REVIEW. Sex with the lights on? A review of bioluminescent sexual dimorphism in the sea

Abstract

This study evaluates the role of protozoa in larval fish feeding by describing protozoa in larval fish diets and testing the hypothesis that, in the Irish Sea, larval fish feed on protozoan prey at rates that potentially sustain their food requirements. Gut contents of 11 taxonomic groups of larval fish were examined, and protist prey occurred in the diet of all of them. Protozoan prey were identified, which provided an insight into their trophic role. Most of the protozoan prey were autotrophic or mixotrophic. In general, larval fish diets were constant over the spring/summer period, regardless of prey availability in the field and the composition of larval fish assemblage (taxonomy and size). A laboratory experiment on ingestion rates of flounder larvae as a function of ciliates concentration was conducted. Combined laboratory and field data showed that, in the Irish Sea, it is unlikely that ciliates are often the primary food source of flounder larvae, and, by implication, other larval fish as well. However, ciliates and other protozoa could be a substantial component of the larval fish diet, and they may potentially prevent food limitation.

Functional physiology of lantern shark (Etmopterus spinax) luminescent pattern: differential hormonal regulation of luminous zones

“…The rate of light emission is very different from one zone to another, thus reinforcing the idea of the multifunctionality of the luminous pattern. Similar versatility in the luminescence emission has been found in lanternfishes (myctophids) which feature a caudal organ that flashes rapidly and is believed to be used in intraspecific communication, and slow glowing ventral photophores involved in camouflage (Young et al, 1980;Herring, 2007). In addition, the data presented here bring, for the first time, evidence of a clear dimorphism in the response to PRL between males and females of E. spinax.…”

“…For example, the differences in L tot and TL max found in this study might reveal the presence of a luminescent courtship display between male and female E. spinax specimens. Such luminous sexual signals have already been documented/suggested in other marine animal species including polychaetes (Tsuji and Hill, 1983), crustaceans (Rivers and Morin, 2008), squids (Herring, 1988) and bony fishes (Crane, 1965;Sasaki et al, 2003;Herring, 2007). Since this sexual dimorphism is only observed in response to PRL, it should be more pronounced when luminescence response to PRL are higher, which appears to be in April, at the winter-spring transition (Claes and Mallefet, 2009a).…”

“…The vast majority of deep-sea organisms rely on luminescence for numerous functions including predation avoidance, predation and intraspecific communication (Buck, 1978;Wilson and Hastings, 1998;Herring, 2007). The possession of photogenic organs (photophores) is a common feature in many of these organisms, including crustaceans, molluscs and fishes (Haddock et al, 2010).…”

Nitric oxide in the control of luminescence from lantern shark (Etmopterus spinax) photophores

“…The presence of NOS in the caudal organ of the myctophid M. punctatum (Krönström and Mallefet, 2009), which is probably used for sexual communication (Herring, 2007), supports the idea that the effects of NO on luminescence are not restricted to the counterilluminating behaviour in fishes. It is therefore possible that NO modulation also exists in luminous zones of E. spinax that are not involved in counterillumination, but this needs further analysis.…”

Light and vision in the deep-sea benthos: II. Vision in deep-sea crustaceans

“…As mentioned above, several species of mesopelagic oplophorid shrimp have both UV-sensitive and blue-sensitive visual pigments. Those species with the dual visual pigment system possess both light-emitting organs called photophores, which are used for counterillumination and hypothesized to play a role in sexual signaling (reviewed in Herring, 2007) and a bioluminescent spew (i.e. vomit), which probably serves a defensive function (Herring and Barnes, 1976).…”