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University of California Publications in Zoology [Vol.22 



Harrington (1920) reports experiments on the effect of low 

 salinities upon the larvae of a teredo, probably T. norvegica. He 

 shows that these larvae were able to survive for at least a short time 

 in salinities as low as 10 parts per 1000, although swimming was 



TABLE 2 

 Survival of Teredo navalis, Experimentally Exposed, in Various Salinities 



inhibited below 17.5 parts per 1000. No observations of this kind 

 have been made on the larvae of T. navalis. Since T, norvegica is 

 usually found in open sea water (i.e., water of 35 parts per 1000 

 salinity or thereabouts), however, it is probable that the larvae are 

 less adapted to low salinity than are the larvae of T. navalis, which 

 inhabits brackish waters. It may be expected that the larvae of the 

 latter form might be able to live in approximately the same salinities 

 as the adult. 



Natural Protection against Unfavorable Salinity 



Although teredos exposed by splitting away the block around the 

 pallets were soon killed when placed in salinities less than 5 parts per 

 1000 (see table 2), individuals in specimen blocks which had not been 

 exposed in this manner lived for much longer periods in the same 

 salinities. Table 3 gives the per cent of organisms surviving various 

 periods of exposure to salinities of and 2 parts per 1000. 



Table 4 gives comparative results from tables 2 and 3, showing 

 that in the same salinities, unexposed teredos lived much longer than 

 exposed individuals. The organisms therefore received some protection 

 from their burrows, through their ability to prevent the entrance of 

 water from the outside by plugging the burrow entrance with the 

 pallets when the salinity of the water fell below the danger point 

 (5 parts per 1000), and at the same time to retain a quantity of salt 

 water within their burrows. 



