Paralebbeus mollis, Komai, Tomoyuki, 2013
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publication ID |
https://doi.org/ 10.11646/zootaxa.3646.2.5 |
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publication LSID |
lsid:zoobank.org:pub:A9D81B4F-8E7F-480A-8ED9-8D7B27BAE117 |
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DOI |
https://doi.org/10.5281/zenodo.5676880 |
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persistent identifier |
https://treatment.plazi.org/id/093987C7-156E-1739-32D4-A43C5289DA82 |
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treatment provided by |
Plazi |
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scientific name |
Paralebbeus mollis |
| status |
sp. nov. |
Paralebbeus mollis n. sp.
( Figs. 1–5A View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5. A )
Material examined. Holotype: ovigerous female (cl 15.3 mm), Coral Seamount, southwestern Indian Ocean, 41°21.41264’S, 42°55.09195’E, 952 m, November 2011, manipulator installed on ROV ‘Keel 6000’, OUMNH.ZC.2013-01-001.
Description. Body ( Fig. 1 View FIGURE 1 ) robust; integument thin, soft, surface glabrous.
Rostrum ( Figs. 2 View FIGURE 2 A, B) nearly straight, directed forward, not reaching distal margin of first segment of antennular peduncle, about 0.3 times as long as carapace; dorsal margin armed with 1 small tooth located at midlength; ventral margin with 1 small subterminal tooth, ventral lamina absent; lateral carina sharply defined, extending to base of supraorbital tooth. Carapace ( Figs. 1 View FIGURE 1 ; 2A, B) without postrostral median carina or postrostral teeth; dorsal surface elevated, dorsal outline in lateral view strongly convex; supraorbital tooth conspicuous, directed forward, arising at level of posterior margin of orbit; orbital margin with slight convexity posteriorly; moderately deep, U-shaped notch present below base of supraorbital tooth; suborbital lobe prominent, triangular, reaching nearly as far as antennal tooth; anterolateral margin between antennal and pterygostomial teeth strongly sinuous with deep concavity just inferior to antennal tooth; pterygostomial tooth small but conspicuous.
Pleon ( Fig. 1 View FIGURE 1 ) dorsally rounded. Second pleomere with shallow transverse groove on tergum. Pleura of anterior four pleomeres rounded; fifth pleuron with moderately strong posteroventral tooth, lateral margin noticeably sinuous. Sixth pleomere about 1.5 times longer than fifth pleomere and 1.6 times longer than high, bearing tiny posteroventral tooth; posterolateral process terminating acutely. Telson ( Fig. 2 View FIGURE 2 C) 1.5 times longer than sixth pleomere, 2.7 times longer than greatest width, tapering to broad, roundly truncate posterior margin, bearing 3 pairs of dorsolateral spines (anteriormost spine located at posterior 0.4 of telson length); dorsal surface with scattered shallow pits; posterior margin with 2 pairs of markedly unequal lateral spines and 7 setulose spiniform setae ( Fig. 2 View FIGURE 2 D).
Eye ( Fig. 2 View FIGURE 2 A, B) subpyriform with eyestalk not markedly narrowing proximally. Cornea slightly wider and shorter than eyestalk, its maximum width 0.15 of carapace length; ocellus absent.
Antennular peduncle ( Fig. 2 View FIGURE 2 A, B) reaching distal one-fourth of antennal scale. First segment distinctly longer than distal two segments combined, slightly falling short of midlength of antennal scale, dorsodistal margin armed with 3 acute teeth laterally; stylocerite overreaching distolateral margin of first peduncular segment, acuminate, mesial margin gently convex, approximated to lateral surface of first segment. Second segment with l strong dorsolateral distal tooth; articulating membrane between second and third segments broad. Third segment bearing 1 small dorsodistal tooth. Lateral and mesial flagella damaged in both sides.
Antenna ( Fig. 2 View FIGURE 2 A, B, E) with basicerite bearing moderate ventrolateral tooth; carpocerite reaching midlength of antennal scale. Antennal scale 0.5 times as long as carapace and 2.5 times longer than wide; lateral margin nearly straight; distolateral tooth slightly falling short of broadly rounded distal margin of lamella.
Mouthparts not dissected.
Third maxilliped ( Fig. 3 View FIGURE 3 A) somewhat elongate, overreaching antennal scale by nearly full length of ultimate segment. Ultimate segment about 0.8 times as long as carapace, 4.4 times as long as penultimate segment, very slender, gradually tapering distally, with 9 distal spines arranged in nearly circle ( Fig. 4 View FIGURE 4 A); lateral surface with short transverse rows of stiff setae. Penultimate segment short. Antepenultimate segment with minute spinule on distolateral margin, followed by 2 longer spinules on lateral surface. Exopod absent.
Strap-like, terminally hooked epipods present on third maxilliped to third pereopod, corresponding setobranchs present on first to fourth pereopods.
First pereopod ( Fig. 3 View FIGURE 3 B) stout, overreaching distal margin of antennal scale by about half length of chela. Dactylus ( Fig. 4 View FIGURE 4 B) about 0.4 times as long as palm, bearing 2 terminal corneous claws arising from nearly same levels and reaching unequal distances distally, and 1 additional slender, rod-like accessory spine proximal to base of each claw ( Fig. 4 View FIGURE 4 C). Fixed finger bearing single corneous claw ( Fig. 4 View FIGURE 4 C). Palm elongate, about 3.2 times as long as wide. Carpus cup-shaped, about half-length of palm. Merus about 3.8 times longer than wide, with minute tubercle proximodorsally.
Second pereopod ( Fig. 3 View FIGURE 3 C) overreaching antennal scale by about 0.3 length of carpus; anteriorly extended merus extending as far as merus of anteriorly extended third pereopod. Carpus divided into 7 articles, third article longest. Merus slightly longer than ischium.
Third to fifth pereopods moderately long and slender, similar in shape but decreasing in length and width toward posterior ( Fig. 3 View FIGURE 3 D–F). Third pereopod ( Fig. 3 View FIGURE 3 D) overreaching antennal scale by 0.2 length of propodus; dactylus ( Fig. 4 View FIGURE 4 D, E) less than 0.2 times as long as propodus, stout (about 2.5 times as long as wide), terminating in acute, curved unguis, armed with 5 accessory spinules on flexor margin, distalmost accessory spinule longer and much wider than others, blade-like with strongly convex upper margin, making tip of dactylus appearing biunguiculate; propodus with 2 rows of minute spinules on flexor surface ( Fig. 4 View FIGURE 4 D); carpus about half length of propodus; merus slightly narrowing distally, unarmed. Fourth pereopod ( Fig. 3 View FIGURE 3 E) reaching antennal scale by dactylus; merus unarmed. Fifth pereopod ( Fig. 3 View FIGURE 3 F) not reaching distal margin of antennal scale; propodus with grooming setae distally; merus unarmed.
Protopods of second to fifth pleopods each with fairly expanded ventrolateral lobe ( Fig. 1 View FIGURE 1 ). Uropods exceeding telson ( Fig. 1 View FIGURE 1 ).
Eggs large, 2.2 × 2.3 mm.
Coloration in life. Body and appendages entirely red; cornea dark brown, reflective; claws of fingers of first pereopod and unguis of ambulatory dactyli dark brown. Eggs greenish gray. See Fig. 5A View FIGURE 5. A .
Distribution. Known only from Coral Seamount, southwestern Indian Ocean, at a depth of 952 m.
Ecology. The shrimp was associated with an unidentified hexactinellid sponge ( Fig. 5 View FIGURE 5. A B), inhabiting the atrium inside.
Etymology. The specific name is derived from the Latin mollis (= soft) in reference to the soft body integument.
Remarks. The present new species is assigned to Paralebbeus because of the absence of postrostral teeth on the carapace and the lack of lateral spines on the meri of the last three pairs of pereopods, though it is readily distinguished from the two known congeners, P. zotheculatus and P. z y g i u s, by the dorsally and ventrally dentate rostrum and the small but distinct pterygostomial tooth on the carapace. Other differentiating characters between P. mollis n. sp. and the latter two species are summarized in Table 1 View TABLE 1 . The assignment of the present new species requires minor emendation to the original generic diagnosis: rostrum feebly developed, acute, edentate or weakly dentate with 1 tooth on each dorsal and ventral margin.
Paralebbeus zotheculatus was originally described from the Australian Northwest Shelf at depths of 452–506 m and subsequently recorded from the Philippines at a depth of 720 m (Chace 1997). Paralebbeus zygius was originally described from Indonesia (Halmahera and Sulawesi) at depths of 763–1023 m and subsequently recorded from Japan (depth not recorded) (Hayashi & Mitsuhashi 2003). The present new species greatly extends the geographical range of the genus to the southwestern Indian Ocean.
Characters/Species P. mollis n. sp. P. zotheculatus P. zygius Extension of merus of reaching as far as merus of distinctly overreaching reaching as far as merus of
anteriorly extended second anteriorly extended third merus of anteriorly extended anteriorly extended third
pereopod pereopod third pereopod pereopod
TABLE 1. Comparison between Paralebbeus mollis n. sp. with the two known congeneric species.
| Rostral armature | armed with 1 tooth on each dorsal and ventral margin | unarmed | unarmed |
|---|---|---|---|
| Supraorbital tooth on carapace | conspicuous | conspicuous | rudimentary or absent |
| Anterolateral margin of carapace | strongly sinuous, with deep concavity just inferior to antennal tooth | faintly sinuous, without concavity inferior to antennal tooth | strongly sinuous, with deep concavity just inferior to antennal tooth |
| Pterygostomial tooth | moderately strong | minute | rudimentary or absent |
| Telson dorsolateral spines | 3 on each side | 4–6 on each side | 1–3 on each side |
| Ultimate segment of third maxilliped | very slender | moderately stout | moderately stout |
| Distal spines on ultimate segment of third maxilliped | 9 spines arranged nearly in circle | 10–12 spines arranged in nearly circle | about 18 spines arranged in compressed oval pattern |
| Dactylus of first pereopod | bearing 2 terminal corneous claws arising from nearly same levels and reaching unequal distances distally | bearing 2 terminal corneous claws arising from nearly same levels and reaching about same distances distally | bearing 2 terminal corneous claws arising from difference levels and reaching unequal distances distally |
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