Bradycalanus A. Scott, 1909

Bradford-Grieve, Janet M., Blanco-Bercial, Leocadio & Boxshall, Geoffrey A., 2017, Revision of Family Megacalanidae (Copepoda: Calanoida), Zootaxa 4229 (1), pp. 1-183 : 51-53

Genus Bradycalanus A. Scott, 1909

Differential diagnosis. As for Megacalanidae plus following character states: Anterior head rounded or crested. Rostral filaments slender and tapering to point. Female antennule ancestral segment XXIII with aesthetasc. Dorsal surface of antennular ancestral segments I–V each with small hair sensillum without maculae cribrosae. Right male antennule ancestral segments XXI–XXIII fused, segments XIX, XX and XXI with gripping elements. Antennal exopod ancestral segments I–III each bearing relatively well-developed seta each longer than its segment, or shorter than its segment ( Br. abyssicolus n.sp.), seta on segment IV extending short of distal border of exopod. Mandibular gnathobase with ventral tooth set at oblique angle to main plane of gnathobase therefore appearing broader than other teeth, remaining tooth row more or less in line (not set anterior and posterior as in Bathycalanus ); endopod segment 1 with 4 setae, endopod segment 2 with 9 large setae and 2 vestigial setae. Maxillule praecoxal arthrite with 4 posterior surface setae, coxal endite with 4 + 1 small or 2 setae ( Br. abyssicolus ); basal endites 1 and 2 with 2, 4 setae, respectively; endopod segments 1–3 usually with 2, 1 + 1 vestigial, 5 + 1 small posterior surface setae, respectively. Maxilla relatively enlarged compared with other megacalanids; longest setae extend as far as mid labrum and only setae of praecoxal endites 1 and 2 and coxal endite 1 with auxiliary setules; proximal inner seta of endopod segment 2 vestigial, convex border of distal inner seta of endopod segment 2 naked. Maxilliped not enlarged compared with other megacalanids, longest setae extend to rostrum, endopod segments 3–5 with variable numbers of setae poorly developed. Leg 1 basis without hooked process, exopod segments 1 and 2 each bearing distolateral articulated spine, segment 3 with 2 outer border spines. Maculae cribrosae absent. Male leg 5 specialised seta on left leg tapering evenl y, bordered by very long setules.

Type species. Bradycalanus typicus A. Scott, 1909 .

Type locality. 0o 17.6’S, 129o 14.5’E.

Description. Female. Anterior margin of head in dorsal view rounded or crested, rostrum extending into two long, ventroposteriorly-directed, tapering points that appear to be direct extensions of cuticle. Pedigerous somites 1–5 separate, posterior border of somite 5 rounded or extended into small, sharp or obtuse projections in lateral view. Urosome of four free somites. Genital double-somite symmetrical in dorsal view, lateral borders slightly convex, approximately as long as wide and widest at variable locations anterior to posterior; in lateral view distinct ventral genital bulge anteriorly placed or with posterior ridge ( Br. abyssicolus n. sp.). Caudal rami with seta I absent, setae II and III lateral, setae IV–VI terminal (seta V longest), seta VII inserted at inner distal corner on small projection.

Antennule extending as far as posterior border of caudal rami or several segments beyond; ancestral segments II–IV and X–XI fused, segments XXVII and XXVIII separate. Most setae modified; one plumose or naked seta on segment I and naked seta on segment XXVIII. Segments I–V each with dorsal surface hair sensillum, without maculae cribrosae. Setation of segments as follows (based on Br. abyssicolus because specimens of other species not in good condition): I—1 ms, 1a, 2 ss (or 1 ss and 1 plumose setae); II to XXI—2ms + 1a; XXII to XXIII—1ms + 1a; XXIV —1ms + 1a anteriorly, 1 ms posteriorly; XXV —1 ms + 1a anteriorly, 1 large ms posteriorly; XXVI to XXVII—1ms + 1; XXVIII—3ms, 1a, 1ss, no maculae cribrosae present.

Antenna with separate coxa and basis; coxa with 1 inner plumose seta with very long setules along both sides and inner tuft of setules, basis with 2 inner setae each with 2 rows of short setules. Exopod slightly longer than endopod; endopod 2-segmented although line of fusion between ancestral segments II and III visible on posterior surface; segment 1 with 2 inner naked setae and short longitudinal row of outer setules, terminal segment with 9+7 setae; exopod ancestral segment I separate from ancestral segment II, usually with 1 inner disal seta longer than its segment (in Br. abyssicolus n. sp. shorter than its segment). Segment IV seta extends short of distal border of exopod. Segments II–IV fused on posterior surface although line of demarcation visible on anterior surface; segments V–VIII separate, each with long plumose seta; segments IX–X fused, segment X bearing 3 terminal setae.

Mandible coxal gnathobase heavily sclerotised, without macula cribrosa, very broad terminally with six large, complex teeth; largest ventral tooth oriented obliquely to plane of gnathobase thus appearing very wide at base; teeth 2–5 at right angles to main plane of gnathobase, dorsal-most teeth not complex: 2 small and 1 large tooth adjacent to non-articulated lash-like element bordered by 2 tooth rows; basis with 4 inner setae; endopod 2- segmented, segment 1 bearing large inner lobe and 4 distal inner setae (distalmost seta small), segment 2 with 11 terminal setae, 2 of them on one surface, vestigial; exopod 5-segmented with 1, 1, 1, 1, 2 setae.

Maxillule praecoxal arthrite with full complement of 15 setae, 4 of these on posterior and 2 on anterior surface; coxal endite with 5 or 2 setae, epipodite with 7 long and 2 proximal short setae; basal endites 1 and 2 with 2 and 4 setae, respectively, exite with 1 seta; basis and endopod segment 1 fused or separate; endopod with ancestral segments I and II fused, with 2, 1 + 1 vestigial, and 5 + 1 small seta, respectively; exopod with 11 setae, without macula cribrosa.

Maxilla enlarged relative to other megacalanids, longest setae extend as far as mid labrum. Praecoxal endite 1 with 6 setae plus 1 small triangular spine, praecoxal endite 2 with 3 setae; coxal epipodite with 1 vestigial seta; coxal endites 1 and 2 with 3 setae each; basal endite longest with 4 setae; endopod segment 1 with lobe bearing 3 vestigial + 1 large seta, endopod segments 2–4 with 3 (inner proximal seta vestigial, distal seta naked), 1, 2 setae, respectively, most of them strong and curved along whole length. One seta on inner surface of praecoxal endite 1 and coxal endites 1 and 2 shorter and more densely lined with long spinules; longest setae of praecoxal endite 2 and coxal endites 1 and 2 with closely spaced short setules as well as long sparse auxiliary setules. Basal endite and endopod setae strong and spine-like with distal two thirds of concave border lined with closely spaced setules; inner distal long seta of endopod segment 2 with fine spinules on distal proximal-facing (concave) border and naked distally-facing (convex) border.

Maxilliped directed ventrally so that setae on syncoxa and basis directed into animal’s midline; syncoxa with 1, 2, 4, 3 short + l long setae, respectively (on endite 4, long seta toothed and extending as far as third basal seta); basis with 3 setae and with or without long row of very small spinules; endopod segment 1 bearing 2 setae, longer seta plumose along both borders, shorter seta with smooth basal part and tapering distal part bordered by 2 rows of spinules, separate from or partially incorporated into basis; endopod segments 2–6 with 4, 1+3 small, 1+2 small, 1+2 small +1 outer, 2+2 small setae, respectively, 3 of 4 setae on endopod segment 2 with long setules along one border, distal-most seta longest, bordered by short spinules along distal two thirds of one border.

Legs 1–5 biramous, each ramus 3-segmented with following setal formula (Roman numerals indicate spines, Arabic numerals indicate setae; outer border setation listed first):

Leg 1 (Coxa 0-1. Basis 1-1. Exopod I-1; I-1; II,1,4. Endopod 0-1; 0-2; 1,2,3);

Leg 2 (Coxa 0-1. Basis I-0. Exopod I-1; I-1; III,1,5. Endopod 0-1; 0-2; 2,2,4);

Leg 3 (Coxa 0-1. Basis I-0. Exopod I-1; I-1; III,1,5. Endopod 0-1; 0-2; 2,2,4);

Leg 4 (Coxa 0-1. Basis 1-0. Exopod I-1; I-1; III,1,5. Endopod 0-1; 0-2; 2,2,3);

Leg 5♀ (Coxa 0-0. Basis 1-0. Exopod I-0; I-1; II,1,4. Endopod 0-1; 0-1; 2,2,2);

Leg 1 inner seta on coxa arising from inner posterior surface; basis without macula cribrosa, with inner distal S-shaped seta arising on anterior surface and curving across distal border of endopod segment 1, outer seta vestigial; distolateral corner of endopod segment 1 rounded; distolateral exopod spines of various lengths and exopod segments of varying length: width proportions. Legs 2–4 coxal seta on inner margin; pore openings located on anterior surface at base of outer edge spines of exopod segments 1–3, and endopod segment 1 outer distal corners with small rounded or pointed protrusions. Leg 5 with outer distal corner of endopod segment 1 rounded; pore openings on anterior surface at base of outer border spines. On legs 2–5 outer borders of endopod segments 1–2 and proximal outer border of segment 3 lined with fine setules, apart from leg 5 endopod segment 1; proximal inner border of endopod segments 2 and 3 lined with fine setules. Fine setules line outer border of exopod segment 2 and proximal outer border of exopod segment 3 of legs 2–5; fine setules line inner borders of exopod segments 1 and 2 and proximal inner border of segment 3 of legs 2–5, except for naked inner border of exopod segment 1 of leg 5.

Male. Anterior margin of head similar to that of female. Rostrum extending ventroposteriorly into two long, tapering points appearing to be direct extensions of cuticle. Urosome of five free somites, genital somite short. Caudal rami seta I absent, setae II and III lateral, setae IV–VI terminal (seta V longest), seta VII inserted at inner distal corner onto small projection; setules decorating inner border.

Antennules asymmetrical, geniculate on right. Aesthetascs larger than in female with stiffened posterior border. Left antennule with ancestral segments II–IV, IX–XI fused, segments XXVII and XXVIII separate, with aethetascs doubled on segments I, III, V, VII, IX, XI–XIV. Most setae of modified (ms) type, or aesthetascs (a); and few naked simple setae (ss). Setation of segments as follows: I—1 ms, 2a, 2ss; II– IV—6 ms, 4a; V—2 ms, 2a; VI—2 ms, 1a; VII—2 ms, 2a; VIII—2 ms, 1a; IX– XI—6 ms, 5a; XII to XIV—2ms; 2a; XV to XXI—2ms, 1a; XXII to XXIII—1ms, 1a; XXIV to XXV—2ms, 1a; XXVI—1 + 1ms; XXVII—1 + 1ms; XXVIII—3ms, 1a, 1ss. Right antennule geniculate between segments XX and XXI, with ancestral segments II–IV, IX–XI, XXI–XXIII fused; XXVII and XXVIII separate. Setation of segments as follows: I—2 ss, 2a; II– IV—6 ms, 4a; V—2 ms, 2a; VI—2 ms, 1a; VII—2 ms, 2a; VIII—2 ms, 1a; IX– XI—6 ms (presence of clavate seta could not be confirmed because of damage to setae), 5a; XII to XIII—2ms; 2a; XIV to XVIII—2ms, 1a; XIX—1ms, 1 gripping element, 1a; XX—1 gripping element, 1ms, 1a; XXI–XXIII—2 gripping elements, 1a, 1ms; XXIV to XXV—2ms, 1a; XXVI—2ms; XXVII—2ms; XXVIII—3ms, 1a, 1ss.

Antenna, mandible, maxillule, maxilla, maxilliped and legs 1–4 similar to those of female, although setae on antenna exopod segments I–IV shorter.

Leg 5 with following setal formula (Roman numerals indicate spines, Arabic numerals setae, outer border setation listed to the left in each group separate by ‘;’):

Leg 5♂ left (Coxa 0-0. Basis 1-0. Exopod I-0; I-I; II,1,0. Endopod 0-0; 0-1; 2,2,2);

Leg 5♂ right (Coxa 0-0. Basis 1-0. Exopod I-0; I-0; II,1,0. Endopod 0-0; 0-1; 2,2,2).

Leg 5 almost symmetrical apart from specialised seta on inner distal border of left exopod segment 2 and asymmetrically inserted single seta on inner border of exopod segment 3 (these homologous with terminal spine of female). Male left leg 5 exopod segment 2, specialised seta evenly tapering bearing dense longitudinal rows of long setules not extending onto basal part; outer proximal border bearing small tapering lobe. Outer distal corner of endopod segment 1 rounded. Pore openings on anterior surface at base of outer spines. Basis inner distal border with patch of elongate setules.

Remarks. Four species have been included in this genus: Bradycalanus typicus A. Scott, 1909 ; Br. gigas Sewell, 1947 ; Br. pseudotypicus Björnberg, 1968 ; and Br. pseudotypicus enormis Björnberg, 1968 .