Lebbeus rufomaculosus, Komai & Matsuzaki, 2022

Komai, Tomoyuki & Matsuzaki, Koji, 2022, Three new species of the thorid shrimp genus Lebbeus White, 1847 (Decapoda: Caridea) from Nemuro Strait, Hokkaido, Japan, with supplemental note on L. fujimotoi Matsuzaki, Hibino & Komai, 2015, Zootaxa 5133 (2), pp. 151-181 : 156-162

publication ID	https://doi.org/ 10.11646/zootaxa.5133.2.1
publication LSID	lsid:zoobank.org:pub:6B6B0F37-8D98-4930-9038-EEE9F0E7B674
DOI	https://doi.org/10.5281/zenodo.6521119
persistent identifier	https://treatment.plazi.org/id/9A43150D-5600-4CA8-B65D-009CE345EA7A
taxon LSID	lsid:zoobank.org:act:9A43150D-5600-4CA8-B65D-009CE345EA7A
treatment provided by	Plazi
scientific name	Lebbeus rufomaculosus
status	sp. nov.

Treatment

Lebbeus rufomaculosus n. sp.

[New Japanese name: Akamadara-ibara-mo-ebi]

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype. CBM-ZC 16695 , ovigerous female (cl 16.5 mm), Nemuro Strait, 800–1200 m deep, commercial gill net, June 2019, coll. K. Matsuzaki, DNA voucher.

Paratypes. CBM-ZC 16696 , 2 ovigerous females (cl 15.0, 15.2 mm), Nemuro Strait, 500–700 m deep, 31 August 2018, commercial shrimp trap, coll. K. Matsuzaki ; CBM-ZC 16697 , 1 ovigerous female (cl 16.5 mm), similar locality, 500–800 m deep, August 2019, commercial shrimp trap, coll. K. Matsuzaki.

Diagnosis. Rostrum ( Fig. 2A View FIGURE 2 ) somewhat curving dorsally, distinctly overreaching distal margin of antennal scaphocerite, 1.3–1.4 times as long as carapace; dorsal margin armed with 4 or 5 small teeth, including 2 or 3 on proximal 0.3–0.4 of rostrum and 2 postrostral (posteriormost tooth located at 0.3 of carapace length); ventral blade narrow, armed with 6 or 7 teeth. Carapace ( Fig. 2A View FIGURE 2 ) with low postrostral ridge; supraorbital spine small, arising at level of posterior margin of orbit; no notch below supraorbital spine; pterygostomial spine small; anterolateral margin between antennal and pterygostomial spines slightly sinuous. Pleon ( Fig. 2B View FIGURE 2 ) with pleura of anterior four pleomeres rounded, unarmed, that of pleomere 5 with posteroventral spine. Telson ( Fig. 3C, D View FIGURE 3 ) armed with 6 or 7 dorsolateral spiniform setae on either side; posterior margin triangular, with 2 pairs of unequal spiniform setae and 5 medial pairs of short setae. Antennular peduncle ( Figs. 2A View FIGURE 2 ; 3A View FIGURE 3 ) slender; article 1 with small spine on dorsolateral distal angle; stylocerite falling far short of distal margin of peduncular article 1, proximolateral lobe developed into hook-like projection ( Fig. 3E View FIGURE 3 ). Antenna ( Figs. 2A View FIGURE 2 ; 3A, F View FIGURE 3 ) with scaphocerite 3.2 times as long as wide, distolateral spine far exceeded by distomesially produced, rounded lamella; carpocerite reaching midlength of scaphocerite. Maxilliped 3 ( Fig. 4A View FIGURE 4 ) overreaching distal margin of antennal scaphocerite by 0.2 length of ultimate article; ultimate article 2.8 times as long as penultimate article, bearing row of 4 cuspidate setae on distomesially. Pereopod 1 ( Fig. 4D View FIGURE 4 ) relatively slender, reaching midlength of scaphocerite. Pereopod 3 ( Fig. 4F View FIGURE 4 ) relatively slender, overreaching antennal scale by 0.8 length of propodus; dactylus ( Fig. 3J View FIGURE 3 ) slightly less than 0.2 times as long as propodus, 4.5 times longer than wide, with 6–8 accessory spiniform setae on entire flexor margin; merus armed with 7–10 spiniform setae on lateral surface. Strap-like epipods on maxilliped 3 and pereopod 1, no epipods on pereopods 2 and 3 ( Fig. 3M View FIGURE 3 ).

Description. Holotype. Body ( Figs. 1 View FIGURE 1 ; 2A, B View FIGURE 2 ) moderately stout; integument moderately firm, surface glabrous.

Rostrum ( Fig. 2A View FIGURE 2 ) somewhat curving dorsally, distinctly overreaching distal margin of antennal scaphocerite, about 1.3 times as long as carapace (tip broken off); dorsal margin armed with 5 small teeth including 3 on rostrum proper (anteriormost tooth located at 0.4 rostral length, and then anterior 0.6 leaving unarmed) and 2 postrostral (posteriormost tooth located at 0.3 of carapace length); ventral blade narrow, deepest at proximal 0.4 length, margin armed with 6 subequal teeth more widely spaced anteriorly; lateral carina obsolete. Carapace ( Fig. 2A View FIGURE 2 ) with low postrostral ridge extending beyond midlength of carapace length, becoming broader and blunt posteriorly; dorsal profile in lateral view almost straight; orbital margin slightly sinuous, ventral part limbed marginally, postorbital region shallowly depressed just posterior to margin; supraorbital spine small, arising at level of posterior margin of orbit; no notch below supraorbital spine; suborbital lobe distinct, rounded ( Fig. 3B View FIGURE 3 ); antennal spine small, well exceeding beyond suborbital lobe; pterygostomial spine small, directed slightly ventrally; anterolateral margin between antennal and pterygostomial spines slightly sinuous; no conspicuous ridges on lateral surface.

Pleon ( Fig. 2B View FIGURE 2 ) with pleura of anterior four pleomeres rounded, unarmed, that of pleomere 5 with relatively slender posteroventral spine. Pleomere 2 tergum with deep transverse groove. Pleomere 3 rounded dorsally, posterodorsal margin substantially produced posteriorly. Pleomere 6 2.7 times as long as pleomere 5, 2.4 times as long as high, with small posteroventral spine and posterolateral process terminating in small spine. Telson ( Figs. 2B View FIGURE 2 ; 3C, D View FIGURE 3 ) reaching posterior margin of uropodal endopod, 1.3 times as long as pleomere 6, relatively narrow, armed with 6 (left) or 7 (right) dorsolateral spiniform setae; posterior margin triangular, with 2 pairs of unequal spiniform setae (mesial pair longer and stouter than lateral pair) and 5 medial pairs of short setae.

Eye ( Figs. 2A View FIGURE 2 ; 3A View FIGURE 3 ) subpyriform; cornea large, darkly pigmented, its maximum width 0.26 of carapace length; ocellus absent. Eyestalk short, cup-shaped.

Antennular peduncle ( Figs. 2A View FIGURE 2 ; 3A View FIGURE 3 ) slender, reaching distal 0.2 of antennal scaphocerite. Article 1 longer than distal two articles combined, with small spine on dorsolateral distal angle; stylocerite moderately slender, partially in touch with first article mesially, slightly curving dorsally, terminating in acute spine falling far short of distal margin of peduncular article 1, proximolateral lobe with small terminal tubercle, making proximolateral lobe as hook-like projection ( Fig. 3E View FIGURE 3 ). Article 2 subcylindrical, armed with small spine at dorsolateral distal angle. Article 3 short, with small spine on dorsodistal margin. Lateral flagellum with thickened aesthetasc-bearing portion approximately half-length of carapace; lower flagellum distinctly longer than upper flagellum.

Antenna ( Figs. 2A View FIGURE 2 ; 3A, F View FIGURE 3 ) with moderately stout basicerite, bearing blunt dorsolateral projection and small ventrolateral spine. Scaphocerite 0.8 times as long as carapace, 3.2 times as long as wide; lateral margin nearly straight; distolateral spine relatively slender, far exceeded by distomesially produced, rounded lamella. Carpocerite reaching midlength of scaphocerite.

Mouthparts not dissected. Maxilliped 3 ( Fig. 4A View FIGURE 4 ) relatively slender, overreaching distal margin of antennal scaphocerite by 0.2 length of ultimate article; ultimate article 2.8 times as long as penultimate article, bearing 9, including 4 on mesial margin, darkly pigmented cuspidate setae circumscribing terminal margin ( Fig. 3B View FIGURE 3 ); antepenultimate article slightly shorter than distal two articles combined, with 1 minute spiniform seta at ventrolateral distal angle, dorsodistal margin with 1 minute spine, dorsolateral margin with 1 tiny medial spine flanked by 2 long stiff setae on distal margin ( Fig. 3C View FIGURE 3 ); exopod absent.

Pereopod 1 ( Fig. 3G View FIGURE 3 ; 4D View FIGURE 4 ) relatively slender, reaching midlength of scaphocerite. Chela 1.2 times as long as carpus, 5.3 times as long as wide; dactylus 0.6 times as long as palm, terminating in 2 black corneous claws and slender, accessory claw at base of shorter terminal claw ( Fig. 3H View FIGURE 3 ); fixed finger terminating in single black claw ( Fig. 3H View FIGURE 3 ); palm 3.3 times as long as wide, with short row of grooming setae on mesial face proximally. Carpus subcylindrical; grooming apparatus consisting of rows of stiff setae circumscribing deep depression on subdistal portion on dorsal face and subdistal cluster of short stiff setae on mesial face. Merus 6.2 times as long as wide, with minute spine on near dorsal margin proximally and short row of minute spiniform setae on ventral margin proximally ( Fig. 3I View FIGURE 3 ). Ischium with minute spiniform setae on ventrodistal margin ( Fig. 3I View FIGURE 3 ).

Pereopod 2 ( Fig. 4E View FIGURE 4 ) moderately slender, overreaching antennal scale by length of chela and distal 2 carpal segments. Chela approximately 0.2 times as long as carpus, with tufts of short setae on fingers; dactylus 0.4 times as long as palm. Carpus subdivided into 7 segments, length ratio of segments: 1: 0.6: 2.3: 1.1: 0.7: 0.9; distalmost segment with prominent tuft of setae. Merus 1.1 times as long as ischium.

Pereopod 3–5 ( Fig. 4F–H View FIGURE 4 ) relatively slender, generally similar. Pereopod 3 ( Fig. 4F View FIGURE 4 ) overreaching antennal scale by 0.8 length of propodus; dactylus ( Fig. 3J View FIGURE 3 ) 0.15 times as long as propodus, 4.5 times longer than wide, terminating in moderately slender, clearly demarcated unguis, with 7 accessory spiniform setae on entire flexor margin, increasing in length distally, distalmost accessory seta curved; propodus 18.6 times longer than wide with evenly spaced minute spiniform setae arranged in 2 rows on flexor margin; carpus 0.5 times as long as propodus, unarmed: merus armed with 9 spiniform setae on lateral surface; ischium unarmed. Pereopod 4 ( Fig. 4G View FIGURE 4 ) similar to pereopod 3, overreaching antennal scale by 0.6 length of propodus; dactylus ( Fig. 3K View FIGURE 3 ) 0.17 times as long as propodus, with 7 accessory spiniform setae on flexor margin; merus with 7 spiniform setae on lateral surface. Pereopod 5 ( Fig. 4H View FIGURE 4 ) generally similar to pereopods 3 and 4, overreaching antennal scaphocerite by 0.5 length of propodus; dactylus ( Fig. 3L View FIGURE 3 ) 0.19 times as long as propodus, with 8 accessory spiniform setae on flexor margin; propodus with cluster of grooming setae on flexor surface in distal 0.2 of flexor margin; merus with 1 spiniform seta at ventrolateral distal angle of lateral face.

Strap-like epipods present on maxilliped 3 and pereopod 1, both terminally hooked, interacting with setobranchs on pereopods 1 and 2, respectively ( Fig. 3M View FIGURE 3 ).

Pleopods without distinctive features.

Uropod ( Figs. 2B View FIGURE 2 ; 3C View FIGURE 3 ) reaching posterior margin of telson. Protopod terminating in strong spine posterolaterally. Exopod subequal in length of endopod, with small posterolateral spine exceeded by tiny spiniform seta arising at its mesial base.

Eggs oval, large, approximately 2.3× 3.1 mm.

Paratype. Generally similar to holotype. Rostrum 1.4 times as long as carapace, dorsally armed with 4 or 5 teeth, 2 or 3 on proximal 0.3–0.4 of rostrum and 2 postrostral; ventral margin with 6 or 7 teeth. Telson armed with 6 or 7 dorsolateral spiniform setae on either side. Maxilliped 3 ultimate article bearing 7 or 8 cuspidate setae circumscribing distal margin, including 4 on distomesial margin. Pereopods 3–5 dactyli each with 5–8 accessory spiniform setae on flexor margin; meri with 6–10 spiniform setae in third, 5–9 in fourth and 2 or 3 in fifth.

Colouration in life. Carapace and rostrum reddish, carapace dorsum darker; pleon mottled with red and white; tail fan (telson and uropods) red; cornea black; antennular and antennal peduncle generally red, flagella also uniformly reddish; maxilliped 3 and pereopod 1 generally red; pereopods 3–5 generally red, with white markings on dorsal faces of meri and extensor faces of carpi to propodi; pleopods 2–5 also generally red, each with distal white blotch on ventral expansion of protopod; eggs greenish gray ( Fig. 1 View FIGURE 1 ).

Distribution. Presently known only from Nemuro Strait, at depths of 500–1200 m.

Remarks. Lebbeus rufomaculosus n. sp. belongs to the group of species characterised by the possession of epipods only on the maxilliped 3 and pereopod 1, which is represented by seven previously described taxa ( Table 1 View TABLE 1 ). All but L. vicinus montereyensis share also a relatively long rostrum that is subequal in the length to or longer than the carapace and a small supraorbital spine lacking an inferior notch ( Rathbun 1904; Kobjakova 1937; Wicksten & Méndez 1982; Hayashi 1992; Fransen 1997; Komai & Collins 2009; Schiaparelli et al. 2015; Chan & Komai 2017). In L. vicinus montereyensis , the rostrum is distinctly shorter than the carapace (in the holotype, it is 0.7 times as long as the carapace; Wicksten & Méndez 1982: 116). Lebbeus rufomaculosus n. sp. is notable in having a prominent projection on the proximolateral portion of the antennular stylocerite ( Fig. 3E View FIGURE 3 ). In the other seven taxa in this informal species group, there is no such a projection; at most an obtuse convexity is present in those seven comparative species ( Wicksten & Méndez 1982; Hayashi 1992; Fransen 1997; Komai & Collins 2009; Schiaparelli et al. 2015; Chan & Komai 2017).

The status of L. rufomaculosus n. sp. is well supported by the genetic analyses: COI divergence between L. rufomaculosus n. sp. and the known congeneric species ranges from 6.0 to 21.2% ( Table 3 View TABLE 3 ); 16S divergence ranges from 3.3 to 7.8% ( Table 4 View TABLE 4 ).

Etymology. From the combination of the Latin, “ rufus ” (= red) and “ maculosus ” (= mottled) in reference to the body colour of this new species.