sediment -water interface, indicating that A^. incisa may perforate sediment at 

 all levels down to its size -limited depth. 



Temporal Aspects of Burrowing 



Rate of new burrow formation is temperature-dependent. Figure 20-7 

 illustrates both the numbers of new burrows formed per week and its 

 reciprocal, duration of burrow occupancy, at five temperatures spanning the 

 annual thermal range. At O^C, burrow turnover averages one new burrow built 

 every two weeks. At 6^^, an average of 1.5 burrows are built per week; 3-3.5 at 

 12 ; 3.5-4 at 18° and 6.5-7 burrows were observed per week at 24°C. 



BURROW FORMATION RATE (PER WEEK) 



m 



■D 



m 



> 



-\ 

 c 

 :d 

 m 



o 

 O 



— IV) 



OJ 



Ui 



O) 



-^ 



00 



(D 



O 



cn 



IV) 



00 



rv) 



-J— 1 Lll 1 J 1 l_ 



o o o> -t^ 



ro 



DURATION OF BURROW OCCUPANCY (DAYS) 



Figure 20-7. Relationship between Nephtys incisa burrow 

 formation rate and burrow occupancy to temperature. 



NOTE: Mean and range observed indicated by -0- (range limits refer only to 

 burrowing rate axis). N = 6 for each temperature level. 



312 



