65 



zard is given, including behavior in captivity where it laid 2 eggs. 

 Captive courtship and mating behavior between _C. inornatus males and 

 C. exsanguis and _C. tesselatus females is described in detail. This 

 type of behavior is probably due to (or at least facilitated by) crowd- 

 ing in captivity, but since the population from which the natural hy- 

 brid came from was dense, perhaps overcrowding (high density) is re- 

 quired for interspecific hybridizations to occur. The cytological ev- 

 ents leading to tetraploidy in Cnemidophorus are discussed, and a very 

 interesting summary of genetic mechanisms of parthenogenesis and the 

 implications thereof is given. It is suggested here that triploid _C. 

 tesselatus arose from a single hybridization event between diploid tes- 

 selatus and _C. sexlineatus. The absence of tetraploid species of Cnem- 

 idophorus is attributed to the rarity of achieving parthenogenetic com- 

 petence in interspecific hybrids. Interspecific hybrids are not rare 

 (witness the _C. perplexus situation plus events like the aberrant in- 

 dividual reported on here) so the achievement of parthenogenetic compe- 

 tence is the critical event. 



17*. — . and P. S. Gerald. 1968. Lactate dehydrogenase isozymes in 

 parthenogenetic teiid lizards (Cnemidophorus ). SCIENCE 160: lOO'f-1005. 



Lactate dehydrogenase (LDH) isozymes consist of two distinct sub- 

 units, A <5c B, associated in tetramers; there are thus 5 possible sub- 

 unit combinations. Subunit synthesis is controlled by structural genes 

 at two distinct loci, a & b. The sexual species Cnemidophorus tigris , 

 _C. inornatus and _C. gularis , and the parthenogenetic species _C. exsan - 

 guis all possess the same A subunit, but _C. tigris possesses a B vari- 

 ant, B'. Electrophoresis of C. neomexicanus and _C. tesselatus E reveal 

 more than 5 possible LDH subunit combinations (= heterozygosity), thus 

 3 different subunits (A, B, and B') must be present. _C. tigris is 

 therefore implicated as one parent for both of the preceding hybrid 

 parthenogenetic species. Electrophoretic patterns reported on here are 

 very similar to those of other vertebrate hybrids, both natural and ar- 

 tificial. 



175. — . and — . 1969. Gene dosage at the lactate dehydrogenase lo- 

 cus in triploid and diploid teiid lizards. SCIENCE 16^*: 557-558. 



The densities of electrophoretic bands of heterozygous triploid 

 Cnemidophorus tesselatus are unequal, showing higher proportions of B 

 over B' subunits of LDH. These proportions are consistent with the ex- 

 planation that each allele is expressed equally, therefore the diploid 

 tesselatus genotype is b'/b and the triploid genotype b'/b/b. The b' 

 allele is contributed by _C. tigris and the b allele by one or more spe- 

 cies of the sexlineatus group of Cnemidophorus . 



