Haplostoma mammiferum, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 160-162

Haplostoma mammiferum sp. nov.

( Fig. 104 )

Type material. Holotype ♀ (MNHN-IU-2014-21519, dissected and mounted on a slide) from ieptçclẚnẚdes sp.; Papua New Guinea, CRRF coll.,1999.

Etymology. The name reflects the presence of a prominent posterodorsal mammiform process on the last metasomite of the female.

Description of female. Body ( Fig. 104A, B ) eruciform, consisting of cephalosome, 4-segmented metasome, and 2-segmented genitoabdomen. Body length 1.37 mm; maximum width 435 μm across second metasomite. Ceph- alosome 280×330 μm, narrower than metasome; 4 metasomites distinctly defined by deep constrictions; last meta- somite compound, comprising fourth and fifth pedigerous somites, subdivided by ventral constriction, characteristically bearing distinct median tubercle posterodorsally (indicated by arrowhead in Fig. 104B, C ). Genitoabdomen ( Fig. 104C ) small; anterior somite 130×237 μm; genital apertures located dorsally; posterior somite (free abdomen) clearly articulated from anterior somite, 46×62 μm. Caudal ramus ( Fig. 104D ) about 1.3 times longer than wide (33×25 μm) tapering; armed with 2 equal setae and 2 unequal spines, larger distal spine twice as long as smaller subdistal spine.

Rostrum ( Fig. 104E ) short, semicircular, fringed with thick, transparent surface layer. Antennule ( Fig. 104F ) indistinctly 2-segmented; armed with 2 setae on proximal segment and 16 setae on small distal segment; all setae small. Antenna ( Fig. 104G ) 2-segmented; proximal segment slightly longer than wide, unarmed; distal segment (endopod) about 2.4 times longer than wide (45×19 μm); armed with 5 stout spines (2 distal and 3 on inner margin), third inner margin spine largest and outermost of distal spines smallest.

Labrum ( Fig. 104H ) with 4 transparent lobes on posterior margin, 2 median lobes larger and semicircular, and 2 lateral lobes smaller, nipple-shaped. Mandible ( Fig. 104H ) positioned lateral to labrum, as lobe tipped with 1 seta. Maxillule and maxilla absent. Maxilliped ( Fig. 104I ) robust, 4-segmented; second segment bearing 2 small setae, other segments unarmed; terminal claw unarmed and unornamented.

Leg 1-4 consisting of protopod, exopod, and endopodal protrusion; exopods evenly tapering. Leg 1 ( Fig. 104J ) exopod armed with 1 seta and 3 small simple spines; endopod much broader than long. Legs 2 and 3 shaped and armed as leg 1. Leg 4 ( Fig. 104K ) exopod armed with 1 seta and 4 spines; endopod narrower than for legs 1-3.

Leg 5 ( Fig. 104L ) small, stout, as long as wide, bearing 3 setae (1 proximal and 2 distal). Leg 6 ( Fig. 104M ) represented by 2 broad, pointed processes and 5 smaller, dentiform elements on genital operculum.

Male. Unknown.

Remarks. eaplçstçma mammẚferum sp. nov. exhibits three unique features, each of which clearly differentiates it from other species, as follows: (1) the last metasomite bears a distinct median tubercle posterodorsally; (2) the labrum bears 4 lobes on the posterior margin, 2 larger median and 2 smaller lateral lobes; and (3) the exopod is armed with 1 seta and 3 spines in legs 1-3, but with 1 seta and 4 spines in leg 4. This last feature is especially remarkable because in legs 1-4 of all previously known species of eaplçstçma, the numbers of armature elements on the exopods of legs 1 to 4 generally reduce from anterior (leg 1) to posterior (leg 4).

Figures

FIG. 104. eaplçstçma mammẚferum sp. nov., female. A, habitus, dorsal; B, habitus, left; C, posterior end of body, dorsal; D, caudal ramus; E, rostrum; F, antennule; G, antenna; H, labrum; I, maxilliped; J, leg 1; K, leg 4; L, leg 5; M, genital aperture. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D-K, M, 0.02 mm; L, 0.05mm.