FAUNA AND FLORA O F MANGROVE SWAMPS
1!)5
all other mud-skippers, often does a half roll on to one side and back
again. They were frequently seen apparently being bitten by mosquitoes which landed just behind the eyes and above the pectoral
f i ns to the obvious annoyance of the fish.
Both Boleophthalmus boddaerti and Scartelaos viridis push themselves
into the soft mud tail first.
It
would appear that while these burrow with the mouth the former two
merely push their way into the mud.
B. boddaerti, S. viridis and P. schlosseri seem to be able to remain subyerged during a great part of or, the whole of the period of tidal flooding.
When submerged all mud-skippers swim with ease but rather slowly
in normal fashion. On alarm they skelter along the surface, most of
the body submerged but with the head and particularly the eyes above
the surface, or flying-fish-like they come right out of the water skimming
the surface. On land they proceed by a series of skips and jumps. P.
chrysospilos can also climb trees. The ability to perform these movements is the result of modifications of the skeleton and musculature.
Eggert (1 929a) made studies of several periophthalmine fishes and
compared them with normal gobies, in an attempt to trace the modifications associated with migration towards land. Lele and Kulkarni
(1939) described the skeleton of P. barbarus (= P. kalolo). Petit (1921)
gave the first description of the mechanism of skipping on land. Van
Dijk (1960) and Harris (1960) describe and discuss more fully the
methods of movement and Harris attempts to correlate the different
types of movement with the musculature. He studied P. koelreuteri in
west Africa. Van Dijk studied the Periophthalmus occurring near
Durban, South Africa (probably P. kalolo).
I n addition to normal swimming Harris recognizes three types of
locomotion.
(1) Ambipedal progression or " crutching ". I n this the pectoral fins
are used as crutches (Figs. 69 and 70)-they are stretched forwards and
then the fish swings on them and at the end of the stroke the weight is
transferred to the pelvic fins. There are no sinuous movements of the
body, no alternation of limbs in a time sequence as is done by lower
tetrapods such as urodeles and lizards. Hence van Dijk is mistaken in
calling this type of progression " walking ".
( 2 ) Skipping on laml. This is normally an escape reaction, but is
also used in feeding. I n this action the tail is bent forwards and to one
side, the caudal fin rays dig into the mud. The body is straightened
and the fish is projected forwards and upwards into the air. The
vertical component is provided by the thrust of the pelvic fins and the
pcctorals act as stabilizers.
The periophthalmines go head first.
1!)5
all other mud-skippers, often does a half roll on to one side and back
again. They were frequently seen apparently being bitten by mosquitoes which landed just behind the eyes and above the pectoral
f i ns to the obvious annoyance of the fish.
Both Boleophthalmus boddaerti and Scartelaos viridis push themselves
into the soft mud tail first.
It
would appear that while these burrow with the mouth the former two
merely push their way into the mud.
B. boddaerti, S. viridis and P. schlosseri seem to be able to remain subyerged during a great part of or, the whole of the period of tidal flooding.
When submerged all mud-skippers swim with ease but rather slowly
in normal fashion. On alarm they skelter along the surface, most of
the body submerged but with the head and particularly the eyes above
the surface, or flying-fish-like they come right out of the water skimming
the surface. On land they proceed by a series of skips and jumps. P.
chrysospilos can also climb trees. The ability to perform these movements is the result of modifications of the skeleton and musculature.
Eggert (1 929a) made studies of several periophthalmine fishes and
compared them with normal gobies, in an attempt to trace the modifications associated with migration towards land. Lele and Kulkarni
(1939) described the skeleton of P. barbarus (= P. kalolo). Petit (1921)
gave the first description of the mechanism of skipping on land. Van
Dijk (1960) and Harris (1960) describe and discuss more fully the
methods of movement and Harris attempts to correlate the different
types of movement with the musculature. He studied P. koelreuteri in
west Africa. Van Dijk studied the Periophthalmus occurring near
Durban, South Africa (probably P. kalolo).
I n addition to normal swimming Harris recognizes three types of
locomotion.
(1) Ambipedal progression or " crutching ". I n this the pectoral fins
are used as crutches (Figs. 69 and 70)-they are stretched forwards and
then the fish swings on them and at the end of the stroke the weight is
transferred to the pelvic fins. There are no sinuous movements of the
body, no alternation of limbs in a time sequence as is done by lower
tetrapods such as urodeles and lizards. Hence van Dijk is mistaken in
calling this type of progression " walking ".
( 2 ) Skipping on laml. This is normally an escape reaction, but is
also used in feeding. I n this action the tail is bent forwards and to one
side, the caudal fin rays dig into the mud. The body is straightened
and the fish is projected forwards and upwards into the air. The
vertical component is provided by the thrust of the pelvic fins and the
pcctorals act as stabilizers.
The periophthalmines go head first.