Intramolgus heardensis, Kim & Boxshall, 2021
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publication ID |
https://doi.org/ 10.11646/zootaxa.5013.1.1 |
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publication LSID |
lsid:zoobank.org:pub:BBB1CB11-1AEA-4678-8F6C-B43B7F35E453 |
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persistent identifier |
https://treatment.plazi.org/id/8D4A87BF-FFBF-FF86-FF19-FDB39F5EFAEC |
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treatment provided by |
Plazi |
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scientific name |
Intramolgus heardensis |
| status |
sp. nov. |
Intramolgus heardensis sp. nov.
( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )
Type material. Holotype ♀ (MNHN-IU-2014-21592) and paratype ♀ (MNHN-IU-2014-21593), plus 1 ♀, 1 ♂ dissected paratypes (MNHN-IU-2014-21486) from molyzoa opuntẚa Lesson , 1830: Heard Island, southern Indian Ocean.
Etymology. The type locality, Heard Island, provides the name of the new species.
Description of female. Body ( Fig. 1A View FIGURE 1 ) consisting of extremely swollen prosome and slender urosome; body length 1.70 mm. Cephalothorax almost spherical, consisting of fused cephalosome and first and second pedigerous somites, 1.33 mm long, and 0.93 mm in dorsoventral depth. Cephalosome obscurely defined from first pedigerous somite by partial trace of dorsal articulation. Third and fourth pedigerous somites free and small. Urosome ( Fig. 1B View FIGURE 1 ) 5-segmented; fifth pedigerous somite 75×159 μm; genital double-somite as long as wide (152×150 μm), with trans- verse row of fine spinules in middle of ventral surface ( Fig. 1F View FIGURE 1 ); genital apertures located dorsolaterally, slightly anterior to midlength. Three free abdominal somites 45×118, 34×109, and 57×102 μm, respectively; anal somite ornamented with fine spinules along posteroventral margin ( Fig. 1C View FIGURE 1 ). Caudal ramus ( Fig. 1C View FIGURE 1 ) about twice as long as wide (77×38 μm) and ornamented with fine spinules along posteroventral margin: armed with 6 setae; seta I absent; outer lateral seta (seta II), outer distal seta (seta III) and inner distal seta (seta VI) spiniform, flagellate (tipped with setule); dorsal seta (seta VII) naked; setae II and III unilaterally pinnate along medial margin; setae IV-VI bipinnate; seta II positioned at 36% of ramus length.
Rostrum ( Fig. 1D View FIGURE 1 ) narrowing distally towards truncate apex bearing pair of minute, transparent lobes. Antennule ( Fig. 1E View FIGURE 1 ) 225 μm long, 7-segmented; first segment with stout, pointed process anterodistally; armature formula 3, 11, 3, 4, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked; third segment with 1 minute vestigial seta in addition to 3 setae. Antenna ( Fig. 1F View FIGURE 1 ) 4-segmented, consisting of coxobasis and 3-segmented endopod; all endopodal segments ornamented with rows of fine spinules along outer side: coxobasis armed with 1 seta distally; first endopodal segment with 1 seta on inner margin and 1 small tubercle at inner distal corner; second endopodal segment with 2 small tubercles proximally, 3 setae (proximal seta small) plus 1 claw (claw not articulated at base); third endopodal segment about 2.3 times longer than wide (65×28 μm), armed with 3 short claws and 4 setae.
Labrum ( Fig. 1G View FIGURE 1 ) much wider than long, with broad median incision and 2 pairs of small lobes near centre of medial incision. Mandible ( Fig. 1H View FIGURE 1 ) armed with 5 elements consisting of lash-like, serrate terminal element incompletely articulated at base, 2 spinulose spines on convex outer margin of blade, and 2 unequal, spinulose spines (1 shorter and 1 longer setiform) on inner margin. Paragnath ( Fig. 1I View FIGURE 1 ) as setulose lobe. Maxillule ( Fig. 1J View FIGURE 1 ) distally bilobed; narrower inner lobe tipped with 3 setae; broader outer lobe with row of spinules and 5 setae, one positioned on outer margin, separated from other 4. Maxilla ( Fig. 1K View FIGURE 1 ) 2-segmented; proximal segment (syncoxa) unarmed; distal segment (basis) terminating in spiniform process bearing 2 rows of spinules along its length, with 2 subequal, simple setae proximally and 1 inner spine ornamented with several spinules along both margins. Maxilliped ( Fig. 2A View FIGURE 2 ) 4-segmented; first segment (syncoxa) broad, unarmed; second segment (basis) longest, armed with 2 setae on inner margin, distal seta slightly larger than proximal seta; small third segment unarmed; fourth segment terminating in strong claw, with 2 unequal, proximal setae.
Legs 1–4 ( Fig. 2B–E View FIGURE 2 ) biramous with 3-segmented rami. Armature formula for legs 1–4 as in type species, as follows:
Coxa Basis Exopod Endopod
Leg 1: 0-1 1-0 I-0; I-1; II, I, 4 0-1; 0-1; I, 2, 3
Leg 2: 0-1 1-0 I-0; I-1; II, I, 5 0-1; 0-2; I, II, 3
Leg 3: 0-1 1-0 I-0; I-1; II, I, 5 0-1; 0-2; I, II, I+2
Leg 4: 0-1 1-0 I-0; I-1; II, I, 5 0-1; 0-2; I, II, I
Leg 5 ( Fig. 2F View FIGURE 2 ) represented by 2 setae (pinnate outer and naked inner setae) on ventral margin of fifth pedigerous somite. Leg 6 ( Fig. 2G View FIGURE 2 ) represented by 2 setae and 1 small spine on genital operculum.
Male. Body ( Fig. 3A View FIGURE 3 ) narrow, not inflated; body length 985 μm; prosome 650×340 μm, consisting of cepha- losome and 4 pedigerous somites. Urosome ( Fig. 3B View FIGURE 3 ) 6-segmented; fifth pedigerous somite 113 μm wide; genital somite 136×145 μm, subquadrate; genital operculum ornamented with fine spinules on ventral surface. Four ab- dominal somites 40×98, 31×75, 22×69, and 33×69 μm, respectively. Caudal ramus about 2.07 times longer than wide (58×28 μm), armed as in female.
Rostrum as in female. Antennule 5-segmented ( Fig. 3C View FIGURE 3 ); second segment with 2 pointed processes (proximal and subdistal) on anterior margin; armature formula 3, 12+3 aesthetascs, 3, 4+2 aesthetascs, and 13+3 aesthetascs; aesthetascs large, constricted at distal quarter and tapering distal to constriction. Antenna as in female.
Labrum as in female. Mandible ( Fig. 3D View FIGURE 3 ) atrophied to form tapering lobe bearing 1 spinulose seta apically. Maxillule ( Fig. 3E View FIGURE 3 ) similar to that of female. Maxilla ( Fig. 3F View FIGURE 3 ) atrophied; proximal segment (syncoxa) bearing 2 small lobes near base of distal segment; distal segment (basis) as small lobe bearing 3 naked setae. Maxilliped ( Fig. 3G View FIGURE 3 ) slender, 4-segmented; first segment (syncoxa) unarmed; second segment (basis) with 2 small setae on inner margin and several rows of minute spinules; small third segment unarmed; fourth segment produced into long claw armed with 2 unequal setae proximally and ornamented with fine spinules along distal half of concave margin.
Legs 1–5 as in female. Leg 6 ( Fig. 3B View FIGURE 3 ) represented by 2 setae and 1 small cusp on genital operculum.
Remarks. fntramolgus heardensẚs sp. nov. is morphologically very similar to the type species, although they were found at opposite ends of the world. The shapes of the caudal setae, the structure and setation of the antennae and mandibles, and the armature of the swimming legs are the same in the two species. The main differences between the species are: (1) the second segment of the female antennule is armed with 11 setae in the new species but with 13 setae in f. arctẚcus; (2) the first and second endopodal segments of the antenna are ornamented with 1 and 2 tubercles, respectively, in the new species, but with 5 and 4 spinules, respectively, in f. arctẚcus (as illustrated by Marchenkov & Boxshall, 1995); (3) the maxillule is armed with 8 setae and is distally bilobed in the new species but is unilobate with 7 setae in f. arctẚcus; (4) the syncoxa of the female maxilla is smooth in the new species but ornamented with patch of spinules in f. arctẚcus; and (5) leg 5 consists of 1 naked and 1 pinnate seta in the new species but comprises 2 naked setae in f. arctẚcus. These differences are sufficient to justify the recognition of a new species to accommodate the material from Heard Island.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.