Pseudaeginella telukrimau, Lim & Azman & Takeuchi & Othman, 2017

Lim, Jacqueline Hui Chern, Azman, Bin Abdul Rahim, Takeuchi, Ichiro & Othman, Bin Haji Ross, 2017, Pseudaeginella telukrimau sp. n., a new species of caprellid (Crustacea: Amphipoda) from Malaysia, Zootaxa 4282 (1) : -

Pseudaeginella telukrimau sp. n

( Figs. 1–5 )

Type materials. Holotype, Male, 3.24 mm, UMTCrus00473 ( Fig. 1 ), coral reef, Teluk Rimau , Pulau Besar , Johor, 02°27.594'N; 103°58.705'E; diving, 25 March 2010, 11.51 am, depth 7.7 m; coll. Azman, B.A.R, Gan, S.Y., Lim, J.H.C., Khoo, M.L. & Shamsul B.

Allotype, Female, UMTCrus00474 ( Fig. 4 ), same locality as male.

Paratypes, 15 males, UMTCrus00475; 28 females, UMTCrus00476; 48 premature males, 24 premature females, UMTCrus00477; same station data.

Type locality. Teluk Rimau , Pulau Besar, Johor, Malaysia.

Description. Male, Body length, 3.24 mm. UMTCrus00473. Head, 0.33 mm and pereonite 1, 0.285 mm; head and pereonite 1 partially fused (suture clear); head with 1 long anteriorly curved dorsal projection; pereonite 1 with 1 small dorsodistal acute triangular projection. Pereonite 2, 0.53 mm with a pair of anteriorly curved mid-dorsal projections, a small anterolateral projection and an unpaired dorsodistal round projection. Pereonite 3, 0.69 mm, longest, with 1 pair of round mid-dorsal projection, 1 anteroventral triangular projection, 1 mid-lateral truncateliked projection, 1 mid-ventral triangular projection and 1 dorsodistal round projection. Pereonite 4, 0.54 mm, subequal with pereonite 2 with 1 pair of round mid-dorsal projection, 1 anteroventral triangular projection, 1 midlateral truncate projection, 1 mid-ventral triangular projection, 1 ventrodistal triangular projection and 1 pair of round dorsodistal projection. Pereonite 5, 0.45 mm with 1 pair of triangular mid-dorsal projection, 1 small anteroventral triangular projection and 1 pair of mid-ventral triangular projection. Pereonite 6 and 7 not fused. Pereonite 6, 0.22 mm with 1 mid-dorsal acute triangular projection, one small mid-lateral round projection and one small anteroventral triangular projection. Pereonite 7, 0.19 mm with no projections. Antenna 1, 0.6 x body length; peduncular article 2 longest, 1.35 x article 1 with several setae; article 3 shortest, 0.32 x article 2; flagellum 1.18 x peduncle with 10 articles, proximal article composed of 2 articles. Antenna 2, 0.33 x body length and 0.5 x antenna 1; peduncular article one shortest with ventrodistal projection; article 2 with several setae at ventrodistal corner; article 3, 0.28 x article 2 with several setae; article 4 longest, 1.29 x article 3; flagellum with 2 articles, 0.18 x peduncle with tuft of 8 setae at distal margin.

Upper lip notched, wider than deep, forming rounded projections. Lower lip well developed, inner lobe partially fused with a cleft medially, outer lobes rounded without setae, provided with a wing-liked projection medially on each side. Mandible right incisor with 5 teeth followed by lacinia mobilis with many small teeth and 2 serrated trapezoid structures and one accessory bundles setae; molar absent; palp 3-articulate; article 2, 2.1 x article one with one distal seta; article 3 subequal with article 2 with setal formula 1-5-1 and one distal knob. Mandible left incisor with 5 teeth followed by three serrated trapezoid structures and 1 accessory bundled seta; molar absent; palp 3-articulate; article 2, 2.19 x article 1 with one distal seta; article 3 subequal with article 2 with setal formula 1-5-1 and one distal knob. Maxilla 1 outer plate with 6 stout apical setal-teeth; palp biarticulate, article 2, 2.45 x the length of article 1 with 2 triangular projections at distal margin, armed with 2 slender setae and 1 plumose seta; facially with 1 normal seta. Maxilla 2 inner plate with 5 long and short apical setae; outer plate with 5 apical setae. Maxilliped basal endite (inner plate) deeper than wide, subrectangular with 1 stout tooth, 1 normal seta and 1 long facial seta; ischial endite (outer plate) 1.56 x inner plate with 2 setae on inner margin and 3 normal setae distally; palp 4 articulate; article one with one seta on inner margin; article 2, 1.55 x article 1 with 2 short setae and 1 long seta on inner margin; article 3 subequal with article 2 with 6 distal setae; palp article 4 (dactylus) falcate with 1 proximal seta on outer margin and 2 setae at distal margin; inner margin with row of fine setae.

Pereon. Gnathopod 1 basis shorter than ischium, merus and carpus combined, 0.74 x pereonite 1, sparsely setose; ischium 0.31 x basis with one plumose seta at posterodistal corner; merus with 2 short and 2 long plumose setae at posterodistal corner; carpus subequal with merus, equipped with a row of 5 distal plumose setae; propodus longer than wide (1.8 x width) with 2 rows of submarginal plumose setae and group of long and short setae at distal margin, palm begins 1/4 along posterior margin with a pair of robust/stout proximal setae and several short and long setae along entire margin; dactylus falcate with sparse and fine setae on inner margin, distally with 1 teeth and 3 tubular setae. Gnathopod 2, 3.3 x longer than gnathopod 1, robust, begins 2/5 along anterior margin of pereonite 2; coxa weakly lobated; basis longer than ischium, merus and carpus combined, 0.97 x the length of pereonite 2 with an acute anterodistal projection provided with 3 small setae; ischium subrectangular with 1 large trapezoid anterior projection provided with 3 weak triangular projections and small setae distally; merus subsemicircular with 2 setae on posterior margin; carpus subtriangular with 2 small setae; propodus large, subovate, nearly as long as basis (0.86 x length of basis) sparsely setose, palm begins 1/7 along posterior margin, proximal projection with 1 robust seta (grasping spine) and one slender seta, mid palmar triangular projection with one small seta followed by a triangular sinus and 2 smaller triangular projections, palm with several short and long setae along entire margin; dactylus falcate, with several fine setae on inner margin. Gill 3 length 0.45 x the length of pereonite 3, oval. Pereopod 3 very small, 1-articulate, 0.08 x gill 3 length, conical in shape with 2 setae apically. Gill 4 subequal in length with gill 3, 0.57 x the length of pereonite 4, oval. Pereopod 4 subequal in length with pereopod 3, 1- articulate, conical with 1 long seta apically. Pereopods 5–7 well developed, 6 articulate, becoming more robust progressively. Pereopod 5 basis with several setae on anterior margin; ischium with 1 anterodistal seta; merus expanding posterodistally with several seate on anterior and posterior margin; carpus subequal with merus with several setae, distally with 1 triangular projection; propodus longer than basis (1.13 x longer) with a pair of proximal grasping spines, palm with row of marginal setae, distally with several setae; dactylus falcate, with one plumose seta on anterior margin at proximal region. Pereopod 6 basis 1.17 x broader than basis of pereopod 5, with several setae on anterior margin; merus expanded posterodistally with 2 setae; carpus subcylindrical with row of paired setae on anterior margin, distally with 1 triangular projection; propodus 1.29 x longer than propodus of pereopod 5, proximal projection with 1 pair of grasping spines followed by a row of marginal robust setae on palm, distally with several long and short setae; dactylus falcate, with 1 plumose seta on anterior margin at proximal region. Pereopod 7 basis subequal in length with basis of pereopod 6, 1.14 x broader; ischium with setae at anterodistal corner; merus expanded posterodistally with 2 setae and row of marginal setae on anterior margin; carpus subrectangular with row of paired setae on anterior margin, distally with 1 triangular projection; propodus 1.2 x longer than propodus of pereopod 6, proximal projection with 1 pair of grasping spines followed by a row of marginal robust setae on palm, distally with several long and short setae; dactylus falcate, with several fine setae on inner and outer margin.

Pleon. Penes semicircular, positioned medially. Uropod 1 ramus vestigial, degenerated into 2 short and 1 long setae. Uropod 2 ramus vestigial, with 3 setae, submarginally with 4–5 setae. Telson with a pair of plumose setae.

Female. Body length, 3.28 mm. UMTCrus00474. Head length 0.37 mm and pereonite 1, 0.17 mm; head and pereonite 1 partially fused (suture clear); head with 1 long anteriorly curved dorsal projection; pereonite 1 with 1 dorsodistal triangular projection. Pereonite 2, 0.63 mm with 1 pair of anteriorly curved mid-dorsal projections and an unpaired dorsodistal round projection. Pereonite 3, 0.68 mm, longest, with 1 anterodorsal round projection, 1 small anterior lateral projection, 1 mid-dorsal round projection, 1 dorsodistal round projection, posteroventral corner of pereonite 3 slightly pronounced. Pereonite 4, 0.57 mm, with 1 mid-dorsal round projection and 1 dorsodistal plate-like projection. Pereonite 5, 0.47 mm, with 1 pair of mid dorsal round projection, 1 anteroventral triangular projection. Pereonite 6, 0.19 mm, with 1 anteroventral triangular projection. Pereonite 7, 0.20 mm, with no projections. Antenna 1, 0.63 x body length; peduncular article 2 longest, 1.4 x longer than article 1; article 3 shortest, 0.43 x shorter than article 2; flagellum with 10 articles, proximal article composed of 2 articles. Antenna 2, 0.32 x body length and 0.5 x antenna 1; peduncular article one shortest with ventrodistal projection; article 2 with several setae at ventrodistal corner; article 4 longest; flagellum with 2 articles, article 2 shorter than article 1 (0.5 x shorter) with tuft of setae at distal margin.

Pereon. Gnathopod 1 basis shorter than ischium, merus and carpus combined; merus with several setae at posterodistal corner; carpus 1.15 x merus with several setae on distolateral margin; propodus 2.06 x carpus with 2 rows of submarginal setae and several setae at distal margin, palm begins 1/4 along posterior margin with a pair of robust/stout proximal setae and several short and long setae along entire margin; dactylus falcate, distally with 1 tooth and 2 tubular setae. Gnathopod 2, begins 1/5 along anterior margin of pereonite 2, coza weakly lobated; basis 1.75 x longer than ischium, merus and carpus combined; basis with 1 acute anterodistal triangular projection provided with 3 setae; ischium with 1 triangular projection at anterodistal margin; merus round with several setae; carpus subtriangular; propodus 0.88 x basis; palm begins 1/6 along posterior margin, proximal projection with 1 robust seta (grasping spine), mid palmar region with 1 small triangular projection followed by 2 smaller round projections, palm with several short and long setae, equipped with serratiform teeth between grasping proximal projection and mid-palmar projection; dactylus falcate, with several fine setae on outer and inner margin. Gill 3 length 0.62 x the length of pereonite 3, oval. Pereopod 3, 0.03 x pereonite 3, 0.05 x gill 3 length, 1 articulate, conical, with 2 setae apically. Oostegite 3, 1.13 x longer than wide, scarcely setose. Gill 4, 0.67 x the length of pereonite 4, oval. Pereopod 4 subequal in length with pereopod 3, 0.07 x gill length, 1-articulate, conical, with 2 setae apically. Oostegite 4, 1.08 x longer than wide, setose along entire margin. Pereopods 5–7 well developed, 6 articulate, becoming more robust progressively. Pereopod 5 carpus subequal in length with merus, distally with 1 projection; propodus subequal in length with basis, proximal projection with a pair of grasping spines, dactylus falcate, distal margin with tuft of setae. Pereopod 6 merus expanded posterodistally; carpus distal margin with 1 triangular projection; propodus proximal projection with 1 pair of grasping spines; dactylus falcate. Pereopod 7 merus expanded posterodistally; carpus subrectangular, distally with 1 triangular projection; propodus proximal projection with 1 pair of grasping spines followed by a row of marginal robust setae on palm; dactylus falcate, with several fine setae on inner and outer margin.

Pleon. Uropod 1 ramus vestigial, degenerated into 1 setae. Uropod 2 ramus vestigial, with 2 setae. Telson with a pair of plumose setae

Remarks. Species of Pseudaeginella are easily distinguishable from one another through observation of its body spinations or projections. Among the 11 species of Pseudaeginella , P. telukrimau sp. n. is closest to P. montoucheti ( Quitete, 1971) and P. tristanensis ( Stebbing, 1888) based on the numerous body spines/projections.

Pseudaeginella montoucheti was first described as Fallotritella montoucheti by Quitete (1971) based on a male (3.2 mm) and female specimen (2.9 mm) collected from sargassum in Pernambuco, a state located northeastern of Brazil. Recently, Lacerda et al (2011) provided a detailed re-description of P. montoucheti collected from Santa Catarina, Brazil. Compared with Lacerda et al.’s (2011) description of P. montoucheti , the present species is similar to P. montoucheti in terms of its unpaired dorsodistal projections on pereonites 2 and 3, paired mid-dorsal projections on pereonites 2–4, 1 mid-ventral triangular projection over gill 3 and 4, 1 anteroventral triangular projection on pereonite 5, pereonite 7 without projections and basis of gnathopod 2 with 1 triangular projection but differs from P. montoucheti in terms of having 1 small anterolateral projection on pereonite 2 but no mid-lateral projection (paired acute anterolateral projection and paired acute mid-lateral projection in P. montoucheti ), presence of 1 anteroventral triangular projection on pereonites 3–4 (only present on pereonite 4 in P. montoucheti ), presence of 1 ventrodistal triangular projection on pereonite 4 (absent in P. montoucheti ), presence of a paired mid-dorsal and mid-ventral projection on pereonite 5 (only a paired mid-dorsal projection and a paired anterolateral projection in P. montoucheti ), pereonite 6 with mid-dorsal projections (absent in P. montoucheti ), antenna 1 more than half of total length (antenna 1 equal or shorter than half of body length in P. montoucheti ) and gnathopod 2 propodus width 0.53 x length (0.67 x in P. montoucheti ).

P. telukrimau sp. n., can be differentiated from P. tristanensis ( Mayer 1903; Laubitz 1995; Lacerda et al. 2011) by the following characteristics: i) mid-dorsal projections: Paired projections on pereonite 2–5 and 1 unpaired projection on pereonite 6 in P. telukrimau (unpaired on pereonites 2–6 in P. tristanensis ); ii) dorsodistal projections: Unpaired projection on pereonites 2–3 and paired projections on pereonite 4 in P. telukrimau (unpaired on pereonites 2–4 in P. tristanensis ); iii) mid-lateral projections: found on pereonites 3–5 in P. telukrimau (found on pereonites 2–4 in P. tristanensis ); iv) antenna 1: longer than half of total length in P. telukrimau (equals half body length in P. tristanensis ); v) total of projections on pereonites: more than 30 projections in P. telukrimau (less than 30 projections in P. tristanensis ); vi) gnathopod 2: basis with 1 triangular projection anterodistally in both P. telukrimau and P. tristanensis ; ischium with 1 large trapezoid projection in P. telukrimau (ischium with 1 triangular projection in P. tristanensis ); propodus width about half its length.

Local distribution. Pulau Tinggi, Pulau Pemanggil, Pulau Sibu, Pulau Harimau, Pulau Rawa, Pulau Tengah, Pulau Hujung, Pulau Besar.

Distribution. Currently only known from Johor, Malaysia.

Figures

FIGURE 1. Pseudaeginella telukrimau sp. n., male, holotype, 3.24 mm, UMTCrus 00473, Coral reef, Teluk Rimau, Pulau Besar, Johor. Scales for A 1, A 2 and G 2 represent 0.2 mm; G 1 and G 1 magnified represent 0.1 mm; whole body represents 0.5 mm.

FIGURE 2. Pseudaeginella telukrimau sp. n., male, holotype, 3.24 mm, UMTCrus 00473, Coral reef, Teluk Rimau, Pulau Besar, Johor. All scales represent 0.05 mm.

FIGURE 3. Pseudaeginella telukrimau sp. n., male, holotype, 3.24 mm, UMTCrus 00473, Coral reef, Teluk Rimau, Pulau Besar, Johor. Scales for ABD (L), P 3, P 4 and P 5 represent 0.1 mm; ABD (V) represents 0.05 mm, P 6 and P 7 represent 0.2 mm.

FIGURE 4. Pseudaeginella telukrimau sp. n., female, allotype, 3.28 mm, UMTCrus 00474, Coral reef, Teluk Rimau, Pulau Besar, Johor. Scales for A 1, A 2 and G 2 represent 0.2 mm; G 1 and G 1 magnified represent 0.1 mm; whole body represents 0.5 mm.

FIGURE 5. Pseudaeginella telukrimau sp. n., female, allotype, 3.28 mm, UMTCrus 00474, Coral reef, Teluk Rimau, Pulau Besar, Johor. Scales for ABD (L), P 3 magnified and P 4 magnified represent 0.1 mm; ABD (V) represents 0.05 mm; P 3, P 4, P 5, P 6 and P 7 represent 0.2 mm.