La. Barker et Fwh. Beamish, Gonadogenesis in landlocked and anadromous forms of the sea lamprey, Petromyzon marinus, ENV BIOL F, 59(2), 2000, pp. 229-234
Gonad morphology and cytology were examined in landlocked and anadromous se
a lamprey, Petromyzon marinus, larvae. Larvae examined from both population
s had gonads that were easily distinguished as female or male; however, man
y had gonads that upon microscopic examination appeared atypical as compare
d to previous descriptions. Atypical status was confirmed for approximately
90% of the larvae from each population based on quantitative assessment. D
ifferences in gonad development were observed between the anadromous and la
ndlocked sea lamprey. Gonad area and oocyte diameter were greater in ovarie
s from the landlocked population. In addition, gonad area, perimeter and sh
ape were also significantly greater in testes from landlocked population. E
arlier studies on landlocked sea lampreys and non-parasitic species of lamp
reys have indicated that sex ratios fluctuate with lamprey abundance and th
at in non-parasitic lampreys, sex is labile and subject to environmental in
fluence. It appears that sex in landlocked and anadromous sea lampreys is l
abile and the atypical gonads observed are in transition from one sex to an
other.