Maera loveni ( Bruzelius, 1859 )

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 : 453-459

Maera loveni ( Bruzelius, 1859)

[Japanese name: Ō- sunnariyokoebi, new]

( Figs 2–5 )

Gammarus loveni Bruzelius, 1859: 59 , pl. 2, fig. 9.

Moera loveni .— Bate, 1862: 193, pl. 35, fig. 1.— Oldevig, 1917: 36.

Maera loveni .— Norman, 1868: 416, pl. 21, figs 11–12.— Sars, 1895: 519, pl. 182, fig. 2.— Stebbing, 1906: 438.— Stephensen, 1927: 114.— Shoemaker, 1930: 116.— Stephensen, 1940a: 311.— Stephensen, 1940b: 55.— Gurjanova, 1951: 757, fig. 526.—Krapp-Schickel & Jarret, 2000: 34, fig. 4.

Moera lovenii .— Stephensen, 1913: 194.

not Maera loveni .— Barnard, 1962: 103, fig. 19 (= Maera nelsonae Krapp-Schickel & Jarrett, 2000 ).

Material examined. Male, 58.3 mm (OMNH-Ar-10623) and female, 51.7 mm (OMNH-Ar-10624), Sea of Japan, north of Masuda City, Yamaguchi Prefecture, 35°50ʹ26ʹʹN 131°46ʹ31ʹʹE ( Fig. 1C ), 300 m depth, using trawl, 28 August 2011, coll. Y. Kogure.

Type locality. Bohuslän in Sweden, 73–100 m depth .

Diagnosis. Eyes present. Mandible, palp article 1 with acute distal tooth. Gnathopod 1, coxa anteroventral corner roundly produced. Gnathopod 2 in both sexes, palm slightly oblique, defined by blunt tooth bearing strong robust seta. Pereopods, dactyli simple; bases of pereopods 5–7 rectangular, posterodistal corners square. Pleonal e pimera 1–3 each with small tooth. Uropod 3 rami subequal, twice as long as peduncle. Telson longer than wide, distal margins each with small notch bearing short seta.

Description. Based on male, 58.3 mm (OMNH-Ar-10623).

Head ( Figs 2–3 ). Eyes, pigments faded. Antenna 1 about 0.6 times as long as body, weakly setose; peduncle with ratio of lengths of articles 1–3 1:1.15:0.35, article 1 with 4 small posteromedial robust setae; accessory flagellum with 10 articles, terminal article minute, length about 0.2 times primary flagellum; primary flagellum with 42 articles, terminal article short. Antenna 2 about half length of antenna 1, heavily setose posteriorly, with ratio of lengths of peduncular articles 3–5 1:2.7:2.1; flagellum with 15 articles, terminal article minute. Upper lip, ventral margin rounded, weakly setose. Mandible, incisor bearing 5 and 4 cusps in left and right, respectively, left lacinia mobilis 4-dentate, right lacinia mobilis 3-dentate, both with many accessory setae; palp article 1 with acute distal tooth, articles 1 – 3 length ratio (excluding distal tooth of article 1) 1:2.8–2.9:1.6, articles 2 – 3 setose. Lower lip with inner lobes, distal margins of outer lobe weakly setose, mandibular processes small. Maxilla 1, inner plate with 3 long and 3 minute apical setae, medial and lateral margins bearing feeble setae, outer plate with 9 apical robust setae and lateral feeble setae, palp with many apical setae. Maxilla 2, outer plate larger than inner plate; both plates bearing many apical setae, medial margin of inner plate with 2 normal and many feeble setae. Maxilliped, inner plate truncate, distally setose; outer plate with many long-to-short robust setae on distomedial margin; palp 4-articulate, article 2 setose medioventrally, article 3 with many distolateral setae, article 4 with large apical robust seta.

Pereon ( Fig. 4 ). Gnathopod 1, coxa anteroventral corner produced, but rounded, anteroventral margin with several short setae; basis setose on anterior and posterior margins and medial surface; ischium and merus each with setae on posterior margin; carpus swollen posterodistally, posterior margin and medial surface heavily setose; propodus about 85% as long as carpus, anterior and posterior margins setose, palmar margin bearing many small robust setae laterally and medially; dactylus slender, almost straight, anterior margin setose. Gnathopod 2, coxa subtrapezoidal, posteroventral margin with 3 minute notches; basis relatively narrow, about 2.7 times as long as width, anteroproximal margin, anterodistal corner and posterior margin setose; merus with acute posterodistal spine; carpus swollen posterodistally, anterior and posterior margins setose; propodus subrectangular, length about 1.3 times width, anteromedial surface and posterior margin setose; palm slightly oblique, defined by blunt tooth bearing strong robust seta, palmar margin with 9 small teeth, bearing 8 lateral and 17 medial small robust setae; dactylus curved distally, anterior margin with many (> 40) setae.

Pereopods 3–4, shapes subequal, pereopod 3 about 1.1 times length of pereopod 4; coxae trapezoidal, gills large, subequal to bases lengths; bases rectilinear, anterior and posterior margins setose proximally; dactyli slender, simple. Pereopods 5–7, shapes subsimilar, about 1.2, 1.6, 1.7 times length of pereopod 4 respectively; coxa 5 anterior lobe minutely serrated ventrally, anteroventral margins of coxae 6–7 with 5 and 3 robust setae, respectively; bases rectangular, lengths about 2.7, 2.4, 2.2 times widths respectively, posteroproximal corners projected, anterior margins with many short robust setae, posterior margins minutely serrate, posterodistal corners square; dactyli short, simple.

Pleon ( Fig. 5 ). Epimera 1–3 each with small tooth on posteroventral corner and lateral ridge, ventral margins with 4, 12, 16 robust setae respectively. Pleopods 1–3, pleopod 3 shortest; peduncles with 7, 7, 9 coupling hooks respectively; both rami each with 20–25 articles. Uropod 1, peduncle with 6 dorsolateral and 15 dorsomedial robust setae, bearing large distolateral robust seta; outer ramus subequal length to inner ramus, about 0.8 times as long as peduncle, with 8 dorsomedial and 2 terminal robust setae; inner ramus with 4 lateral, 14 dorsomedial and 4 terminal robust setae. Uropod 2 about 65% length of uropod 1; peduncle laterodistal corner projected, dorsolateral margin, dorsomedial margin and distomedial corner with 3, 5 and 4 robust setae, respectively; outer ramus about 0.9 times length of inner ramus, about 95% length of peduncle, with 6 dorsomedial and 2 terminal robust setae; inner ramus with 5 lateral, 16 dorsomedial and 3 terminal robust setae. Uropod 3 about 1.1 times as long as uropod 2; peduncle laterodistal and mediodistal corners bearing 5 and 1 robust setae, respectively; both rami rectilinear, outer ramus slightly shorter than inner ramus, about 2.1 times length of peduncle, lacking vestigial second article; lateral and medial margins of both rami lined with robust setae, distal margins bearing a few setae, longest seta about 0.1 times length of outer ramus. Telson about 1.5 times longer than wide, each lateral margin with 5–7 small robust setae, tips acutely projected, each with inner notch bearing 0–1 short robust seta.

Description of female (51.7 mm, OMNH-Ar-10624). Gnathopod 2 ( Fig. 5 F-G2) subsimilar to that of male except for oostegite.

Coloration. Unknown.

Remarks. Morphological characters of the present specimens almost agree with those in the literature ( Bruzelius 1859, Sars 1895, Krapp-Schickel & Jarrett 2000). However, a few characters as follows are different: (1) mandibular palp article 1 acutely projected, (2) distal setae of uropod 3 rami fewer and shorter, and (3) short robust setae present on lateral margins of telson. Body sizes of the specimens (58.3 mm in male, 51.7 mm in female) are also different from the previous records [maximum: 37 mm ( Shoemaker 1930)]. This species is characterized by the strong robust setae directly sitting on the palmar corner of the gnathopod 2 ( Krapp-Schickel & Jarrett 2000).

Habitat. Clay, sand or shell bottom ( Bryazgin 1997), 20–400 m depth ( Gurjanova 1951). Burrowing in sandymud bottom ( Atkinson et al. 1982).

Distribution. From the Gulf of St. Lawrence, Nova Scotia and W. Greenland to Spitzbergen, N. Norway and Great Britain ( Stephensen 1940a, b). Russia: Barents Sea, Sea of Okhotsk ( Gurjanova 1951). Northeast Pacific: Washington ( Krapp-Schickel & Jarrett 2000). Sea of Japan (present study).

Figures

FIGURE 1. Map showing collecting sites of the examined specimens. A, Sagami Bay, off Jōgashima Island in Miura City, Kanagawa Prefecture; B, Tagurazaki coast, Wakayama City in Wakayama Prefecture; C, Sea of Japan, north of Masuda City in Yamaguchi Prefecture.

FIGURE 2. Maera loveni (Bruzelius, 1859). Male, 58.3 mm (OMNH-Ar-10623). Habitus.

FIGURE 3. Maera loveni (Bruzelius, 1859). Male, 58.3 mm (OMNH-Ar-10623). Scales: 0.4 mm.

FIGURE 4. Maera loveni (Bruzelius, 1859). Male, 58.3 mm (OMNH-Ar-10623). Scales: 0.7 mm.

FIGURE 5. Maera loveni (Bruzelius, 1859). All but F, male, 58.3 mm (OMNH-Ar-10623); F, female, 51.7 mm (OMNH-Ar- 10624). Scales (except for CH): 1 mm.