Caprella acanthogaster Mayer, 1890

Takeuchi, Ichiro, Nagano, Kohsei & Keable, Stephen J., 2022, A New Species of Caprella (Crustacea: Amphipoda: Caprellidae) from Gippsland Lakes, Australia, with a Redescription of Caprella acanthogaster Mayer, 1890 from Northern Japan, Records of the Australian Museum (Rec. Aust. Mus.) 74 (1), pp. 1-12 : 3-5

Caprella acanthogaster Mayer, 1890

Figs 1–3

Caprella acanthogaster Mayer, 1890: 80 , pl. 7 figs 52–53; 1903: 78–79, pl. 3 fig. 3.—Utinomi, 1943b: 281–282, fig. 1.—Utinomi, 1947: 71.— McCain & Steinberg, 1970: 11.— Marelli, 1981: 656, figs 1A, B.— Takeuchi, 1995: 201, figs 21–185.— Hosono & Munehara, 2001: 12–15, fig. 1.

Caprella (Spinicephala) acanthogaster . —Arimoto, 1976: 169–175, figs 91–93 (in part).

Not Caprella acanthogaster .—Guerra-García & Takeuchi, 2004: 996–1103, figs 22–26 (= C. tamboensis sp. nov.).

Material examined. Male, AM P.105618, mature female AM P.105619, 3 males and 2 mature females AM P.105620, all 30 Apr 1992, 39.3467°N 141.9334°E, Research facility for Undaria pinnatifida (Harvey) Suringar, 1873 , off Otsuchi Marine Research Center, Ocean Research Institute (currently International Coastal Research Center, Atmosphere and Ocean Research Institute), the University of Tokyo, Otsuchi Bay , Otsuchi, Iwate Prefecture, Japan, coll. I. Takeuchi.

Description

Male, AM P.105618, body length, 38.06 mm. Head, 1.33 mm; pereonite 1, 9.27 mm; pereonite 2, 9.59 mm; pereonite 3, 5.55 mm; pereonite 4, 4.64 mm; pereonite 5, 4.80 mm; pereonite 6, 1.56 mm; Pereonite 7, 1.32 mm, respectively. Pereonite 2 longest.

Head and pereonites elongate; eye large, distinct. Pereonite 2 with small anterolateral projection, small anterodorsal projection, paired mid-dorsal projections, and paired posterodorsal projections. Pereonites 3–4 with numerous lateral and dorsal projections. Pereonite 5 with small anterolateral projection and numerous dorsal projections. Pereonites 6–7 each with paired mid-dorsal projections.

Mouthparts. Upper lip wider than deep, bilobed, setose. Lower lip, inner lobe round. Right mandible right incisor with 5 teeth, lacinia mobilis with 4 teeth followed by 2 setulate setae, molar distinct with small molar flake. Left mandible incisor with 5 teeth, lacinia mobilis with 5 teeth followed by 3 setulate setae, molar distinct. Maxilla 1 outer plate with 7 stout apical setal-teeth; palp 2-articulate; article 2 6.0 × article 1 with 10 lateral robust or slender setae and single line of apical stout setae. Maxilla 2 inner plate oval, with ca. 30 setae; outer plate with ca. 15 apical setae. Maxilliped inner plate (basal endite) distal margin with a line of setae on entire length and 2 stout setae on inner half; outer plate (ischial endite) 1.5 × inner plate (basal endite) with ca. 20 setae on inner margin; palp 4-articulate, article 2 longest, setose along entire inner margin; article 3 2.0 × article 1, setose on lateral to distal part; dactylus falcate.

Antenna 1 elongate, 0.8 × body length; peduncle article 3 longest, 1.10 × peduncle article 2 length; flagellum short 0.25 × peduncular length, with 17 articles, proximal article composed of 3 partially fused articles. Antenna 2 slender, 0.30 × antenna 1 length; peduncle article 2 to flagellum article 1 with dense plumose setae (swimming setae).

Gnathopod 1 slender, setose on carpus to propodus. Gnathopod 2 inserted 0.20 along posterior margin of corresponding pereonite; coxa vestigial; basis 1.0 × length of pereonite 2, with projection near distal margin; propodus ovate, large, length 2.5 × width with several setae on dorsal margin, palm proximal projection with 1 robust (grasping) seta, palm margin convex, with large triangular mid-palmar projection and shallow distal shelf, sinus present. Gills 3–4 slender, length ca. 1.1 × corresponding pereonite length.

Pereopod 5 slender; basis shorter than propodus; carpus anterior margin setose; propodus palm with 1 pair of robust setae (grasping setae) ca. 0.4 palm length from articulation with carpus and ca. 20 setae along palm; dactylus curved. Pereopods 6–7 progressively longer than pereopod 5.

Penis elongated. Uropod 1 peduncle short; ramus round (length 1.6 × width) with 3 lateral setae. Uropod 2 vestigial with 7 setae.

Mature female, AM P.105619, body length, 12.37 mm. Head, 0.80 mm; pereonite 1, 0.98 mm; pereonite 2, 2.41 mm; pereonite 3, 2.24 mm; pereonite 4, 2.01 mm; pereonite 5, 2.07 mm; pereonite 6, 1.01 mm; pereonite 7, 0.85 mm, respectively. Pereonite 2 longest.

Head with paired dorsal projections. Pereonite 1 with 2 paired dorsal projections. Pereonite 2 with 3 paired dorsal projections. Pereonite 3 with numerous lateral and dorsal projections. Pereonites 4–5 with numerous lateral and dorsal projections. Pereonites 6–7 each with 2 paired dorsal projections.

Antenna 1 elongate, 0.85 × body length; peduncle article 2 longest; flagellum 0.80 × peduncular length, with 20 articles, proximal article composed of 2 articles. Antenna 2 slender, 0.55 × antenna 1 length. Gnathopod 2 inserted 0.30 along anterior margin of corresponding pereonite; basis 0.55 × length of pereonite 2; propodus oval. Gill 3 slender, length 0.70 × corresponding pereonite length. Gill 4 slender, length 0.85 × corresponding pereonite length.

Distribution ( Fig. 4 ).

Type locality. Mouth ofAmur River , at Strait of Tartary (Mamiya Strait) between the Sea of Okhotsk and the Sea of Japan .

Other localities. Hokkaido to Miyagi Prefecture, Japan ( Mayer, 1890; Utinomi, 1943b; Takeuchi, 1995; Hosono & Munehara, 2001; and the present study).

Remarks its description and a lateral view of the specimen. Mayer

(1890) noted the presence of paired projections on the Taxonomy, previous records. Caprella acanthogaster head, but the corresponding projections are absent in the was first reported by Mayer (1890) from the mouth of description and figure provided by Marelli (1981). the Amur River, at the Strait of Tartary (Mamiya Strait) Material examined from Japan in the present study between Sakhalin Island and the Eurasian Continent, based matches the description and figure of C. acanthogaster on 4 males (25 mm maximum body length) and 1 female. in Marelli (1981) in the following characteristics: smooth Mayer (1890) provided a brief description of the species, head, elongate pereonite 1, elongate pereonite 2 with several with figures of gnathopod 2 and pereonite 3, but was mainly dorsal spines, setae on pereonite 2 absent, large triangular focused on its differences from C. eximia Mayer, 1890 . The projection present on the middle of propodus of gnathopod type specimens were deposited at the Hamburg Museum, 2, and elongated gills on pereonite 4. Germany, according to McCain and Steinberg (1960) In addition to the Siberian coast of the Sea of Japan and Marelli (1981). Mayer (1890) also reported a male and northern Japan, C. acanthogaster s.l. has been widely specimen of C. acanthogaster at the Museum Godeffroy, reported from South Korea (Hong, 1988; Lee & Lee, 1993; Hamburg, Germany. The sampling location of this specimen Lee & Hong, 2011; Heo et al., 2020) to China (Wang et al., is unknown, and Mayer (1890) concluded that it most likely 1989; Cao et al., 2012; Wei et al., 2016; Chen et al., 2018) originated from Australia after consultations with G. Pfeffer, in East Asia. although Mayer (1890) also speculated that the specimen For the Korean records Lee & Hong (2011) provide a was collected from De Castries Bay, Sakhalin Island in Far description and figures of a male C. acanthogaster (20.0 East Asia or from the Le Maire Strait at the southern tip of mm in body length) from Yeongdeok, South Korea, and South America before contacting G. Pfeffer (see remarks noted that the species is widely distributed along the South under C. tamboensis sp. nov. for further discussion of this Korean coast. Heo et al. (2020) also described in detail C. specimen). Mayer (1903) also reported this species from acanthogaster from South Korea based on a 15.3 mm long the Sea of Japan near Vladivostok, Russian Far East, from male specimen. Based on Lee & Hong (2011) and Heo et al. a collection deposited in the Moscow Museum without a (2020), C. acanthogaster s.l. from South Korea is distinct specified sampling location, and from Nakabuta, Hokkaido, from the C. acanthogaster s.str. described in the present Japan deposited at the Hamburg Museum. In the same report, paper in having many tiny tubercle-like projections on Mayer (1903) provided a brief description and the lateral pereonite 1, dorsal part of pereonite 2, and basis of gnathopod view of entire C. acanthogaster based on the male specimen, 2. These records apparently represent a different species. 42 mm in body length, deposited in the Moscow Museum. This may be similar to the situation Ito et al. (2007) reported Schurin (1937) reported and briefly described a specimen where the geographic isolation of the East/South China Sea of C. acanthogaster from Peter the Great Bay, and cited the and the paleo-Japan Sea from the Pacific Ocean by tectonic differences between C. acanthogaster and C. eximia following processes promotes high species diversity of the coastal fish the notes in Mayer (1890, 1903). However, in the lateral view genus Girella Gray, 1835 around Japan. Schurin (1937) provided for C. acanthogaster minute setae To the best of our knowledge, there are no detailed are present on pereonite 2 and gnathopod 2, a character typical descriptions and/or figures of C. acanthogaster from for C. mutica . Therefore, Vassilenko (1974) concluded that C. the Chinese coastline. However, the record from fouling acanthogaster reported in Schurin (1937) was a misidentified assemblages in the sub-tropical area of Hainan Island in sample of C. mutica . Caprella acanthogaster s.l. recorded southern China (Chen et al., 2018) is questionable because from Onagawa Bay, Miyagi Prefecture, northern Japan this location is currently disjunct from other records in the (Utinomi, 1943a) is similar to the above C. acanthogaster more temperate regions contiguous with the type locality. s.l. from Peter the Great Bay. Furthermore, recent studies have confirmed that the huge Vassilenko (1974) also described and provided figures amount of freshwater from the Yangtze River entering the of C. acanthogaster s.l. that was collected from Peter East China Sea forms a barrier to several species of Mollusca the Great Bay. The male specimen in Vassilenko (1974) and Crustacea where the duration of the pelagic larval stage possesses paired posterodorsal projections on pereonite is <10 days ( Ni et al., 2017). Since the Amphipoda including 1 and paired mid-lateral and posterodorsal projections on Caprella spp. lack a pelagic larval stage, the outflow from pereonite 2. These features make the C. acanthogaster s.str. the Yangtze River may act as a distinct barrier for the species determination questionable. Therefore, further detailed study distribution along the coast of China in a similar way. on these C. acanthogaster s.l. specimens from Peter the Great We therefore conclude a detailed comparison of C. Bay and Onagawa Bay is needed. Vassilenko (1974) noted acanthogaster from northern China and Korea with those that C. acanthogaster differs from C. eximia by the smaller from other localities should be conducted. Particularly as body size and presence of two to four projections around the recent detailed comparisons of common species of Caprella base of gills on pereonites 3 and 4. and related genera in the Caprellidae and the Phtisicidae, Regarding C. acanthogaster s.l. from Japan, Arimoto previously regarded as cosmopolitan examples from (1976) described C. acanthogaster collected from Kesennuma different geographical localities, shows that these records are Bay, Miyagi Prefecture, northern Japan, and illustrated separated into region-specific species (Takeuchi & Lowry, specimens that possessed intermediate features or a mixture of 2007, 2016, 2019; Takeuchi & Oyamada, 2013; Hughes traits between C. acanthogaster and C. mutica , as pointed out & Takeuchi, 2016; present study). Similarly, Takeuchi & by Marelli (1981) and Vassilenko (2006), and it is considered Oyamada (2013) conducted a detailed comparison of C. that there were both of these species among his material. californica Stimpson, 1857 s.l. from Japan and California, Marelli (1981) studied a syntype of C. acanthogaster and proposed C. scauroides Mayer, 1903 as the correct name deposited at the Hamburg Museum, Germany, and presented for the Japanese specimens. Ecology. Caprella acanthogaster is one of the dominant species among Caprella spp. inhabiting gill nets and scallop and seaweed aquaculture facilities along the coast of Iwate, Aomori, and Hokkaido, Japan (Arimoto, 1976; Hosono & Munehara, 2001; Takeuchi et al., 2001, 2004; Hosono & Sakurai, 2006). Hosono & Sakurai (2006) reported on the population dynamics of C. acanthogaster in an aquaculture facility of Japanese kelp Laminaria japonica on the Pacific coast of southern Hokkaido, Japan, which showed the population of C. acanthogaster is influenced by immigration of large individuals to the facility in spring (April), their density increases with increasing water temperature during summer, and then rapidly decreases in September and remains low until the following spring ( Hosono & Sakurai, 2006). Hosono (2014) noted that at 5°C, females of C. acanthogaster reach maturity after 4 months, whereas males require a longer period.

Figures

Figure 1. Caprella acanthogaster Mayer, 1890 from Otsuchi Bay, Iwate, Japan. Male,AM P.105618, 38.06 mm. Female, AM P.105619, 12.37 mm. Bar indicates 1.0 mm.

Figure 2. Caprella acanthogaster Mayer, 1890 from Otsuchi Bay, Iwate, Japan. Male, AM P.105618, 38.06 mm. Bar indicates 1.0 mm, except for 0.1 mm to AB.

Figure 3. Caprella acanthogaster Mayer, 1890 from Otsuchi Bay, Iwate, Japan. Male, AM P.105618, 38.06 mm. Bar indicates 0.1 mm.

Figure 4. Distribution of Caprella acanthogaster Mayer, 1890 and related species.Data is based on Mayer (1890), Schruin (1937), Utinomi (1943a,b), Arimoto (1976), Vassilenko (1974), Wang et al. (1989), Lee & Lee (1993), Hosono & Munehara (2001), Guerra-García & Takeuchi (2004), Takeuchi (2005), Lee & Hong (2009, 2011), Cao et al. (2013), Wei et al. (2016), Heo et al. (2020), and the present study.