538 THE BIOLOGY OF MARINE ANIMALS 



of the spectral composition of the light produced by the photogenic 

 cells. 



The brightness of luminescence has been determined in only a few 

 instances. The luminous organ of the East Indian fish Photoblepharon 

 palpebratus has a brightness in the neighbourhood of 2 mL. The lumin- 

 escence of the ctenophore Mnemiopsis has a brightness of 0-3 mL, and 

 moistened fragments of the dried light-glands of Cypridina give values of 

 2-16 mL. Some recent estimations of radiant flux are assembled in Table 

 13.4. The brightest light recorded from marine animals is that of cteno- 

 phores, > 0T9 //W/cm 2 receptor surface at a distance of 1 cm (14a, 28, 

 36a, 49c). 



The biological efficiency of the light emitted by any animal needs to be 

 related to the sensitivity of particular photoreceptors. The light may have 

 intraspecific or interspecific significance, and each animal would have to be 

 considered separately in terms of the spectral composition of the light 

 emitted and the sensitivity curve of the photoreceptors involved. Com- 

 parisons of the relative spectral composition of the light emitted by an 

 animal, and of its spectral sensitivity, have been made for Pholas and 

 Euphausia. In the case of Pholas the two curves have about the same range, 

 but their maxima do not coincide ; in Euphausia the shape and maxima of 

 the two curves are fairly similar (36a, 49 d). 



DISTRIBUTION OF LUMINESCENCE IN 

 MARINE ANIMALS 



Light-production is known to occur with some degree of certainty in ten 

 phyla and about thirty-five orders of marine animals. These are surveyed 

 in Table 13.1, but this list is not exhaustive. An extensive bibliography 



TABLE 13.1 



Some Light-Producing Marine Animals 

 Protozoa 



Mastigophora: Dinoflagellata : Noctiluca, Ceratium, Peridinium, Proro- 

 centrum, Pyrodinium, Gonyaulax, Blepharocysta, Pyrocystis, Gymno- 

 dinium 

 Rhizopoda: Radiolaria: Thalassicolla, Myxosphaera, Collosphaera, 

 Sphaerozoum, Collozoum 



Porifera Grantia 1 



Coelenterata 



Hydrozoa: Hydromedusae: Stomatoca, Rathkea, Laodicea, Phialidiunu 



Liriope, Solmissus 

 Siphonophora : Praya, Hippopodius, Diphyes, Abyiopsis, Agalma 

 Scyphomedusae : Pelagia 

 Anthozoa: Gorgonacea: Ceratoisis, Isis, Mopsea 



Pennatulacea : Pennatula, Veretillum, Cavernularia, Funiculina % 

 Umbellula, Leioptilus, Pteroeides, Renilla 



1 See Harvey (28) for an evaluation of luminescence in these genera. 



