Atacamorchestia atacamensis, Pérez-Schultheiss & Fernández & Ribeiro, 2024

Pérez-Schultheiss, Jorge, Fernández, Leonardo D. & Ribeiro, Felipe Bezerra, 2024, Two new genera of coastal Talitridae (Amphipoda: Senticaudata) from Chile, with the first record of Platorchestia Bousfield, 1982 in the southeastern Pacific coast, Zootaxa 5477 (2), pp. 195-218 : 198-205

Atacamorchestia atacamensis sp. nov.

( Figs. 1A , 2–6 )

http://zoobank.org/ urn:lsid:zoobank.org:act:700F7841-3E19-4DC6-B7FD-F09081EC841F

Material examined: Male holotype (6.84 mm, MNHNCL AMP-15250): Chile: Bahía Salado , Región de Atacama, -27.6237 -70.9027, 2016-05-27, coll. J. Pérez-Schultheiss & C. Vásquez, Rocky intertidal, under stones. Male paratypes (MNHNCL AMP-15252, MNHNCL AMP-15253, SCBUCN-8186, MHNV-CBTI 0001 and MZUC-CCC 47919 ), female paratypes (MNHNCL AMP-15251, MNHNCL AMP-15256, MNHNCL AMP-15257, SCBUCN-8187 and MHNV-CBTI 0002 ), and male paratype A (illustrated, MNHNCL AMP-15255), all same data as holotype. Female paratype B ( MZUC-CCC 47920 ): Chile: Parque Nacional Fray Jorge, Región de Coquimbo, -30.6205 - 71.7092, 2017-11-05, coll. J. Pérez-Schultheiss, under boulders, supratidal, JP-291. 1 male, 3 females (MNHNCL AMP-15961): Chile: Estuario Rio Limarí , Ovalle , Región de Coquimbo, -30.7319 -71.6959, 2018-11-13, Coll. J. Pérez-Schultheiss, Moving on dry mud, among Sarcocornia , JP-376. 1 female (MNHNCL AMP-16003): Muelle Barón , Valparaíso, Región de Valparaíso, -33.0417 -71.6082, 2013-04-27, coll. J. Pérez-Schultheiss, Boulders intertidal, under stones, N°650. 11 males, 10 females (MNHNCL AMP-15962): Carrizal Bajo , Huasco , Región de Atacama, -28.0832 -71.144, 2016-05-24, coll. Cristina Coccia, Pitfall traps, associated to Sarcocornia . 1 male, 1 juvenil (MNHNCL AMP-15963): Punta de Tralca , El Quisco , Región de Valparaíso, -33.4252 -71.7073, 2016- 08-27, Coll. J. Pérez-Schultheiss, under stones, freshwater seepage, between rocks. 1 female, 2 males (MNHNCL AMP-15964): Parque Nacional Fray Jorge , Región de Coquimbo, -30.6205 -71.7092, 2017-11-05, Coll. J. Pérez-Schultheiss, Under boulders, supratidal, JP-291. 4 males, 4 females (MNHNCL AMP-15965): Carrizal Bajo , Huasco , Región de Atacama, -28.0832 -71.144, 2016-10-15, Coll. Cristina Coccia, Pitfall traps, associated to Sarcocornia .

Etymology: The specific epithet is based in the name “ Atacama ”, the region where specimens were collected, and the suffix -ensis, that denote place or locality of origin.

Diagnosis: Atacamorchestia atacamensis sp. nov. can be recognized among all talitrids, by the following combination of characters: merus, carpus and propodus of gnathopod 1 with well-developed lobes with palmate setae, male gnathopod 2 with dactylus distally attenuated, male antenna 2 and pereopods 3-6 with T setae, sexual dimorphism absent in male pereopod 7, exopodite of uropod 1 generally without robust dorsal setae, but present in terminal fully developed adults, and telson with only one robust seta dorsolaterally.

Description: Holotype male, 13.9 mm. Eye medium, 1/5–1/3 head length. Antenna 1 (fig. 2A1) short, not reaching the midpoint of peduncle article 5 of antenna 2, flagellum with 6 articles. Antenna 2 (fig. 2A2) longer than head and first 3 pereonites, reaching to mid pereonite 5; peduncular articles narrow and with sparse T setae in posterior margin of article 3 and 4, and in both margins of article 5; flagellum 23-articulate, with four long slender setae (longer than half the width of segment) ordered radially in each article, forming longitudinal rows along the flagellum. Mandible left lacinia mobilis 4-dentate (fig. 3ML). Maxilliped palp (fig. 3MXP), article 2 with distomedial lobe, article 4 distinct and small.

Gnathopod 1 (fig. 4GN1a) sexually dimorphic; subchelate; posterior margin of merus, carpus and propodus with lobe covered in palmate setae; propodus subtriangular; palm transverse; dactylus shorter than palm, simplidactylate. Gnathopod 2 (fig. 4GN2a) sexually dimorphic; subchelate; merus without medial lobe; carpus triangular, reduced, enclosed by merus and propodus; palm acute, convex, smooth, posterodistal corner defined but without an especially robust seta placed behind an abrupt slope; dactylus longer than palm, attenuated distally. Coxae 2–4 wider than deep (fig. 4GN2, 5P3, 5P4). Pereopods 3–7 cuspidactylate; dactylus without row or patch of dorsal short setae. Pereopod 4 (fig. 5P4) slightly shorter than pereopod 3. Pereopod 4 dactylus similar to pereopod 3 dactylus. Pereopod 5 (fig. 6P5) propodus distinctly longer than carpus. Pereopod 6 (fig. 6P6) not sexually dimorphic; shorter than pereopod 7; carpus slender. Pereopod 7 (fig. 6P7) basis posterodistal lobe rounded, slightly dentate; distal articles slender. Coxal gills slightly lobate. Pereopods 3–5 gills subequal in size to gills 2 and 6.

Pleopods 1–3 well developed and biramous. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior and ventral margins smooth, without setae, posteroventral corner rounded. Uropod 1 (fig. 1U1) peduncle with 4–7 robust setae; distolateral robust seta present, large, about 1/3 length of outer ramus; inner ramus slightly longer than outer ramus; inner ramus with 4 marginal robust setae; outer ramus with 2 marginal robust setae (setae absent in smaller specimens). Uropod 2 (fig. 1U2) peduncle with 3–4 robust setae in one row; inner ramus subequal in length to outer ramus; inner ramus with 2 marginal robust setae; outer ramus with 2 marginal robust setae. Uropod 3 (fig. 1U3) peduncle with 2 robust setae; ramus shorter than peduncle, less than 3 times longer than wide, narrowing distally, without marginal seta, and 6 apical setae. Telson (fig. 1T) about 1.5× longer than wide; apically incised; with 1 laterodorsal robust seta and 4–5 apical robust setae per lobe; dorsal midline entire.

Female (sexually dimorphic characters), paratype B (11.10 mm, MZUC-CCC 47920), 10.2 mm. Antennae 1 with 6 articles. Antenna 2 with 21 articles. Gnathopod 1 (fig. 4GN1b) propodus subrectangular; dactylus subequal in length to palm. Gnathopod 2 (fig. 4GN2b) mitten-shaped; basis narrow, 2.7× longer than wide; posterior margin of merus, carpus and propodus with rugose lobe; dactylus shorter than palm. Oostegites (fig. 4GN2b) longer than wide; setae simple. Oostegites 2–4 moderately setose, with 36, 26 and 21 setae respectively. Uropod 3 peduncle with 3 robust setae.

Distribution: The species has been observed in north-central Chile, from Bahía Salado (Atacama Region) to Punta de Tralca (Valparaíso Region) ( Fig. 12B ), in rocky supratidal habitats ( Fig. 13B ).

Remarks: Among the Chilean species of beachflies, Atacamorchestia atacamensis gen. et sp. nov. can be easily recognized by the antenna 2 particularly slender and setose, with flagellum composed of over 20 articles, whose setae length exceed half the width of each respective segment. In addition, almost all pereopod segments are especially setose, with T setae in male pereopods 3–7, a feature that does not appear in any other species of talitroid. Also, so far A. atacamensis sp. nov. is the only Chilean species whose dactyl of male gnathopod 2 is apically attenuated.

Figures

FIGURE 1. Habitus of new species of Talitridae. A: Atacamorchestia atacamensis sp. nov., male holotype (MNHNCL AMP- 15250). B: Lafkenorchestia oyarzuni sp. nov., male paratype I (MNHNCL AMP-15967).

FIGURE 2. Atacamorchestia atacamensis gen. et sp. nov., male holotype (MNHNCL AMP-15250), antennae, uropods and telson. Abbreviations:A1= antenna 1; A2= antenna 2; U1–3= uropods 1 to 3; T= telson.

FIGURE 3. Atacamorchestia atacamensis gen. et sp. nov., male paratype A, mouthparts. Abbreviations: ML: left mandible; MR= right mandible; Ul= upper lip; Ll= lower lip; MX1= maxilla 1; MX2= maxilla 2; MXP= maxilliped.

FIGURE 4. Atacamorchestia atacamensis gen. et sp. nov., male holotype (MNHNCL AMP-15250) (a) and female paratype B (MZUC-CCC 47920) (b), gnathopods. Abbreviations: GN1= gnathopod 1; GN2= gnathopod 2.

FIGURE 5. Atacamorchestia atacamensis gen. et sp. nov., male holotype (MNHNCL AMP-15250), pereopods 3–4. Abbreviations: P3= pereopod 3; P4= pereopod 4.

FIGURE 6. Atacamorchestia atacamensis gen. et sp. nov., male holotype (MNHNCL AMP-15250), pereopods 5–7. Abbreviations: P5= pereopod 5; P6= pereopod 6; P7= pereopod 7.

FIGURE 12. Distribution of the studied taxa, with localities of collection for material examined. A, Platorchestia sp. B, Atacamorchestia atacamensis sp. nov. C, Lafkenorchestia oyarzuni sp. nov.

FIGURE 13. Habitat of the studied taxa, ordered from north to south in the Chilean coast.A, small coastal creek in Antofagasta (23.61336 -70.39204), habitat of Platorchestia sp. B, coastal area in Fray Jorge National Park (-30.6205 -71.7092), habitat of Atacamorchestia atacamensis sp. nov. C, Lliuco river estuary (-40.8904 -73.84912) and D, el Galpón beach (-40.8905 - 73.8485), typical habitats of Lafkenorchestia oyarzuni sp. nov.