Maera Leach, 1814

Ariyama, Hiroyuki, 2020, Species of the Maera - clade collected from Japan. Part 3: genera Maera Leach, 1814, Meximaera Barnard, 1969 and Orientomaera Ariyama, 2018 (addendum), with a key to Japanese species of the clade (Crustacea: Amphipoda: Maeridae), Zootaxa 4743 (4), pp. 451-479 : 452

Maera Leach, 1814

[Japanese name: Hon-sunnariyokoebi-zoku, new]

Maera Leach, 1814: 403 .— Barnard, 1969b: 243 (in part).—G. Karaman & Ruffo, 1971: 113 (in part).— Barnard & Barnard, 1983: 622 (in part).— Krapp-Schickel & Jarrett, 2000: 26.— Krapp-Schickel, 2008a: 14.— Lowry & Myers, 2013: 36.

Type species. Cancer (Gammarus) grossimanus Montagu, 1808 , monotypy.

Emended diagnosis. Body smooth. Head, rostrum obsolescent, lateral cephalic lobe rounded, antennal sinus distinct, anteroventral corner usually produced; eyes usually present, reniform or oval. Antennae slender; antenna 1, peduncular articles 1–2 longer than article 3, accessory flagellum with 4–11 articles. Mandible, molar developed; palp article length 2>3>1 or 2=3>1, article 1 with acute distal tooth or obliquely lengthened. Maxilla 1, inner plate bullet-shaped; palp 2-articulate. Coxae short; anteroventral corner of coxa 1 produced or rounded, coxae 5–6 lobate; gills present on coxae 2–6, oostegites present on coxae 2–5. Gnathopod 1 smaller than gnathopod 2, subchelate; carpus longer than or subequal to propodus; palm oblique. Gnathopod 2 large in both sexes, symmetrical, subchelate; carpus short, slightly lobate; propodus large, length 1.3–2.0 times width; palm slightly or moderately oblique, defined by small tooth, sculptured; dactylus with many setae (=> 8) on anterior margin. Pereopods, dactyli simple or bifid; pereopods 3–4 slender; bases of pereopods 5 – 7 rectangular or weakly expanded, each with posterodistal corner square or rounded. Pleonal epimeron 3 with small tooth or projected acutely posteroventrally. Uropods biramous; uropod 1 peduncle with basofacial robust seta, rami subequal, with marginal and distal robust setae; uropod 2 similar to uropod 1, both rami bearing marginal and distal robust setae; uropod 3, rami usually subequal in length, outer ramus 1.0 – 2.6 times length of peduncle, distal margins of rami truncate, with a few to many robust setae, longest seta about 0.1 – 0.9 times length of outer ramus. Telson deeply incised, distal margins of both lobes usually with notch, longest apical seta 0.1 – 0.9 times as long as telson.

Included species (19). Maera anoculata Rabindranath, 1983 ; M. bousfieldi Krapp-Schickel & Jarrett, 2000 ; M. danae ( Stimpson, 1853) ; M. edwardsi Chevreux, 1927 ; M. fusca ( Bate, 1864) ; M. grossimana ( Montagu, 1808) ; M. hirondellei Chevreux, 1900 ; M. irregularis Myers & Nithyanandan, 2016 ; M. jerrica Krapp-Schickel & Jarrett, 2000 ; M. loveni ( Bruzelius, 1859) ; M. lucinae Krapp-Schickel, 2004 ; M. nelsonae Krapp-Schickel & Jarrett, 2000 ; M. pachytelson G. Karaman & Ruffo, 1971 ; M. sagamiensis sp. nov.; M. schieckei G. Karaman & Ruffo, 1971 ; M. similis Stout, 1913 ; M. sodalis G. Karaman & Ruffo, 1971 ; M. tenera Sars, 1885 ; M. umarae García-Madrigal, 2010 .

Remarks. Species of this genus can be readily distinguished from the other species in the Maera -clade by the setose dactylus of the gnathopod 2. The dactylus in Clessidra Krapp-Schickel &Vader, 2009 has 3–4 setae and those in the other genera have only a single seta. Although Krapp-Schickel (2008a) included Maera tinkerensis Kunkel, 1910 in the genus, this species was removed to Clessidra ( Krapp-Schickel &Vader 2009) .