Protella Dana, 1852

Takeuchi, Ichiro, Lim, Jacqueline Hui Chern & Inoue, Yuki, 2014, Description of two species of Protella Dana, 1852 (Crustacea: Amphipoda): P. gracilis Dana, 1853, from Balabac Strait, the Philippines, and P. amamiensis, new species, from southern Japan, Raffles Bulletin of Zoology 62, pp. 53-65 : 54

Genus Protella Dana, 1852

Diagnosis. Head fused (suture present) with pereonite 1. Antenna 1 well developed; flagellum with more than 2 articles. Antenna 2 well developed; flagellum with 2 articles. Mandible well developed; molar present, well developed; palp 3-articulate, setal formula 1-x-y-1. Maxilliped well developed; inner plate (basal endite) smaller than outer plate (ischial endite); outer plate (ischial endite) well developed; palp article 3 without distal projection; palp article 4 well developed. Pereonite 4 clavate appendage absent. Pereonites 6 and 7 separated (dorsal suture oblique). Pereopod 3 vestigial, with 1–2 articles. Pereopod 4 vestigial, with 1–2 articles. Pereopod 5 well developed, with 7 articles, with sparse, short setae and well-developed dactylus. Pereopods 6 and 7 well developed, with 7 articles. Gills on pereonites 3 and 4. Pleopods absent. Uropods 2 pairs; Uropod 1 uniarticulate, uniramous, with knob-liked appendage. Uropod 2 uniramous, vestigial (unclear). Telson (dorsal lobe) present.

Remarks. Although the authors managed to clarify most of the generic diagnosis for Protella Dana, 1852 , its mouthparts morphology are still unclear because the larger specimen among the types was lacking its head to pereonite 2 and the origin of the smaller specimen is questionable (see Remarks of Protella gracilis Dana, 1853 ). The state of its missing pereonites and consequently missing mouthparts such as maxilliped and mandibles, usually used for generic diagnosis, cannot be determined, and that is an issue because the genus Protella Dana, 1852 , is one of the oldest genera in the Caprellidea, with several genera derived from this genus, i.e., Paraprotella Mayer, 1903 , Protellopsis Stebbing, 1888 , Metaprotella Mayer, 1890 , and Orthoprotella Mayer, 1903 . The diagnosis of antennae 1 and 2 and mouthparts are tentatively inferred from the descriptions of Protella amamiensis , new species. Thus, it is imperative that revision of the generic diagnosis for Protella and other related genera is conducted in the near future based on a complete specimen of P. gracilis [sensu stricto] collected from the type locality or adjacent areas by providing detailed descriptions and illustrations.

With respect to the generic diagnosis, it was recently determined that the fusion or distinct segmentation of pereonites 6 and 7 is an important aspect of the Caprellidae (see Lim & Takeuchi, 2012). However, it has been widely described in many taxonomical papers of the Caprellidae as either “Pereonites 6 and 7 separated” like in most of the genera of the Caprellidae including Caprella (see Takeuchi, 1993; Krapp-Schickel & Takeuchi, 2005) or “Pereonites 6 and 7 completely fused (dorsal suture absent)” in the genus Metaprotella ( Takeuchi & Lowry, 2007a; Lim & Takeuchi, 2012). Unlike the original figure of P. gracilis [sensu stricto] from Dana (1855), which showed pereonites 6 and 7 of P. gracilis clearly separated (as seen from pereonites 2–6), this study revealed that P. gracilis [sensu stricto] retained an intermediate trait between the two characteristics. Therefore, the generic diagnosis for Protella Dana, 1852 , concerning fusion of pereonites 6 and 7 is revised to “Pereonites 6 and 7 separated (dorsal suture oblique).”