Myanmarorchestia peterjaegeri Hou

Hou, Zhonge & Zhao, Shuangyan, 2017, A new terrestrial talitrid genus, Myanmarorchestia, with two new species from Myanmar (Crustacea, Amphipoda, Talitridae), ZooKeys 705, pp. 15-39 : 18-20

Myanmarorchestia peterjaegeri Hou sp. n. Figs 1, 2, 3, 4, 5, 6, 13

Material examined.

Holotype: female (IZCAS-I-A1692-1), 7.8 mm, Nat Ma Taung National Park (21.21°N, 94.02°E) (Mt. Victoria), altitude 2150 m, Chin State, Myanmar, May 11, 2014, collected by Peter Jäger. Paratype: male (SMF50714), 7.0 mm (without head), same data as holotype, GenBank accession number MF663279; paratypes, 3 females (SMF50715).

Etymology.

The specific name honours Peter Jäger, the collector of specimens used in this study and an excellent scientist supporting the diversity research in Myanmar; noun (name) in genitive case.

Diagnosis.

Eyes sub-rounded (Fig. 1); maxilla I palp with two articles, terminal article very small; gnathopod II merus and carpus protuberant on posterior margin; coxal gills convoluted, with marginal filamentous projections; telson with nicks on surface.

Description of holotype female

(IZCAS-I-A1692-1), 7.8 mm.

Head. (Fig. 2A): Eyes sub-rounded, medium in size, approx. 1/3 of head length.

Antenna I (Fig. 1; Fig. 2B): peduncle articles I–III in length ratio 1.0: 1.2: 1.4; flagellum with five articles and one fine distal article, a little shorter than peduncle, each article with short distal setae.

Antenna II (Fig. 2C): peduncle articles III–V in length ratio 1.0: 1.7: 2.3, with setae on anterior and posterior margins; flagellum with ten articles, each article with setae on dorsal and ventral margins.

Upper lip (Fig. 2D): ventral margin rounded, bearing minute setae.

Mandible (Fig. 2F, G): incisor of left mandible with five teeth; lacinia mobilis with four teeth; spine row with six plumose setae; molar with a plumose seta; incisor of right mandible with four teeth, lacinia mobilis bifurcate, with small teeth.

Lower lip (Fig. 2E): inner lobes indistinct, outer lobes covered with thin setae.

Maxilla I (Fig. 2H): inner plate with two terminal strong setae, outer plate with nine serrated apical spines, palp with two small articles.

Maxilla II (Fig. 2I): inner plate narrower and shorter than outer plate, with plumose and simple setae on medial margin, outer plate with two rows of apical spines.

Maxilliped (Fig. 2J): inner plate with three stout apical spines and numerous plumose setae; outer plate bearing four setae on interior margin, some simple setae and two plumose setae apically; palp with four articles, first two articles broad; articles I–III in length ratio 1.0: 0.8: 0.7; article II with three setae on interior side and one seta on exterior side; article III 0.6 times as wide as article II, with some setae and two spines, much wider than article IV; article IV short, with one spine and three simple setae apically.

Pereon.Gnathopod I (Fig. 3A, B): coxal plate bearing six setae on distal margin, anterior margin processed proximally; basis with fine setae on anterior and posterior margins; merus, carpus, and propodus in length ratio 1.0: 1.8: 1.2; merus bearing setae on posterior margin; carpus with setae on anterior and posterior margins; propodus with setae on anterior margin and two spines accompanied by setae on posterior margin; dactylus with one spine on posterior margin and two spines at hinge of unguis.

Gnathopod II (Fig. 3C, D): coxal plate with 11 setae on distal margin, posterior process prominent; basis with two fine setae on anterior margin and one seta on posterior margin; merus protuberant on posterior margin; carpus 1.5 times as long as wide, with tumescent hump at posterodistal corner, and several fine setae at base of hump, anterior margin with three setae; propodus with tumescence, with setae on surface and palm margin; dactylus with two setae on posterior margin and one seta at hinge of unguis.

Pereopod III (Fig. 4A, F): coxal plate with posterior cusp, bearing 13 setae on distal margin; basis longest, with spines accompanied by fine setae on anterior and posterior margins; merus, carpus, and propodus in length ratio 1.0: 0.7: 0.9; carpus and propodus with spines on posterior margins; dactylus not pinched, with two spines at hinge of unguis. Pereopods III–VII simplidactylate.

Pereopod IV (Fig. 4B, G): similar to pereopod III; slightly shorter; coxal plate with posterior cusp, bearing eight setae on ventral margin; merus, carpus, and propodus in length ratio 1.0: 0.8: 1.1; dactylus not pinched.

Pereopod V (Fig. 4C, H): coxal plate bilobed, anterior lobe bigger than posterior lobe, bearing six setae and one seta on anterior and posterior lobes, respectively; basis suboval, with three spines on anterior margin and seven setae on posterior margin, anterodistal corner with two spines; merus, carpus, and propodus in length ratio 1.0: 1.0: 1.2, with spines on both margins; dactylus with two spines at hinge of unguis.

Pereopod VI (Fig. 4D, I): coxal plate bilobed, anterior lobe much smaller than posterior lobe, bearing three setae on posterior lobe; basis suboval, with five spines on anterior margin and seven setae on posterior margin, anterodistal corner with three spines; merus, carpus, and propodus in length ratio 1.0: 1.0: 1.3, with spines on both margins; propodus and dactylus slender, dactylus with two spines at hinge of unguis.

Pereopod VII (Fig. 4E, J): coxal plate non-lobate, shallow, posterodistal corner with one seta; basis oval, with five spines on anterior margin and eight setae on posterior margin, anterodistal corner with three spines; merus, carpus, and propodus in length ratio 1.0: 1.1: 1.5, with spines on both margins; propodus and dactylus slender, dactylus with two spines at hinge of unguis.

Coxal gills (Fig. 3 I–M): present on gnathopod II and pereopods III–VI; gill of gnathopod II lobed, each lobe with marginal filamentous projections; gill of pereopods III and IV similar, lobed and convoluted, one lobe with marginal filamentous projections; gill of pereopod V smallest, lobed and convoluted, one lobe with marginal filamentous projections and one lobe ridged; gill of pereopod VI lobed and convoluted, each lobe ridged.

Oostegites (Fig. 3 E–H): slender, present on gnathopod II and pereopods III–V.

Pleon.Epimeral plates (Fig. 2 K–M): acuminate posterodistally, distal margins without armature; plate I with one fine seta on posterior margin; plate II with one fine seta on posterior margin, anterodistal corner with one nick; plate III shorter, with two fine setae on posterior margin.

Pleopods I–III (Fig. 5 A–C): similar, peduncle with two retinacula on interior margin, exterior margin with dense plumose setae and fine setae; outer ramus 85% of peduncle, outer ramus shorter than inner ramus, both inner and outer rami fringed with plumose setae.

Urosome.Uropods I–III (Fig. 5 D–F): uropod I peduncle longer than rami, with three spines on interior margin and four spines on exterior margin, distolateral spine approx. twice of subdistal one; inner ramus with three spines on interior side and five terminal spines; outer ramus with four terminal spines. Uropod II short, peduncle bearing one spine on interior margin and four spines on exterior margin; inner ramus with three spines on interior side and five terminal spines; outer ramus slightly shorter than inner ramus, with four terminal spines. Uropod III peduncle expanded, with one long posterodistal spine; ramus short, 0.5 times as long as peduncle, with one long slender spine and one short spine apically.

Telson (Fig. 2N): notched, with suture on distal 1/3, each lobe with one apical spine.

Description of paratype male

(SMF50714), head missing, 7.0 mm.

Pereon.Gnathopod I (Fig. 6A, B): similar to that of female, coxal plate bearing five setae and one spine on distal margin, anterior margin processed proximally; basis with fine setae on anterior and posterior margins; merus, carpus, and propodus in length ratio 1.0: 1.4: 1.0; merus bearing setae on posterior margin; carpus with setae on anterior and posterior margins; propodus with setae on anterior margin and three spines accompanied by setae on posterior margin; dactylus with one spine on posterior margin and three spines at hinge of unguis.

Gnathopod II (Fig. 6C, D): coxal plate with 11 setae on distal margin, posterior process prominent; basis slender, anterior margin weakly sinuate, with two fine setae on posterodistal corner; merus protuberant on posterior margin; carpus with tumescent hump at posterodistal corner, and several fine setae at base of hump, anterior margin with two setae; propodus anteroventrally produced, with tumescence, wider than that of female, with setae on surface and palm margin; dactylus robust, with two nicks at surface, five setae on posterior margin and two setae at tip.

Pereopods III–VII (Fig. 6 E–I): similar to those of female.

Coxal gills (Fig. 5 K–N): similar to those of female, coxal gill of pereopod IV lost.

Urosome. As is the female except: Uropod I (Fig. 5G) outer ramus with three terminal spines; Uropod II (Fig. 5H) peduncle bearing two spines on interior margin and four spines on exterior margin, inner ramus with four spines on interior side and five terminal spines; outer ramus with three terminal spines; Uropod III (Fig. 5I) peduncle a little wider than that of female.

Telson (Fig. 5J): notched, each lobe with four nicks on surface and one apical spine.

Habitat.

This species was collected from a disturbed primary forest of the Nat Ma Taung National Park (Fig. 13).

Remarks.

The new species is characterised by the complex lobed gills with filamentous projections. This structure may be related to its terrestrial habitats at high elevations. The convoluted feature can increase the surface area of the gills to keep respiration.