3. • Acoustico is the inner-ear region and Lateralis
is the lateral-line organs located in the skin,
forming a sensory system that conveys
environmental information to the brain of a
fish: the lateral-line organs respond to
changes in water pressure and displacement,
the inner ear responds to sound and gravity.
Generally such a system is found in aquatic
lower vertebrates (e.g. lampreys, sharks, bony
fish, and one or two amphibians).
4. • In sharks, hearing and vibration detection (The
Acoustico-Lateralis System) are fundamentally
linked. For sharks the inner ears are nestled
inside the posterior part of the braincase on
top of the head. The only external
manifestation of a shark's ears are two small
openings on top of the head, just behind the
eyes, known as endolymphatic pores.
5. Structure of the Lateral Line and the
Inner Ear:
• The functional unit of both the shark inner ear
and lateral line is the hair cell. Each hair cell
consists of a more-or-less globular basal body
from one end of which project a series of cilia
(hair-like structures). One of these cilia, called
aklinocilium, is much longer than the others.
6. The Inner Ear:
• The shark inner ear is a fluid-filled structure
consisting of a cartilaginous sac to which is
attached three semicircular cartilaginous
tubes. These fluid-filled tubes are set at right
angles to one another and are lined with hair
cells. Each semicircular tube responds only to
accelerations within the plane parallel to its
orientation.
7. Sound Detection:
• Recently de-classified U.S. Navy studies have
revealed that the ocean is criss-crossed by
meandering ribbons of very cold, dense water
surrounded by warmer, less dense water.
Since sound travels more efficiently in dense
materials, these liquid ribbons act as 'sound
tunnels'.
8. Hair cells
• The hair cells are the primary auditory
receptor cells and they are also known as
auditory sensory cells, acoustic hair cells,
auditory cells or cells of Corti. The organ of
Corti is lined with a single row of inner hair
cells and three rows of outer hair cells.
9.
10. • Pillar cells are found in the organ of Corti and
act as supporting cells for hair cells. They are
divided into two types: inner and outer.
• Boettcher's cells are found in the organ of
Corti where they are present only in the lower
turn of the cochlea.
• Claudius' cells are found in the organ of Corti
located above rows of Boettcher's cells.
11. • Deiters' cells (phalangeal cells) are a type of
neuroglial cell found in the organ of Corti and
organised in one row of inner phalangeal cells
and three rows of outer phalangeal cells.
12. • Hensen's cells are high columnar cells that are directly
adjacent to the third row of Deiters’ cells.
• Hensen's stripe is the section of the tectorial
membrane above the inner hair cell.
• Nuel's spaces refer to the fluid filled spaces between
the outer pillar cells and adjacent hair cells and also
the spaces between the outer hair cells.
• Hardesty's membrane is the layer of the tectoria
closest to the reticular lamina and overlying the outer
hair cell region.
• Reissner's membrane is composed of two cell layers
and separates the scala media from the scala vestibuli.
• Huschke's teeth are the tooth shaped ridges on the
spiral limbus that are in contact with the tectoria and
separated by interdental cells.
13. Lateralis System:
• Lateral line system, also called lateralis system,
a system of tactile sense organs, unique to
aquatic vertebrates from cyclostome fishes
(lampreys and hagfish) to amphibians, that
serves to detect movements and pressure
changes in the surrounding water. It is made
up of a series of mechanoreceptors called
neuromasts (lateral line organs) arranged in an
interconnected network along the head and
body.
14.
15. Lateral Line Structure and Function:
• The shark lateral line consists of a fluid-filled,
hair cell-lined tube extending along each
flank, just beneath the skin. This tube
connects to the external environment via
secondary fluid-filled tubules that branch off
from the main tube and penetrate the skin at
regular intervals. The lateral line system is
visible on the surface of the skin by the
presence of small pores known as
mechanosensory neuromasts.
16. Lateral Line use in Feeding Behaviour
• The best known behavioural use of the lateral
line in sharks is in prey detection. Other uses
of the lateral line, particularly in bony fish,
include schooling behaviour, social
communication, hydrodynamic imaging,
predator avoidance and rheotaxis.
18. • The major unit of functionality of the lateral
line is the neuromast. The neuromast is a
mechanoreceptive organ which allows the
sensing of mechanical changes in water. There
are two main varieties of neuromasts located
in animals, canal neuromasts and superficial
or freestanding neuromasts
19. Electric Sense Organs:
• Evolved from lateral line neuromastorgans
• Found in many bony fishes e.g., sturgeon and
elasmobranchs(sharks and their relatives)
• Extremely sensitive to electric current, such as
those produced by muscle movements
