Effects of the Parasitic Copepod Cardiodectes medusaeus on the Lanternfishes Diaphus theta and Tarletonbeania crenularis off Central California

Abstract

In two distinct survey areas, offshore from the Farallon Islands and in the vicinity of Pioneer Canyon off central California, Diaphus theta was significantly more prone to infection by the parasitic copepod Cardiodectes medusaeus than Tarletonbeania crenularis. In addition, D. theta was more heavily parasitized in the Pioneer Canyon area than in the Farallon Islands area. A linear relationship was shown between loge-transformed otolith size and loge-transformed SL and between loge-transformed dry weight and loge-transformed SL for D. theta and T. crenularis in both survey areas. A test of slopes showed differences between the two survey areas for both species. Lower dry weights were observed for both D. theta and T. crenularis, in parasitized versus non-parasitized specimens in the Pioneer Canyon area. In the Farallon Islands area, however, no differences were observed. Larger otolith sizes were observed in parasitized D. theta versus non-parasitized specimens in the Pioneer Canyon area, while no differences were observed in the Farallon Islands area. In contrast, T. crenularis had larger otolith sizes in parasitized versus non-parasitized specimens in the Farallon Islands area, while no significant differences were observed in the Pioneer Canyon area. These findings provided evidence of geographic and interspecific variability in both the prevalence and the physiological effects of parasitism.