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Blepharisma in Introductory Biology

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Blepharisma in Introductory Biology tected from bright light and so are naturally "self- Blepharisma in stained" and much easier for a beginning student to see than colorless ciliates. They are also slower swimmers than Paramecium; they are, therefore, much easier to follow and pick up if isolation is Introductory Biology desired. The mouthparts (peristome) are more com- plex than in Paramecium, with membranelles (con- sisting of rows of interdigitated "fused" cilia forming paddles, which make a food-gathering vortex) on the left side of the oral groove, and an undulating ARTHUR C. GIESE membrane (also made of "fused" cilia to form a tongue, which helps in food engulfment) on the right ANNE MULLER SMITH side. Usually at any time five to seven metachronal Downloaded from http://online.ucpress.edu/abt/article-pdf/35/7/407/30722/4444465.pdf by guest on 26 September 2021 ALTHOUGH Blepharisma (fig. 1) is available in biology supply houses and sometimes appears in introductory courses, it is more often used as a Macronucleus curiosity, not as an example of a ciliate, in part - . tUndulatingi f because Paramecium is traditional and illustrated in membrane all elementary textbooks, in part for lack of a source of information. Now that a monograph on the genus MembranellIe Blepharisma is available (Giese et al. 1973), perhaps - cytostome a short discussion of how it might be used for teach- ing purposes, as Stolte (1926) long ago suggested, Micronucleus now has more point than before. Blepharisma, a pink, bottom-dwelling protozoan, is commonly found in freshwater ponds. It is a mem- ber of the class Ciliata, subclass Spirotricha, order Heterotricha. The ciliary rows on the spindle-shaped body are spirally arranged, and in the region of the oral groove the cilia are fused and differentiated into membranelles and an undulating membrane to form a peristome, which gathers particulate food, mostly bacteria. When ponds dry up or freeze, it forms cysts, from which active cells emerge on re- turn of favorable conditions. The classification of the ~~Food- ~~~I:t. vacuole genus is still incomplete, because many species were sketchily described from a few field specimens; but a total of 21 species have been differentiated into four main groups on the basis of macronuclear shape -that is, whether it is dumbbell-shaped, elongate, Contractile vacuole beaded or compact (see below). Cytopyge General Characteristics Fig. 1. Blepharisma japonicum. Note the elongate filiform Blepharisma is easy to grow in an infusion of macronucleus. The micronuclei are the minute bodies clus- powdered cereal greens. Rich cultures can be ob- tered along the length of the macronucleus. An undulating tained in test tubes three membrane protrudes from the right side of the mouth region days after inoculation. At (peristome), and a band of membranelles lines the left side. this time the blepharismas (to use the generic name The oral groove terminates in a cone-shaped gullet, at the as popular name) are often aggregated at the top of bottom of which is the mouth, where the food vacuoles are the tube and can be readily decanted into a dispenser. formed. A contractile vacuole is present at the very posterior The species of Blepharisma-B. americanum, com- end of the cell. Note that the entire body is covered with cilia and that the cilia occur in rows forming lines on the mon in this country, and B. japonicum, common in body. Between the rows of cilia are rows of pigment granules India, Japan and Africa-are pink or red when pro- (not illustrated). 407 beats (like the waves caused by wind on a grain Arthur C. Giese is professor emeritus of field) may be seen on the membranelles. The con- biology, Department of Biological Sciences, tractile vacuole is terminal and large but contracts Stanford University, Stanford, Calif. 94305. more slowly than in Paramecium-about ev-.ry 90 A 1928 graduate of the University of Chi-. seconds at room temperature. Blepharismas will eat cago, he received his Ph.D. in 1933 from not only Stanford, where he taught from 1929 until staple food bacteria but also small proto- 1970, when he retired (although he is con- zoans, becoming enlarged as they do. When diverse tinuing his research there). Giese has pub- in size after starvation, blepharismas may eat each lished some 200 articles, chiefly on photo- other. (Cannibals appear routinely in our cultures physiology and on the reproductive cycles of marine in- after three weeks.) Cannibalism and encystment (a vertebrates; and his book Cell Physiology (Saunders) is now in its fourth edition. Since 1964 he has edited the annual reaction of some stocks to worsening environment) review Photophysiology; and he is coeditor, with John might make interesting student research topics. Pearse, of the seven-volume treatise Reproduction in Marine Blepharisma varies in size, some species being less Invertebrates, forthcoming from Academic Press. than 100 ,um in length and other species reaching a A biographic footnote (delayed) about coauthor Anne Muller Smith length of almost 0.33 mm. Cannibal blepharismas are will appear with a forthcoming article. sometimes more than twice as long and wide as bacteria-fed individuals of the same species. plasm. Cell divison (fig. 2) may be observed in The shape of Blepharisma is variable, depending actively growing cultures of Blepharisma, although Downloaded from http://online.ucpress.edu/abt/article-pdf/35/7/407/30722/4444465.pdf by guest on 26 September 2021 on nutritive conditions. When well-nourished, they the fraction in division at any one time is small. become pyriform or spindle-shaped, expanded pos- teriorly; when undernourished, they become elon- Culture gate and cylindric. Generally, the anterior half of the body is flattened laterally, and the posterior half Materials for the culture of Blepharisma are test is expanded and almost circular in cross-section. tubes (2 cm by 15 cm are good) with steel or plastic Like other ciliates, Blepharisma has two kinds of caps or cotton plugs; O.1-M NaH2PO4 and 0.1-M nuclei: macronuclei and micronuclei. The macro- Na2HPO4; powdered cereal greens or lettuce (Chlo- nuclei serve housekeeping functions; the micronuclei rovim, a mixture of powdered organic grasses with transfer genetic information. As in other ciliates, the additives, or alfalfa tablets [about 0.5 g each] are macronucleus arises anew during conjugation (sex- both suitable, and can be bought at health food ual reproduction) from the zygotic nucleus. Macro- stores); 1-L graduate; serologic pipettes (gradu- nuclei are large and can readily be observed in live ated), 1 ml and 5 ml; 2-L beaker; balance; and non- animals even under low power. toxic water. Water is always a problem in protozoan The macronucleus of Blepharisma varies in shape, culture. Distilled water may be toxic, as may tap depending upon the species. Four types are recog- water, even after boiling to remove chlorine. Spring nizable in the vegetative cell: (i) dumbbell-shaped water or unpolluted water from a pond or stream (halteriform), with two terminal nodes connected may be good but should be tested, and may vary by a thick strand; (ii) elongate-cylindric (filiform), with the season. We have tested a variety of com- sometimes with more or less enlarged ends; (iii) mercially available water types and found Feather beaded (moniliform), consisting of a string of macro- River Canyon Purified Water (deionized), Feather nuclear nodes connected by slender strands; and River Spring Water Co., Sacramento, Calif. 95814, (iv) ovoid-compact, a single mass. A filiform macro- and Sierra Spring Water Company, Inc., 1825 "R" nucleus is characteristic of B. japonicum; a beaded Street, Sacramento, Calif., both very good. Distilled nucleus is characteristic of B. americanum, the water from a local high school (testing should be species most likely to be available in supply houses. done on any local distilled or deionized water sup- Micronuclei are numerous and close to the macro- ply), and deionized water from a local high school, nucleus in vegetative cells. Because of their small were both good, though cultures did not grow as size, they can be seen only in stained specimens, best well as in the commercial samples listed. However, under oil immersion. In many species they are Black Mountain Spring Water, San Carlos, Calif. vesicular: the dense internal portion is surrounded 94070, proved variable but still satisfactory, inas- by a clearly defined halo. During cell division and much as the culture medium made up with it sup- conjugation the micronuclei move from the proxi- ported growth. mity of the macronucleus to the surrounding cyto- To the beaker add 0.5 g of cereal green (or lettuce) Fig. 2 (opposite). Division of a Blepharisma americanum with a beaded macronucleus. This species is smaller than the one illus- trated in fig. 1. A, vegetative stage; B, early division stage, showing at a an early anlage (forerunner) of the new peristome; C, later stage, showing clearly the developed peristome anlagen (mza, uma, pfa); D, still later division stage in peristome anlage, which is well formed, and the anterior peristome is also reorganizing and the macronucleus (ma) condensed; E, stage showing the beginning of the division line (tl) (note elongated but nodeless macronucleus); F, final (dumbbell) stage of division (note that the macronucleus is again noded). The following abbreviations have been used: a, anlage, or forerunner, of each structure; um, undulating membrane (uma is the anlage of the um); mz, membranellar zone or band (mza is the arlage of the mz); pf, peristomal field (pfa is the anlage of the pf); cp, cytopyge (cpa is the anlage of the cp); ma, macronucleus; ps, pigment stripe; cs, ciliary stripe; cp, contractile vacuole; ta, division anlage; ra, reorganization anlage of the peristome of the anterior in- dividual; tl, division line; tr, end of the membranellar band; VTp, peristome of the anterior individual.
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