464
JAMES E. DEACON AND W. L MINCKLEY
In Cynolebias ladigesi some eggs were hatchable at 3-7 months, and
others developed only after 8-15 months (Foersch, 1961); thus the entire
population of embryos would not be subject to catastrophe that might result from periodic or unreliable filling of their waterholes. Although the
temperature ranges tolerated by eggs and adults of these fishes appear similar to those to be expected under hot, or fluctuating, desert climates, the
tolerances to total dissolved solids indicated in the literature available to
us seems too low for survival (a maximum of about 325 mg/liter in Nothobranchius brieni; or "water salty to the taste," Myers, 1952). We have
not, however, reviewed salinity tolerances for this group and have maintained a number of kinds in aquaria at total dissolved solids of more than
1200 mg/liter. It must also be noted that some aquarists feel that addition
of a small quantity of seawater stimulates final development of eggs in
some species (Breder and Rosen, 1966). As might be expected, young
of the annual fishes develop rapidly, and sexual maturity may be attained
in fewer than 6 weeks after hatching (Turner, 1964; Bay, 1966). The
ease with which they may be maintained, and the unique life cycles, now
have attracted experimental biologists (Walford and Liu, 1965), so that
much additional information may soon be expected.
Delayed hatching of eggs of the marsh killifish (Fundulus conftuentus)
and the gulf killifish (Fundulus grandis) stranded in air on grassy swales in
Florida salt marshes was reported by Harrington and Haeger (1958) and
by Harrington (1959). They suggested that other species of that large
genus might also have such capabilities.
Species of Fundulus inhabiting the western, semiarid Plains region of
North America (Koster, 1948; Minckley and Klaassen, 1969b) are not
known to have delayed-hatching ova, although stranding in wet sands of
the streams they inhabit is a distinct possibility in periods of fluctuating
levels. Habits of the Fundulus species of California and Baja California,
to our knowledge, have yet to be described or are not known to include
delayed hatching of eggs (Hubbs, 1965).
Hatching of stranded eggs of marsh killifish is unique since they are
left exposed among plant litter rather than buried in moist soils as in the
annual fishes (Harrington, 1959). But it seems likely that some eggs of
the latter develop similarly (Sterba, 1967). As in the annuals, Fundulus
embryos hatch rapidly when flooded, usually within 15-30 minutes.
Delayed hatching is also known in another cyprinodontoid, Oryzias
melastigma, in the vicinity of Madras, India (Jones, 1944). The eggs typically hatch in 8-10 days, but if water is not changed in summer, hatching
may be delayed for up to 42 days. Addition of fresh water, such as would
occur with natural rainfall, stimulated hatching immediately. As pointed
out by Harrington, however, work by Ishida (1944a,b) on Oryzias latipes
JAMES E. DEACON AND W. L MINCKLEY
In Cynolebias ladigesi some eggs were hatchable at 3-7 months, and
others developed only after 8-15 months (Foersch, 1961); thus the entire
population of embryos would not be subject to catastrophe that might result from periodic or unreliable filling of their waterholes. Although the
temperature ranges tolerated by eggs and adults of these fishes appear similar to those to be expected under hot, or fluctuating, desert climates, the
tolerances to total dissolved solids indicated in the literature available to
us seems too low for survival (a maximum of about 325 mg/liter in Nothobranchius brieni; or "water salty to the taste," Myers, 1952). We have
not, however, reviewed salinity tolerances for this group and have maintained a number of kinds in aquaria at total dissolved solids of more than
1200 mg/liter. It must also be noted that some aquarists feel that addition
of a small quantity of seawater stimulates final development of eggs in
some species (Breder and Rosen, 1966). As might be expected, young
of the annual fishes develop rapidly, and sexual maturity may be attained
in fewer than 6 weeks after hatching (Turner, 1964; Bay, 1966). The
ease with which they may be maintained, and the unique life cycles, now
have attracted experimental biologists (Walford and Liu, 1965), so that
much additional information may soon be expected.
Delayed hatching of eggs of the marsh killifish (Fundulus conftuentus)
and the gulf killifish (Fundulus grandis) stranded in air on grassy swales in
Florida salt marshes was reported by Harrington and Haeger (1958) and
by Harrington (1959). They suggested that other species of that large
genus might also have such capabilities.
Species of Fundulus inhabiting the western, semiarid Plains region of
North America (Koster, 1948; Minckley and Klaassen, 1969b) are not
known to have delayed-hatching ova, although stranding in wet sands of
the streams they inhabit is a distinct possibility in periods of fluctuating
levels. Habits of the Fundulus species of California and Baja California,
to our knowledge, have yet to be described or are not known to include
delayed hatching of eggs (Hubbs, 1965).
Hatching of stranded eggs of marsh killifish is unique since they are
left exposed among plant litter rather than buried in moist soils as in the
annual fishes (Harrington, 1959). But it seems likely that some eggs of
the latter develop similarly (Sterba, 1967). As in the annuals, Fundulus
embryos hatch rapidly when flooded, usually within 15-30 minutes.
Delayed hatching is also known in another cyprinodontoid, Oryzias
melastigma, in the vicinity of Madras, India (Jones, 1944). The eggs typically hatch in 8-10 days, but if water is not changed in summer, hatching
may be delayed for up to 42 days. Addition of fresh water, such as would
occur with natural rainfall, stimulated hatching immediately. As pointed
out by Harrington, however, work by Ishida (1944a,b) on Oryzias latipes