areas; habitats in which organic matter can ac- 

 cumulate and oxypfen can become depleted, are 

 often inhabitated by large populations of a few 

 species of oligochaetes, especially Tubificidae. 

 For example, in the San Francisco Bay system 

 Brinkhurst and Simmons (19(58) found that the 

 Tubificidae formed up to 97.8 ^r of the total bot- 

 tom fauna in grossly polluted habitats, and con- 

 cluded that "changes in abundance of certain 

 species may yield good supporting evidence of 

 the nature and source of pollution materials" 

 (p. 193). 



The major types of habitats in which marine 

 or brackish water oligochaetes can be found may 

 be summarized as follows: 



1. Littoral zone. 



a. In damp sand and mud ( Enchytraeidae, 

 Tubificidae, Megascolecidae) . 



b. In and under decaying seaweed (En- 

 chytraeidae, Megascolecidae) . 



c. Under stones and rocks lying on sand 

 (Tubificidae). 



d. In or near sources of fresh water on the 

 beach (Enchytraeidae, Tubificidae). 



2. Sublittoral zone. 



a. In the sediment (Enchytraeidae, Tubi- 

 ficidae. Naididae). 



b. On sediment or plant surfaces (Naidi- 

 dae). 



Collecting Methods 



Marine Oligochaeta are collected by extracting 

 fixed or living worms from the sediment or veg- 

 etable material in which they live. In the lit- 

 toral zone the substrate may be collected simply 

 by digging or scoo])ing material into containers, 

 or by a simple coring device. Any of the various 

 automatic corers, dredges or grabs, or in very 

 shallow water a fine mesh hand net, are suitable 

 for obtaining sublittoral material. If samples 

 can be processed immediately to extract living 

 worms (especially for Enchytraeidae) , the sed- 

 iment is washed through a series of wire screens, 

 the finest having a mesh diameter of 0.5 mm or 

 less; all but the very small oligochaetes are re- 

 tained by the latter. Material to be killed and 

 fixed (before or after sorting) is treated as fol- 

 lows: animals are narcotized in 0.015% pro- 

 pylene phenoxetol, fixed in 10'"r Formalin solu- 

 tion for 48 hr, and stored in 85% ethanol. 



Examination Procedure 



The anatomy of the oligochaetes can be studied 

 by a variety of methods ; the keys have been de- 

 signed so that wherever possible taxonomic 

 charactei-s can be observed using a minimum of 

 manipulation or treatment. Characters used in 

 couplets 1 to 11 can be seen by mounting fixed 

 worms temporarily in glycerol or Amman's 

 lactophenol (400 g carbolic acid. 400 ml lactic 

 acid, 800 ml glycerol, 400 ml water) . The latter 

 clears tissue by maceration and is therefore not 

 recommended when subsequent treatment may 

 be necessary; it is, however, a useful medium 

 for mounting large collections for routine iden- 

 tification (Brinkhurst, 1963). In general, ex- 

 ternal characters and cuticular structures can be 

 examined by simple whole mounts. From coup- 

 let 12, however, internal characteristics assume 

 increasing importance and are best examined 

 using stained, whole, or dissected, animals. The 

 following procedure has proven eflFective; worms 

 are stained in acetic haematoxylin, washed, and 

 transferred to acid alcohol (5 drops of hydro- 

 chloric acid per 50 ml of 70% ethanol) until 

 they are almost completely destained (to a very 

 light red or pink color); the animals are then 

 "blued" in alkaline alcohol (5 drops of concen- 

 trated ammonium hydroxide per 50 ml of 10% 

 ethanol) and dehydrated in 100 ''r ethanol. One 

 of two procedures may then follow: (a) the 

 whole animal may be cleared in xylol and mount- 

 ed in Canada balsam or (b) the genitalia of the 

 worms may be dissected out using microscalpels 

 or fine sharpened needles, and the parts cleared 

 in xylol and mounted in Canada balsam. 



Most characters used in the key can be ob- 

 served on whole stained animals, but dissection 

 may be necessary for a critical examination of 

 the genitalia of some species. If only one or two 

 individuals are available for identification, it is 

 recommended that a stained whole worm, mount- 

 ed temporarily in xylol (xylol is highly volatile 

 and the fumes are inflammable and toxic, there- 

 fore great care should be exercised) should be 

 examined briefly to decide whether any further 

 treatment is necessary. If dissection is needed 

 the animal is returned to 100% ethanol because 

 xylol makes the tissues very brittle and dissection 

 almost impossible. 



If living material is available, small specimens 

 can be examined microscopically by mounting 



