segmented endopod. Praecoxa with spinules around base of endites and near distal outer corner; proximal endite with five (four pinnate, one smooth), distal with two pinnate setae. Coxa with two cylindrical endites, with three pinnate setae each. Allobasis produced into endite, bearing fused pinnate claw, two strong pinnate spines and four setae (three pinnate, one smooth). Endopod three-segmented (figure 5C); segments 1–2 each with three setae; segment 3 small, with two basally fused setae; all setae smooth.

Maxilliped (figure 6B) phyllopodial, two-segmented, comprising undivided protopod and one-segmented endopod; incomplete suture indicating boundary between syncoxa and basis. Inner margin of protopod with 12 setae/spines; with rows of small spinules on surface; outer margin with row of long setules. Endopod with 11 setae; inner and apical setae (seven) pinnate, outer ones (four) plumose.

All swimming legs with well-developed praecoxae and three-segmented rami; coxae with distinct spinular pattern on anterior surface as figured.

P1 (figure 7A) smaller than other swimming legs. Intercoxal sclerite wide and narrow. Coxa with long, inner pinnate seta. Basis with long, heavily ornamented outer seta and strong bipinnate inner spine. Inner margin of both coxa and basis with long setules. Exp-1 outer spine unipinnate, outer margin with strong spinules, inner margin with finer spinules; exp-2 outer spine serrate, inner seta long and plumose; exp-3 distinctly longer than exp-2, outwardly directed, with three serrate spines along outer margin, one bipinnate and two plumose setae along inner margin and one apical spine bearing combination of setules and spinules as figured. Endopod much longer than exopod; enp-1 with long, multipinnate inner seta inserting proximally and long setules along outer margin; enp-2 with long, multipinnate inner seta and spinules along both inner and outer margins; enp-3 with two bipinnate spines along outer margin, three strongly pinnate setae along inner margin and one short spine (with subterminal tubular extension) at the apex.

P2 (figure 8A, C). Intercoxal sclerite larger and broader than in P1. Coxa with inner pinnate seta; inner distal corner produced, with row of sharp teeth. Basis with bipinnate outer seta; posterior surface with large recurved process bearing several rows of marginal teeth (figure 8C). Exp-1 and -2 with pinnate outer spine and outer distal corner forming spinous process; exp-1 with spinular patch and exp-2 with plumose inner seta; exp-3 with four spines and three setae. Enp-1 with pinnate inner seta, proximal half of segment covered by basis; anterior surface produced into long mucroniform process, extending to distal margin of enp-2 where it fits into a spinuleflanked groove on the outer spinous process (figure 8C). Enp-2 with pinnate seta and spinular row along inner margin. Enp-3 with three spines and two setae; anterior surface with two pores.

P3 (figure 8B): intercoxal sclerite similar to P2. Coxa with pinnate inner spine; inner margin with row of small spinules. Basis attenuated into cylindrical pedestal for endopod; with pinnate outer seta; posterior surface with dorsally recurved spinous process. Exp-1 and -2 with pinnate outer spine accompanied at base by spinular patch; outer distal corner forming spinous process; exp-2 also with inner seta; exp-3 with four spines and one seta. Endopod much longer than exopod; enp-1 and -2 each with pinnate inner seta and outer distal corner produced into process bearing strong spinules; enp-3 with four spines; anterior surface with a pore.

P4 (figure 9): intercoxal sclerite similar to P2–P3. Coxa with short, smooth inner spine. Basis elongate, forming long cylindrical pedestal, displacing exopod to more marginal position; with long pinnate outer seta; posterior surface with small process. Exp-1 and -2 with pinnate outer spine (that of exp-2 much longer and more slender) accompanied at base by strong spinular patch; exp-2 also with very long, pinnate inner seta; exp-3 with one slender spine and three setae, spinular patch and pore on anterior surface, outer terminal seta typically crossing over inner terminal seta. Endopod much longer than exopod; enp-1 and -2 with coarse spinules around distal margin; enp-1 with very long pinnate inner seta; enp-2 unarmed; enp-3 with two spines and two setae, anterior surface with pore.

Spine and seta formulae as follows:

Exopod Endopod

P1 0.1.313 1.1.222

P2 0.1.322 1.1.221

P3 0.1.122 1.1.121

P4 0.1.121 1.0.121

P5 (figure 2B) vestigial, incorporated into somite; with four plumose setae; outermost seta (= homologue of outer basal seta; arrowed in figure 2B) separated from others; middle one of other three longest and with very long setules.

Genital field (figure 2A, C) large, extending over three-quarters of ventral surface of genital double-somite. Copulatory pores paired, posteriorly displaced to inner margin of wing-like processes; each pore wide (arrowed in figure 2C) and leading via copulatory duct to median seminal receptacle. Gonopores located far anteriorly, closed off by P6 bearing one long smooth seta and two internal projections (one large, one small; = vestigial armature elements) involved in subsurface interlocking mechanism. Ventral surface covered with small spinules.

Caudal rami (figure 2A, D) broad at base, produced into posteriorly directed hook-like extension at inner proximal margin; outer distal corner with dense patch of strong spinules, increasing in length posteriorly; with two pores on ventral surface and one at inner margin; with seven setae. Seta I spiniform, unipinnate and short, positioned ventrally on outer margin near pore; seta II plumose, with bulbiform base, located halfway on inner margin; seta III long and multipinnate, implanted on dorsal pedestal as in W (figure 7B). Distal margin of ramus with three setae; setae IV and V well developed and strongly pinnate; seta V about three times longer than seta IV (figure 1A); seta VI short and smooth, fused at base to seta V; seta VII plumose, short, bi-articulate at base, displaced to inner margin.

Male (figures 7B, C, 10A–E, 11A, B, 12A, B). Body length 830–1062 m m (N = 4, mean = 922 m m). Sexual dimorphism in antennule, P3, P5, abdomen and caudal ramus.

Antennule (figures 11A, B, 12A, B) four-segmented, with geniculation between segments 3 and 4. First segment very large; with sutures around posterior margin, possibly indicating ancestral segmentation; with three rows of long setules in proximal part; with 23 setae/spines (four bi-articulate at base) and two aesthetascs. Segment 2 short, with two pinnate setae anteriorly and one short plumose seta (bi-articulate) posteriorly. Segment 3 large and swollen, with constricted proximal part (figure 11A); with very long plumose seta proximally (figure 12A), four additional setae in proximal half (three pinnate, one smooth) and three setae near geniculation (one pinnate, two smooth); distal anterior margin with modified ribbed element (arrowed in figure 12B). Segment 4 small; produced into backwardly directed recurved process (arrowed in figure 12A), interlocking with modified element on segment 3; armature consisting of two pinnate and five smooth setae.

P3 (figure 10E): enp-3 with large, transparent, modified tube-pore along inner margin at level of outer spine.

P5 (figure 10D): with armature as in X but outer basal seta distinctly longer.

Urosome (figure 10A–C) consisting of P5-bearing somite, genital somite and three postgenital somites. Genital somite largest, with paired lateral, posteriorly directed spinous extensions. First abdominal somite with mid-ventral nodular process bearing setules laterally and transparent lanceolate spinules medially (figure 10B, C). Genital apertures (arrowed in figure 10C) closed off by modified sixth legs (figure 10A–C). P6 fused to genital somite, each produced into large spinous process bearing short naked seta on ventral surface; additional element arising from inner proximal part of P6, fused at base, very long (extending to distal margin of anal somite), dark brown, distal half with denticulate raised ridge and characteristically twisted apex.

Caudal rami (figure 7B, C): as in X except seta II not modified, without bulbiform base.

Etymology

The species is dedicated to our friend and colleague Dr Michael Gee, in recognition of his excellent contributions to the systematics and phylogeny of harpacticoid copepods.