whether from local stocks (S. niloticus B, Ein Hamifrats Israel) or from
different countries in Africa (Uganda, Ghana, Kenya), all possess a unique
esterase band, electrophoretically distinct (Rm 74.3%) from that of S.
aureus. All F1 S. niloticus x S. aureus hybrids were found to possess both SE
bands (Plate 5). Thus, the SE test was found very useful in controlling
broodstocks. It is noteworthy that the same gels, after being stained for SE
can undergo an additional staining for proteins (using Coomasie blue) or
alternatively can serve for both LDH (upper part of the gel) and SE (lower
part of the gel) tests.
Plate 5. Electropherogram showing
serum esterase patterns (El, Ez).of
Sarotherodon aureus (SA), S. ndo-
ticus (SN) and their hybrids (HB).
6% polyacrylamide gel.MSP(+Plate 6. Electropherogram of Sarothero-
don aureus serum in 7% polyacrylamide
gel showing the male sex protein band
(MSP) and the overlapping of transferrins
(T) by the albumin band (A); m, male;
f, female.Male Sex-Protein (MSP)Male-specific bands were found in 7% polyacrylamide gel electrophero-
grams of S. aureus, one band (Plate 6); S. niioticus, 2 bands and S. gaiilaeus,
2 bands (Avtalion et al. 1975, 1976). The position of these bands in the
electropherograrn was found to be species-specific. This subject is now under
study in our laboratory and some preliminary results have been obtained.
This protein was purified using preparative electrophoresis and its molecular
weight as determined by sodium dodecyl sulfate (SDS) electrophoresis is
40,100 A. Anti-MSP antibody raised in rabbits gave a single precipitin
line when tested against MSP. However, this antibody was also reactive
against female serum (Avtalion et al., in prep.). This result suggests that
another serum protein might exhibit cross antigenicity with MSP, or that
MSP exists in mother form in females. At any rate, the antigenic determi-