Bathycalanus adornatus, Bradford-Grieve, Janet M., Blanco-Bercial, Leocadio & Boxshall, Geoffrey A., 2017

Bradford-Grieve, Janet M., Blanco-Bercial, Leocadio & Boxshall, Geoffrey A., 2017, Revision of Family Megacalanidae (Copepoda: Calanoida), Zootaxa 4229 (1), pp. 1-183 : 110-115

Bathycalanus adornatus n. sp.

( Figs 46 , 71–73 )

Type locality. 25.082o S, 0 9.584o E.

Material examined. ANTXIV/1, MOC10: Stn 8, 3992– 4390 m, 1♀ (10.9 mm) Co441.1.1, holotype; Stn 6, 3993– 5110 m, 1♀ (11.8 mm) Co022.3.1, paratype.

Type specimens. Deposited in the collection of the National Institute of Water and Atmospheric Research, New Zealand: Holotype female: NIWA 85234 Co441.1.1 (1 vial, 2 slides) . Paratype female: NIWA 85235 Co 0 22.3.1 (1 vial, 1 slide).

Genetic material. Co022.3.1. GenBank numbers in Table 6.

Morphological description. Following description based on specimen from ANTXXIV/1, Stn 8. As for genus with following specific level features.

Female ( Fig. 71 A–D). Total length 11.8 mm (mean = 11.4 mm, range = 10.9–11.8 mm, n = 2). Anterior margin of head in dorsal view produced into distinct short rounded projection dorsal to base of rostrum bearing pair of stout small spine-like processes. In lateral view posterior corners of pedigerous somite 5 extended into irregularlyshaped, lightly sclerotised lappets that appear asymmetrical in illustrated specimen, but possibly symmetrical.

Posterolateral borders of pedigerous somite 4 also extended into symmetrical, irregularly-shaped, lightly sclerotised lappets. Genital double-somite symmetrical in dorsal view, with pair of small dorsolateral papillae and ventrolateral swelling; together these features contribute to lateral borders appearing angular when viewed dorsally. Genital double-somite wider than long (length: width = 0.86), widest at anterior one-third, with small ventral genital operculum just anterior to midlength, seminal receptacles not observed.

Antennule ( Figs 71 B, 72A–C) broken, longest remnant with ancestral segment XIX present. Lengths of antennule segments (µm) as follows. Measurements taken along posterior border of each segment but two (posterior (shortest) and anterior) measurements taken of ancestral segment I. I (315, 734); II–IV (421); V (261); VI (276); VII (658); VIII (386); IX (388); X–XI (685); XII (478); XIII (488); XIV (612); XV (744); XVI (822); XVII (901); XVIII (990); XIX (1030); XX (-); XXI (-); XXII (-); XXIII (-); XXIV (-); XXV (-); XXVI (-); XXVII (-); XXVIII (-). Anterior and posterior borders on ancestral segments XVI–XIX naked.

Antenna ( Fig. 73 A) exopod ancestral segment IV with short seta extending short of distal border of exopod segment VIII and bearing short setules.

Maxillule ( Fig. 73 D, E) praecoxal arthrite with 13 setae including 2 on posterior surface and 2 setae on anterior surface, 1 of them small; basal endite 2 with 3 setae; endopod segments with 2 (unequal), 2 (unequal), 5+1 anterior surface seta.

Maxilliped ( Fig. 73 I) syncoxal endite 4 with longest seta extending beyond distal border of endopod segment 2.

Leg 1 ( Fig. 71 E) exopod with articulation between exopod segments 2 and 3 well developed.

Male. Unknown

Distribution. Bathycalanus adornatus n. sp. is an abyssopelagic species so far found only in the southeastern Atlantic over the abyssal plains off Namibia and Angola ( Fig. 46 , Table 1 ). It was taken in hauls between approximately 4000 and 5000 m.

Species comparisons. Bathycalanus adornatus n. sp. is very like Ba. richardi except the genital doublesomite in dorsal view is wider than long, with angular corners at the anterior one third, and the posterolateral borders of pedigerous somites 4 and 5 are extended into irregularly shaped, conspicuous lappets ( Table 10 ). Genetic data suggest that this species is indistinguishable from some specimens of Ba. bradyi (see Fig. 113 , Tables 14–17). Nevertheless, we do not hesitate to describe it as ‘new’ because of its morphological distinctness.

Etymology. Species name derived from Latin adjective “ adornatus ” meaning decorated, embellished, referring to the lappets on the posterolateral borders of pedigerous somites 4 and 5.

Figures

FIGURE 46. Distribution of Bathycalanus species: filled triangle = Bathycalanus bradyi; open triangle = Ba. milleri n. sp.; filled square = Ba. richardi; open square = Ba. dentatus n. sp.; open circle = Ba. tumidus n. sp.; open diamond = Ba. adornatus n. sp.; filled star = Ba. pustulosus; filled diamond = Ba. unicornis; filled circle = Ba. bucklinae n. sp.; cross = Ba. eximius.

FIGURE 71. Bathycalanus adornatus n. sp. female: A, dorsal view; B, lateral right view; C, lateral view of anterior head; D, lateral left view of genital double-somite; E, anterior view of leg 1. Scale bar represents 1.0 mm on figures A, B, D, E; 0.1 mm on remaining figure. Illustrated specimen from ANTXXIV / 1, Stn 8, 3992 – 4390 m.

FIGURE 72. Bathycalanus adornatus n. sp. female antennule ancestral segments: A, segments I – IX; B, segments X – XV; D, segments XVI – XIX. Legs, anterior view: D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bar represents 1.0 mm on all figures. Illustrated specimen from ANTXXIV / 1, Stn 8, 3992 – 4390 m.

FIGURE 73. Bathycalanus adornatus n. sp. female: A, antenna; B, mandibular palp; C, mandibular gnathobase; D, anterior view of maxillule; E, posterior view of praecoxal arthrite of maxillule to show 2 posterior surface setae; F, maxilla; G, inner view of distal part of maxilla; H, outer view of endopod of maxilla; I, maxilliped. Scale bar represents 1.0 mm on figures F, I; 0.1 mm on remaining figures. Illustrated specimen from ANTXXIV / 1, Stn 8, 3992 – 4390 m.

FIGURE 113. Reconstructed phylogeny trees of the Megacalanidae and out-groups, showing the topology (upper panel) and branch lengths (lower panel) corresponding to the ML analysis. Numbers at nodes indicate statistical support under ML / Bayesian / MP / NJ (bootstrap recovery when> 50 %; Bayesian Posterior Probability when> 0.8). On the lower panel, ML distances are showed for branches within node “ A ”, comprising the Megacalanidae. Each colour represents a different genus. All genera are recovered as monophyletic, and relationships between genera resemble the morphology-based phylogeny. ML = maximum likelihood; MP = maximum parsimony; NJ = neighbour joining.