POLYCHAETE WORMS, PART 1 



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pigmented prostomiiim, greenish, greenish yellow or pale red pos- 

 teriorly, dotted with white, or dark over entire dorsum; color, pre- 

 served: darkly pigmented anteriorly, including prostomium and bases 

 of parapodia. 



Both male and female heteronereids show marked changes from the 

 atokous form. They are considerably shorter due to the antero- 

 posterior flattening of the segments. The eyes are enlarged and they 

 are attracted to light. Body is divided into 3 regions: anterior region 

 (13-18 setigers) with setae similar to the atokous form; middle or na- 

 tatory region (29-40 setigers) with flattened parapodia with swimming 

 setae, with thin flattened extra lamellae on the parapodia! lobes and 

 bases of the dorsal and ventral cirri; a posterior region or "tail" (25-56 

 setigers) with parapodia similar to the atokous form (this region thus 

 shows the characteristic straplike upper uotopodial ligulos, although 

 this region may be broken off). The anal segment or pygidium is 

 crenulate, shorter than in the asexual form. Tal)le 2 below shows 

 how the sexually dimorphic males and females differ. 



Table 2. — Differences between sexually dimorphic males and females 

 in N. (Neanthes) succinea 



