Scoliosoma dimerosum, Kim & Boxshall, 2020
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publication ID |
https://doi.org/ 10.11646/megataxa.4.1.1 |
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DOI |
https://doi.org/10.5281/zenodo.5728097 |
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persistent identifier |
https://treatment.plazi.org/id/03C487CB-ED63-3800-FCEF-F89FFD39FE91 |
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treatment provided by |
Plazi |
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scientific name |
Scoliosoma dimerosum |
| status |
gen. et sp. nov. |
Scoliosoma dimerosum gen. et sp. nov.
( Figs. 377 View FIGURE 377 , 378 View FIGURE 378 )
Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21415 ) from a flat gall on the branchial wall of the ascidian Polycarpa rima Monniot F. & Monniot C., 1996 (Holotype MNHN-IT-2008-6761 = MNHN S1/POL.B/318), CRRFOCDN A3, Eastern Fields Atoll, Coral Sea, Papua New Guinea, depth 30 m, 22 October 1993.
Etymology. The specific name is derived from the Greek di (=two) and mer (=a part), referring to the twosegmented endopod of the maxilla in the new species.
Descriptionoffemale. Body ( Fig. 377A View FIGURE 377 ) curved ventrally; body length 2.65 mm. Prosome tapering anteriorly, divided by 3 constrictions into cephalosome, first and second pedigerous somites, and fused third and fourthpedigerous somites; cephalosome ( Fig. 377B View FIGURE 377 ) 364×382 μm, with weak lateral constriction near middle; dorsal cephalic shield extended ventrally. Fused third and fourth pedigerous somites forming swollen, globular brood pouch. Urosome ( Fig. 377C View FIGURE 377 ) 6-segmented, tapering posteriorly; first urosomite not articulated from brood pouch. Genitalsomite (second urosomite) 160×377 μm; 4 abdominalsomites 227×340, 168×245, 154×168, and 105×123 μm, respectively. Caudalramus ( Fig. 377D View FIGURE 377 ) small, 42×28 μm, incompletely articulated from anal somite, covered with minute spinules; armed with 3 small setae.
Rostrumshortandsemicircularasin D. haplomerosum gen. etsp. nov. Antennule ( Fig. 377E View FIGURE 377 ) broad, leaf-like, about 1.3 times longer than wide, with several incomplete suture lines (or wrinkles) along posterior surface, armed with 11 smallsetae (grouped as 2, 3, and distal 6), and with minute spinules on anterior surface. Antenna ( Fig. 377F View FIGURE 377 ) stout, 4-segmented; proximal 3 segments unarmed; terminal (secondendopodal) segment 50×18 μm; armed with 5 smallsetae (grouped as 1, 2, and 2) plus small, strongly curved terminal claw, about one-third as long as terminal segment.
Labrum ( Fig. 377G View FIGURE 377 ) shortand broad, with patches of minute spinules posterolaterally. Mandible ( Fig. 377H View FIGURE 377 ) with broad coxal gnathobase bearing numerous surface spinules; medial margin of gnathobase with pronounced distal tooth, 1 spiniform toothand 1 serrate projectionnear middle, and serrate proximal part: palp consisting of welldefined basis, exopod, and 2-segmented endopod; basis with weakly pinnate seta at mediodistal corner; exopod with 4 naked setae; first and second endopodal segments with 1 and 4 naked setae, respectively. Maxillule ( Fig. 377I View FIGURE 377 ) bilobed distally; inner lobe (precoxal arthrite) with 5 pinnate setae on margin; smaller outer lobe (palp) bearing total of 5 setae, inner distal seta weakly pinnate, other 4 naked. Maxilla ( Fig. 377J View FIGURE 377 ) 4-segmented; syncoxawith 2 endites and 2 and 1 setaeon first and second endites, respectively; basis with strong claw fringed with narrow membrane along concave margin; endopod small with 1 seta on first segment and 3 setae (1 large and 2 small) on second. Maxilliped ( Fig. 377K View FIGURE 377 ) assmalllobe bearing 2 pinnate setae apically.
Legs 1–4 ( Fig. 378 View FIGURE 378 A-D) rudimentary, lacking defined protopods. Legs 1–3 represented by lobate, blunt rami. Leg 4 as single small lobe (exopod). Both rami subequal in leg 1, but endopodal lobe markedly smaller than exopodal lobe in legs 2 and 3. Exopod of legs 1–4 with 1 small seta proximally on outer margin. Additional minute setae present: 2 distally on endopod of leg 2, and 4 each on inner margin of exopod of legs 3 and 4. Both rami of leg 1 and exopod of legs 2 and 3 ornamented with minute spinules. Leg 5 absent.
Male. Unknown.
Remarks. Scoliosoma dimerosum gen. et sp. nov. closely resembles the type species S. haplomerosum gen. et sp. nov. They share a similar body form, short caudal rami bearing 3 setae, broad, leaf-like antennules, an almost identically reduced maxillule, and very similar swimming legs. Nevertheless, thereare significantdifferences between them, including; the rami of the mandibular palp are not demarcated in S. haplomerosum gen. et sp. nov., unlike D. dimerosum gen. et sp. nov. in which the palp is clearly divided into the basis, exopod, and 2-segmented endopod, and the maxillary endopod is unsegmented in the type species but 2-segmented in S. dimerosum gen. et sp. nov.
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