PRELIMINARY SURVEY OF THE RELATIONSHIP BETWEEN THE FEEDING HABIT AND THE STRUCTURE OF TIIE MOUTH‐PARTS OF MARINE COPEPODS1

Abstract

The feeding of 6 copepods (Calanus finmarchicus, Acartia tonsa, Centropages hamatus, C. typicus, Labidocera aestiva, and Tortanus discaudatus) was examined with 3 different foods—a) diatoms (Thalassiosira fluviatilis) alone, b) diatoms plus Artemia nauplii, and c) Artemia alone—and compared with the structure of their mouth‐parts. Calanus finmarchicus is predominantly an herbivore, but in absence of plant food can definitely capture small motile animals. Acartiatonsa is a typical omnivore which can cat either plant or animal food efficiently. Centropages hamatus and C. typicus are also omnivorous, but both prefer an animal diet. Although Labidocera aestiva is predatory, some setae used for filtering food are found at the base of the second maxillae. Finally, Tortanus discaudatus is a typical predatory copepod. There is close relationship between the structure of the mouth‐parts and the feeding habits of these species. In herbivorous species (Calanus finmarchicus), the 2nd antennae, mandibular palps, 1st maxillae, and maxillipeds are well developed to produce a pair of “feeding swirls.” The 2nd maxillae are also formed as efficient filtering nets. The cutting edges of the mandibles are provided with grinding teeth. In predatory species (Tortanus discaudatus), the mouth‐parts have few setae and are on the whole much simpler. The 1st maxillae, 2nd maxillae, and maxillipeds are modified as prehensile appendages. The cutting edges of the mandibles have very sharp teeth. In omnivores, these appendages generally have a structure intermediate between those of the two previous types; the 2nd maxillae are used partly for filtering and are partly prehensile. The teeth are heavier than those of the herbivores, but they are not as stout as for predators.