Lonchidiopsis hartmeyeri Vanhöffen, 1917

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 : 447-451

Lonchidiopsis hartmeyeri Vanhöffen, 1917

( Figs. 296–298 )

Material examined. 22 ♀♀, 18 ♂♂ (MNHN-IU-2018- 1884) and dissected 2 ♀♀, 2 ♂♂ from Ascidia sydneiensis Stimpson, 1855 , Guadeloupe; 2 ♀♀ (MNHN-IU-2018- 1885) from Symplegma brakenhielmi (Michaelsen, 1904) , Saint François, Guadeloupe No. 18; 3 ♀♀ (MNHN-IU-2018-1886) from A. sydneiensis, Porte de Case Pilote , Martinique; 14 ♀♀, 8 ♂♂ (MNHN-IU-2018-1887) from A. sydneiensis, Riviere Sens , Guadeloupe; 6 ♀♀, 1 ♂ (MNHN-IU-2018-1888) from Ascidia canaliculata Heller, 1878 , Victoria harbour, Seychelles, 1995; 12 ♀♀, 3 ♂♂ (MNHN-IU-2018-1889) and 1 dissected ♀ from A. canaliculata , Victoria, Seychelles, 1995; 2 ♀♀ (MNHN-IU-2017-2149) from A. sydneiensis, MADIBENTHOS Stn AD 208 (14°31.7 Ń, 61°05.3 Ẃ), depth 5-10 m, 07 September 2016; 3 ♀♀ (MNHN-IU-2017-2150) from A. sydneiensis, MADIBENTHOS Stn AB 187 (14°38 Ń, 60°51.2 Ẃ), depth 5 m,; 2 ♀♀ (MNHN-IU-2017-2151) from A. sydneiensis, MADIBENTHOS Stn AB 189 (14°44.1 Ń, 60°50.8 Ẃ), depth 16 m, 18 September 2016.

Descriptionoffemale. Body ( Fig. 296A ) linear, dorsoventrally depressed; consistingof cephalosome, short neck, large trunk and small free urosome. Body length 2.50 mm. Cephalosome ( Fig. 297A ) 430×550 μm, divisible into narrower frontal (antennal) part, 320 μm wide, and laterally expanded posterior part bearing posterolateral extensions on each side. Neck consisting of indistinctly defined first and second pedigerous somites. Trunk forming brood pouch, variable in size, 1.59×0.64 mm in dissected specimen, consisting of fused third to fifth pedigerous somites; legs 3 and 4 positionedanteriorly on trunk, and leg 5 posteriorly. Eggs serially arranged internally along both sides of brood pouch. Urosome ( Fig. 296B ) 320×242 μm, taperingdistally, unsegmented but with traces of 2 articulations. Caudal ramus ( Fig. 296C ) small, weak, easily detachable from urosome; armed with 6 smallsetae.

Rostrum ( Fig. 296D ) on frontal surface of cephalosome; small, tapering, tipped with spinous process; few setules present on ventral surface. Antennule ( Fig. 296E ) strongly geniculate between fourth and fifth segments; first and second segments extremely broad; third segment inserted into middle of second segment; articulations obscure between second and third, and between third and fourth segments; 4 distal segments slender; armatureformula 2, 17, 6, 2, 3, 2+aesthetasc, 2, and 7+aesthetasc; all setae naked, 2 on first and 4 on second segment large, other setae small. Antenna ( Fig. 296F ) robust, consistingof coxa, allobasis, and 1- segmented endopod; allobasis 100×60 μm, unarmed; free endopodal segment 70×30 μm; armed with 6 small setae (arranged as 1, 2, and 3) plus terminal claw 60 μm long, only slightly shorter than segment.

Labrum ( Fig. 296G ) with lateral margins parallel proximally, but strongly tapering distally, paired semicircular lobes present subdistally on lateral margins, and paired patches of minute setules subdistally on ventral surface. Mandible ( Fig. 296H ) with 5 teeth onmedial cuttingmarginand 1 smallsetaonproximalmarginof coxal gnathobase: basis fused with first endopodal segment, armedwith 1 seta subdistally and 3 setae distally; exopod notarticulated from basis, armedwith 5 setae; proximal seta shortest, second and third setae of medium length, and 2 distalsetae longest; endopod 1-segmented, armed with 10 setae; 3 distal setae on basis and 2 smaller medial setae on endopod ornamented with short spinules (instead of setules). Maxillule ( Fig. 296I ) with 9 setaeon medial margin of arthrite, 1 long seta on coxal endite, 2 unequal setaeon epipodite, 4 setae (second seta small) onmedial margin of basis; exopod with 4 large, subequal setae distally; endopod with 5 unequal setae (second seta curved outwards, and outermost distal seta much longerthan other 4). Maxilla ( Fig. 297B ) 3-segmented, consistingof syncoxa, basis, and 1-segmented endopod; syncoxawith 4, 1, 2, and 3 setae on first to fourth endites, respectively; basis with robust claw bearing spinules along convex margin plus 2 unequal setae; endopod small with 5 small, naked setae. Maxilliped ( Fig. 297C ) unsegmented but divisible into broader proximal and narrow distal parts; proximal part with 5 spinulose setae on medial margin, distal part with 3 pinnate setae (2 medial and 1 apical).

Legs 1–4 biramous with 2-segmented rami ( Fig. 297 D-G); innercoxalsetaabsent. Outersetaonbasis large in leg 1, much smaller in legs 2–4. Inner distal spine on basis of leg 1 well-developed, spinulose. Inner margin of basis and outer margin of endopod setulose in leg 1 but naked in legs 2–4. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 297H ) very small, consistingof small lateral papilla tipped with seta and free exopodal segment 3 times longer than wide (30×10 μm): armed with short subdistal seta and long distal seta.

Description of male. Body ( Fig. 298A ) very different from that of female, elongate (body length 1.50 mm), cylindrical, 11-segmented, without distinct prosome-urosome boundary. Body segmentation distinct, except less distinct articulation between cephalosome and firstpedigerous somite. Cephalosome 270×450 μm, expanded laterally. Remaining part of body gradually narrowing posteriorly. Genital somite with weak paired genital opercula. Four abdominal somites longerthan wide, anterior somites wider than long. Caudal ramus longerthan that of female, about 7.1 timeslongerthan wide (155×22 μm).

Rostrum as tiny anterior process on cephalosome ( Fig. 298A ). Antennule ( Fig. 298B ) 8-segmented, tapering distally; first and second segments only slightly expanded; articulations between second and fourth segments obscure; armatureformula 2, 13, 8, 2, 3, 3, 2, and 7+aesthetasc. Antenna ( Fig. 298C ) forming powerful chelate grasping organ, very different in shape from that of female; 3-segmented; coxa weak; basis expanded, with strong, tapering inner projection with pointed apex, and with blunt tubercle distal to inner projection; subchela comprising endopod with 2 minute vestigial setae subdistally, and terminal claw, only partially articulated from endopod, bearing 4 minute setae proximally: tip of claw opposing apex of inner projection on basis. Labrum as in female. Mandible ( Fig. 298D ) with 1 short proximal and 4 equally long distal setae; basis with 1 subdistal plus 2 distal setae derived from incorporated exopodal segment; free endopodal segment with 9 setae. Maxillule, maxilla, and maxilliped as in female.

Leg 1 as in female. Rami of legs 2–4 more slender than those of female. Second endopodal segment of legs 2 and 3 armed with 4 slender spines and 1 setae, formula I, I+1, II ( Fig. 298E ). Rami of leg 4 ( Fig. 298F ) armed with setae, instead of spines as in female. Leg 5 ( Fig. 298G ) as in female. Leg 6 ( Fig. 298G ) represented by 2 smallsetae on apex of genital operculum.

Remarks. Ooishi & Illg (1986) redescribed this species in detail. There are a few minor differences between our specimens and their redescription, including: (1) the mandible bears 4 setae on the basis-first endopodal segment complex and 10 setae on the second endopodal segment, comparedto 5 and 9 setae, respectively, in Ooishi & Illg; (2) the mandible of the male is armed with 3 setae on the basis+first endopodal segment complex and 9 setae on the second endopodal segment (Ooishi & Illg stated that the male mandible is armed as in the female); and (3) the female maxilliped is unsegmented, compared to the 2-segmented condition in Ooishi & Illg’s specimens.

The type species, L. hartmeyeri , was previously known only from the type host Ascidia sydneiensis in the Pacific. The ascidians Symplegma brakenhielmi and Ascidia canaliculata reported here, are new host records. With the additional distribution records from Guadeloupe in the Caribbean to the Seychelles in the Indian Ocean, L. hartmeyeri turns out to be a very widely distributed species.

Figures

FIGURE 296. Lochidiopsis hartmeyeri Vanĥffen, 1917, female. A, habitus, dorsal; B, urosome, dorsal; C, caudal ramus, lateral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, 0.2 mm; B, 0.1 mm; C, 0.02 mm; D, 0.01 mm; E–I, 0.05 mm.

FIGURE 297. Lochidiopsis hartmeyeri Vanĥffen, 1917, female. A, anterior part of prosome, dorsal; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, exopod of leg 3; G, leg 4; H, leg 5. Scale bars: A, 0.1 mm; B–H, 0.02 mm.

FIGURE 298. Lochidiopsis hartmeyeri Vanĥffen, 1917, male. A, habitus, dorsal; B, antennule; C, antenna; D, mandible; E, leg 2; F, leg 4; G, legs 5 and 6. Scale bars: A, 0.2 mm; B–G, 0.02 mm.