1277 



Menzel, R. W. 1967. 



Studies of the F^ and F 2 hybrids of the northern and southern quahog clams. 

 Proc. Natl. Shellf. Assn. 57: 2 (abstract). 



During the first half of five years' observation of northern and southern 

 parents and reciprocal hybrids, southern species grew fastest and northern 

 slowest. Growth of hybrids was intermediate, but closer to the southern 

 parent. During the latter half of the observation period growth rates of 

 hybrids surpassed both parents. The F-, hybrid of the cross, female 

 Mevoenavia oampeehiensis x male Mevoenavia mevoenavia, grew larger than 

 those of a reciprocal cross. All 4 possible F2 crosses have been made. 

 Although still too small for final characterization, they so far resemble 

 the southern parent in shell morphology. - D.L. 



1278 



Menzel, R. W. 1968. 



The species and the distribution of quohog clams (Mevoenavia) . ASB Bull. 

 15(2) : 46 (abstract) . 



Two species of quohog, M. mevoenavia and M. oampeehiensis, and several 

 recognized subspecies inhabit the Atlantic and Gulf of Mexico coasts of the 

 United States. The northern quohog extends northward to Canada. In the 

 Gulf it is represented by the subspecies M. m. texana. This species is con- 

 fined to inshore waters of bays, inlets, and estuaries of proper salinity. 

 The southern species occurs only offshore in the more northern part of its 

 range (up to H. J.) but occurs inshore south of Cape Canaveral and in the 

 Gulf of Mexico as well as offshore. M. m. texana is found inshore south of 

 Cape Canaveral along with typical northern and southern forms. The two 

 species hybridize readily in the laboratory and the F2S have been reared. 

 Morphology of F 2 s is very similar to M. m. texana and it is surmised that 

 the subspecies is a naturally occurring hybrid. - J.L.M. 



1279 



Menzel, R. W. 1968. 



Chromosome number in nine families of marine pelecypod mollusks. Nautilus 

 82(2) : 45-50, 53-58. 



Acetocarmine squashes of eggs and zygotes which have been fixed in acetic 

 acid-ethanol are reliable for rapid chromosome analysis. Mevoenavia 

 mevoenavia and M. oampeehiensis have 19 chromosomes (2N=38). It is suggested 

 that chromosome numbers are constant within a family, thus may be important 

 in systematic studies. - J.L.M. 



1280 



Menzel, R. W. 1968. 



Cytotaxonomy of species of clams (Mevoenavia) and oysters (Cvassostvea) . 

 Proc. Symposium on Mollusca, Pt. 1 (Mar. Biol. Assn., India): 75-84, 3 pis. 



Ranges of the quahogs Mevoenavia mevoenavia and M. oampeehiensis overlap from 

 central coast of N.J. to central east coast of Fla. For most of this distance, 

 and farther north where it has no close relative, M. mevoenavia is usually 

 confined to more saline bays and inlets. M. oampeehiensis is found in outer 

 coastal waters north of central east coast of Fla. but also in coastal bays 

 farther south and in Gulf of Mexico. A subspecies, M, m. texana, is found 

 from about Cape Kennedy south, and also in Gulf of Mexico, but this subspecies 

 apparently has not been taken south of the vicinity of Miami on the east 

 coast, or on the west coast of Fla. West and south of the west coast of Fla. 

 M. oampeehiensis and M. m. texana occur together. Northern and southern 

 quahog hybridize readily in the laboratory. Thus, co-occurrence of the two 

 species along the lower east coast of Fla. presents ample opportunity for 

 interbreeding. Laboratory-reared hybrids resemble M. m. texana, suggesting 



357 



