Marine Planktonic Copepods

General Morphology of Marine Planktonic Copepods

1. Introduction 2. General morphology 3. Morphology of the various body parts and appendages 4. Dimensions 5. Body forms 6. Principal structural modifications 7. The antennules 8. The antennae 9. The buccal frame 10. The Mandibles 11. The Maxillules 12. The Maxillae 13. The Maxillipeds 14. The swimming legs 15. Variation in segment number 16. Nomenclature and Metamerism 17. Tegumental structures and organs 18. Visual organs 19. Morphological variations 20. Sex-ratio 21. Gynandromorphism and intersexuality 22. Mating 23. Parthenogenesis 24. Characteristics of egg-laying 25. Larval stages 26. Duration of development 27. Growth 28. Regeneration 29. Anomalies 30. Classification and Phylogeny 31. References 32. Photo gallery

Visual organs

Fig. G15: Structure of the nauplius eye in Eucalanus elongatus (Calanoida)

In the great majority of free-living forms there exists an unpaired, median eye corresponding to the eye of the nauplius larva, and therefore commonly called the "nauplius eye". It is generally situated between the antennules on the ventral surface of the head. Its structure was studied by Vaissiere (1961) in Eucalanus elongatus (fig. G15), by Fahrenbach (1964) in a cyclopoid by electron microscopy, and then by Park (1966) who studied the ocular complex in a calanoidan belonging to the family Pontellidae.

It is rendered visible by its coloration due to orange-red, blue or green pigments (Lwoff, 1927). These carotenoid-protein pigments may coexist with black pigment platelets (pro-melanins). The nauplius eye persists unchanged in most Copepods, but in a number of them (Boxshall, 1992) it undergoes considerable transformations that may reach the extreme, as in the bathypelagic calanoid genus Cephalophanes.

The modifications generally consist of a widening of the three ocelli, the doubling of the dorsal ocelli, but above all the appearance of translucent cuticular dioptric lenses, as in the family Pontellidae, the Miracidae (Harpacticoida), the Sapphirinidae and Corycaeidae (Poecilostomatoida).

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