| Summary: | 碩士 === 東海大學 === 生物學系 === 85 === The euryhaline and highly terrestrial fish, mudskipper
(Periophthalmus cantonesis), lives in complex variable mangrove
swamps or estuary mudflat habitata. Withinthesis habitats an
array of environmental factors such as salinity fluctuations
that occur both spatially and seasonal has various efects on the
physiological adaptation of this species. The ion change in the
environment is dramatic.Moreover P. cantonesis was completely
out of contact with tide pool from the field observations. In
order to understand the relationship between ambient ion
variations and amphibious behavior of P. cantonesis, the effect
of amphibiousbehavior on ion regulation in P. cantonesis was
investigated in this study. P. cantonesis was first acclimated
in 35 g/l SW and freemode and was subjected to two exercise
modes (free mode and aquatic mode). Sodium ion concentrationand
behavior performance of these fish were recorded. A series of
three experiments was conducted in this study. In the long term
salinity acclimation experiment(FW, 35 g/l SW, 60 g/l SW), there
was no difference in plasma sodium ion concentration between
exercise modes and among salinity treatments, and no difference
in muscle sodium ion concentration between exercise modes was
found. However, there was a difference in muscle sodium ion
concentration among salinitytreatments. In the extreme salinity
transfer experiment (FW -> 60 g/l SW), theextent of variations
in plasma and muscle sodium ion concentrations in free modegroup
was less than those in aquatic mode group (92 -116 % and 95 -191
% respectively). In free mode group, most P. cantonesis stayed
in air, while some fish died in aquatic mode 2 hours after
salinity transfer. In salinity simulationexperiment (35 g/l -> 0
g/l, 6 hr ->35 g/l, 6 hr), free mode group maintaineda constant
plasma sodium ion cincentration (95 -108 %),wheres aquatic mode
grouphad it changed with ambient salinity. Within the first 6
hrs, plasma sodium ionconcentration from the aquatic mode
individuals dropped (74 -101 %), and then returned to their
original levels (74 - 93 %) in the following 6 - 12 hrs. The
behavior performance parameters (time of out of water, times out
of water) did notchange after two salinity transfers. Salinity
preference experiment was conducted.Regardless of the acclimated
salinity, the mudskipper, in general, had a preferencefor 35 g/l
SW among the three salinities provided (FW, 35 g/l SW, 60 g/l
SW).In summary, amphibious behavior prevents the body ion
concentration of P. cantonesisfrom changing with its ambient
salinity in natural habitat. Finally, there werea lot of MR
cells in both filaments and lamella in the gill of P.
cantonesis.And the possible evolutionarysignificance of this
observation was discussed.
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