Systematics and zoogeography of the deep-sea hyperbenthic family Arietellidae (Copepoda: Calanoida) collected from the Sulu Sea Author Ohtsuka, Susumu Author Nishida, Shuhei Author Machida, Ryuji J. text Journal of Natural History 2005 2005-06-30 39 27 2483 2514 http://dx.doi.org/10.1080/00222930500087408 journal article 10.1080/00222930500087408 1464-5262 5217766 Metacalanalis hakuhoae n. sp. ( Figures 1–3 ) Material examined Adult female ( holotype ), collected from the central Sulu Sea ( 08 ° 52.669N , 120 ° 25.289E , 08 ° 53.979N , 120 ° 25.509E ; depth 2430–2450 m ) with NORPAC net set on OBT; 7 December 2002 ; appendages dissected on glass slides, and body proper in vial; NHM 2005.157. Copepodid V female ( paratype ), damaged, whole specimen; NHM 2005.158 . Description Female ( holotype ). Body ( Figure 1A, B ) 1.55 mm, compact, plump; prosome 2.6 times as long as urosome. Cephalosome slightly asymmetrical in dorsal view; rostrum ( Figure 1B, C ) strongly curved, with pair of thick filaments; ventrolateral corners expanded posteriorly to cover anterior margin of pediger 1. Pedigers 1–3 with ventrolateral corners produced posteriorly; prosomal posterior ends almost symmetrical, each produced into round lobe reaching midway along genital double-somite ( Figure 1D ). Urosome four-segmented; genital double-somite wider than long, with ventral transverse ridge midway; genital system ( Figure 1E ) asymmetrical, with right seminal receptacle larger than left; paired gonopores and copulatory pores located at mid-length; each copulatory pore slit-like, located at inner corner of gonopore, connected to curved, thick copulatory pore; anal somite relatively long; caudal rami symmetrical, lacking seta I; seta VII located at base of seta VI, bent at midlength. Two large, mature eggs visible within prosome ( Figure 1B ). Antennules considerably asymmetrical, with left ca 1.5 times longer than right. Left antennule ( Figure 1F, G ) 21-segmented; fusion pattern and armature as follows: I–IV59+2ae, V52+ae, VI52, VII52+ae, VIII52, IX52+ae, X52 (one spiniform seta), Figure 1. Metacalanalis hakuhoae n. gen., n. sp. , female (holotype). (A) Habitus, dorsal; (B) habitus, lateral; (C) rostrum, ventral; (D) last compound pedigerous somite and genital double-somite, lateral; (E) genital doublesomite, ventral; (F) left antennule; (G) terminal segments of left antennule; (H) right antennule; (I) terminal segment of right antennule; (J) terminal segments of antennary endopod; (K) antennary exopod, terminal segments missing. Scale bars in mm. Figure 2. Metacalanalis hakuhoae n. gen., n. sp. , female (holotype). (A) Antenna; (B) mandible; (C) maxillule; (D) maxilla; (E) basal spine of maxilla; (F) maxilliped; (G) fourth endopodal segment of maxilliped, largest seta omitted; (H) fifth endopodal segment of maxilliped, largest seta omitted. Scale bars in mm. XI52+ae, XII52+ae (vestigial), XIII52+ae, XIV52 (one spiniform seta)+ae, XV52 (one missing)+ae, XVI52+ae, XVII52+ae, XVIII52+ae, XIX52+ae, XX52+ae, XXI52+ae, XXII51, XXIII51, XXIV–XXVIII512+2ae. Right antennule ( Figure 1H, I ) with same fusion pattern and armature as left except for distinct aesthetasc on segment XII. Antenna ( Figures 1J, K , 2A ) with unarmed coxa; basis with inner seta half as long as exopod; Figure 3. Metacalanalis hakuhoae n. gen., n. sp. , female (holotype). (A) Leg 1, posterior; (B) third exopodal segment of leg 1, posterior; (C) outer lateral margin of endopod of leg 1, posterior; (D) inner basal seta of left leg 1; (E) inner basal seta of right leg 1; (F) right leg 2, anterior; (G) third exopodal segment of left leg 2; (H) phoront of apostome ciliates (?) on intercoxal sclerite of leg 2; (I) right leg 3, anterior; (J) second and third exopodal segments of left leg 3, anterior; (K) left leg 4, posterior; (L) first exopodal segment of right leg 4, posterior, second and third segments missing; (M) leg 5, posterior. Phoronts of apostome ciliates (?) indicated by arrowheads. Scale bars in mm. endopod indistinctly three-segmented, first segment with seta at two-thirds of inner margin; second and third segments almost coalescent with suture clearly visible; second segment with three unequal setae terminally; third segment with five distal setae; exopod indistinctly 10-segmented, with setal formula of 0, 0, 1, 1, 1, 1, 1, 1, 0, 2; terminal segment lacking vestigial element as seen in Metacalanus (cf. Ohtsuka et al. 1994 ). Mandible ( Figure 2B ) without patch of long setules on gnathobase; cutting edge with two patches of minute spinules and four teeth, dorsalmost of which tricuspid; endopod rudimentary, onesegmented, with two plumose setae terminally; exopod five-segmented, with setal formula 1, 1, 1, 1, 2; terminal setae well developed. Maxillule ( Figure 2C ) with one naked short, and four serrate long spines on inner distal corner of praecoxal arthrite; coxal endite with moderately developed, serrate seta; coxal epipodite bearing six setae; basal seta absent; endopod one-segmented, bulbous, with two unequal setae; exopod one-segmented, lamellar, bearing three terminal setae. Maxilla ( Figure 2D, E ) stout; first praecoxal endite with two unequal spinulose setae and vestigial element; second praecoxal to second coxal endites each bearing two spinulose setae; basal spine ( Figure 2E ) highly sclerotized, with short row of three or four spinules at mid-length; endopod four-segmented, with setal formula 1, 3, 2, 2; setae bearing longitudinal row of large spinules. Maxilliped ( Figure 2F– H ) with syncoxa bearing one middle and two subterminal serrate setae and terminal patch of short spinules; basis as long as syncoxa, with two serrate medial setae, row of setules along proximal half of inner margin, and longitudinal patch of spinules; first endopodal segment almost separate from basis, with serrate seta; second to fifth endopodal segments bearing four, four, three, and three setae, respectively; sixth endopodal segment with setae a and b not reduced. Seta and spine formula of legs 1–4 ( Figure 3A–G, I–L ) shown in Table I . Both rami of legs 1–3 and endopod of leg 4 three-segmented (exopods of leg 4 broken or aberrant). Asymmetry in legs 1–4. Leg 1 ( Figure 3A–E ) with inner basal setae asymmetrical, left ( Figure 3D ) thicker than right ( Figure 3E ); outer distal corners of three endopodal segments acutely pointed ( Figure 3C ). Leg 2 ( Figure 3F, G ) with outer spines on third exopodal segments asymmetrical in number, size and location. Leg 3 ( Figure 3I, J ) with outer spines on second and third exopodal segments asymmetrical in length and shape. Left leg 4 ( Figure 3K ) with aberrant exopod, with first segment unarmed and second bearing outer long spine and six modified setae. Terminal exopodal segments of right leg 4 missing ( Figure 3L ). Leg 5 ( Figure 3M ) nearly symmetrical; coxae and intercoxal sclerite separate; basis bearing thick, subterminal seta on posterior surface; endopod lacking; exopod one-segmented, with two lateral and two terminal spines; acute process present at base of inner terminal spine; outer terminal process more acutely pointed in right leg than in left. Male. Unknown. Table I. Spine and seta formula of legs 1–4 of Metacalanalis hakohoae n. gen., n. sp.
Coxa Basis Exopod Endopod
Leg1 0–1 1–1 I–1;I–1;I,1,4 0–1;0–2;1,2,2
Leg2 0–1 0–0 I–1;I–1;II,I,5 0–1;0–2;2,2,4
Leg3 0–1 0–0 I–1;I–1;II,I,5 0–1;0–2;2,2,4
Leg4 0–0 1–0 I–1;–; – 0–1;0–2;2,2,3
Some elements on distal exopodal segment of left leg 2 missing, but identified as spines based on their sclerotized bases. Distal two exopodal segments of leg 4 missing (–). Remarks Asymmetry of legs 1–3 (maybe, leg 4 also) may be related to an as yet unknown swimming behaviour of the new genus as observed in Paramisophria spp. that swim with the left lateral side parallel to the bottom and the left antennule extended anteriorly ( Fosshagen 1968 ; Ohtsuka and Mitsuzumi 1990 ). Bowman and González (1961) insisted that hyperbenthic calanoid copepods generally bear stouter outer spines on the exopods of legs in comparison with pelagic ones. Hence the longer spines on the second and third exopodal segments of left legs 2–4 suggest a possible peculiar swimming behaviour as found in Paramisophria spp. The inner basal seta of leg 1 is considered to play a role in grooming ( Vaupel Klein 1972 ). The thicker inner basal seta of left leg 1 of the new species is likely to be adaptive for grooming the longer left antennule. Gut content analysis revealed that the new species fed upon copepods. Stalked cysts on legs (see Figure 3A, F, H, K ) are possibly assignable to phoronts of apostome ciliates (cf. Grimes and Bradbury 1992 ; Ohtsuka et al. 2004). Etymology The new specific name, hakuhoae , refers to the RV Hokuho-maru , University of Tokyo , that carried out the survey in the Sulu Sea in 2002.