Monday, August 6, 2018

[Crustacea • 2018] Caridina variabilirostris • A New Species of Freshwater Shrimp (Decapoda: Atyidae) from Pohnpei (Micronesia)

Caridina variabilirostris 
Mazancourt, Marquet & Keith, 2018

Recently, the status of a new species of atyid shrimp from Pohnpei (Micronesia) was discussed in relation to C. brachydactyla De Man, 1908 and C. mertoni J. Roux, 1911. By combining morphological data with a phylogenetic analysis with closely related species, this species is here described as Caridina variabilirostris sp. nov. Notes on its ecological distribution are also provided. The new species is characterized by a highly variable rostrum and is present in rivers all over Pohnpei Island. The status of this new species is clarified and it is shown that neither C. brachydactyla De Man 1908 nor C. mertoni J. Roux, 1911 occur on Pohnpei Island. 

Keywords: 16S, molecular, integrative taxonomy, island, morphology. 

Class Malacostraca Latreille, 1802 
Order Decapoda Latreille, 1802 

Family Atyidae De Haan, 1849 
Genus Caridina H. Milne Edwards, 1837 

Fig. 3.Caridina variabilirostris sp. nov.,
 showing the variation in rostrum length related to the altitude (a– c), drawings made from different specimens. a, m–n. ♂, cl 3.5 mm (MNHN-IU-2018-244). a. Rostrum. m. First pleiopod. n. Second pleiopod. b. ♀, cl 5.6 mm, rostrum (MNHN-IU-2018-252). c, j, o. ♀, cl 4.0 mm (MNHN-IU-2018-253) c. Rostrum. j. Uropodial diaeresis. o. Eggs. d–i, k. ♀, cl 3.5 mm (MNHN-IU-2018-250). d. First pereopod. e. Second pereopod. f. Third pereopod. g. Dactylus of third pereopod. h. Fifth pereopod. i. Dactylus of fifth pereopod. k. Telson. l. ♀, cl 4.3 mm, pre-anal carina (MNHN-IU-2018-256). of third pereopod. h. Fifth pereopod. i. Dactylus of fifth pereopod. k. Telson. l. ♀, cl 4.3 mm, pre-anal carina (MNHN-IU-2018-256).

Fig. 5. Caridina variabilirostris sp. nov., live coloration (Photos: P. Keith)

Caridina variabilirostris sp. nov. 

Etymology: The new species is named variabilirostris for its variable rostrum length.

Habitat: This species is found among macrophytes in flowing fresh water of the rivers of Pohnpei all along the course, showing good adaptability to different temperatures and hydrological conditions. It is more abundant in higher elevations due to reduced predator pressure.

Distribution: This new species is currently known from Pohnpei Island only. 

Valentin de Mazancourt, Gerard Marquet and Philippe Keith. 2018. Caridina variabilirostris (Crustacea: Decapoda: Atyidae), A New Species of Freshwater Shrimp from Pohnpei (Micronesia). European Journal of Taxonomy.  453; 1–16. DOI: 10.5852/ejt.2018.453