Eurydice andamanensis, Anil & Jayaraj, 2023

Anil, Pathan & Jayaraj, K. A., 2023, Two new species of Eurydice Leach, 1815 (Crustacea: Isopoda: Cirolanidae) from the Andaman Islands, northern Indian Ocean, Journal of Natural History 57 (13 - 16), pp. 976-995 : 978-985

Eurydice andamanensis sp. nov.

( Figures 2–5 )

Material examined

Holotype. Male (3.4 mm), sta. Corbyns Cove (mid-tide zone), 11.37′483°N, 92.45′140°E, South Andaman, Andaman Islands, intertidal sand, coll. Pathan Anil, 18 November 2016 (Reg. no. PUMB 3582 ).

Paratypes. 1 male (3.4 mm) 5 females (3.3, 3.3, 3.3, 3.4, 3.4 mm) same data as holotype (Reg. no. PUMB 3583 ) . 4 males (3.3, 3.3, 3.4, 3.5 mm) 2 females (3.3, 3.4 mm): sta Marina Park (low-tide zone), 11.40′18°N, 092.44′58°E, South Andaman, Andaman Islands, intertidal sand, coll. Pathan Anil, 7 December 2016 (Reg. no. PUMB 3584 ; Reg. no. BAKRZRL 2701 , 2702 , 2703 ) .

Description of male. Body about 2.2 times as long as greatest width; maximum width at pereonites 4 and 5. Cephalon anterior margin rounded, without rostral point. Eyes prominent. Coxae 2–6 posteriorly rounded with short minute setae, posterolateral angles of coxae 7 acute not produced, with short minute setae. Pleonite 1 not concealed by pereonite 7, ventral margins of pleonites 2–4 produced with acute points. Pleotelson about 81% as long as pleon in lateral view; lateral distal margins sinuate; posterior margin of pleotelson one-fourth of pleotelson anterior width, weakly convex with 11 PMS and 4 RS, dorsally with minute thin setae; anterodorsal surface with distinct depression.

Antennula peduncle article 1 anteriorly with 1 simple, 1 brush-tipped setae; article 2 slightly shorter (0.82) than 3; article 2 posterior angle with 4 pappose setae, anterodistal angle with 1 simple seta; article 3 anterodistal angle with 2 simple, 1 pappose setae; flagellum about 0.7 times as long as peduncle, with 5 articles, article 1 of which is longest, about 1.6 times as long as article 2; flagellum extending to posterior of pereonite 1. Antenna peduncle article 1 anterodistal angle without setae, article 2 anterodistal angle with 1 slender simple seta; article 3 short and wide, about 0.8 times as long as wide and about 1.4 times as long as article 2, anterior margin with 9 simple long setae, posteroproximal margin with 1 pappose seta and distal margin with 2 simple long setae; article 4 longest, about 2.2 times as long as 3, anterior margin with 6 simple long setae and 2 brush-tipped setae, posterior distal margin with 2 long simple setae and 2 brush-tipped setae; flagellum extends to pleonite 2, composed of about 15 articles, articles 2–15 with plicate process.

Frontal lamina distinct; clypeus blade prominent. Mandible spine row with 8 spines; molar process anterior margin with about 20 teeth; palp article 2 about 2.7 times as long as 1, with about 5 simple setae along dorsal margin; article 3 less than half (0.2) as long as article 2, with 4 apical simple setae. Maxillule lateral lobe with 13 RS which are weakly serrate, medial lobe with 3 CPS and 1 short simple seta. Maxilla lateral lobe with 4 stiff simple setae, middle lobe with 5 weakly serrate setae, medial lobe with 5 simple and 3 CPS. Maxilliped palp article 1 with 2 long simple setae on proximal lateral margin and 1 long simple seta on distolateral margin, article 3 medial margin with 4 setae, lateral margin without setae; article 4 medial margin with 3 setae, lateral margin with 3 setae; article 5 with 6 distal and 2 medial long simple setae; endite with 3 simple setae and 1 long CPS.

Pereopod 1 basis 3.1 times as long as greatest width, superior margin with 3 small sensory palmate setae, inferior distal angle with 3 long setae; ischium 0.5 times as long as basis, superior distal margin with 9 long setae, dorsal posterior margin with 2 long setae, inferior distal angle with 3 long setae; merus inferior angle with 3 RS and 2 long setae, superior distal angle with 5 long setae; carpus inferior distal angle with 1 RS and 2 long setae; propodus 3.6 times as long as width, inferior margin with 4 RS and 5 long setae; dactylus about half as long as propodus; robust seta opposing dactylus large, extending to accessory unguis; accessory unguis slender, 0.7 times length of unguis.

Pereopods 2 and 3 similar to pereopod 1, pereopod 2 basis about 3.7 times as long as wide, superior margin with 4 small sensory palmate setae, inferior distal angle with 6 long setae; ischium 2 times as long as basis, inferior distal angle with 6 long setae, dorsal posterior margin with 4 long setae, superior distal margin with 8 long setae; merus inferior angle with 6 RS and 4 long setae, superior distal angle with 6 long setae; carpus inferior distal angle with 2 RS and 4 long setae; propodus 3.9 times as long as width, inferior margin with 3 RS and 5 long setae; dactylus about half as long as propodus; robust seta opposing dactylus extending to accessory unguis; accessory unguis 0.8 times length of unguis.

Pereopod 3 basis superior margin with 2 small sensory palmate setae, inferior distal angle with 5 long setae; ischium inferior margin with 7 long setae, dorsal medial margin with 3 setae, superior distal angle with 6 long setae; merus inferior margin with 5 RS and 7 long setae, dorsal medial margin with 2 short setae, superior distal angle with 6 long setae; carpus inferior distal angle with 2 RS and 3 long setae; propodus inferior margin with 3 RS and 7 long setae; dactylus less than half as long as propodus; robust seta opposing dactylus extending near to accessory unguis. Pereopods 5–7 similar to each other.

Pereopod 6 basis 5.4 times as long as wide, superior margin with 3 small sensory palmate setae and 6 long setae, inferior margin with 10 long setae; ischium 0.6 times as long as basis, inferior distal angle with 13 RS and 7 long setae, superior margin with 3 RS and 9 long setae; merus 0.3 times as long as ischium, 1.6 times as long as wide, inferior margin with 6 RS and 3 long setae, superior margin with 5 RS, 5 long setae and 1 distal plumose seta; carpus 0.7 times as long as ischium, 2.3 times as long as wide, inferior margin with 11 RS and 3 long setae, superior margin with 6 RS, 4 simple long setae and 1 distal plumose seta; propodus 0.4 times as long as ischium, 4.7 times as long as wide, inferior margin with 9 RS and 3 long setae, superior margin with 3 RS, 5 long setae and 1 palmate seta; dactylus 0.4 times as long as propodus.

Pereopod 7 basis 5.6 times as long as wide, superior margin with 4 small sensory palmate setae and 7 long setae, inferior margin with 13 long setae; ischium 0.8 times as long as basis, inferior margin with 8 RS and 5 long setae, superior margin with 4 RS, 8 long setae; merus 0.5 times as long as ischium, 1.8 times as long as wide, inferior margin with 7 RS, 1 bi-serrate seta and 3 long setae, superior margin with 5 RS, 1 bi-serrate seta and 5 long setae; carpus 0.9 times as long as ischium, 2.5 times as long as wide, inferior margin with 7 RS, 1 bi-serrate seta, 1 uni-serrate seta and 2 long setae, superior margin with 6 RS, 2 uni-serrate setae and 5 long setae; propodus 0.6 times as long as ischium, 4.9 times as long as wide, inferior margin with 8 RS and 2 bi-serrate setae, superior margin with 7 RS, 4 long setae and 1 distal palmate seta.

Penes 1.7 times as long as basal width, lateral margin convex and distal margin rounded.

Pleopod 1 exopod 1.4 times as long as wide, lateral margin weakly convex, distally narrowly rounded with weakly oblique medial margin, mesial margin strongly convex, with PMS from distal one-fourth, with 20 PMS; endopod 2.1 times as long as wide, distally narrowly rounded, lateral margin weakly convex, with PMS from distal one-third, mesial margin with PMS from distal one-fifth, endopod with 13 PMS; peduncle 0.6 times as wide as long, mesial margin with 4 coupling setae and 3 plumose setae. Pleopod 2 exopod with 17 PMS, endopod with 8 PMS; appendix masculina arises from medial margin of the endopod, proximally narrow, sinuate with minute setae, distally broad, widely rounded, curved medially and mesial margin with 4 small acute cuticular scales and appendix masculina 0.8 times as long as endopod, projecting slightly beyond endopod distal margin by one-third of its length; peduncle with 3 coupling setae and 2 plumose setae. Pleopod 3 exopod with 22 PMS, endopod with 8 PMS. Pleopod 4 exopod with 24 PMS, endopod with 8 PMS. Pleopod 5 exopod with 26 PMS, endopod is naked. Pleopods 3–5 exopods with complete sutures.

Uropod peduncle lateral margin with 5 stiff PMS; exopod slightly obliquely truncate, about 0.8 times as long as length of endopod lateral margin, medial margin with about 11 PMS and 3 RS; endopod lateral margin weakly straight, with 2 short simple setae, medial margin obliquely truncate, with 2 RS and about 22 PMS.

Female. As for male but body broader, about 1.8 times as long as greatest width; antennulae shorter, reaching anterior margin of pereonite 1; antennae shorter, reaching anterior margin of pereonite 5; pleotelson about 78% as long as pleon in lateral view.

Colour. Body white; black chromatophores occur densely on the dorsal surface of the pereion, pleon and pleotelson.

Remarks. The characters that diagnose Eurydice andamanensis sp. nov. are the posterior margin of pleotelson one-fourth of pleotelson anterior width, weakly convex with 11 plumose marginal setae and 4 robust setae; appendix masculina 0.8 times as long as endopod, projecting slightly beyond endopod distal margin by one-third of its length,proximally narrow, sinuate with minute setae, distally broad, widely rounded, curved medially and mesial margin with 4 small acute cuticular scales; the antenna flagellum extending to pleonite 2.

In comparison to the Indian Ocean Eurydice species, Eurydice andamanensis sp. nov. is somewhat similar to Eurydice indicis Eleftheriou and Jones,1976 ,which was described from the west coast of India and shares some characters such as propodus with 4 robust setae on inferior margin,and coxae 7posterior margin terminating in moderately well-developed point. Eurydice andamanensis sp. nov. differs from E. indicis in antennula flagellum extending to posterior of pereonite 1 (vs beyond the posterior margin of the cephalon), pleotelson one-fourth of pleotelson anterior width (vs one-fifth), pleotelson posterior margin weakly convex with 11 plumose marginal setae (vs straight with 8 plumose marginal setae), appendix masculina mesial margin with 4 small acute cuticular scales (vs lacking), appendix masculina extending slightly beyond the posterior margin of pleopod 2 by one-third of its length (vs one-sixth of its length), and uropodal endopod medial margin obliquely truncate (vs triangular).

Eurydice andamanensis sp. nov. can be distinguished from Eurydice peraticis Jones, 1974 as follows. In E. andamanensis sp. nov. the antennula flagellum extends to the posterior of pereonite 1 (vs not reaching beyond the eye), pleotelson posterior margin is one-fourth of pleotelson anterior width (vs one-third), pleotelson posterior margin is weakly convex with 11 plumose marginal setae (vs almost straight with 13 plumose marginal setae), appendix masculina mesial margin with 4 small acute cuticular scales (vs lacking).

Morphologically, Eurydice andamanensis sp. nov. appears similar to Eurydice kensleyi Bruce and Soares, 1996 , from Atlantic South Africa. In E. andamanensis sp. nov. the pleotelson posterior margin bears 11 plumose marginal setae (vs 9 plumose marginal setae), appendix masculina is 0.8 times as long as endopod, projecting slightly beyond by one-third of its length (vs 1.4 times as long as endopod, extending beyond endopod by half of its length), antennula flagellum extends to posterior of pereonite 1 (vs extending to pereonite 1), uropodal exopod is slightly obliquely truncate (vs rounded).

Distribution. Known only from the type locality: South Andaman, Andaman Islands.

Etymology. Eurydice andamanensis sp. nov. is named for the type locality.

Figures

Figure 2. Eurydice andamanensis sp. nov. Holotype (PUMB 3582): (a) dorsal view; (b) lateral view; (c) pleon; (d) antennula; (e) antenna; (f) pleotelson.

Figure 3. Eurydice andamanensis sp. nov. Holotype (PUMB 3582): (a) maxilliped; (b) mandible; (c) mandible palp; (d) maxilla; (e) maxillule.

Figure 4. Eurydice andamanensis sp. nov. Holotype (PUMB 3582): (a) pereopod 1; (b) pereopod 2; (c) pereopod 3; (d) pereopod 6; (e) pereopod 7.

Figure 5. Eurydice andamanensis sp. nov. Holotype (PUMB 3582): (a) pleopod 1; (b) pleopod 2; (c) pleopod 3; (d) pleopod 4; (e) pleopod 5; (f) uropods.