198 PKOVASOLI [CHAP. 8 



However, this result could not be repeated with other samples of sea-water ; 

 the artificial sea-water media are inadequate for growth. U. lactuca responds 

 also to indoleacetic acid and gibberellins. 



5. Crustacea and Organic Solutes 



Recent work on two Crustacea, Tigriopus japonicus and Artemia salina grown 

 aseptically, exhumes again the hypothesis of Putter on the nutritional role of 

 dissolved organic substances for marine animals. In feeding Tigriopus with a 

 variety of aseptic algal flagellates, it was observed that Chroomonas sp. and 

 Isockrysis galbana, fed singly, cause larval mortality and adult infertility in 

 Tigriopus after supporting several normal generations: respectively, after four 

 and eight generations. The number of generations before mortality sets in 

 indicated that biologically potent micro-nutrients could be responsible. The 

 addition of a vitamin mixture or glutathione to the medium restored normal 

 growth for several additional generations (Shiraishi and Provasoli, 1959). This 

 experiment obviously does not tell us whether vitamins added as solutes to the 

 two-membered culture alga Tigriopus (a) modify the metabolism of the prey, 

 or (b) become concentrated in the algae, or (c) are ingested directly from the 

 medium by Tigriopus. It does show that vitamins in sea-waters affect, directly 

 or indirectly, growth and fertility of the herbivores. Other effects of vitamins 

 on Crustacea have been described. The addition of 200 mg/1. of pantothenic 

 acid to septic cultures of Daphnia fed on Chlamydomonas tripled the life span 

 and increased egg production tenfold (Fritsch, 1953). All the barnacles (Balanus 

 sp.) in a tank when exposed to a maximal concentration of 14 (xg/1. of ascorbic 

 acid, immediately initiated copulating activities (Collier, Ray and Wilson, 1956). 



The axenic culture of Artemia on artificial media shows that organic solutes 

 can be utilized by Crustacea (Provasoli and Shiraishi, 1959). The main nutrients 

 (blood serum, peptone, liver infusion, vitamins, nucleic acids, etc.) are added 

 as solutes. Artemia grows to adulthood in this medium if particles (starch or 

 cellulose) are present in abundance, but it dies, soon after the second meta- 

 nauplius has consumed its yolk, if the particles are omitted. The nutrient solutes 

 support growth only if enough drinking takes place ; drinking in turn depends 

 upon the feeding reaction caused by ingestion of particles ; without particles 

 they do not drink enough. The ecological significance is obvious : the soluble 

 organic matter in sea-water is utilized, but since the quantities of nutrients dis- 

 solved are very small, the nutritional dependence of Crustacea on nucleic acids, 

 proteins or amino acids eventually present in sea-water is minimal ; only 

 substances like vitamins and hormones, which act at extreme dilutions, can be 

 ecologically significant. 



6. Data from Biological Analysis of Sea-Water 



The problem of "good" and "bad" waters — the fisherman's preoccupation — 

 parallels frustrations of biologists trying to rear marine animals in the labora- 

 tory. 



The change of water-masses around Plymouth caused a change in fauna and 



