Fucus. Ulva. etc. Most of these forms are also adapted for 

 a free-swimming existence and are either cyclopoid in 

 shape (Tisbc. Diarthrodes). flattened, shield-shaped 

 {Scutellidium. Porcellidium) or laterally compressed and 

 amphipodlike (Parategastes). All of these forms probably 

 feed on the associated microbiota of the plants and 

 usually cling very closely to the fronds or leaves with 

 their strongly prehensile first legs. 



The truly free-swimming (euplanktonic) harpacticoids 

 (Miracia. Euterpina, Microsetella, etc.) comprise a very 

 small proportion of the order. They are among the largest 

 harpacticoids known and have elongate setae or unique 

 body shapes, as do many pelagic organisms, to stay 

 afloat. 



I have not exhausted the habitats nor the body forms 

 of the harpacticoids, but suggest the interested reader 

 see Noodt (1971) for review. 



Harpacticoids are the most sensitive of the 

 meiobenthic organisms to changes in oxygen tension and 

 are often the first to disappear if conditions become 

 anaerobic. Harpacticoid copepods feed primarily on 

 diatoms, bacteria, and small protozoans. Although there 

 are many literature reports of harpacticoids feeding on 

 "detritus," it is now thought they are actually feeding on 

 the microbiota on the detritus particles. 



Population densities of harpacticoids are highest in 

 shallow areas and the highest densities so far reported 

 are from New Jersey salt marshes. The high density areas 

 are usually represented by a limited number of species 

 (10-20). Some harpacticoid assemblages, however, have 

 been reported with 60-70 species. Diversity of copepod 

 fauna increases into the deep sea, whereas density in the 

 deep sea is two or three orders of magnitude less per unit 

 area than in shallow water. 



Collecting 



Sampling technique varies depending on the habitat to 

 be examined and entails extracting the animals from the 

 sediment or plant materials in which they live. Intertidal 

 meiobenthic forms can be collected by either coring or 

 digging into the substrate, narcotizing the samples (with 

 isotonic MgCL:73.2 g/liter) then sieving the sample 

 through nets or wire screens less than 500 /Lim so that the 

 animals will be retained. Whereas samples for most 

 meiobenthic taxa must be narcotized, this is not ab- 

 solutely essential for removal of the harpacticoids since 

 agitation (shaking) of the sand will generally free most of 

 the animals. Subtidally most harpacticoids occur in the 

 upper 2-.'} cm of the sediment and can be collected with 

 grabs and corers, or by scooping up the top sediment 

 layers. 



Phytal animals are most easily collected by agitating 

 the plant in a bucket of water (with or without narcotiza- 

 tion) and then screening the residual water through fine 

 meshes or by dragging a plankton net through the plant 

 stands. The euplanktonic forms are collected, as are all 

 zooplankters, by towing nets. 



Samples can be stored in 4'; buffered Formalin for 

 long periods of time with little or no decomposition of the 



animals. To facilitate sorting of preserved meiobenthic 

 samples, add a few grains of the vital stain "Rose 

 Bengal" to the sediment-seawater before adding 4'i For- 

 malin to the mixture. The animals will stain red, while 

 the sediment particles remained unstained, and thus the 

 animals can be easily spotted. For permanent storage the 

 preserved animals should be transferred to TO'r ethyl 

 alcohol. 



Examination Procedure 



In order to use the following key it will generally be 

 necessary to dissect the animal and mount it on a slide. 

 However, if many individuals are available, all the body 

 parts necessary for identification will probably be visible 

 if 6-10 individuals are mounted randomly on the slide 

 and then observed. 



After sorting a sample to collect all the harpacticoids 

 the following procedure can be used, with a dissecting 

 microscope: 



1. Sort into groups of specimens all the "look-alikes" 

 isolating each "look-alike" group into em- 

 bryological staining dishes, or watch glasses, etc. 



2. With the first group, put several (3 or 4) animals 

 into a depression slide with glycerol or Hover's 

 mounting media (dissolve 8 g gum arable in 10 ml 

 distilled water; add 75 g chloral hydrate, 5 ml 

 glycerine, and 3 ml glacial acetic acid; strain 

 through clear muslin or glass wool), or Reyne's 

 mounting media (dissolve 10 g chloral hydrate in 10 

 ml distilled water; add 2.5 ml glycerine and mix: 

 add 6 g gum arable and stir very cautiously — avoid 

 bubbles; let sit 1 wk — no filtering necessary) or un- 

 diluted lactic acid (see Humes and Gooding 1964, 

 for this technique!. Cover one-half to three-fourths 

 of the liquid filled depression with a 22 X 22 mm 

 coverlsip, allowing the other one-half to one-fourth 

 to remain uncovered. Put slide on compound scope 

 (phase contrast microscopy is extremely helpful) 

 and by pushing the coverslip you can roll the 

 animals over and see many of the body parts 

 necessary without damaging them. 



3. After observing the animals in the depression slide, 

 remove the coverslip being careful not to harm 

 them. If you deem it necessary to dissect an animal 

 you may do so in the depression slide; if not, return 

 it to the container. 



4. Dissection: Using tungsten needles (0.005-mm 

 diameter and sharpened by dipping into molten 

 sodium nitrite) expoxied into 0.5-mm diameter 

 capillary tubing, cut and separate each somite and 

 its associated appendages from anterior to posterior 

 one at a time. After each somite is removed mount 

 it on a slide, then dissect and mount the next 

 somite, etc. up to the 5th pair of legs. Retain the 

 urosome in toto and mount this. 



5. Mounting: Kach copepodologist probably has his 

 own technique, but I place all the dissected body 

 parts from one animal on the same slide, with each 



