Protella amamiensis, Takeuchi & Lim & Inoue, 2014

Takeuchi, Ichiro, Lim, Jacqueline Hui Chern & Inoue, Yuki, 2014, Description of two species of Protella Dana, 1852 (Crustacea: Amphipoda): P. gracilis Dana, 1853, from Balabac Strait, the Philippines, and P. amamiensis, new species, from southern Japan, Raffles Bulletin of Zoology 62, pp. 53-65 : 58-64

Protella amamiensis , new species

( Figs. 3–7 )

Protella gracilis . Mayer, 1890: 21–23, pl. 1 figs. 10–11, pl. 3 figs. 17–20, pl. 5 figs. 15–17, pl. 6 figs. 6, 21;? Arimoto, 1929: 123–126, pl. 1 figs. 7–15;? Hiro, 1937: 311, pl. 22 figs. 3–4; Utinomi, 1964: 14, 24–25, pl. 2 fig. 4; McCain & Steinberg, 1970: 69–70 (in part);? Arimoto, 1976: 50–53, figs. 21–22; Arimoto & Kikuchi, 1977: 96–97, fig. 4K;? Arimoto, 1980: 105; Takeuchi, 1999: 6. [not Protella gracilis Dana, 1853 ].

Material examined. Holotype, 1 male, KMNH IvR 500,682, 10.35 mm, off Sakinome , Amami Oshima Island, Amami Islands, Kagoshima Prefecture, Japan, 28°10'53"N, 129°15'46"E, hydroids, 17 m depth, 29 August 2000, coll. K. Hagiwara. Paratype, 1 male, KMNH IvR 500,683, 1 mature female, KMNH IvR 500,684, 1 mature female, KMNH IvR 500,685, 5 mature females, 1 premature female and 1 juvenile, KMNH IvR 500,686, 2 males and 2 mature females, MCZ 25221 , 1 male and 2 mature females, AM-P.90992, location and station data same as holotype .

Type locality. Amami Oshima Island , Amami Islands, Ryukyo Archipelago, Japan .

Other localities. Amakusa Islands, west coast of Kyushu, western Japan, Tanabe Bay, Kii Peninsula, Misaki, the entrance of Tokyo Bay, and? Tateyama Bay, central Japan.

Etymology. Named after the type locality, Amami Oshima Island, Amami Islands.

Description. Male (holotype), Body length, 10.86 mm, KMNH IvR 500,682. Head, 0.61 mm. Pereonite 1, 0.56 mm. Head and pereonite 1 fused, suture present; head smooth, no dorsal or lateral projections; eye round, distinctive. Pereonite 2, 1.96 mm, dorsally smooth. Pereonite 3, 2.35 mm with 1 small anterolaeral round projection. Pereonite 4, 2.26 mm, subequal with pereonite 3. Pereonite 5, 2.00 mm. Pereonite 6, 0.56 mm. Pereonite 7, 0.56 mm. Antenna 1, 1.2× body length; peduncular article 1 with 5 fine/plumose proximal setae, article 2, 2.7× article 1, article 3 longest, 1.2× article 2, with fine marginal setae on inner and outer margin; flagellum 0.57× peduncle, with 19 articles, proximal article composed of 3 articles. Antenna 2 slender, 0.38× antenna 1; peduncular article 1 short, gland cone reaching tip of peduncular article 2; peduncular article 2 scarcely setose; peduncular article 3, 3.7× article 2 with long and short setae along ventral margin; article 4 longest, with long and short setae along ventral margin; flagellum 0.2× length of peduncle, 2-articulate, article 2, 0.2× article 1.

Upper lip notched, wider than deep, forming rounded quadrilateral projections each with rows of flake-liked structures. Lower lip well developed, inner lobe distal margin pubescent, shoulders broad, with fine distal setae. Mandible left incisor with 5 teeth, lacinia mobilis with 5 teeth followed by 3 bundled setae and row of fine setae; molar flake present, small; molar well developed, truncate, edge serrated; palp 3-articulate, article 1 shortest, article 2, 2.5× article 1, with 3 long and 3 short simple setae and 2 long distal setae, article 3 subequal in length with article 2, slightly curved, tapering towards tip with setal formula of 1-21-5-1. Mandible right incisor with 5 teeth, lacinia mobilis with many fine teeth followed by 3 bundled setae and row of fine setae; molar flake present, larger than left molar flake; molar well developed, truncate, terminally with teeth-liked process; palp 3-articulate, subequal in length with left mandibular palp, article 2 with 3 long and 3 short simple setae and 2 long distal setae, article 3 tapering to a pointed tip with setal formula of 1-20-5-1. Maxilla 1 inner plate absent; outer plate armed with 7 stout apical setal-teeth; palp biarticulate, article 1 short, article 2, 5.67× article 1, subequal in length with outer plate, terminally with 7 short and 1 long robust setae, distally with row of 3 facial slender setae. Maxilla 2 inner plate with 7 slender setae at distal margin; outer plate 0.7× inner plate with 14 slender apical setae. Maxilliped basal endite (inner plate) with 2 stout tooth and 4 simple setae apically; ischial endite (outer plate) 2.2× the length of inner plate with 2 simple setae apically, inner margin scalloped with 2 setae medially; palp 4-articulate, article 1 shortest, inner margin scarcely setose; article 2 longest, 2.3× article 1, setose on entire inner margin; article 3, 0.8× article 2, without triangular distal projection, distal margin with tuft of long and short setae; article 4 (dactylus) falcate, with row of setules on inner margin.

Pereon. Gnathopod 1 basis subequal with merus and carpus combined; ischium posterodistal corner with several long and short setae; merus subquadrate, posteroventral corner setaceous; carpus subequal in length with propodus, posterior margin densely setaceous, facially with 4 rows of setae; propodus with 5 rows of submarginal setae, distal margin with several long setae, palm begins 1/5 along posterior margin, straight, finely setose along entire margin, with 1 robust/stout proximal seta; dactylus slightly curved, inner margin with serriformed teeth. Gnathopod 2 begins 1/3 along anterior margin of pereonite 2, coxa bilobate; basis 1.2× the length of pereonite 2, with an acute anterodistal projection equipped with 1 seta; ischium with an acute laterodistal projection; merus posteroventral corner with 4 setae; carpus subtriangular; propodus enlarged, 2.2× as long as wide, anterodistal corner pronounced/acute, palm begins 1/3 along posterior margin, proximal projection with 1 robust seta (grasping spine), mid-palmar triangular projection followed by a wide concaved area, and 2 additional triangular projections with a narrow sinus in between followed by a small triangular projection proximally, palm with pegs between grasping proximal and mid-palmar projection, concaved area lined with setae; dactylus falcate with fine marginal setae on inner and outer margin. Gill 3 length 0.6× pereonite 3, oval. Pereopod 3 slender, 0.3× pereonite 3, 2-articulate; article 1 long, with 5 distal setae; article 2 small, 0.04× article 1 with 1 long and 2 short apical setae. Gill 4 length 0.6× pereonite 4, oval. Pereopod 4 slender, 0.3× pereonite 4, subequal in length with pereopod 3, 2-articulate; article 1 with 6 distal setae; article 2 small, with 1 long and 2 short apical setae. Pereopods 5–7 well developed, basis and carpus of pereopods 5–7 becoming shorter and more robust progressively. Pereopod 5 basis and ischium with 2–5 setae on antero and posterodistal corner; merus slightly expanded posterodistally with tuft of setae; carpus longest, 1.7× merus with row of robust setae along entire inner margin, distally with one small triangular projection and 6 setae; propodus subcylindrical, same length as ischium and merus combined, with a pair of proximal grasping spines, palm with 9 setae, distal margin of propodus with group of longer setae; dactylus falcate, fitting onto palm, smooth. Pereopod 6 basis shorter than pereopod 5 basis (0.87× shorter), with 5–6 setae on antero and posterodistal corner; ischium 0.25× basis; merus slightly expanded posterodistally with tuft of setae; carpus 1.3× merus, with row of robust setae along entire inner margin, distally with one small triangular projection and 8 setae; propodus same length as basis, palm with a pair of proximal grasping spines followed by several fine and robust setae, outer margin of propodus becoming more dense and long moving towards distal margin; dactylus falcate, fitting onto palm, smooth. Pereopod 7 shorter than pereopod 5 but longer than pereopod 6, basis subequal in length with ischium and merus combined, with 3–5 setae on antero and posterodistal corner; merus expanded posterodistally; carpus subequal in length with merus, inner margin with row of robust setae, posterodistal corner with tuft of setae; propodus palm with a pair of proximal grasping spines followed by several fine and robust setae, outer margin with many long setae especially at distal margin; dactylus falcate, fitting onto palm, smooth.

Pleon (based on male, body length, 10.36 mm, KMNH IvR 500,683). Penes small, bilobate, positioned laterally. 2 setae present between penes and uropod 1. Uropod 1 peduncle with 3 long setae; ramus elongated, 7× peduncle and curved outwards, with 3–4 fine facial setae, distally with a small, knob-liked appendage, equipped with 1 short and 3 long setae. Uropod 2 ramus vestigial, with one seta. Telson round, with a pair of plumose setae.

Female (paratype), Body length, 9.48 mm, KMNH IvR 500,684. Head 0.69 mm. Pereonite 1, 0.48 mm. Head and pereonite 1 fused, suture present; head smooth, no dorsal or lateral projections; eye round, distinctive. Pereonite 2, 1.83 mm, dorsally smooth. Pereonite 3, 2.00 mm. Pereonite 4, 1.56 mm. Pereonite 5, 1.96 mm. Pereonite 6, 0.48 mm. Pereonite 7 equal with pereonite 6, 0.48 mm. Antenna 1 long, 1.2× body length; peduncular article 1 scarcely setose, peduncular article 2, 2.7× longer than peduncular article 1, peduncular article 3 longest, 1.2× article 2, with fine marginal setae on inner and outer margin; flagellum 0.55× peduncle, with 17 articles, proximal article composed of 4 articles. Antenna 2 slender, 0.7× antenna 1; peduncular article 1 short, gland cone reaching tip of peduncular article 2; peduncular article 2, 2.0× article 1; peduncular article 3, 4.25× peduncular article 2 with long and short setae along ventral margin; peduncular article 4 longest, 1.24× peduncular article 3, with long and short setae along ventral margin; flagellum 0.22× length of peduncle, 2-articulate, article 2, 0.2× article 1.

Pereon. Gnathopod 2 begins 1/3 along anterior margin of pereonite 2, coxa bilobate; basis 0.90× the length of pereonite 2, with an acute anterodistal projection equipped with 1 seta; ischium with an acute laterodistal projection; merus posteroventral corner with several setae; carpus subtriangular; propodus enlarged, 1.25× basis, 2.4× as long as wide, anterodistal corner pronounced/acute, palm begins 1/4 along posterior margin, proximal projection with 1 robust seta (grasping spine), mid-palmar triangular projection not distinct, followed by a concaved area, and 2 additional triangular projections with a narrow sinus in between, palm provided with pegs/serriformed teeth between grasping proximal and mid concaved area; dactylus falcate with fine marginal setae on inner and outer margin. Gill 3 length 0.8× pereonite 3, oval and elongated. Pereopod 3 slender, 0.36× pereonite 3, 0.46× gill 3 length, 1-articulate with 10 distal setae. Gill 4 length 0.9× pereonite 4, oval and elongated. Pereopod 4 slender, 0.40× pereonite 4, 0.44× gill 4 length, subequal in length with pereopod 3, 1-articulate with 9 distal setae.

Pleon (based on mature female, body length, 10.65 mm, KMNH IvR 500,685). Uropod 2 ramus vestigial, degenerated into 1 seta, present on inner margin. Telson round, with 1 pair of plumose setae and 1 pair of normal setae.

Remarks. The present specimens of Protella gracilis [sensu lato] were collected from Amami Islands, which are situated in the northern part of the Ryukyu Archipelago between Kyushu Island and Taiwan. According to Spalding et al. (2007), Amami Island is situated at the border of temperate and tropical regions, namely the Temperate Northern Pacific (realm), Warm Temperate Northwest Pacific (province), Central Kuroshio Current (ecoregion) and the Central Indo- Pacific (realm), South Kuroshio (province), South Kuroshio (ecoregion).

Compared with descriptions and figures of the types of

Protella gracilis [sensu stricto], Protella gracilis [sensu

lato] from Amami Islands, Japan differs in the following

characteristics:

1. Pereopods 3 and 4 of the type specimen is 1-articulate, while that of P. gracilis [sensu lato] from Amami Islands is 2-articulate.

2. Penes of the type specimen is large with presence of 4 setae between penes and uropod 1, while P. gracilis [sensu lato] from Amami Islands is provided with 2 setae between penes and uropod 1.

3. Uropod 1 of the type specimen is short and subconical in shape with a group of 11 long setae at the base; ramus is subequal in length with peduncle with a very small knob-liked appendage. On the contrary, in P. gracilis [sensu lato] from Amami Islands, Japan, ramus of uropod 1 is elongated, ca. 7 times of peduncle with a knob-liked appendage at distal margin, equipped with 3 long and 1 short setae.

Examination of the characters above showed that the difference in number of articles in pereopods 3 and 4 (1-articulate in Protella gracilis [sensu stricto]) could be due to the condition of the old material making it difficult to observe its segmentation. Meanwhile, character of the penes and abdomen are more distinctive. These clear differences indicate that P. gracilis [sensu lato] from Amami Islands, Japan, is a different species from the type P. gracilis [sensu stricto]. Moreover, the male type P. gracilis [sensu stricto] is estimated to be larger, 13.70 mm; by using the body somite ratio of P. gracilis [sensu lato] from Amami Islands, 9.48 mm. Thus, P. gracilis [sensu lato] from southern Japan is described as a separate species, P. amamiensis , new species, as described in this paper. Recently, Takeuchi & Lowry (2007b) reported that Orthoprotella berentsae Takeuchi & Lowry, 2007b , can be distinguished from O. mayeri K. H. Barnard, 1916 , mainly by the characteristics of the uropod 1, although characteristics of body somites resemble each other.

Protella gracilis [sensu lato] was described and illustrated in detail based on specimens collected from the Temperate Northern Pacific in one of the 12 major realms (see Mayer, 1890; Arimoto, 1929, 1976). The characteristics of P. amamiensis , new species, agrees well with P. gracilis [sensu lato] in Mayer (1890) and Arimoto (1929, 1976) in: 1) antenna 1 longer than body length; 2) antenna 1 peduncular article 3 longest; 3) propodus of gnathopod 2 has two additional triangular projections near the middle region of the palm; 4) pereopods 3 and 4 are slender; and 5) uropod 1 is elongated. However, pereopods 3 and 4 of P. amamiensis , new species, are 2-articulated, while those of Mayer’s (1890) and Arimoto’s (1929, 1976) specimens are 1-articulated. In addition, uropod 1 of P. amamiensis , new species, and that of Mayer’s (1890) specimen is curved outwards, while Arimoto’s (1929, 1976) specimen is curved inwards. But as mentioned above, the segmentation of pereopods 3 and 4 could be sometimes obscured. These differences indicate that Protella gracilis [sensu lato] in Arimoto (1929, 1976) might be an undescribed species or subspecies of P. amamiensis , new species, endemic to the Temperate Northern Pacific. Further detailed studies on Protella spp. from different ecoregions along the Singapore coast and the Japanese Archipelago needs to be conducted in the near future.

Figures

Fig. 3. Protella amamiensis, new species, holotype, male, 10.35 mm, KMNH IvR 500,682 and paratype, mature female, 9.48 mm, KMNH IvR 500,684, off Sakinome, Amami Oshima Island, Amami Islands, southern Japan.

Fig. 4. Protella amamiensis, new species, holotype, male, 10.35 mm, KMNH IvR 500,682, off Sakinome, Amami Oshima Island, Amami Islands, southern Japan.

Fig. 5. Protella amamiensis, new species, holotype, male, 10.35 mm, KMNH IvR 500,682, off Sakinome, Amami Oshima Island, Amami Islands, southern Japan.

Fig. 6. Protella amamiensis, new species, hototype, male, 10.35 mm, KMNH IvR 500,682 (P3, P3 & GL3, P4, P4 & GL4, P5, P6, and P7) and paratype, male, 10.36 mm, KMNH KMNH IvR 500,683 [ABD(V) and (ABD(L)] off Sakinome, Amami Oshima Island, Amami Islands, southern Japan.

Fig. 7. Protella amamiensis, new species, paratypes, mature female, 9.48 mm, KMNH IvR 500,684 (A1, A2, G2, P3, P3 & GL3, P4, and P4 & GL4) and mature female, 10.65 mm, KMNH IvR 500,685 (ABD), off Sakinome, Amami Oshima Island, Amami Islands, southern Japan.