PAUh-A AND FLORA O F MANGROVE SWAMPS
199
This would suggest that no accessory respiratory surfaces are required.
When feeding the fish makes a sudden lunge to seize its prey and simultaneously expels the air and water, forcefully and audibly, through the opercular openings, wet patches or bubbles appearing on the surface of the partly
dried mud. The sound can be heard at a distance of 15-20 feet (46-6 m).
The fish then crawls promptly t o a nearby puddle or to the tide channel,
replenishes the water in its branchial cavity by means of a few seconds of
rapid pumping with the mouth under water and once again gulps air at the
surface, distending the opercular region. . . . Expulsion of air and water also
occurrcd in captive animals in the absence of feeding.
Stebbins and Kalk go on t o describe feeding :
Here, then, we see a mechanism of exchange of water, both while
feeding and at other times, once again suggesting that there is no need
for accessory surfaces. The accounts given by Harms, by Schottle and
by Willems and Bolaert all indicate that they were not entirely convinced that they had found such accessory respiratory surfaces but
that they were impelled to find them following preconceived ideas. My
own observations at many localities favour the ideas of Stebbins and
Kalk, and suggest that they apply equally t o P. chrysospdos, Periophthalmodon schlosseri and Boleophthalmus boddaerti.
Khoo (1966) has studied the food and feeding of the four mudskippers common a t Singapore. He finds that Boleophthalmus boddaerti
is a herbivore. I n feeding it emerges from the water, then makes rapid
side-to-side movements of the head, skimming off a thin layer of
mud and algae from the surface. This mouthful of material is then
manoeuvred round the mouth, as can be seen by the vibrating movements of the lips and opercular region. Muddy water is then squirted
from the mouth and from the gill openings. The fish then repairs to
the water’s edge, dips its mouth into the water and may be seen to
drink, so replenishing the water in the branchial cavity. The intestine
oE this species is very long when compared to that of non-herbivorous
mud-skippers.
Scartelaos viridis is more omnivorous ; its feeding technique is
different. It rasps off the top layer of the mud and collects the mud
into a ball under the lower jaw and this mass of food and mud is then
taken into the mouth. After some sorting process in the mouth the
mud is squirted out. The stomach contents show both plant and
animal material. Khoo demonstrated that lifting the surface film of
mud with a prepared coverslip showed only algae, whereas scraping the
surface with a slide removed algae, nematodes and harpacticoid
copepods which were, presumably, living just beneath the surface film.
199
This would suggest that no accessory respiratory surfaces are required.
When feeding the fish makes a sudden lunge to seize its prey and simultaneously expels the air and water, forcefully and audibly, through the opercular openings, wet patches or bubbles appearing on the surface of the partly
dried mud. The sound can be heard at a distance of 15-20 feet (46-6 m).
The fish then crawls promptly t o a nearby puddle or to the tide channel,
replenishes the water in its branchial cavity by means of a few seconds of
rapid pumping with the mouth under water and once again gulps air at the
surface, distending the opercular region. . . . Expulsion of air and water also
occurrcd in captive animals in the absence of feeding.
Stebbins and Kalk go on t o describe feeding :
Here, then, we see a mechanism of exchange of water, both while
feeding and at other times, once again suggesting that there is no need
for accessory surfaces. The accounts given by Harms, by Schottle and
by Willems and Bolaert all indicate that they were not entirely convinced that they had found such accessory respiratory surfaces but
that they were impelled to find them following preconceived ideas. My
own observations at many localities favour the ideas of Stebbins and
Kalk, and suggest that they apply equally t o P. chrysospdos, Periophthalmodon schlosseri and Boleophthalmus boddaerti.
Khoo (1966) has studied the food and feeding of the four mudskippers common a t Singapore. He finds that Boleophthalmus boddaerti
is a herbivore. I n feeding it emerges from the water, then makes rapid
side-to-side movements of the head, skimming off a thin layer of
mud and algae from the surface. This mouthful of material is then
manoeuvred round the mouth, as can be seen by the vibrating movements of the lips and opercular region. Muddy water is then squirted
from the mouth and from the gill openings. The fish then repairs to
the water’s edge, dips its mouth into the water and may be seen to
drink, so replenishing the water in the branchial cavity. The intestine
oE this species is very long when compared to that of non-herbivorous
mud-skippers.
Scartelaos viridis is more omnivorous ; its feeding technique is
different. It rasps off the top layer of the mud and collects the mud
into a ball under the lower jaw and this mass of food and mud is then
taken into the mouth. After some sorting process in the mouth the
mud is squirted out. The stomach contents show both plant and
animal material. Khoo demonstrated that lifting the surface film of
mud with a prepared coverslip showed only algae, whereas scraping the
surface with a slide removed algae, nematodes and harpacticoid
copepods which were, presumably, living just beneath the surface film.