Australatya keithi, Lorang & Marquet & Mazancourt, 2021

Australatya keithi View in CoL sp. nov.

( Figure 2 View FIGURE )

Material examined — Holotype. Vanuatu (Aneityum): Inwe Lengei River , 1♂, cl 5.5 mm ( MNHN-IU-2018-3302 ; DNA: CA1957), 20 ° 12.4090 S, 169 ° 48.1310 E, June 24, 2015, 200 m a.s.l., coll. D. Kalfatak, C. Lord, G. Segura GoogleMaps . Paratypes. Vanuatu (Aneityum): 1♀ ovig., cl 6.8 mm ( MNHN-IU-2018- 3303 ; DNA: CA1958), same data as holotype; GoogleMaps Vage River , Solomon Islands (Kolombangara): 1♀ ovig., cl 4.0 mm ( MNHN-IU-2018-3300 ; DNA: CA1934), 08 ° 05.1120 S, 156 ° 59.8670 E, November 10, 2015, coll. P. Keith, G. Marquet, C. Lord; GoogleMaps Maravari River , Vella Lavella: 1♀ ovig., cl 4.0 mm ( MNHN-IU-2018-3301 ; DNA: CA2359), 1 specimen ( MNHN-IU-2018-3308 ; DNA: CA1944), 07 ° 51.7030 S, 156 ° 41.7480 E, October 10, 2016, coll. P. Keith and C. Lord; GoogleMaps Ma’ epu stream , Savai ( Samoa): 1♂ juvenile, cl 3.2 mm ( MNHN-IU-2018-3307 ), 13 ° 51.9190 S, 171 ° 41.1740 W, July 07, 2014, 20–50 m a.s.l., coll. P. Gerbeaux; GoogleMaps Tuafaleloa River (Upolu): 1♀ ovig., cl 5.3 mm ( MNHN-IU-2018- 3304 ; DNA: CA1947) and 1♀ ovig., cl 5.7 mm ( MNHN-IU-2018-3305 ; DNA: CA1948), 13 ° 53.6440 S, 171 ° 30.9220 W, July 08, 2014, 100 m a. s.l., coll. P. Gerbeaux; GoogleMaps Faleata River , 1♀ ovig., cl 5.0 mm ( MNHN-IU-2018-3306 ; DNA: CA2422), 13 ° 43.7410 S, 172 ° 18.8320 W, July 12, 2014, 195 m a.s.l., coll. P. Gerbeaux; GoogleMaps Vainifao River , Futuna (Wallis and Futuna): 1♀, cl 6.1 mm ( MNHN-Na-15761 ; DNA: CA2133) and 1♂ ( MNHN-Na-15761 ; DNA: CA2433), 14 ° 17.8020 S, 178 ° 8.4230 W, October 12, 2004, 151 m a.s.l., coll. P. Keith, G. Marquet, N. Mary GoogleMaps .

Comparative material — Australatya hawkei Choy, Page & Mos, 2019

Australia. MNHN-Na-14383 . Freshwater creek in Big Table Land , 1♀ ovig., cl 10.0 mm, North-East Queensland, November 18, 1993, coll. K. McDonald .

Description — Cephalothorax ( Figure 2 M View FIGURE ): Carapace length 4.0– 6.1 mm (N = 7). Carapace smooth, inferior orbital angle fused with a distinct antennal tooth; pterygostomian margin rectangular rounded. Rostrum short, 0.2–0.3 of cl, reaching near to end of basal segment of antennular peduncle, with feebly marked lateral carina, dorsal ridge unarmed. The number of ventral teeth on the rostrum varies from 0 to 4. Rostrum formula 0/0–4. Eyes well developed. Antennular peduncle stout, 0.56 (♀)–0.46 (♂) times as long as carapace; basal segment shorter than half length of antennular peduncle, second segment longer than third segment. Stylocerite reaching 0.86 length of the basal segment of antennular peduncle.

Pereiopods: P1 and P2 similar in size and shape. P1 chela ( Figure 2 A View FIGURE ) atyoid in shape, without palm, 4.5–5.3 times as long as wide, without hooks; dactylus 4.9–5.8 times as long as wide, with tufts of long setae distally; carpus short, cup-like 1.3–1.8 times as long as wide. P2 chela ( Figure 2 B View FIGURE ) atyoid in shape without palm, 4.4–5.3 times as long as wide, tips of fingers rounded, without hooks, dactylus 5.1–6.0 times as long as wide, with tufts of long setae distally; carpus short, cup-like 1.2–1.7 times as long as wide. P3 ( Figure 2 C View FIGURE ) moderately strong, with a row of small plumose setae on lateral margin from ischium to propodus; dactylus ( Figure 2 E View FIGURE ) 1.4–2.71 times as long as wide (terminal spiniform seta included), terminating in one large claw with 5–6 accessory spiniform setae on flexor margin, first spiniform setae distinctly smaller than second; propodus with numerous small spiniform setae on ventral margin, distal pair of spiniform setae not much prolonged, propodus 3.3–4.4 times as long as wide, 2.4–6.1 times as long as dactylus; merus with an interno-inferior margin forming a very distinctive carina with 5–7 strong, teeth-like spiniform setae. P5 ( Figure 2 D View FIGURE ) slender, dactylus ( Figure 2 F View FIGURE ), 1.6–3.5 times as long as wide (terminal spiniform seta included), terminating in one large claw, with 23–32 spiniform setae on flexor margin extending lateral to distal claw; propodus 6.3–8.6 times as long as wide, 3.6–6.8 times as long as dactylus.

Abdomen: Sixth abdominal somite 0.43 length of carapace, 1.25 times as long as fifth somite, 0.87 times as long as telson.

Telson ( Figure 2 J View FIGURE ): slightly tapering distally, 2.4–3.5 times as long as proximally wide, distal margin broadly rounded with a median projection, lateral angles not overreaching distal margin, dorsal with 4–5 pairs of short spiniform setae and one pair of short spiniform setae dorsolateral; distal margin with 2 strong spiniform setae lateral, in between 6–10 long, plumose setae overreaching lateral spiniform setae.

Pl1 ( Figure 2 K View FIGURE ): Endopod of male subtriangular, 2.3 times as long as wide, reaching 0.29–0.41 times of exopod, with an appendix on the subdistal outer margin which reaches beyond distal end of endopod with most of its length.

Pl2 ( Figure 2 L View FIGURE ): Appendix masculina on second pleopod reaching 0.54–0.56 times length of endopod; appendix interna reaching 0.77 of appendix masculina.

Triangular preanal carina ( Figure 2 I View FIGURE ) with a spine.

Uropodal diaeresis ( Figure 2 H View FIGURE ) with 15–21 spinules.

Eggs ( Figure 2 G View FIGURE ): developed (visible eyes) 0.32–0.45 × 0.52–0.71 mm, undeveloped 0.33–0.34 × 0.51–0.57 mm.

Etymology — This new species is named keithi in honor of Philippe Keith, professor at the MNHN, who made extensive collections of both freshwater fish and crustaceans for more than 20 years in the Pacific islands in particular in Kolombangara, Vella Lavella ( Solomon Islands), in Santo ( Vanuatu archipelago), and Futuna island, where he collected, with one of us, the new species here described, and photographed it ( Figure 3 View FIGURE ); we appreciate his flawless friendship, his constant enthusiasm in the field and his dedication to his team.

Habitat — This species, largely rheophile, was collected in the uppermost sections of streams ( Figure 3 B View FIGURE ). It shared this habitat with other “ Atya -like” shrimp ( Atyoida pilipes , Atyopsis spinipes ) and with medium sized palaemonids like Macrobrachium latimanus (von Martens, 1868) .

Color pattern — Body overall dark with white dorsal stripes on the abdomen ( Figure 3 A View FIGURE ).

Distribution — This species occurs in Melanesia ( Solomon Islands, Vanuatu) and in West Polynesia ( Futuna and Samoa) ( Figure 4 View FIGURE ).

Comparison

Genus Australatya Chace, 1983 now includes four species: Australatya keithi sp. nov., A. striolata (MacCulloch and McNeill, 1923) , and A. hawkei Choy, Page and Mos, 2019 , both from Australia, and A. obscura Han and Klotz 2015 from Taiwan, the Philippines, and Ryukyu islands. Morphologically, specimens of the new species differ from A. striolata by their rostrum armed with fewer ventral teeth 0–4 (vs 4–8 in A. striolata ) and their shorter P3 propodus, 3.3–4.4 times as long as wide (vs 5.1–6.3). They differ from A. hawkei by their rostrum armed with fewer ventral teeth 0–4 (vs 5–8 in A. hawkei ) and their shorter P3 propodus, 3.3–4.4 times as long as wide (vs 5.0–6.7). They differ from A. obscura by their longer P1 carpus and P2 carpus 1.3–1.8 (vs 0.8–1.0 in A. obscura ) and 1.2–1.7 (vs 0.9–1.0), their P3 shorter propodus 3.3–4.4 times as long as wide (vs 5.3–6.9), and simple dactyli of the fifth pereiopod (vs. biunguiculate).

Remarks

According to Han and Klotz (2015), the row of prominent, teeth-like spiniform setae on the interno-inferior margin of the merus of the third pereiopod, always present in adult specimens of Australatya , with the sexual dimorphism of the distal segment of the third maxilliped seems to be the best character to distinguish this genus from all other Atya -like genera of the Indo-Pacific region. Our new species here described presents these same characteristics, thus confirming its placement within Australatya .

Furthermore, Australatya keithi is differentiated from Atyopsis spinipes by its much smaller body size; its merus of male specimens lacking a massive spur vs. having a massive spur in large males; its endopod of males first pleopod tapering from proximal to distal vs. not tapering from proximal to distal, rhomboidally oval, submarginally spinose; appendix masculina on second pleopod of males with spinose area distal to tip of appendix interna vs. spinose over more than half length; lateral angles of telson not overreaching distal margin vs. overreaching.

The new species is distinguished from Atyoida pilipes by its chelae not sexually dimorphic vs. dimorphic, with palm in male specimens, and its appendix masculina on second pleopod of males with spinose area distal to tip of appendix interna vs. spinose area overlapping a part of the appendix interna.