Description of Stenothoe lowryi sp. nov. (Crustacea: Amphipoda: Stenothoidae), from the Straits of Malacca, Malaysia Author Azman, Abdul Rahim text Records of the Australian Museum 2023 Rec. Aust. Mus. 2023-12-06 75 4 371 379 http://dx.doi.org/10.3853/j.2201-4349.75.2023.1878 journal article 10.3853/j.2201-4349.75.2023.1878 2201-4349 10413924 3D6F00F6-54E6-40F8-97E4-59CA19672E79 Stenothoe lowryi sp. nov. urn:lsid:zoobank.org:act: 27D7AC0F-003D-4D24-92D1-FFAB571B22BD Figs 2–4 Holotype : Male, 5.3 mm (from tip of rostrum to apex of telson), UKMMZ-1133, Peninsular Malaysia , Pangkor Island , Teluk Nipah beach, 4°14'00.0"N 100°31'00.0"E , intertidal area, rock washing, 0–1 m depth , B. A. R. Azman , S. Y. Gan , J. H. C. Lim , C. F. Liong , 12 January 1996 ( UKM I.D. PKR 1.3923) . Allotype : Female, UKMMZ-1134, same station data as holotype; dissected appendages were kept in five semi-permanent slides mounted on glycerol. Figure 2 . Stenothoe lowryi sp. nov. , holotype male, 5.3 mm, UKMMZ-1133. Diagnosis . Stenothoidae with long antenna 1 (distinctly longer than head and pereonites 1–4) with peduncular article 1 2× longer than broad. Maxilliped palp article 3 short. Maxilla 2 well developed, with outer plate 2-articulate. Gnathopod 1 propodus about 2× as long as broad. Gnathopod 2 propodus with palmar margin moderately convex. Pereopod 7 basis proximally or slightly expanded (more than 1.5–1.8× as long as broad). Uropod 2 rami with single robust seta on medial margin. Uropod 3 article 2 distinctly longer than article 1, not rugose. Telson apically subacute. Description . Male (based on holotype , 5.3 mm ). Body smooth. Head. Antenna 1 long (distinctly longer than head and pereonites 1–4), subequal in length to antenna 2; peduncle not geniculate; peduncular article 1 2× longer than broad, without anterodistal lobe, without posterodistal lobe; peduncular article 2 without anterodistal lobe; accessory flagellum absent; flagellum 20-articulate. Mandible palp absent; incisor process well developed. Maxilliped palp article 3 short. Maxilla 1 palp 2-articulate. Maxilla 2 well developed with outer plate 2-articulate. Pereon. Gnathopods 1–2 dissimilar in shape; gnathopod 1 subchelate; merus enlarged, produced distally; carpus short (about as long as broad); propodus anterior and posterior margins subparallel (not expanded distally), about 2× as long as broad. Gnathopod 2 coxa posterior margin straight; basis anterodistal margin smooth; merus posterior margin convex, with setae; propodus narrow, oval, without posterodistal expansion, medium length (about twice as long as broad) (2.1), not transverse, palmar margin moderately convex, ventral margin with crenulation, (distally crenulate), with dense row(s) of fine setae; dactylus reaching distinctly further than half length of propodus, acute. Pereopod 3–7 setose. Pereonite 4 not elongate (similar length to pereonite 3); without dorsal carina. Pereopod 4 coxa ventral margin convex. Pereopod 5 basis not expanded. Pereopod 6 basis fully expanded; posterior margin straight. Pereopod 7 basis proximally or slightly expanded (more than 1.5× as long as broad), posterior margin convex (slightly), with crenulation; merus distally twice as wide as ischium, with ventral row of robust setae, expansion not reaching to mid-length of carpus; dactylus small (distinctly smaller than carpus). Pleon. Epimeron 3 posteroventral corner subquadrate/ rounded. Uropod 1 peduncle with a distoventral spur; inner ramus well developed, subequal in length to outer ramus. Uropod 2 inner ramus well developed, subequal in length to outer ramus, rami with single robust seta on medial margin. Uropod 3 with peduncle and ramus; ramus subequal or longer than peduncle; peduncle longer than article 1; ramus 2 articulate; article 1 without marginal robust setae; article 2 distinctly longer than article 1, proximally swollen, not rugose. Telson laminar, with dorsolateral robust setae, apically subacute. Female (sexually dimorphic characters). Gnathopod 1 propodus about 3× as long as broad. Gnathopod 2 propodus medium length (about 2 times as long as broad). Uropod 3 article 2 not swollen. Telson apically acute or subacute. Etymology . This species is named after the late Dr J. K. Lowry, world-renowned amphipod taxonomist, in recognition for his outstanding taxonomic and systematic work on the amphipod fauna of the world. Remarks . The material at hand is similar to Stenothoe gallensis Walker, 1904 , a distinctive species originally described from Galle, Sri Lanka . It should be noted, however, that in Walker’s original illustration, he mistakenly labelled pereopod 7 as pereopod 5. After thorough observation of the specimens from Pangkor Island, it is clear that they are not attributable to S. gallensis . Table 1 summarizes the characters and states reviewed from literature and the present study. Krapp-Schickel (2015) reviewed and reassessed most of the previously synonymized records of S. gallensis from various localities and placed S. irakiensis Salman, 1985 as a junior synonym of S. gallensis . Comparing the descriptions and illustrations in the original texts ( Salman, 1985 ), this new species is most morphologically similar to Salman’s material of S. gallensis Walker, 1904 from the Arabian Gulf, in the shape of male gnathopod 2; outer plate of maxilla 2 with 2 articles; and article 2 longer than article 1 of uropod 2. Despite showing greatest morphological similarity, S. gallensis and S. lowryi sp. nov. have slight differences, with the latter having: 1) gnathopod 2 propodus with palmar margin moderately convex; 2) uropod 2 rami with only one robust seta on medial margin; 3) uropod 3 article 2 distinctly longer than article 1, proximally swollen, not rugose. In S. lowryi , the separated articles of the outer plate of the second maxilla is also present in S. andamanensis Krapp-Schickel, 2015 , but the new species can be recognized by: uropod 2 with only one robust seta on medial margin of rami (versus 2 or more robust setae in S. andamanensis ); uropod 3, article 2 distinctly longer than article 1 (length subequal in S. andamanensis ); and uropod 3 article 2 not rugose (article 2 rugose in S. andamanensis ). Figure 3 . Stenothoe lowryi sp. nov. , from Pangkor Island, Malaysia. Holotype male, 5.3 mm, UKMMZ-1133. Allotype female, 4.9 mm, UKMMZ-1134. Scales: A1, A2 = 0.4 mm; Mx2, Md = 0.1 mm; Mx1, Mp, G1 = 0.2 mm; remainder = 0.5 mm. Figure 4 . Stenothoe lowryi sp. nov. , from Pangkor Island, Malaysia. Holotype male, 5.3 mm, UKMMZ-1133. Allotype female, 4.9 mm, UKMMZ-1134. Scales: P3–P7 = 0.5 mm; PL1–PL3 = 0.2 mm; remainder = 0.1 mm. Table 1 . Morphological variation in species of Stenothoe from Southeast Asia, including S. lowryi sp. nov.
Character S. irakiensis S. irinae S. nhatrangensis S. andamanensis S. lowryi sp. nov.
Maxilla 2 outer plate separated fused fused separated separated
Gnathopod 2 palmar margin (male) moderately concave convex concave moderately concave moderately convex
Coxa 2 posterior margin n/a rounded rounded rounded and concave straight
Uropod 2 rami medial margin setae 2 or more robust setae 1 robust setae 2 or more robust setae 2 or more robust setae 1 robust seta
Uropod 3 article length article 2 slightly longer than article 1 subequal article 2 distinctly longer than article 1 articles subequal article 2 distinctly longer than article 1
Uropod 3 article 2 surface rugose rugose not rugose rugose not rugose
Stenothoe irakiensis Salman, 1985 (junior synonym: S. gallensis Walker, 1904 ); S. irinae Marin & Sinelnikov, 2018 ; S. nhatrangensis Marin & Sinelnikov, 2018 ; S. andamanensis Krapp-Schickel, 2015 . Table 2 . Literature records of Stenothoe gallensis Walker, 1904 ; * indicates type locality.
location author illustrations
Indian Ocean
* Galle, Sri Lanka Walker (1904) yes
East coast, India Sivaprakasam (1968) no
Madras Coast, India Nayar (1959) yes
Dar-es-Salaam Schellenberg (1928) no
Seychelles Walker (1909) no
Zanzibar Walker (1909) no
Mauritius Ledoyer (1978) no
Tuléar, Madagascar Ledoyer (1972 , 1979 , 1986 ) yes
Mozambique Griffiths (1973) no
South-eastern Africa K. H. Barnard (1916, 1925) no
Natal Griffiths (1974a , b) no
Red Sea K. H. Barnard (1937) no
Red Sea Ruffo (1969) no
Suez Canal Monod (1937) yes
Atlantic Ocean
Banjul, Gambia Reid (1951) yes
Roscoff, France Chevreux & Fage (1925) yes
Plymouth, England Lincoln (1979) yes
Puerto Rico Shoemaker (1935) yes
Cuba Ortiz & Lalana (1993) no
North Carolina Estuaries Williams & Bynum (1972) no
Chesapeake Bay, USA Feeley & Wass (1971) no
York River, Va, USA Marsh, 1973 no
Pacific Ocean
Hong Kong Ren (1994) yes
Seto Inland Sea, Japan Nagata (1965) no
French Polynesia Chevreux (1907, 1908) yes
From S. nhatrangensis Marin & Sinelnikov, 2018 , S. lowryi can be distinguished by the following features: maxilla 2 outer plate with separated articles (fused in S. nhatrangensis ); gnathopod 2 palmar margin of male moderately convex (concave in S. nhatrangensis ); coxa 2 posterior margin straight (rounded in S. nhatrangensis ); and uropod 2 with only one robust seta on the medial margin of the rami (with two or more robust setae in S. nhatrangensis ). Finally, S. lowryi sp. nov. can be distinguished from S. irinae Marin & Sinelnikov, 2018 by: maxilla 2 outer plate with separated articles (fused in S. irinae ); coxa 2 posterior margin straight (rounded in S. irinae ); uropod 3 article 2 distinctly longer than article 1 (subequal in length in S. irinae ); and uropod 3 article 2 not rugose (article 2 rugose in S. irinae ). Distribution . Pangkor Island, Peninsular Malaysia .