Doroixys amicta, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 475

Doroixys amicta sp. nov.

( Figs. 314 , 315 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21367 ) anddissectedparatype (♀, figured) from membranous cysts of Leptoclinides sp. (MNHN-IT-2008- 4855 = MNHNA 2/ LEP /108), CRCHO 555, Baluan, Papua New Guinea (02°32.27’S, 147°17.97’E), depth 15 m, P. Colin coll., 23 June 2003.

Etymology. The specific name is derived from the Latin words amict (=wrapped up), referring to the finding of the new species in the membranous cyst.

Descriptionoffemale. Body ( Fig. 314A ) inflated, strongly curved ventrally: body length 860 μm. Dorsal cephalic shield expanded ventrolaterally, produced into paired posterolateral processes ( Fig. 314D ) each with acutely pointed tip and 2 semicircular tubercles on outer margin; ornamented with numerous minute sensillae (or setules) on surface. Metasome consistingof 4 pedigerous somites; fourth pedigerous somite spherical, forming brood pouch. Freeurosome ( Fig. 314B ) 5-segmented, curved ventrally. Caudalramus ( Fig. 314C ) indistinctly articulated from anal somite, 3.0 times longerthan wide (54×18 μm) and about 1.2 timeslongerthan anal somite, narrowing distally; and ornamented with numerous setules on all surfaces: armed with 6 setae (outer lateral, dorsal, and 4 distal), outer lateral and dorsal setae attenuated, positioned at 46 and 61% of ramus length, respectively; 4 distal setae bluntly tipped.

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; I-1; I, 1, 4	0-1; 0-1; 1, 2, 3
Leg 2	0-0	1-0	1-0; 1-0; 3, 1, 5	0-0; 0-0; 1, 2, 2
Leg 3	0-0	1-0	1-0; 1-0; 3, 1, 5	0-0; 0, 3, 1
Leg 4	0-0	1-0	1-0; 1-0; 3, 1, 4	0-0; 0, 3, 0

Rostrum ( Fig. 314E ) longerthanwide (52×48 μm), tapering towards blunt apex; ornamented with numerous setules. Antennule ( Fig. 314F ) broad, 102 μmlong, 7- segmented; armatureformula 2, 11, 3, 3+aesthetasc, 3+aesthetasc, 1, and 11+aesthetasc; all setae naked; aesthetascs short, rod-shaped. Antenna ( Fig. 314G ) 4- segmented; proximal 3 segments (coxa, basis, and first endopodal segment) unarmed; compounddistalendopodal segment narrowest, about 3.4 times longer than wide (37×11 μm); armed with 3 setae plus small terminal claw, 12 μm long, aboutone-thirdaslongas segment.

Labrum ( Fig. 314H ) with smooth, convex, posterior marginand broad, denselysetulose posteromedian lobe. Mandible ( Fig. 314I ) bearing 5 sharply pointed teeth and 1 thin seta on coxal gnathobase; basis with 1 seta distally on medial marginand setules on outer margin; exopod short, armed with 5 unequal setae becoming gradually shortened from medial to outermost; endopod with 1 and 4 setae on first and second segments, respectively; seta on first segment broad; 2 median distal setae on second segment subequal and longer than other 2 setae. Maxillule ( Fig. 314J ) armed with 8 setae on arthrite; coxal endite present, tipped with 1 small seta; epipodite with 1 seta; basiswith 1 setaonmedial margin; exopodwith 4 equal setae; endopodwith 3 or 2 setae. Maxilla ( Fig. 315A ) consistingof syncoxa, basis, and 2-segmented endopod; syncoxa with 4, 2, and 2 setae on first to third endites, respectively; basiswith narrow claw plus 1 seta; endopod with 1 and 3 setaeon first and second segments, respectively. Maxilliped ( Fig. 315B ) unsegmented with 4 setae distally.

Legs 1 and 2 ( Fig. 315C, D ) with 3-segmented rami. Legs 3 and 4 ( Fig. 315E, F ) with 3-segmented exopods and 2-segmented endopods. Inner coxal seta absent in all swimming legs. Inner distal spine of basis of leg 1 very short, 6 μm long. First exopodal segment of swimming legs ornamented with setules on outer margin, 4, 4, 5, and 2 in legs 1–4, respectively. Third exopodal segment of leg 1 armedwith 1 spineand 5 setae. Compound distal endopodal segment of leg 3 retaining trace of articulation. Setae on rami of legs 2–4 generally bluntly tipped. Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 315G ) consisting of unarmed, blunt outer protopodal lobe and tapering, pointed exopodal process bearing 1 seta on its outer margin; both protopodal lobe and exopodal process ornamented with setules.

Male. Unknown.

Remarks. Doroixys amicta sp. nov. displays three outstanding features: the maxillule has a coxal endite tipped with a small seta, the maxilliped is armed with only 4 setae, and the third exopodal segment of leg 1 is armed with only 6 (not 7) armature elements. These character states are unique within the genus and allow the new species to be distinguished from all congeners. The absence of an armature element on the protopodal lobe of leg 5 and the discovery of the copepod specimens inside membranous cysts in the host also are unusual features in Doroixys .

Figures

FIGURE 314. Doroixys amicta sp. nov., female. A, habitus, right; B, leg 5 and urosome, right; C, right caudal ramus, dorsal; D, posterolateral process of cephalic shield; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible; J, maxillule; K, palp of maxillule. Scale bars: A, 0.1 mm; B, 0.05 mm; C–K, 0.02 mm.

FIGURE 315. Doroixys amicta sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bars: A, C–G, 0.02 mm; B, 0.01 mm.