- SCALE SENSILLAE
- OF THE FILE
AND SOME OTHER
BURROWING
SNAKE
(SERPENTES:
AND
- ACROCHORDIDAE)
- AQUATIC
SNAKES
by
DAVID POVEL and JEROEN VAN DER KOOIJ
Institute
9516, and
- Evolutionary
- (Section
- Sciences,
Netherlands) of 2300 RA
- Dynamic
- Ecological
The
Morphology,
- Box
- Leiden
- P.O.
Leiden,
University,
ABSTRACT
- are
- in
- with
- environments
- It
- The acrochordidsnakes
- often a
- poor visibility.
- aquatic, living
therefore was scalesrevealed how these animalsdetect their investigated
Two earlier studies of their hairlike prey.
- a rather
- scale
- of
- and
complex
no organ,composed was
- protrusions
- plate-like
an of Acrochordus body
revealed pictures for the structures structures. undefinedsensilla or a
- However,
- found,
- satisfactoryexplanation
- e.g.,
- given
Skin were studied.
- from various
- of the
- sites
- gland.
- samples
Scanning seven
- and A.
- electron
- javanicus
- granulatus
that microscopic
- the keeled of the
- scales
- the
- to
- and
- each scale of
- headcontains
- eachof
tissue on stainingprocedure sensillae,
Allochrome up
Also a
- has one.
- modified
body
performed samples
- nerve
- of
- to detect
of which is known to occur in discoidal slidesrevealed
- endings
- glycogen,
organs reptiles. Lightmicroscopic in a small small nerves glycogen of an
Moreover, organ. particles area
recognized below the hairlike just
near pillow-shaped were have a protrusions
- for the scale
- No indicationswere found
- location.
- to
by the same function. Becauseof the organs
- when is touched
- a snake
mechanoreceptors. habitats, unicolorand
- it
- reactionsof
sensitive glandular these scale sensillaare reported
- a
- to be
fish,
- proposed
- very
- Comparisons
- were made with the scale
- of snakesfrom various
- viz. the seasnake
- organs
- Lapemis
Their
Cylindrophisrufus. snakes
- and
- such as
- hardwicki,
skin sensillaerevealedto be of a much
- burrowing
- Xenopeltis
simpler
- and
- concentratedon
- outer
- only
- morphology
of the head and neck
- specificparts
- region.
KEY
- WORDS:
- Acrochordus,
aquatic scale sensillae. mechanoreceptor, snake, INTRODUCTION
- Acrochordid snakes are
- and can be found in coastal
- from
areas,
to the North aquatic
- West India to the
- in
- the
- Indo-Australian
East, archipclago
The snakes are up
- coast
- Australia
- as a Southern
- of
- nocturnal
- mainly
- boundary.
- and
- areas of which
- 1960; LILLYWHITE,
- (DOWLING,
- 1991),
- mangrove
&prefer the et
- water
- is often
- SHINE
- 1993;
- SHINE,
at
However,
(HOUSTON fish.
- transparency
- very poor
- The snakes are
- vision is
- on
- al.,
- 1995).
and night feeding daytime murky
- how docs
- waters rendcr it
- ineffective,
- negligible
the snake detect its during prey?
444
- There are three
- known of this
- viz.
A. javanicus
Acrochordus found living species prefers mainly group,
- which
- salt water
conditions, granulatus
- in
- fresh water
- both salt and
ter habitats.
- and A.
- fresh wa-
conditions, arafurae favouring
- which are located almost
- snakes
- Acrochordid
- have small
eyes,
- resemble the Anaconda. Instead
- on
top
of a of their head in which respect they
- in a horizontal
- is
- such an
- plane,
- good eyesight
- eye position
the optimal of environ-
- the water surface for
- to
a
- and
- movements
brighter fish and crustaceans
VORIS &
- inspect
- detecting
- following
- its
- the
- of
- which is contrasted
- outline
snakes feed above,
- by
- prey
- ment.
- on
- Acrochordid
(HOUSTON mainly
&
- SHINE, 1993; LILLYWHITE,1991;
- 1986;
- GLODEK,
- an ambush
- for
type
- SHINE,
- 1980).
- of
- The
- mentioned above are
- conditions
especially good specimen the bottom. The snake
- noticed that a
- of A.
- laid
- DowLING
(1960)
a fish
- hunting style.
- javanicus
still until touched
- by
- browsing along
coil quickly
- a
- it. After this the
- over and around
- the fish
grasped by throwing the head by body
- is seized
- and swallowed. When
- is in the
- of
prey
also, vicinity sidewards prey
- in a
- the head or neck
- and
the clear it can visibility swift, snake could even region
- catch
- The
- directed
strike,
hold
(DOWLING, 1960). prey
- a fish with two different
- one in
- another
holding
- and
- coils
- body
- grasp
its
(DOWLING, 1960). jaws
its
- snake for
- a
- This behaviour
- of the
prey,
the
- suggests
- mechano-sensitivity
- to be
- in
- its skin
- which is
- found
many reptiles
JACKSON
(1977), most receptors. Although probably
- and
- PROSKE
HILLER snakes
- scales
- scale
organs
JACKSON
- of
- have been
- examined,
- e.g.,
(1977a, b), those of the acrochordid
- &
- DOETSCH
(1969a, b),
and SHERBROKE& NAGLE
- (1978),
- (1996),
in The depth. snakes
- have not
- been
- of acrochordid
which these snakes are also known as the has file or wart to examine light microscopic study
and A. He found granulatus. skin
- yet
- investigated
scales with
- keels,
- by
(1918) scale
- snake. SCHMIDT
- a
performed
- in A.
- scales and the
- the
- organs
- javanicus
of a
- which occurred all
- the
- over
- The
- consisted
- scale
body.
plate-like organs organs
- tuft of hairlike
- and a flat
- structure. Schmidt consid-
projections
- the scale
- tactile
- was excluded
- function
- ered
- as
- a
- sensillae, however,
- organs
keel
- of the
- him.
- because the sensilla
- in shallow
- First,
- by
- by
- lay
depressions which he assumed that the sensillar hairs could not be stimulated; second,
- also
- similar
the ventral side of the tive function.
- as found
- on
mechanorecep-
- of the scale
- structures
plate-like
- sensillae
- on the back occurred
and therefore could not have a contra-intuitively body he considered the
However,
tactile possible
- sensors.
- as
organs
- On
- the other
- scales' outer
morphology
PRICE
(1982)
electron studied the hand, by
gland-like openings
- a
- He
- means of
- noticed
- scanning
- microscope.
at the scale
- of the keels and therefore
- the
- of the
- top
- peculiar shape
- interpreted
- function.
- Price did SCHMIDT
- not cite
- as
- a
- organs
- having
- glandular
