Diaphus theta Eigenmann & Eigenmann, 1890
California headlightfish
Diaphus theta
photo by Orlov, A.

Family:  Myctophidae (Lanternfishes), subfamily: Diaphinae
Max. size:  11.4 cm TL (male/unsexed)
Environment:  bathypelagic; marine; depth range 10 - 3400 m
Distribution:  Eastern Pacific: common in California Current region to 20°S (Ref. 31442), including Hawaii (Ref. 4925). Northwest Pacific: throughout subarctic-transitional waters to northern Japan (Ref. 31442).
Diagnosis:  Dorsal spines (total): 0-0; Dorsal soft rays (total): 12-14; Anal spines: 0-0; Anal soft rays: 12-14; Vertebrae: 34-36. Adipose small, narrow based, slender (Ref. 6885). Brown to black on dorsal surface, lighter ventrally; fins pale (Ref. 6885). Branchiostegal rays: 9 (Ref. 31442).
Biology:  Epipelagic to mesopelagic (Ref. 31442). Feed at night or in the morning (Ref. 9199), on euphausiids, copepods, and amphipods (Ref. 11712). Oviparous, with planktonic eggs and larvae (Ref. 31442). Lipid content is 15.8 % in fresh body weight while wax ester is present in trace amounts (Ref. 9197). Minimum depth reported from Ref. 28981.
IUCN Red List Status: Least Concern (LC); Date assessed: 26 June 2018 Ref. (130435)
Threat to humans:  harmless


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