Platorchestia sp.

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 : 205

Platorchestia sp.

( Fig. 7 )

Material examined: 5 males, 1 female (MNHNCL AMP-16002): Antofagasta, Región de Antofagasta, -23.61336 -70.39204, 2022-08-22, coll. J. Pérez-Schultheiss, under stones, partially submerged in small stream, JP-556 .

Remarks: The specimens belong to the Platorchestia platensis complex (sensu Kim et al. 2013), which was originally characterized by the presence of strong sexual dimorphism in the antennae and male pereopod 7 (cf. group 1 of Miyamoto & Morino 2004 or the restricted concept of Platorchestia of Myers & Lowry 2023). The material examined shows a combination of characters that does not match exactly with any described species, but the specimens are apparently more related to Platorchestia pacifica Miyamoto & Morino, 2004 , P. platensis ( Krøyer, 1845) , P. paraplatensis Serejo & Lowry, 2008 and particularly P. oliveirae Myers & Lowry, 2023 , with which it shares the cuspidactylate dactylus of gnathopod 1 (fig. 7GN1), the produced posterior lobe of the coxa 6 (fig. 7CX6), the wide carpus of pereopod 7 (fig. 7P7) and telson with two groups of dorsolateral setae (fig. 7T). It is also similar to Demaorchestia parapacifica ( Kim, Jung & Min, 2013) in the general structure of gnathopod 2 and the appearance of the carpus of pereopod 7, which is widened, but not especially incrassate as in other species of the P. platensis complex. The genus Demaorchestia was recently described by Lowry & Myers (2022), for species originally assigned to P. platensis and other allied species with simplidactylate male gnathopod 1.

The reported morphological observations strongly suggest that we are dealing with a new species, but we refrain from describing it here because unpublished molecular evidence indicates that these specimens are related to material from Bermuda, identified as Platorchestia monodi by Wildish et al. (2016), material posteriorly synonymized under P. oliverae ( Myers and Lowry 2023) . The observed morphological patterns and the variation in some diagnostic morphological characters among specimens of Platorchestia and Demaorchestia species (see e.g. Morino 2023), suggests a complex taxonomic problem, which requires a complete integrative study.

Distribution: Hitherto the presence of Platorchestia in southeastern Pacific has been confirmed only for Antofagasta (Antofagasta Region) ( Fig. 12A ), in a small creek discharged over a mixed, rocky and sandy beach ( Fig. 13A ).

Figures

FIGURE 7. Platorchestia sp., male A (MNHNCL AMP-16002).Abbreviations:A2= antenna 2; GN1= gnathopod 1, with detail of dactylus cuspidactylate; GN2= gnathopod 2; CX6= coxa 6 posterior lobe; P7= pereopod 7; PL2 and PL3= peduncle of pleopod 2 and 3; T= telson.

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.