All nine shrimp surviving 43 days exhibited 

 fast branchial coloring. 



Two lots of approximately 35 small 

 shrimp were given three feedings stained with 

 a 1 -percent solution prepared with distilled 

 water. All chowed bright-red branchiae after 

 the final stained feeding, and this color re- 

 mained fast in all individuals surviving the 11- 

 day test. 



MORTALITY 



The available mortality data for each 

 test with these more successful stains are 

 presented in table 3. Mortality data on simul- 

 taneous staining and control experiments are 

 summarized in table 4. Mortality A refers to 

 deaths known to have been accompanied by 

 ecdysis and cannibalism. Mortality B indicates 

 the percent mortality Known to have occurred 

 without concurrent ecdysis and may be ascribed 

 to experimental procedure, cannibalism, or 

 other unlcnown causes. Shrimp listed as "un- 

 determined" were completely cannibalized, 

 and cause of death could not be ascertained. 

 It was observed that isolated stained and un- 

 stained shrimp, when held for extended periods, 

 could succumb 2 or 3 days after ecdysis . In 

 such cases the exoskeleton did not attain normal 

 firmness, indicating a deficiency of some un- 

 known corfiponent in the environment . In group 

 experiments such mortality could not be recog- 

 nized and, owing to the absence of casts, these 

 deaths would be included under Mortality B. 



DISCUSSION 



In 11 experiments with 8 stains, the 

 marking of shrimp by immersion was consist- 

 ently unsuccessful. Though temporary colora- 

 tion was attained in several cases, fading was 

 always rapid and was usually complete within 

 5 days. One instance of more permanent mark- 

 ing, using Trypan Red, could not be duplicated 

 in subsequent trials . Immersion marking with 

 Nile Blue Sulfate or Trypan Blue, suggested by 

 Racek (1955), was unsatisfactory. Racek gives 

 no data on the source of his stains, and differ- 

 ences in stain characteristics may account for 

 contrasting results. The possibility of differen- 

 tial stain acceptance between the Australian and 

 American shrimp cannot be wholly discounted, 

 however . 



Injection with Fast Green FCF, Niagara 

 Sky Blue 6B, Trypan Blue, or Trypan Red has 

 resulted in fast abnormal colorations, and these 

 show potential value as shrimp -marking agents. 

 Injection is a rapid and efficient method of 

 marking medium and large shrimp, and can be 

 used under most field conditions. Although 

 tuberculin syringes were used in laboratory 

 studies, automatic constant -volume syringes 

 are indicated for most efficient field operation. 



Fast Green FCF was originally suggested 

 as a shrimp -marking agent by Menzel (1955), 

 but he published no data on the source or con- 

 centration of the stain used. Menzel later 

 reported (personal correspondence) that the 

 stain was a National Aniline product in a 1 -per- 

 cent solution, but unfortunately no information 

 was available on the solvent. A sample of this 

 solution was kindly supplied by Dr. Menzel for 

 inclusion in the present experiments. 



Injection with Fast Green FCF results 

 in an immediate bright-green to blue-green 

 general coloration . Abdominal fading is rapid, 

 and this, together with simultaneous green 

 branchial concentration, is usually complete 

 within 72 hours. Menzel reported branchial con- 

 centration following ecdysis, but in the present 

 experiments this occurred either with or without 

 shedding. 



One -percent solutions proved most satis- 

 factory, as less concentrated solutions did not 

 provide a fast stain, and no advantage was found 

 in using more concentrated solutions. Experi- 

 mental injection volumes ranged from 0.015 cc . 

 to 0.2 cc. per shrimp, but 0.03 cc. was found 

 adequate for medium shrimp. 



Mortality within the 24 -hour period fol- 

 lowing injection average 4 percent with this stain, 

 and no difference was observed in initial mortal- 

 ity between injections of the National Aniline and 

 Harleco products. It was difficult to arrive at 

 the experim ental mortality in view of the preva- 

 lence of cannibalism and deaths from unknown 

 causes. Reference to table 4 will show the max- 

 imum difference in total mortality of control and 

 stained animals to be 15 percent over 84 days. 



Comparison 6f staining characteristics 

 shows the National Aniline product to be superior 

 to that of Harleco for present purposes . Although 



17 



