On the shedding of gill raker processes in grey mullets

Luther, G (1964) On the shedding of gill raker processes in grey mullets. Journal of the Marine Biological Association of India, 6 (2). pp. 251-256.

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Abstract

The unidentifiable item (Plate I) formed a significant proportion of the stomach contents of nearly 35% of a total number of 1147 fish of both the species in different size groups. Occurrence of this item in the stomachs of mullets from the sea (Palk Bay), however, was negligible. It was found that the gill raker processes (the tiny processes present in double row on the inner face of the gill rakers) of mullets are similar in structure to this item. Examination of the branchial apparatus of the two other common fishes viz., Chanos chanos and Nematalosa nasus and many other fishes in the lagoon (Tampi, 1959) revealed that the gill raker processes of these fishes do not bear resemblance to those of the mullets. Fishes with gill raker processes in their stomachs showed the processes on their gill rakers intact indicating that the fish does not swallow its own gill raker processes. In a detailed study of the food habits of the above two species of mullets, the fish have been arbitrarily separated into two groups viz., those with stomach contents predominated by decayed organic matter and foraminifera (Type A stomachs), and those with stomach contents formed virtually of gill raker processes (Type B stomachs). While copepods were seen neither to occur regularly nor to form any appreciable proportion in type A stomachs during the period of observation they were of common occurrence in the type B stomachs (Table I) indicating an association of copepods with the gill raker processes. The copepods, Harpacticus spp., MkroseteUa rosea and Metes jousseumi met with in type B stomachs are known to be omnivorous and benthic found on sea weeds and other organisms. Besides copepods foraminifera, diatoms, sand grains and spicules which are common at the bottom were also found in type B stomachs.

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