vertical and horizontal burrowing, it was concluded that no pattern of burrow 
gallery formation existed but that burrowing was a meandering extension of 
past burrows. 
Depth of sediment penetration likewise correlates with worm size (Figure 
20-6). The lower vertical limit of burrows for first-year worms (up to 0.1 g wet 
weight) is 2-3 cm beneath the sediment-water interface. Second-year worms 
(up to 0.4 g) limit burrowing to 7-8 cm. Three-year old worms (up to 1 g) may 
burrow as deep as 14-15 cm. N. incisa of all sizes may be found near the 
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WORM WEIGHT (g WET WT) 
Figure 20-6. Nephtys incisa Mean Depth of Burrowing in 
Relation to Worm Size. 
311 
