Graphics Reference
In-Depth Information
Flat fish such as the European plaice
Pleuronectes platessa
have their fins
located around their outer edges, with the caudal fin remaining distinct but
flattened.
The manta ray
Manta birostris
has a flattened body and pectoral fins that have
developed into extended wings. The anal fin is completely absent.
In addition to the overall variations in body shape among fish, there are three
distinctive mouth shapes in most of the fish that have jaws:
•
Terminal
•
Superior
•
Subterminal
(a)
(b)
(c)
FIG 4.68
The different mouth
configurations of fish. a: Superior.
b: Subterminal (inferior). c: Terminal.
Terminal Mouth
A mouth that is located at the very tip of the head is known as
terminal
. This
is illustrated clearly in the wrasse
Labridaea
, a family of fishes of around 500
separate species. They have protractile mouths that reveal their short, sharp
teeth, which enable them to feed by dislodging limpets and mussels from
rocks or, as in the cleaner wrasse, enabling a symbiotic relationship with other
fish feeding on dead tissues and the scales and parasites that infect their
partner species.
Superior Mouth
Mouths that are upturned with the lower jaw protruding beyond the upper
jaw are known as
superior
. The rudd
Scardinius ertythropthalmus
is one such
fish. The orientation of the mouth makes the fish supremely suited to feeding
from the surface and upper layers of the water. However, not all fish that feed
from the surface have this kind of mouth.
Subterminal Mouth
A mouth that is located on the underside of the fish's head, as with the tench
Tinca tinca
, is termed
subterminal
or
inferior
. Fish with such mouths are more
suited to feeding on the bottom; though this does not prevent them from
feeding higher in the water column or taking food from the surface, it is less
likely they will do so.
