574 THE BIOLOGY OF MARINE ANIMALS 



rather lengthy latent period. The numerous photophores of the teleost 

 Porichthys lighten under electrical stimulation (Fig. 13.8(6)). With bursts 

 of induction shocks luminescence appears after a latency of 8-10 sec, 

 increases to a maximum in about 15 sec, and then slowly fades. Light can 

 also be evoked in this species and in the bathypelagic Echiostoma cteno- 

 barba by the injection of adrenaline. Anatomical studies of Lampanyctus, 

 Cyclothone and Argyropelecus have shown that the photophores are 

 innervated by branches of the trigeminal, facial and spinal nerves. The 

 action of adrenaline suggests that adrenergic fibres are responsible for 

 mediating the luminescent response, and these presumably are sympathetic 

 fibres running to the photophores in the nerves just mentioned. Suprarenal 

 tissue is also present in the anterior kidney region of teleosts, and the 

 secretion of adrenaline into the blood stream may also be concerned with 

 the luminescent response. 



Indirect Nervous Control 



Most of our information about indirect control of luminescence in 

 marine animals is based on inferences from morphology, and few functional 

 data are available. Several types of control can be recognized, but there is 

 much specific variation in the way in which it is achieved. Examples of 

 neuromuscular regulation of secretion may be considered first. One of the 

 best-known is Cypridina, in which contraction of muscles squeezes granules 

 of luciferin and luciferase out of separate glandular cells. On meeting in 

 the sea water the luciferase catalyses the oxidation of luciferin, and lumines- 

 cence results. In the teleost Malacocephalus there are ventral light-glands 

 which are provided with smooth muscle and nerves (Fig. 13.22). The 

 discharge of luminous slime in this fish results, in all probability, from the 

 action of muscles which squeeze the gland (32, 33). Probably belonging to 

 the same category are certain myopsid squid such as Heteroteuthis, 

 which discharge a luminous cloud in a manner analogous to the discharge 

 of ink in other forms. It is possible that muscular control may also be 

 involved in certain Crustacea such as Gnathophausia, which pour forth a 

 luminous material. 



Of a somewhat different nature are those animals in which muscular 

 action regulates the emission of light from photophores. In the bathy- 

 pelagic cephalopod Vampyroteuthis infernalis there is near the apex of the 

 body a pair of photophores which can be occluded by folds of skin. The 

 teleosts Anomalops and Photoblepharon, which utilize symbiotic bacteria, 

 have achieved regulation of luminescence in two different ways. In 

 Photoblepharon a screen of black tissue is present, which can be raised over 

 the light-organ like a lower eye-lid. In Anamolops the light-organ itself can 

 rotate, thus exposing or concealing the light-source, and the fish flashes 

 its lights on and off as it swims through the water. Pelagic stomiatoid 

 teleosts are also able to regulate the emission of light by rotating the 

 post-orbital light-organ (2, 26). 



Another type of muscular regulation is presented by those luminescent 



