Photis Krøyer, 1842

Souza-Filho, Jesser F. & Serejo, Cristiana S., 2010, Two new species of the family Photidae (Amphipoda: Corophiidea: Photoidea) from Brazilian waters, with description of Rocasphotis gen. nov., Journal of Natural History 44 (9 - 10), pp. 559-577 : 561

Genus Photis Krøyer, 1842

Photis Krøyer, 1842: 155 . Stebbing, 1906: 605. Barnard, 1962: 26. Barnard, 1969: 274. Barnard, 1973: 22. Conlan, 1983: 42. Barnard and Karaman, 1991: 224. LeCroy, 2000: 144.

Heiscladus Bate and Westwood, 1863: 411 . Norman, 1869: 255.

Photis (Cedrophotis) Barnard, 1967: 26 .

Pseudophotis Hirayama, 1984: 35 .

Diagnosis

Head lateral cephalic lobe strongly extended and apically rounded; eye, if present, situated completely enclosed in the lobe; anteroventral margin strongly recessed. Antenna 1 subequal to antenna 2; peduncular article 1 subequal to article 3; accessory flagellum absent or rudimentary. Coxae 1 and 2 shorter than coxae 3–5 in male. Maxilla 1 inner plate naked, outer plate with two rows of subequal robust setae. Maxilla 2 inner plate with a row of facial setae. Gnathopods 1 and 2 subchelate; gnathopod 2 larger than gnathopod 1 and sexually dimorphic. Pereopod 5, and often pereopods 6 and 7, with accessory spine on dactyli. Pleon and urosome dorsally smooth. Uropod 3 peduncle longer than rami, inner ramus much reduced, one-quarter or less than outer ramus; outer ramus with a second distal article rudimentary. Telson with an apical pair of knobs.

Type species

Photis reinhardi Krøyer, 1842 .

Generic remarks

Most species of Photis show great variation with age in the male gnathopod 2. Frequently, it is difficult to recognize juveniles, females and adult males as a single species. This may represent a problem if different adult males are found together with juveniles and females in the same sample.

Within the genus Photis a wide variance in important diagnostic characters is observed (e.g. shape and length of lateral cephalic lobe, as well as male coxae 1 and 2, maxilla 2 with or without facial row of setae on inner plate). Barnard (1962), Hirayama (1984), Karaman (1985) and Barnard and Karaman (1991) have shown that Photis represents a complex genus, with groups of species that should be recognized as distinct genera or subgenera. Barnard and Karaman (1991) listed three subgenera of Photis (Cedrophotis, Pseudophotis and Photis ), but the real composition of each subgenus is not clear because in their list of variables within the genus, many species of the subgenus Photis could be placed in another subgenus. In fact, these subgenera have not been used. Hence, only an extensive examination of almost all species of Photis will solve these problems.