Pinkertonius ambiguus, Bradford-Grieve & Boxshall & Blanco-Bercial, 2014, Bradford-Grieve & Boxshall & Blanco-Bercial, 2014

Bradford-Grieve, Janet M., Boxshall, Geoffrey A. & Blanco-Bercial, Leocadio, 2014, Revision of basal calanoid copepod families, with a description of a new species and genus of Pseudocyclopidae, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 171 (3), pp. 507-533 : 517-522

PINKERTONIUS AMBIGUUS GEN. ET SP. NOV.

Material examined ( Table 2): Type specimens deposit- ed in the collection of the National Institute of Water and Atmospheric Research, New Zealand. Holotype: female, Stn 59, top net, NIWA 86594 (three slides). Paratypes : one male, Stn 59, top net, NIWA 86595 (three slides). Paratype lots in 4% formalin: one female, Stn 59, top net, NIWA 86596 (one vial, one slide) ; one female, Stn 59, bottom net, NIWA 86597 (one vial, one slide) ; two females, Stn 121, top net, NIWA 86600 (one vial) ; one female, one male, Stn 121, bottom net, NIWA 86599 (one vial) ; one female, one male, Stn 59, bottom net,

NIWA 86598 in 95% ethanol (one vial); one female, Stn 59, top net , NIWA 85993 , NHMUK 2013.25 .

Etymology: The generic name Pinkertonius (gender masculine) is derived from the name of Dr Matt Pinkerton who is project leader for the NIWA research programme ‘Marine Food Web Dynamics’ on the Chatham Rise, where these specimens were found. The specific name ambiguus derives from the Latin, referring to the ambiguous nature of the morphology of this species in not exactly fitting into any of the previously described families.

Genetic description

The genetic description, from one specimen, is based on the nuclear large (28S) and small (18S) subunits ribosomal RNA and the mitochondrial genes for the proteins cytochrome c oxidase subunit I ( COI) and cytochrome b (cyt b). These sequences were deposited in GenBank accession nos: KF753813 – KF753816 , respectively, which correspond to the catalogued specimen, Co.449.1.1, held in the Marine Science Department , University of Connecticut .

Morphological description

Female: Total length 1.8–2.0 mm, urosome 28% of total length ( Fig. 2A, B ). Prosome ovoid with head (cephalosome) and pedigerous somite 1 separate; pedigerous somites 4 and 5 separate, posterolateral corners of pedigerous somites 1–4 extend into small triangular projections, pedigerous somite 5 produced into pointed lappets extending more than halfway along genital double somite. Rostrum in form of ventrally directed rounded plate with pair of distal filaments ( Fig. 2D ). Urosome of four free somites, first three bordered posteriorly by unevenly serrated hyaline fringe, –, samples not examined. Measurements taken along posterior border of each segment but two (posterior (shortest) and anterior) measurements taken of ancestral segment I.

largely intact ventrally. Genital double somite with slight anterior swelling in dorsal view; in lateral view swollen ventroanteriorly; in ventral view genital field asymmetrical, gonopores slightly unequally developed, being larger on left, genital operculum skewed to left with hinge aligned at about 45° to anterior–posterior axis of somite, so that right gonopore not completely covered, right side of genital field bordered by ridge aligned anterior–posteriorly, no such flange on left, copulatory pore and seminal receptacle not obvious, although sac on left apparently linked to left gonopore ( Fig. 2E ). Caudal rami slightly asymmetrical, longer on right, with seven setae each ( Fig. 2F, G ) more or less symmetrically arranged on each side. Seta I vestigial, seta II spiniform, seta V longest, about 1 mm long, seta IV next longest followed by setae VI and III, seta VII small and spiniform and inserted on dorsoinner distal corner, left caudal ramus inner border lined with fine setules; on right ramus row of long setules arranged obliquely on anterior part of ventral surface.

Antennule ( Table 3): Twenty-seven segmented, extending to posterior border of pedigerous somite 5 ( Fig. 2C ; Fig. 3A, B, C ).

One aesthetasc present on each of segments I, III, VII, XI, XIV, XVI, XVIII, XXI, XXV, and XXVIII; small cuticular thickenings found on segments II–X, XII, XIII, XV, and XVII; one seta on eight proximal segments, wider than other setae, and attenuated distally into curved narrow tip. Setal formula: I, 1s, 1a; II, 2s; III, 2s, 1a; IV, 2s; V, 2s; VI, 2s; VII, 2s, 1a; VIII –X, 2s; XI, 2s, 1a; XII to XIII, 2s; XIV, 2s, 1a; XV, 2s; XVI, 2s, 1a; XVII, 2s; XVIII, 2s, 1a; XIX to XX, 2s; XXI, 2s, 1a; XXII to XXIII, 1s; XXIV, 1 + 1s; XXV, 1 + 1s, 1a; XXVI, 1 + 1s; XXVII– XXVIII, 5s, 1a.

Antenna: Coxa and basis separate, coxa with one seta, basis with two setae ( Fig. 4A ). Endopod two-segmented, with traces of fusion between segments 2 and 3, and between segments 3 and 4; segment 1 with two inner setae, segment 2 with nine plus seven terminal setae and outer transverse row of spinules marking boundary between putative endopod segments 3 and 4. Exopod shorter than endopod, eight-segmented, ancestral segments VIII and IX fused, segments I– VII each with one well-developed seta, compound distal segment VIII – IX with three terminal setae and one inner subterminal seta, outermost seta on terminal endopod segment lined proximally with small spinules.

Mandible: Gnathobase with seven marginal teeth, ventralmost largest, five dorsal teeth bicuspid, small spinulated seta inserted dorsally ( Fig. 4B ). Basis with four apparently naked setae; endopod two-segmented, segment 1 with inner lobe and four setae, segment 2 with ten terminal setae, distoinner border with short row of spinules, transverse row of spinules at about midlength. Exopod five-segmented, with 1, 1, 1, 1, 2 setae.

Maxillule: Praecoxal arthrite with 14 spines and setae, including four on posterior surface and one on dorsal surface ( Fig. 4C ); coxal endite with four setae; basal endites 1 and 2 with four and five setae, respectively; endopod segments 1 and 2 fused, segments 2 and 3 separate, with four, three, and seven setae, respectively; exopod with 11 setae, of which three terminal setae short and bordered by fine setules along inner border; basal exite without seta; coxal epipodite with nine setae, of which three proximal setae short.

Maxilla: Praecoxa, coxa, and basis clearly separated, endites 1–4 with seven (one very short), three, three, and three setae, respectively ( Fig. 3D, E ); basal endite with three setae, one of them stout and spiniform; inner setae on endites 2–5 lined with long spinules; endopod segment 1 endite with three setae, segments 2–4 with two, two, and three setae, respectively.

Maxilliped: First syncoxal endite with one seta ( Fig. 4D ); endites 2 and 3 with two and four spinulose setae, respectively, crescent-shaped row of fine spinules at base of endite 3 on inner surface; endite 4 with three setae

*Illustrated specimen with extra seta, absent in another specimen.

and small peg-like structure, and a few small spinules.

Basis with two setulose setae and proximal border lined by spinules. Endopod well-developed, longer than basis, endopod segment 1 apparently separate from basis, endopod segments 1–6 with two, four, four, three, three plus one, and four spinulose setae, respectively, outer seta of segment 6 wider and longer than adjacent seta, and terminally inserted.

Swimming legs ( Table 4): Legs 1–5 biramous, all rami three-segmented ( Fig. 5 ).

Leg 1 basis with distal lobe on posterior surface situated between exopod and endopod (this lobe is visible in lateral view in the whole animal, as it projects posteriorly); ornamented with transverse row of inner setules; inner distal seta slightly curved. Coxae of legs 2–5 decorated with patches of long spinules on posterior surface; basis of legs 2–4 with blunt tooth on anterior surface between endopod and exopod; outer seta on basis of leg 3 spiniform; outer proximal border of exopod segments 2 and 3 of legs 2–4 each with small knob-like projection; exopods of legs 2–5 with heavily built outer spines bordered by very small blunt denticles, terminal exopod spines also heavily built, and with outer edge lined by tiny small blunt teeth. Surfaces of both rami of legs 1–5 ornamented with patches of very small spinules, most dense on posterior surfaces.

Leg 5 articulation of exopod segment 3 with segment 2, oblique and reminiscent of species of Ridgewayia ( Fig. 1I, H ); proximal end of segment 3 narrowing, distance between two pivot points ( Fig. 2H ) ensures region of articulation is as wide as exopod segment 3 at level of proximal inner seta of exopod segment 3. Outer distal extension of exopod segment 2 not reaching origin of proximal outer spine of exopod segment 3.

Male: Total length 1.80–1.88 mm, urosome 28% of total length ( Fig. 6A, B ). Prosome ovoid with head and pedigerous somite 1 separate; pedigerous somites 4 and 5 separate, posterolateral corners pedigerous somites 1–4 extended into small triangular projections, pedigerous

somite 5 extending into pointed lappets reaching beyond

posterior border of genital somite. Rostrum in form of ventrally-directed rounded plate, with pair of distal filaments. Urosome of five free somites, anterior four somites bordered posteriorly by unevenly serrated hyaline fringe. Caudal rami symmetrical, with seven setae each: seta I vestigial, seta II spiniform, seta V longest, seta IV next longest followed by setae VI and III, seta VII small and spiniform and inserted on dorsoinner distal corner, inner borders of caudal rami lined with fine setules ( Fig. 6D ).

Antennule: Twenty-six segmented on left, 25-segmented on right, extending just beyond posterior border of fourth pedigerous somite; right antennule geniculate between ancestral segments XX and XXI, segments XV– XIX enlarged ( Fig. 7 ). One seta on proximal segment on each side wider than other setae and attenuated distally into curved narrow tip. Left antennule with following setation: I, 1 s, 1a; II– III, 3s, 5a (two on segment II, three on segment III); IV, 2s, 1a; V, 2s, 2a; VI, 2s, 1a; VII, 2s, 2a; VIII to XVIII, 2s, 1a; XIX to XX, 2s; XXI, 2s, 1a; XXII to XXIII, 1s; XXIV, 1 + 1s; XXV, 1 + 1s, 1a; XXVI, 1 + 1s; XXVII– XXVIII, 5s, 1a. Right antennule ( Fig. 8 ) with following setation: I, 1s, 1a; II–IV, 6s, 5a (one on segment II, three on segment III, one on segment IV); V, 2s, 2a; VI, 2s, 1a; VII, 2s, 2a; VIII to XVIII, 2s, 1a; XIX to XX, 2s (on segment XIX distal seta fused spatulate distal extension, segment XX with anterior proximal ridge, proximal seta modified as fused spine-like element and one seta); XXI – XXIII, two fused spine-like elements, 1a, 2s; XXIV– XXV, 2 + 2s (without fused distal process; see Appendix S5), 1a; XXVI, 1 + 1s; XXVII– XXVIII, 5s, 1a.

Antenna, mandible, maxillule, maxilla, maxilliped, and swimming legs 1–4 identical to those of female.

Leg 5: Leg 5 biramous on both sides, with both rami three-segmented, asymmetrical ( Fig. 6E ); exopod slightly longer on right. Right exopod segment 2 with triangular inner attenuation, segment 3 in form of claw with terminal spine, rounded distally, fused to segment, with two articulated spines (one medioproximal, other on outer border more distally inserted), with additional outer fused spinule and pore opening. Left leg exopod segment 2 with inner border swollen, bearing seta modified into scalpel-shaped element thickened along its outer border; exopod segment 3 simple, about twice as long as wide, short terminal spine fused to segment at level adjacent to lateral pore opening, one articu- lated inner spine and outer articulated spine more proximally inserted on posterior surface. Posterior surfaces of exopods and endopods ornamented with scattered patches of very small spinules.

Ecological notes: The samples that contained P. ambiguus sp. nov. came from the hyperbenthic zone above sediments with high pelagic calcium carbonate content on the flanks of the Chatham Rise, but were absent from shallower regions on the Mernoo Saddle or on the scoured slopes of the rise ( Carter, Neil & McCave, 2000). The Chatham Rise traps the Subtropical Front east of New Zealand, and is the location of year-round elevated primary productivity ( Bradford-Grieve et al., 1997).

Remarks: Pinkertonius ambiguus gen. et sp. nov. retains a number of plesiomorphic features: the female genital double somite has a genital operculum; the caudal rami have a vestigial seta I; the female antennule has all of ancestral segments I–XXVII separated; all swimming legs have both rami on each side three-segmented, male leg 5 of relatively simple construction; the proximal seven segments of the antenna exopod are separate; the endopod of the mandibular palp is two-segmented, welldeveloped, and bears ten terminal setae on segment 2; the maxillule has nine setae on the coxal epipodite, four setae on the posterior surface of the praecoxal arthrite, and 11 exopod setae; on the maxilla, endopod segment 1 and its endite are separated from the basis; the maxilliped endopod segment 1 is separate from the basis, and endopod segment 5 has an outer seta.

Superficially, P. ambiguus sp. nov. resembles Miheptneria abyssalis , especially in general body shape, but differs from this species and all other genera currently in the Epacteriscidae , Pseudocyclopidae , Ridgewayiidae , and Boholinidae in having several autapomorphies: in the female the longer caudal ramus is on the right and there is an oblique row of long setules on the ventral surface, which we consider to be homologous with the inner row of setules on the left ramus; the segmental distribution of aesthetascs differs greatly between the sexes (female ancestral segments II, IV– VI, VIII –X, XII–XIII, XV, and XVII are without aesthetascs, whereas the male has aesthetascs on all of segments I to XVIII). Pinkertonius ambiguus gen. et sp. nov. is unique among the above group of families in having the apomorphic condition of multiple aesthetascs on some segments in the male (three on ancestral segment III and two each on segments V and VII on both sides) and one aesthetasc on right segment II and two aesthetascs on left segment II. The proximal outer borders of exopod segments 2 and 3 of legs 2–4 each have a knob-like projection.

The following analyses allow us to place P. ambiguus sp. nov. in a systematic hierarchy.

Figures

Figure 1. Location of samples examined and geographical names used in the text. Isobaths are at 250-m intervals from 250 m.

Figure 2. Pinkertonius ambiguus gen. et sp. nov. Female: A, dorsal view; B, lateral view; C, antennule at same scale as A and B; D, rostrum; E, genital double-somite ventral view; F, caudal rami dorsal view; G, caudal rami, ventral view; H, leg 5 anterior view; I, detail of joint between exopod segments 2 and 3 of leg 5, showing (large, unlabelled arrowheads) location of two pivot points. Selected characters and their states are indicated (e.g. ◀ 5:2). Scale bars: A–C, 1.0 mm; D–I, 0.1 mm.

Figure 3. Pinkertonius ambiguus gen. et sp. nov. female: A, antennule ancestral segments I–XII; B, antennule ancestral segments XIII–XIX; C, antennules ancestral segment XX–XXVIII; D, maxilla; E, maxilla endopod. Scale bars:

Figure 4. Pinkertonius ambiguus gen. et sp. nov. female: A, antenna; B, mandible; C, maxillule; D, maxilliped. Scale bars: 0.1 mm.

Figure 5. Pinkertonius ambiguus gen. et sp. nov. female: A, leg 1, posterior view; B, leg 2, posterior view; C, leg 3, posterior view; D, leg 3, coxa, anterior view; E, leg 4, posterior view; F, leg 4 coxa, anterior surface. Scale bars: 0.1 mm for all figures.

Figure 6. Pinkertonius ambiguus gen. et sp. nov. male: A, dorsal view; B, lateral view; C, right antennule at same scale as A and B; D, caudal rami, dorsal view; leg 5 posterior view (note the deformed left endopod segment 3 that has an extra inner seta – this seta is absent in another specimen). Scale bars: A–C, 1.0 mm; D, E, 0.1 mm.

Figure 7. Pinkertonius ambiguus gen. et sp. nov. male, left antennule ancestral segments: A, segments I–XIV; B, segments XV–XIX; D, segments XX–XXV; E, segments XXVI-XXVIII. Scale bar: 0.1 mm.

Figure 8. Pinkertonius ambiguus gen. et sp. nov. male, right antennule ancestral segments: A, segments I–XIV; B, segments XV–XIX; C, segments XX–XXV; D, segments XXVI–XXVIII. Scale bar: 0.1 mm.