KITTREDGE ET AL.: CHEMICAL SIGNALS IN THE SEA 



"white noise," producing an "uncoded" array of 

 spikes in the chemosensory neurons. 



The best description of behavior suggesting 

 a "cryptic odor" in the marine environment is 

 that given by MacGinitie and MacGinitie (1968). 

 The ink of an octopus is considered a "smoke 

 screen"; however, it can also affect the olfactory 

 sense. The MacGinities observed that after a 

 moray eel swam through the ink cloud of an 

 octopus it could no longer "recognize" an 

 octopus. The moray eel apparently requires 

 both visual and olfactory input for this recogni- 

 tion. They state, "We were surprised to find 

 that the real effect of the ink of an octopus 

 is to paralyze the olfactory sense of its enemies." 

 The melanin of the ink is a polymer of oxidized 

 L-DOPA. The polymerization proceeds through 

 three orthoquinones, dopaquinone (6, Figure 

 1), dopachrome (7), and indole-5, 6-quinone (8). 

 In the biosynthesis of melanin, this oxidation is 

 catalyzed by polypheny 1 oxidases; however, 

 heavy metal ions can also catalyze the oxidation, 

 and it can be readily demonstrated that the 

 trace of heavy metal ions in seawater will rapidly 

 convert L-DOPA to melanin. The octopus ink 

 loses its potency with time, a factor that would 

 indicate that the biological activity of the ink is 

 due to the presence of the unstable monomer 

 orthoquinones in the fresh ink (Kittredge, 

 Takahashi, and Lindsey, unpublished data). 



The observation of Gilbert et al. (1967) that 

 juglone (5-hydroxy-l,4-naphthoquinone) (1. 

 Figure 1) is a deterrent to feeding by the bark 

 beetle, Scolytus multistriatus, suggested a 

 similar function for the polyhydroxynaphtho- 

 quinones occurring in the echinoderms. These 

 spinochromes are all derivatives of juglone (1) 

 or naphthazarin (2). They occur as soluble salts 

 in the tissues and may be present in considerable 

 amounts in the larvae. They also occur as 

 insoluble calcium salts in the spines and tests 

 (Thompson, 1971). The echinoids have 

 received the closest attention, but P. J. Scheuer 

 and his group have demonstrated the presence 

 of these compounds in the other four classes 

 of this phylum — the holothurians, asteroids, 

 ophiuroids, and crinoids (Singh, Moore, and 

 Scheuer, 1967). They also demonstrated the 

 presence of a substituted 2,5-benzoquinone 

 (3) in the genus Echinothnx (Moore, Singh, and 

 Scheuer, 1966). The crinoids are interesting in 

 that they contain primarily a series of poly- 

 hydroxyanthroquinones (e.g., rhodocomatulin, 



OH 

 I II 







I II 



OH 

 (1) 



I II 

 OH 



(2) 



HO- 



O 



'Sr^cH; 



.CH 







(3) 



HO\.^,^^0^/Ar 



H •^^^'-^^-•^^^^O H 

 nu II II UM 



COfCHglgCHj 

 (4) 



00' 



I II 

 OH 



(5) 



0^, 

 



.CH2-CH-COOH 



NHo 



(6) 



0< 

 0' 



to- 



H 

 (7) 



COOH 





(8) 



Figure 1. — Structures of compounds typical of those 

 which may function as "cryptic odors." (1) juglone. (2) 

 naphthazarin, (3) 2, 5-dihydroxy-3- ethylbenzoquinone, 

 (4) rhodocomatulin, (5) fiavone, (6) dopaquinone, (7) 

 dopachrome. (8) indole-5, 6-quinone. 



4) (Sutherland and Wells, 1967; Powell, Suther- 

 land, and Wells, 1967; Powell and Sutherland, 

 1967; Matsuno et al.. 1972; Erdman and 

 Thomson, 1972). 



Utilizing the "feeding response" of the lined 

 shore crab, Pachygmpsus crassipes, which 

 consists of a rapid lateral movement of the 

 mouthparts when presented with a feeding 

 stimulus, we have bioassayed the "feeding 

 inhibitor" activity of juglone and eight repre- 

 sentative spinochromes. The "feeding stimulus" 

 was a 20-iul aliquot of a 3-mM solution of 

 taurine in seawater administered from a repeat- 

 ing syringe close to one of the antennules of the 

 crab. Initially the crabs were immersed in a 

 l-/uM solution of the naphthoquinone and tested 

 for a feeding response. Five experimental and 



