SUSCEPTIBILITY OF BROOK CHARR, SALVELINUS-FONTINALIS TO THE PATHOGENIC HEMOFLAGELLATE, CRYPTOBIA-SALMOSITICA, AND THE INHERITANCE OF INNATERESISTANCE BY PROGENIES OF RESISTANT FISH
Gm. Forward et al., SUSCEPTIBILITY OF BROOK CHARR, SALVELINUS-FONTINALIS TO THE PATHOGENIC HEMOFLAGELLATE, CRYPTOBIA-SALMOSITICA, AND THE INHERITANCE OF INNATERESISTANCE BY PROGENIES OF RESISTANT FISH, Parasitology, 111, 1995, pp. 337-345
Eighty-seven of 175 laboratory raised F1 generation brook charr (Salve
linus fontinalis) were resistant to experimental Cryptobia salmositica
infection. Susceptibility to the pathogen was not related to age nor
to route of infection. Plasma of resistant charr lysed the parasite un
der in vitro conditions while those of susceptible fish did not. Sperm
from 4 susceptible and 4 resistant male charr, from 8 F1 families, we
re used to fertilize eggs from 2 hatchery raised susceptible charr. Su
sceptibility of progenies (F2 families) was determined 4 weeks after i
noculation of the parasite. All progenies (seven F2 families) of 4 sus
ceptible males were susceptible to experimental infection and their pl
asma did not lyse the parasite. It was presumed that these susceptible
progenies were homozygous recessive (rr), and that the resistant alle
le was dominant. All progenies (two F2 families) of 1 resistant male (
presumed RR) and 2 susceptible females were all resistant to infection
and their plasma lysed the parasite. The ratio of resistant to suscep
tible charr in 6 other F2 families from the other 3 resistant males (p
resumed Rr) and two susceptible females was about 1:1. The results sug
gest a single Mendelian locus which determines innate resistance to C.
salmositica infection in brook charr and that it is possible to breed
Cryptobia-resistant fish.