GILL RAKERS MORPHOMETRY AND FILTERING MECHNISM IN SOME MARINE TELEOSTS FROM RED SEA COASTS OF YEMEN

GILL RAKERS MORPHOMETRY AND FILTERING MECHNISM
IN SOME MARINE TELEOSTS FROM RED SEA
COASTS OF YEMEN
NADIR A. SALMAN , GHAITH J. AL-MAHDAWI & HASSAN, M.A. HEBA
*
Department of Marine Biology & Fisheries, Faculty of Marine Science, Hodeidah University,
* Department of Biology, Faculty of Science, Sana
’
a University, Yemen
Key words : Red Sea, Fish, Gill rakers, Feeding habits
ABSTRACT
Functional morphology of gill rakers in eight marine fish spaecies collected from
Yemeni Red Sea coasts near Hodeida was investigated, aiming to study the possible role of
gill raker in feeding stratigy. Considerable variation in the structure, number , length and
width of gill rakers among the studied species were noticed. Shape of gill rakers in
Epinephalus areolatus, Euthynnus affinis, Carangoides malabaricus, Prestipomides
filamentous and Lethrinus mahsena showed typical characters of carnivorous fish of
cylindrical rakers with hook-like ends and hard structure. Blade-like structure and narrowly
triangular shapes represent omnivorous feeding habits of Pomadasys maculatus and Aprion
virescens. Plankton filter feeder Rastelliger kanagurta possesses komb-like dense
rakers.The total number of gill rakers varied significantly among the eight teleost species.
Rastelliger kanagurta showed dense long and thin (0.05 – 0.18 mm) rakers, Euthynnus
affinis and Carangoides malabaricus possess longer rakers reaching 4.5 and 7.5 mm.. On
contrary carnivores such as Lethrinus mahsena and other predators possess thin (0.2-0.4),
short (0.1 – 0.5 mm) and wide seperated rakers to enable predation of large prey. Efficiency
of filteration area increased with decreasing the space between rakers in planktivores
Rastelliger kanagurta, omnivores Euthynnus affinis and large sizes (> 55cm) carnivores
Carangoides malabaricus. Both raker gap and filtering area increased linearily with
increasing body length.