Eumunida multispina, Komai & Chakraborty & Paramasivam & Gidda, 2019

Komai, Tomoyuki, Chakraborty, Rekha Devi, Paramasivam, Purushothaman & Gidda, Maheswarudu, 2019, A new species of the deep-sea squat lobster genus Eumunida Smith, 1883 (Decapoda: Anomura: Eumunididae) from the Arabian Sea off southwestern India, Zootaxa 4590 (4), pp. 440-456 : 442-454

Eumunida multispina n. sp.

( Figs. 1–8 )

Eumunida funambulus .— Pillai et al. 2014: 116, fig. 1.

Material examined. Holotype: CMFRI E.D.4.4.1.5 , male (cl 46.8 mm), southeastern Arabian Sea, off Sakthikulangara Fishing Port , Kollam, Kerala State, India, 08°56'60"N, 76°32'34"E, 250–400 m deep, commercial trawler, 2 February 2018.

Paratype: CMFRI ED.4.4.1.5.1 , 1 male (cl 50.0 mm), southeastern Arabian Sea, off Kalamuku Fishing Port , Kerala State, India, 08°56'60"N, 76°32'34"E, 250–400 m deep, commercial trawler, 2015.

Non-type: CMFRI ED.4.4.1.1 , 1 female (cl 62.1 mm; dried), southeastern Arabian Sea, off Kavaratti Island , Lakshadweep, 10°033’N; 72°38’E, 300 m deep, seawater pumping, 12 May 2011.

Diagnosis. Rostrum approximately 0.3 times as long as carapace. Carapace with 4 epigastric spines (2 submedian and 2 median); transverse ridges on gastric region interrupted submedially and laterally; posterior part bearing complete striae; lateral margin with 4 spines anterior to posterior cervical groove, first (anterolateral) spine strongest, reaching level of sinus between supraocular spines; small second spine arising just posterior to base of anterolateral spine; 1 small extra spine slightly inferior to lateral carapace margin, located in notch formed by anterior cervical groove; branchial margin with 7–10 spines decreasing in size posteriorly. Thoracic sternite 4 with a pair of anterolateral spines. Pleomeres 2 and 3 each with 3 main transverse ridges. Cheliped about 3.8 times as long as carapace; merus with 5 main rows of spines; palm bearing prominent, ovate setal pad located at base of fixed finger. Pereopod 4 merus with spines on lateral surface.

Description. Holotype. Carapace ( Figs. 1 , 2 ) 1.2 times as wide as long (exclusive of rostrum), greatest width across 0.7 length of carapace. Rostrum ( Figs. 3A , 7A ) abnormally short, not reaching inner supraocular spine, slightly inflated basally; inner supraocular spines (tips broken off) ( Fig. 7A ), slightly diverging; outer supraocular spines ( Fig. 7A ) shorter and slenderer than outer supraocular spines, also slightly diverging. Gastric region well defined, convex transversely, armed with 4 epigastric spines, including 2 median and 2 submedian ( Fig. 3A ); hepatic regions each with 6 unequal spines, spine on central area smallest ( Fig. 3A ). Dorsum posterior to posterior cervical groove fairly inflated, strongly sloping laterally. Anterior and posterior cervical grooves distinctly marked. Transverse ridges conspicuous, anterior margin of each ridge minutely granular, bearing dense short setae; spaces between transverse ridges bearing minute to small squamiform striae; transverse ridges on gastric region interrupted submedially and laterally; anterior branchial region with several short squamiform striae; 8 transverse ridges behind cervical groove (including submarginal ridge along posterior margin), all interrupted submedially or laterally; first ridge divided into short, strongly elevated median part and short squamiform striae in lateral parts; 1 short lateral stria inserted between sixth and last transverse ridges. Lateral carapace margins convex; 4 spines anterior to posterior cervical groove ( Figs. 3B , 7B ),first (anterolateral) spine strongest, more than half length of outer supraocular spine, and reaching level of sinus between supraocular spines, slightly longer than third marginal spine; small second spine arising just posterior to base of anterolateral spine; fourth spine subequal in size to second spine; 1 small extra spine slightly inferior to lateral carapace margin, located in notch formed by anterior cervical groove. Left branchial margin (posterior to cervical groove) ( Fig. 7C ) with 10 small spines decreasing in size and becoming blunt posteriorly (right side damaged, then number of spines not countable). Strong anterior spine on pterygostomial margin; pterygostomial flap covered with scale-like, setiferous ridges ( Fig. 3B ).

Thoracic sternum ( Fig. 4A ) medially concave. Sternite 3 ( Fig. 4B ) with pair of spines on anterior margin, separated by U-shaped median notch. Sternite 4 ( Fig. 4B ) with pair of conspicuous anterolateral spines and transverse rows of short, setiferous transverse ridges. Sternite 5–7 ( Fig. 4A, C ) each with deep median groove; Surface of sternite 5 bearing scattered short setiferous ridges, anterolateral margins spinose. Sternites 6 with row of setae on sinuous anterior ridge; surface with tufts of short setae; anterolateral margins spinose. Sternite 7 with row of setae on anterior ridge; posteriorly sloping surface almost glabrous.

Pleomere 1 ( Fig. 2 ) with 1sharp transverse ridge on tergum. Pleomere 2 with 3( Fig. 2 ) main transverse ridges and small, scale-like, setiferous striae on spaces between main ridges; dorsolateral ridge separating tergum and pleuron entire; each pleuron bearing 3 main transverse ridges anteriorly and scale-like striae posteriorly, all bearing setae on margins, second main ridge armed with prominent spine; anterolateral angle with small spine. Pleomere 3 with 3 main transverse ridges and small, scale-like, setiferous striae on spaces between main ridges; dorsolateral ridge separating tergum and pleuron distinct; pleuron with scale-like, setiferous striae. Pleomere 4 with 2main transverse ridges and 1 additional, medially interrupted striae between two main ridges; pleura each with 1 distinct transverse ridge aligned with second main ridge on tergum; no dorsolateral ridge separating tergum and pleura. Pleomere 5 ( Fig. 4C ) with 2 main transverse ridges and 1 stria between main ridges, latter subdivided into some scale-like striae; pleura each with transverse rows of scale-like striae anterior to posterior to distinct transverse ridge. Pleomere 6 ( Fig. 4C ) with 4 main transverse ridges, all medially interrupted and laterally divided into shorter, linear or arcuate ridges; interspaces with scale-like, setiferous striae; posterior margin with pair of deep notches accommodating bases of uropodal protopods, posteromedian margin spinulose. Telson ( Fig. 4C ) much wider than long, with deep, slit-like incision on lateral margin, divided into 2 parts by transverse suture; anterior part with some squamiform striae or tubercles on either side of midline, all setiferous; posterior part further divided in 2 parts by median suture, posterior margin with distinct median notch; surface with numerous small, scale-like striae, all setiferous.

Eye ( Figs. 2 , 3A, B ) short, partially obscured by supraocular spines; cornea subglobose, subequal in width to eye-stalk; eye-stalk constricted medially.

Antennular peduncle ( Fig. 3B ) slightly overreaching distal end of antennal peduncle. Basal article with vertically compressed, distally rounded lobe on lateral side subterminally.

Antennal peduncle ( Fig. 7A, D, E ) moderately slender. Article 1 with short distolateral spine clearly visible in dorsal view. Article 2 with small distolateral spine reaching proximal 0.3 of antennal acicle. Article 3 with relatively small distomesial spine, not reaching distal margin of article 4. Article 4slightly longer than wide, with long ventrodistal spine nearly reaching distal margin of article 5 and 1 additional small spine near base of ventrodistal spine and1 minute subdistal spine on mesial surface. Article 5 with 1 distolateral and 2 distomesial spines, distolateral spine longest (right) and some minute spines on surfaces (distal spines on left article 5 much weaker than those on right article). Acicle spiniform, slender, gently curving dorsolaterally, reaching nearly to distal margin of article 4.

Maxilliped 3 ( Fig. 7F ) reaching midlength of merus of cheliped. Ischium with crista dentata consisting of row of about 15 corneous-tipped spines; ventrodistal angle produced into small spine. Merus strongly curved mesially, forming prominent concavity on mesial face ( Fig. 4A ), armed with prominent subdistal spine on dorsolateral margin; lateral surface with scattered small spines or tubercles; ventrolateral margin armed with 2 conspicuous spines.

Chelipeds ( Figs. 5 A–D, 6A, B) subcylindrical, subequal in length, about 3.8 times as long as carapace (excluding rostrum). Coxa with 1 small but conspicuous spine on dorsolateral angle; ventral and ventromesial margin divided by U-shaped notch, each spinulose; ventral surface with obliquely longitudinal groove and scattered scalelike, marginally multidenticulate ridges or tubercles. Ischium with prominent ventromesial distal spine followed by 7 (left) or 10 (right) small spines on mesial surface; ventral surface mesially with scattered spines increasing in size distally and laterally with small, setiferous tubercles. Merus about 1.6 times as long as carapace, armed with scattered, small, occasionally scale-like, setiferous tubercles, and5main rows of spines (dorsolateral, dorsomesial, mesial, lateral and ventral), spines generally increasing in size distally, those of mesial row particularly strong, while spines on lateral row smallest. Carpus short, armed with small to moderately large, scattered, setiferous tubercles or spines on surfaces; dorsal surface with median row of spines increasing in size distally; lateral surface also with 1 longitudinal row of spines; ventromesial margin with 1 prominent distal spine followed by much smaller spine; ventrodistal margin with 1 prominent spine just mesial to articular knob with chela. Palm about 3 times as long as wide, with scattered numerous small tubercles or spinules partially obscured by dense, short setae; ventral surface with longitudinal row of widely spaced, small spines and prominent, ovate setal pad located at base of fixed finger ( Fig. 6B ). Fingers narrowly gapping proximally, covered with numerous, small setiferous tubercles or granules (setae reduced distally), each terminating in small, strongly curved corneous claw; occlusal margins each with row of closely spaced, small subacute denticles, that of dactylus with slightly differentiated cluster of 5 denticles and corresponding faint concavity on fixed finger; dactylus subequal in length to palm.

Ambulatory legs (pereopods 2–4) ( Fig. 6C ) having numerous scale-like, setiferous ridges or tubercles on meri to propodus. Pereopod 2 (Fig.) reaching distal end of cheliped merus by tip of dactylus; coxa with spinulose ventromesial margin; ischium bearing 1 small dorsodistal spine, ventromesial margin with some small spine or tubercles. Merus 1.1 times as long as propodus, with dorsal row of prominent spines decreasing in size proximally; ventrolateral and ventromesial margins each row of spines (spines of ventromesial row larger than those of ventrolateral row in general), distalmost spines strongest. Carpus with extensor row of 5 (left) or 7 (right) spines increasing in size distally; lateral surface with longitudinal row of small spines; ventrodistal margin with 1 small spine at each lateral and mesial angle. Propodus strongly compressed laterally; extensor surface armed with small spines arranged in irregular 3 rows; lateral surface with shallow longitudinal sulcus on midline; flexor margin armed with 2 or 3 small spiniform setae on distal margin and row of 17 (left) or 20 (right) small spiniform setae each arising at low tubercles. Dactylus ( Fig. 7G ) strongly compressed laterally, approximately half-length of propodus; flexor margin gently sinuous, with 10 (right) or11 (left) accessory spiniform setae decreasing in size proximally and distributed over entire length; surfaces and margins with sparse tufts of stiff setae.

Pereopod 3 similar to pereopod 2, but merus slightly shorter, reaching distal end of propodus of anteriorly extended pereopod 2; spines on ventromesial row on merus much smaller than those of pereopod 2. Carpus with row of 8 spines on extensor margin. Propodus with 2 small spiniform setae on flexor distal margin and row of 13 small spiniform setae on flexor margin. Dactylus with 10 accessory spiniform setae.

Pereopod 4 shorter than preceding pereopods, reaching distal end of propodus of anteriorly extended pereopod 3. Ischium unarmed on dorsal margin. Merus about 0.8 length of that of pereopod 2; extensor margin with row of spines noticeably decreasing in size; lateral surface with median row of 3 moderately large spines on proximal half; spines on ventrolateral and ventromesial margins smaller than those on preceding pereopods. Carpus with row of 6 spines on extensor margin. Propodus and dactylus generally similar to those of preceding pereopods, but spines on extensor margin of propodus smaller than those on pereopods 2 and 3; flexor margin of propodus with 17 spiniform setae; dactylus with 9 accessory spiniform setae.

Pereopod 5 with strongly compressed, triangular chela.

Pleopods absent.

Uropodal endopod and exopod ovate, subequal in length. Outer surface of endopod with small, scale-like, setiferous tubercles medially.

Paratype. Generally similar to holotype ( Fig. 8 ). Rostrum normally developed, spiniform, approximately 0.3 times as long as carapace. Branchial margins of carapace bearing 8 (right) or 10 (left) spines. Only right cheliped and right pereopod 3 preserved. Cheliped about 2.6 times as long as carapace.

Non-type. Very similar to paratype. Branchial margins of carapace bearing 7 spines on each side.

Colouration in life. Carapace, pleon, telson and pereopods generally reddish orange; distal parts of mesial supraocular spines, tips of pleural spines of pleomere 2, pleural margins of pleomeres 3–6, tips of several spines on cheliped meri and dorsodistal portions of propodi of ambulatory legs white; carapace with small white spot posterolateral to base of lateral supraocular spine ( Fig. 1 ).

Remarks. Eumunida multispina n. sp. belongs to a group of species characterized by the possession of a pair of anterolateral spines on the thoracic sternite 4 (cf. de Saint Laurent & Macpherson 1990; de Saint Laurent & Poupin 1996). However, it is unique within the genus in having four epigastric spines (two submedian and two median), four anterolateral spines (anterior to the cervical groove) and eight to 10 spines on the branchial margin (posterior to the cervical groove). In all other 31 congeners, the anterolateral margin has two or three spines; the branchial margin has six or fewer spines ( de Saint Laurent & Macpherson 1990a, 1990b; de Saint Laurent & Poupin 1996; Baba & Lin 2008; Baba et al. 2009; Komai & Tsuchida 2014; Macpherson et al. 2017; Osawa & Higashiji 2019; Baba & Wicksten 2019). Among the known species of the genus, only E. funambulus has epigastric spines, but there are normally only two epigastric spines (paired submedian) ( de Saint Laurent & Macpherson 1990; Baba et al. 2008). Indeed, the new species resembles E. funambulus in many characters, such as the presence of distinct transverse ridges on the carapace, the merus of the maxilliped 3 being armed with a dorsodistal and two ventral spines, the setose palm of the cheliped having a distinct setal pad on the ventral surface and the possession of spines on the propodi of the pereopods 2–4 (cf. Baba et al. 2009). The new species further differs from E. funambulus in having an additional submarginal spine on the anterolateral carapace margin, located in the notch formed by the anterior cervical groove ( Fig. 7B ).

The phylogenetic relationships among the new species and other four congeners for which sequences of 16S rRNA gene are available, was inferred by using the maximum likelihood method (ML). There were a total of 423 positions in the final data set. The tree with the highest log likelihood score (-866.27) is shown ( Fig. 9 ). The ML reconstruction places E. funambulus as a sister group to a clade containing the remaining species. K2P genetic divergences between sequences of the five species of Eumunida ranged from 1.3–3.5% ( Table 2 ). Genetically, the new species is closest to E. picta (the genetic divergence between the two is 1.3 %) among the four congeners. On the other hand, the divergence between the new species and E. funambulus is 2.4%. In spite of the morphological similarity between the new species and E. funambulus , the genetic analysis strongly supports the distinctness between E. multispina n. sp. and E. funambulus .

K2P genetic divergences using the barcoding regions of the COI gene sequences among 17 species of Eumunida , including the new species, were also calculated ( Table 3 ), although a COI sequence is not available for E. funambulus . There were a total of 566 positions in the final dataset. The genetic divergences between E. multispina n. sp. and the other 16 congeneric species range 11–13%, clearly indicating that the new taxon is distinct from those 16 species.

During this study, a female specimen from Lakshadweep, referred to as Eumunida funambulus by Pillai et al. (2014), was reexamined. The specimen agrees well with the holotype and paratype of the new species in most diagnostic aspects, including the possession of four epigastric spines and four anterolateral spines, although there are seven spines on each branchial margin. We refer the specimen from Lakshadweep to the present new species. In other species of Eumunida , the number of the branchial marginal spines is constant (e.g., de Saint Laurent & Macpherson 1990a, b; de Saint Laurent & Poupin 1996). This new species is exceptional in this regard within Eumunida .

Etymology. The specific epithet refers to the numerous epigastric and branchial marginal spines on the carapace, compared with other congeneric species.

Figures

FIGURE 1. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMFRI E.D.4.4.1.5, entire animal in dorsal view, showing colour in life. Right pereopod 4 damaged.

FIGURE 2. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMF E.D.4.4.1.5, carapace, pleomeres 1 and 2, and cephalic appendages, dorsal view.

FIGURE 3. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMFRI E.D.4.4.1.5.A, anterior part of carapace and eye, dorsal view; B, anterior part of carapace, cephalic appendages, lateral view.

FIGURE 4. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMFRI E.D.4.4.1.5.A, thoracic sternum and coxae of pereopods 1–4; B, thoracic sternites 3 and 4; C, thoracic sternites 5 and 6, pleomeres 5 and 6, telson, and uropods.

FIGURE 5. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMFRI E.D.4.4.1.5. A, merus and carpus of left cheliped and distal parts of meri to dactyli of left pereopods 2–4, dorsal view; B, merus of left cheliped, lateral view; C, same, ventral view; D, coxa to ischium of left cheliped, ventral view.

FIGURE 6. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMFRI E.D.4.4.1.5. A, carpus and chela of left cheliped, dorsal view; B, chela of left cheliped ventral view; C, left pereopods 2–4, lateral view.

FIGURE 7. Eumunida multispina n. sp., holotype, male (cl 46.8 mm), CMFRI E.D.4.4.1.5. A, left frontal part of carapace, eye and antenna, dorsal view; B, left anterolateral margin of carapace, dorsal view; C, left branchial margin of carapace, dorsal view; D, left antennal peduncle, lateral view; E, same, ventral view; F, left maxilliped 3, lateral view; G, distal part of propodus and dactylus of left pereopod 3, lateral view. Setae omitted.

FIGURE 8. Eumunida multispina n. sp., paratype, male (cl 50.0 mm), CMFRI ED.4.4.1.5.1, entire animal in dorsal view (only right cheliped and right pereopod 3 are preserved).

FIGURE 9. Maximum Likelihood (ML) tree, showing relationships among five species of Eumunida, based on 16S rRNA gene sequence data. Heteroptychus scambus was used as an out-group for rooting the tree. The tree with the highest log likelihood (-866.27) is shown. Numbers on branches represent bootstrap values expressed in percentage (values<50% are not shown).

Tables

TABLE 2. Genetic divergence of the mitochondrial 16S rRNA gene among the five species of Eumunida based on Kimura 2-parameter model.

	1	2	3	4
1. Eumunida multispina n. sp.
2. Eumunida annulosa	0.02
3. Eumunida funambulus	0.02	0.04
4. Eumunida picta	0.01	0.02	0.03
5. Eumunida sternomaculata	0.02	0.02	0.03	0.02

TABLE 3. Genetic divergence of the COI gene (566 bp) among the 17 species of Eumunida based on Kimura 2-parameter model.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
1. Eumunida multispinosa n. sp.
2. Eumunida annulosa	0.11
3. Eumunida bispinata	0.13	0.14
4. Eumunida capillata	0.11	0.13	0.05
5. Eumunida karubar	0.12	0.13	0.10	0.09
6. Eumunida keijii	0.13	0.10	0.11	0.11	0.13
7. Eumunida laevimana	0.10	0.12	0.09	0.08	0.10	0.09
8. Eumunida marginata	0.11	0.12	0.11	0.08	0.10	0.11	0.08
9. Eumunida minor	0.11	0.12	0.10	0.09	0.09	0.12	0.09	0.10
10. Eumunida multilineata	0.13	0.06	0.13	0.13	0.14	0.10	0.14	0.15	0.13
11. Eumunida parva	0.12	0.14	0.11	0.09	0.01	0.13	0.10	0.10	0.09	0.14
12. Eumunida picta	0.11	0.12	0.12	0.10	0.11	0.08	0.09	0.11	0.12	0.13	0.11
13. Eumunida smithii	0.12	0.13	0.10	0.09	0.00	0.13	0.10	0.10	0.09	0.14	0.01	0.11
14. Eumunida spinosa	0.13	0.11	0.11	0.11	0.13	0.08	0.10	0.10	0.10	0.11	0.13	0.09	0.13
15. Eumunida squamifera	0.12	0.10	0.12	0.12	0.13	0.10	0.11	0.12	0.11	0.10	0.13	0.07	0.13	0.09
16. Eumunida sternomaculata	0.12	0.11	0.11	0.10	0.12	0.06	0.09	0.11	0.10	0.12	0.12	0.08	0.12	0.08	0.09
17. Eumunida treguieri	0.11	0.10	0.11	0.11	0.13	0.07	0.09	0.12	0.12	0.11	0.13	0.08	0.13	0.09	0.10	0.06