Pereionotus tinggiensis, Feirulsha & Rahim, 2020

Feirulsha, NurFara-Syakira binti & Rahim, Azman bin Abdul, 2020, A new species of Pereionotus (Amphipoda, Senticaudata, Phliantidae) from Pulau Tinggi, Sultan Iskandar Marine Park, Malaysia, Zoosystematics and Evolution 96 (1), pp. 195-203 : 195

Pereionotus tinggiensis sp. nov. Figures 2 , 3 , 4 , 5

Type material.

Holotype, female, 2 mm, UKMMZ-1603, Kg. Tg. Balang, Pulau Tinggi, Johor, Malaysia, 2°16'59.5"N, 104°07'21.9"E (DMS), intertidal zone, by washing intertidal rock, Hazmi, Melvin & Azman, 31 August 2016. Paratypes, 3 specimens (2 females, 1 juvenile), UKMMZ-1604, same data as for holotype.

Species composition.

Pereionotus contains 11 species: P. alaniphlias (J. L. Barnard 1970); P. dieteri Coleman & Lowry, 2012; P. hartmuti Coleman & Lowry, 2012; P. hirayamai Coleman & Lowry, 2012; P. holmesi (Gurjanova, 1938); P. japonicus (Tzvetkova, 1968); P. natalensis (K. H. Barnard, 1940); P. testudo (Montagu, 1808); P. thomsoni (Stebbing, 1899); P. tinggiensis sp. nov.; P. yongensis Coleman & Lowry, 2012.

Diagnosis.

Dorsal keel consisting of subequal evenly rising dorsal humps on pereonites 2-7. Antenna 1 robust with subterminal lateral lobe. Coxae 1-4 with sparse long setae on the distal margin. Propodi of pereopods 6 and 7 without additional robust setae on the anterodistal corner of merus and carpus.

Description.

Based on holotype female, 2 mm. Body (Fig. 2 ) depressed, laterally not much expanded, coxae not much splayed. With shallow dorsal keel, each carina on pereonites 2-7 is wide and dorsally truncate. Head small, shorter than pereonite 1, with protruding eyes.

Antenna 1 (Fig. 3 , A1) peduncular article 1 robust with subterminal lateral lobe, almost twice as wide as article 2; peduncular article 2 longer than wide; peduncular article 3 half the width of article 2; flagellum of only one article with long aesthetascs apically. Antenna 2 (Fig. 3 , A2) slender, almost reaching distal margin of article 2 of antenna 1; peduncular article 2 is as long as wide; peduncular article 3 is slightly longer than article 4; peduncular article 4 twice as long as article 5; peduncular article 5 with long flagellum apically.

Upper lip missing. Lower lip (Fig. 5 , LL) apical margin with short mandibular lobes. Mandible (Fig. 5 , MD) dentate incisors with four raker spines. Maxilla 1 (Fig. 5 , MX1) outer lobe with six robust setae of differing size; inner lobe with 1 robust seta. Maxilliped (Fig. 5 , MXP) inner plate subrectangular, apically truncate with four nodular setae and few stout and slender setae; outer plate as long as palp; palp 3-articulate. Maxilla 2 (Fig. 5 , MX2) plates separate apically; inner plate wider than outer plate with three robust setae apically; outer plate with three robust setae apically.

Coxae 1-4 with sparse setae on the distal margin.

Pereopod 1 (Fig. 3 , P1) coxa subrectangular; basis slightly expanded posterodistally, one medial seta on the anterior margin, one apical seta each on the posterior and anterior margin; ischium longer than merus, setae as for basis; merus distally oblique, about the length of carpus, three setae on the posterior margin; carpus expanded anterodistally, one medial seta on the posterior margin, one apical seta each on the posterior and anterior margin; propodus longer than wide, almost as long as merus and carpus combined, medial face with row of stout apically setulose setae, one medial seta on the posterior margin, two apical setae each on the posterior and anterior margin, one apical robust seta on the posterior margin; dactylus falcate, with long unguis. Pereopod 2 (Fig. 3 , P2) coxa wider than that of pereopod 1; basis slightly expanded posterodistally, one medial seta on the anterior margin, one apical seta each on the posterior and anterior margin; mid diameter of ischium is more than half the width of distal basis, one medial seta on the anterior margin, one apical seta each on the posterior and anterior margin; merus distally oblique, three setae on the posterior margin; carpus expanded anterodistally, posterior margin straight with two setae, one apical seta each on the posterior and anterior margin; propodus similar in shape as pereopod 1, without row of robust setae on medial face, one medial seta on the posterior margin, two apical setae each on the posterior and anterior margin, one apical robust seta on the posterior margin; dactylus falcate, with long unguis. Pereopod 3 (Fig. 4 , P3) coxa similar in shape as pereopod 2; basis slightly expanded posterodistally; ischium expanded postero- and anterodistally with one seta on the posterior margin; merus with straight posterior margin and convex anterior margin, distal margin oblique, two medial and one apical seta on the posterior margin, one apical seta on the anterior margin; carpus expanded anterodistally with straight posterior margin, one apical seta on the anterior margin, posterior margin with three medial setae; propodus longer than wide, one medial seta on the posterior and anterior margin, one apical robust seta on the posterior margin, three apical setae on the anterior margin; dactylus subequal to that of pereopod 2. Pereopod 4 (Fig. 4 , P4) coxa widest with posteromarginal subacute lobe; basis expanded posterodistally, straight anterior margin with two medial setae; mid diameter of ischium is 0.8 × the width of distal basis, one apical seta each on the posterior and anterior margin; merus with straight posterior margin and convex anterior margin, distal margin oblique, two medial setae on the posterior margin, one apical seta each on the posterior and anterior margin; carpus expanded anterodistally with one apical seta, two medial seta on the posterior margin; propodus longer than wide, almost as long as merus and carpus combined, two medial, two apical, and one apical robust seta on the posterior margin, one medial and two apical setae on the anterior margin; dactylus subequal to that of pereopod 3. Pereopod 5 (Fig. 4 , P5) basis posteromarginally weakly convex with rounded posterior lobe, expanded ventrally and partly covering the ischium, three medial and two apical setae on the posterior margin; ischium almost as long as wide, two medial and four apical setae on the anterior margin; merus drawn out into slightly rounded posterodistal lobe with three apical setae, one medial and one apical seta on the anterior margin; carpus almost as long as merus, slightly expanded posterodistally with one apical, one medial, and one apical seta on the anterior margin; propodus subequal to the shape of pereopod 4, longer than wide with 2 × the width, two medial and three apical setae on the posterior margin, one medial, two apical, and one apical robust seta on the anterior margin; dactylus falcate, slightly longer compared to that of pereopod 4, with long unguis, six medial setae on the posterior margin and one apical seta on the anterior margin. Pereopod 6 (Fig. 4 , P6) basis with straight anterior margin, posteromarginally weakly convex with rounded posterior lobe, expanded ventrally and partly covering the ischium and merus, distal margin oblique, two medial and apical setae on the anterior margin; ischium subrectangular with two medial and apical setae on the anterior margin; merus expanded posterodistally with one medial and three apical setae; carpus longer than wide as the distal merus, two medial setae on the anterior margin, one apical seta on the posterior margin; propodus longer than wide, 3 × the width, one medial and two apical setae each on the posterior and anterior margin, one apical robust seta on the anterior margin; dactylus is as the same as pereopod 5, one medial seta on the posterior margin and one apical seta on the anterior margin. Pereopod 7 (Fig. 4 , P7) basis posteromarginally weakly convex without rounded posterior lobe with one apical seta on the anterior margin; ischium slightly expanded posterodistally, longer than wide, with one apical seta on the anterior margin; merus expanded posterodistally with one apical seta, one apical seta on the anterior margin; carpus almost as long as merus, longer than wide, with one apical seta on the posterior margin, two apical setae on the anterior margin; propodus as long as that of pereopod 5, longer than wide, two medial and apical setae on the posterior margin, one medial and apical seta, and one apical robust seta on the anterior margin; dactylus falcate, with long unguis, as long as pereopod 5 with one apical seta on the anterior margin.

Pleopod 1 (Fig. 5 , PL1) with subrectangular peduncle, 0.6 × as long as wide, with two coupling hooks; outer ramus slightly longer than inner ramus. Pleopod 2 (Fig. 5 , PL2) peduncle wider than long, with two coupling hooks; rami widened proximally and subequal in length. Pleopod 3 (Fig. 5 , PL3) peduncle wider than long with a tapering medial process ending in an apex with two coupling hooks; outer ramus slightly shortened. Uropod 1 (Fig. 5 , U1) biramous, peduncle as long as outer ramus, slightly expanded anterodistally; outer ramus slightly shorter than inner, with some small setae on the tip. Uropod 2 (Fig. 5 , U2) uniramous, peduncle slightly shorter and wider than rami; both rami subequal, with an apical nodular seta on the tip. Uropod 3 (Fig. 5 , U3) without rami, hidden under telson. Telson triangular and slightly longer than wide (Fig. 5 , T).

Remarks.

Pereionotus tinggiensis sp. nov. shares the diagnostic characters of the genus: body depressed dorsoventrally; coxal plates 1-4 not strongly splayed; maxilla 1 with scale-like inconspicuous palp; maxilla 2 with basally fused palp; maxillipedal palp 3-articulate; basis of pereopods 5 and 6 wide, rounded and ventrally expanded; slightly shortened inner ramus of pleopods 3; uropod 2 uniramous (female), and uropod 3 lacking rami.

The new species shows significant differences from other known species of Pereionotus . However, Pereionotus tinggiensis sp. nov. appears to have some similarities to the neighbouring Australian species, namely P. dieteri , P. hartmuti , P. thomsoni , and P. yongensis . Nonetheless, certain distinct characters were observed, including, i) the presence of additional robust seta half-way on the posterior margin of propodi of pereopods 1-4 and, ii) similar robust setae on the anterior margin of the propodi of pereopods 5-7, distinguishing P. tinggiensis sp. nov. from P. thomsoni . Besides, P. hartmuti and P. yongensis were found to exhibit a dense fringe of long slender setae on the distal margin of coxa 1-4. This unique characteristic is lacking in P. tinggiensis sp. nov. The new species is similar to P. dieteri in having robust subterminal lateral lobe of peduncular article 1 of antenna 1; not having additional robust seta half-way on the posterior margin of propodi of pereopods 1-4; and lacking robust seta on the anterior margin of the propodi of pereopods 1-7, but can be distinguished from P. dieteri by the absence of one or two short robust setae on the anterodistal corner of merus and carpus of pereopods 6 and 7.

Etymology.

This species is named after the type locality, Pulau Tinggi, Johor, Malaysia.

Figures

Figure 2. Pereionotus tinggiensis sp. nov., holotype female, UKMMZ- 1603.

Figure 3. Pereionotus tinggiensis sp. nov., holotype female, UKMMZ- 1603, 2 mm. Scale bars: 0.1 mm.

Figure 4. Pereionotus tinggiensis sp. nov., holotype female, UKMMZ- 1603, 2 mm. Scale bars: 0.1 mm.

Figure 5. Pereionotus tinggiensis sp. nov., holotype female, UKMMZ- 1603, 2 mm. Scale bars: 0.05 mm, except for MD and MX 2, 0.025 mm.