Scottolana bulbifera (Chislenko, 1971)

Mu, Fang-Hong & Huys, Rony, 2004, Canuellidae (Copepoda, Harpacticoida) from the Bohai Sea, China, Journal of Natural History 38 (1), pp. 1-36 : 18-33

Scottolana bulbifera (Chislenko, 1971)

Canuella bulbifera Chislenko, 1971: 151–157 , figures 1–4.

Material examined

Three XX dissected on 13, 17 and 18 slides, respectively; one W dissected on 17 slides; 20 XX and 15 WW preserved in alcohol (NHM reg. nos 2002.235–248) from central part of the Bohai Sea.

Redescription

Female (figures 13A–20B, 22–23). Body length 700–940 m m (N = 14; mean = 833 m m). Body (figure 13A, B) cylindrical, comprising cephalosome, five pedigerous somites and four-segmented urosome. Urosome consisting of genital double-somite and three postgenital somites. Maximum width of cephalic shield measured at onequarter distance from posterior margin; thoracic and abdominal somites both slightly tapering posteriorly. Body somites and posterior zone of cephalosome covered with pattern of minute pimples and spinules varying in size and shape (figure 23A). P1-bearing somite separated from the cephalosome but concealed by cephalic shield in dorsal aspect (figure 13B). Original segmentation of genital double-somite marked by continuous internal chitinous rib laterally (figure 13B) and discontinuous rib dorsally (figure 13A). Intersomitic membranes well developed; hyaline frills smooth (figures 13A, B, 14A). Anal operculum weakly developed (figures 13A, 17A). Anus terminal.

Rostrum (figures 13A, 16D, 22A, B, D) large, bell-shaped; with two sensilla subapically and median integumental pore apically.

Antennule (figure 15A–D) three-segmented. First segment largest, showing three incomplete sutures around posterior margin (figure 22A, C) but no functional articulations; proximal part with setular tuft ventrally (figure 22B) and three rows of long and two rows of short spinules; with 29 pinnate or spinulose setae/spines (four bi-articulate at base) and two aesthetascs. Middle segment short, with three pinnate and one naked setae. Distal segment with one naked and two long plumose setae apically, a short plumose seta posteriorly and four naked plus six pinnate setae around anterior margin.

Antenna (figure 16A, B) comprising coxo-basis, two-segmented endopod and eight-segmented exopod. Coxo-basis relatively short, produced into cylindrical pedestal supporting exopod; with setular patches on anterior surface and at abexopodal margin. Endopod with two setae on proximal segment, one of them minute and smooth; distal segment with incomplete transverse membranous insert indicating original three-segmented condition of endopod; with four lateral and seven apical setae (six pinnate, one smooth). Exopod with eight distinct segments; segments 1–3 and 7 each with plumose seta; segments 4–6 each with pinnate seta; terminal segment with one apical and three subapical pinnate setae.

Mandible (figure 18A): gnathobase with row of five strong teeth superimposed on second row of smaller teeth; dorsal corner with one pinnate 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 one smooth, five pinnate and two plumose setae. Exopod with faint segment boundaries, showing indications of ancestral five-segmented condition with probable setal formula [1, 1, 1, 1, 2]; all setae plumose; apical segment minute and partly embedded in penultimate one.

Maxillule (figure 17B): praecoxa and coxa partly fused. Praecoxal arthrite with eight spines and two setae around distal margin and two tube-setae on anterior surface; posterior surface with one row of spinules. Coxa with epipodite represented by two plumose setae; endite cylindrical, with four smooth and three pinnate setae, anterior surface with one row of spinules. Basis with closely set endites, each with four pinnate setae; with row of strong spinules on posterior surface. Exopod large, foliaceous; with two smooth setae on inner margin, six plumose setae around distal margin and one small, smooth spine 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 five plumose, inner one pinnate.

Maxilla (figure 16C) comprising praecoxa, coxa, allobasis and unsegmented endopod. Praecoxa with spinules on anterior surface and around outer margin; proximal endite with four (three 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 (two pinnate, two smooth). Endopod with one pinnate and seven smooth setae.

Maxilliped (figure 18B) phyllopodial, three-segmented, comprising syncoxa, basis and one-segmented endopod. Inner margin of syncoxa with 10 setae/spines; with rows of small spinules on surface. Basis with two smooth setae; outer margin with row of 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 (figures 19A, 23B) smaller than other swimming legs. Intercoxal sclerite wide and narrow. Coxa with long, inner pinnate seta. Basis with very long, heavily ornamented outer seta and strong bipinnate inner spine. Inner margin of both coxa and basis with long setules. Exp-1 outer spine bipinnate, outer margin with strong spinules, inner margin with setules; exp-2 outer spine serrate, inner seta long and plumose; exp-3 not distinctly longer than exp-2, with three serrate spines along outer margin, one bipinnate and two plumose setae along inner margin and one bipinnate spine apically. Endopod slightly 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, strong spinules along outer margins and setules along inner margin; 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. Enp-3 produced into terminal spinous process displacing apical spine to a more medial position.

P2 (figures 19B, 23C, D): intercoxal sclerite larger and broader than in P1. Coxa with inner pinnate spine. Basis attenuated into cylindrical pedestal for endopod; with bipinnate outer spine; posterior surface with recurved process. Exp-1 and -2 with strong spinular patch at base of pinnate outer spine, and outer distal corner forming spinous process; exp-2 with plumose inner seta; exp-3 with four spines and three setae. Enp-1 with plumose inner seta; anterior surface produced into long mucroniform process with subapical slit (figure 23C, D), extending to distal margin of enp-2 where it fits into a spinule-flanked groove on the outer spinous process. Enp-2 with plumose inner seta and spinular row along inner margin. Enp-3 with three spines and two setae; anterior surface with one pore.

P3 (figure 20A): intercoxal sclerite similar to P2. Coxa with pinnate inner spine. Basis with short pinnate outer seta; posterior surface with 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 outer distal corner produced into long process bearing strong spinules; enp-1 with inner bipinnate spine, enp-2 with inner plumose seta; enp-3 with four spines; anterior surface with a pore.

P4 (figure 20B): intercoxal sclerite similar to P2–P3. Coxa unarmed. Basis with short pinnate outer seta; posterior surface with small process. Exp-1 and -2 with pinnate outer spine (that of exp-2 shortest) accompanied at base by strong spinular patch; exp-2 also with bipinnate inner spine. Exp-3 with one outer, one inner and two apical pinnate spines; long spinous process between inner distal and inner spines; spinular patch and pore on anterior surface. Endopod not distinctly longer than exopod; enp-1 and -2 with coarse spinules around outer distal process; enp-1 with inner bipinnate spine; enp-2 unarmed; enp-3 with four spines, 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 14D) vestigial, incorporated into somite; with four plumose setae; outermost seta (= homologue of outer basal seta; arrowed in figure 14D) slightly separated from others; middle one of other three longest.

Genital field (figure 14A, C) large, extending over anterior half 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 14C) and leading via long copulatory duct to median seminal receptacle. Gonopores located far anteriorly, closed off by P6 bearing one long smooth seta and two internal projections involved in subsurface interlocking mechanism. Mid-ventral surface covered with small spinules. Genital field flanked by spinular patches.

Caudal rami (figures 13A, B, 14B, 17A, C–F) tapering posteriorly, without basal hook-like extension; with one pore on ventral surface at inner margin; with seven setae. Seta I spiniform, dilated and short, positioned ventrally near inner distal corner; seta II typically bulbiform at base (figure 17F), smooth and relatively short, located at inner distal corner; seta III long and smooth, displaced to dorsal surface. Distal margin of ramus with three setae; setae IV and V well developed; unipinnate seta V about three times longer than smooth seta IV (figure 13A); seta VI short and smooth, fused at base to seta V; seta VII plumose, short, bi-articulate at base, displaced to distal inner margin.

Variability: considerable variability was noticed in the shape of seta II on the caudal rami, ranging from distinctly bulbiform (figure 17F; the typical condition observed in the majority of specimens), over slightly swollen (figure 17D, E) to long and slender (figures 14B, 17C).

Male (figures 12C, D, 21A–D). Length 750–980 m m (N = 10, mean = 794 m m). Sexual dimorphism in antennule, P4, abdomen and caudal ramus.

Antennule (figure 12C, D): precise segmentation hard to discern but presumably four-segmented, with geniculation between segments 3 and 4. First segment very large; with two sutures around posterior margin, possibly indicating ancestral segmentation; armature as in S. geei . Segment 2 short, with at least three sutures around the posterior margin; armature as in S. geei . Segment 3 large and swollen, distal posterior corner produced into spinous process; with very long plumose seta around mid-point of anterior margin, and seven additional setae (five pinnate, two smooth); distal anterior margin forming concavity for geniculating terminal segment, with striated zone (arrowed in figure 12D). Segment 4 small; produced into lobate process, with seven smooth setae.

P4 (figure 21D): innermost spinous process on distal margin of exp-3 much smaller than in X.

Urosome (figure 21A) consisting of P5-bearing somite, genital somite and four postgenital somites. Genital somite largest, without lateral spinous extensions. First abdominal somite with mid-ventral patch of fine spinules (figure 21B). Genital apertures closed off by modified sixth legs (figure 21B). P6 fused to genital somite but original demarcation marked by membranous zone; each produced into large triangular process bearing naked seta at apex; additional element arising from around mid-point of inner margin of P6, articulated at base (just extending beyond distal margin of P6), distal half twisted with ventrally recurved blunt apex.

Caudal rami (figure 21C) as in X except for (1) seta I being more slender, straight and spiniform, and positioned at outer margin, and (2) seta II not modified, being long and slender.