Oviposition 



In an effort to determine the influence of salinity upon the rate of op- 

 position in Uro salpinx, Federighi (1931c) distributed 13 cages enclosing drills 

 and oysters over a wide range of salinities hi Hampton Roads, Virginia . The 

 cages were lost in 5 to 7 weeks, but in this interval Federighi obtained the follow- 

 ing average number of eggs per case: 8.9, 8 4, 9.3, and $.9 in the following 

 average salini ties, respectively: 12, 15, 17, and20o/oo. He concludes that the 

 oyster drill reproduces wherever it survives, and that a salinity of 17 o/oo seems 

 to be the optimum salinity for the maximum production of eggs -per case in these 

 waters . The differences obtained by Federighi in oviposition, however, are too 

 slight to be statistically significant; and on the basis of Stauber's (1943) informa- 

 tion on the relationship between drill size, egg case size, and number of ova per 

 case,, Federighi* s correlation is ofTloubtful significance. 



Haskin's (1935) field data fail to confirm Federighi and clearly demon- 

 strate that in Barnegat Bay, New Jersey, drills can survive where they cannot 

 reproduce andlhat in estuafine areas of fluctuating salinities they may be able 

 to oviposit but the ova so deposited may not survive. Stauber (1943) from data 

 accumulated in extensive drill trapping in Delaware Bay, concurs with Haskin, and 

 adds that there is a strong suggestion that salinities close to 15 o/oo are necessary 

 for drill oviposition . 



Egg case stages 



According to Haskin (1935) post hatched stages of Uro salpinx survive in 

 low salinities in which their eggs fail to develop and in which no oviposition occurs. 

 He noticed that uncleaved eggs placed in a salinity of 7 . 9 o/oo failed to undergo 

 cleavage and started to decompose in 19 hours . In general eggs cleaved normally 

 in salinities above 14 o/oo even when removed from the egg capsule . Development 

 of egg case stages varying in age from one to five days was also abruptly termin- 

 ated when the capsules were subjected to a salinity of 7.9 o/oo, and within 18 

 hours all were dead. Haskin concludes that a short period of low salinity, even for 

 the duration of one tide, will probably kill egg case stages up to one week of age . 

 The effect of low salinities on the later protoconch stages was not determined. 

 Sizer (1936) observed that protoconchs continued their development within the 

 egg case over the salinity range of 10-30 o/oo, and when removed from their cases 

 survived in these solutions for a number of days. 



Stauber (1943) extended these studies to include all prehatching stages of 

 the drill. Egg cases containing various stages of development were segregated in 

 four containers in which salinities of 5, 10, 15, and over 15 o/oo respectively were 

 maintained for 42 days at prevaibng summer temperatures. No stages survived 



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