Marine Planktonic Copepods

General Features of the External 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. Main structural modifications 7. The antennules 8. The antennae 9. The oral 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. Integumental 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 forms 26. Duration of development 27. Growth 28. Regeneration 29. Anomalies 30. Classification and Phylogeny 31. References 32. Photo library

General morphology

Fig. G1A: Calanus finmarchicus (female) (schematic lateral view)

Fig. G2: Calanus finmarchicus (female) (schematic ventral view)

The body presents two distinct segmented regions (tagmata): the anterior one, larger and broader, constitutes the anterior body or Prosome; the posterior part, shorter and narrower, forms the posterior body or Urosome. These two parts are articulated in the sagitto-vertical plane.

The anterior body consists of six visible segments: the first corresponds to the head or Cephalosome, bearing five pairs of appendages: the antennules (A1), the antennae (A2), the mandibles (Md), the maxillules (Mx1), the maxillae (Mx2), plus the first thoracic somite, fused to the head, which bears a pair of maxillipeds (Mxp).

The five following segments are termed "thoracic" and constitute the metasome. Each bears ventrally a pair of biramous swimming legs, united by a chitinous plate (intercoxal sclerite) which renders them functionally coupled (P1 to P5). This characteristic gave its name to this class (or subclass), derived from the Greek kopion: small oar, and podos: foot, more commonly translated as oar-shaped leg.

The posterior body, called the "abdomen" or urosome, is composed of four segments in the female and five in the male, all lacking appendages. The first, articulated with the anterior body, is the "genital segment" (Sgn); the last presents the anus (An) medio-dorsally: this is the anal segment (San), on which the caudal rami (furca) are inserted, consisting of two independent, parallel and more or less flattened rods. Each bears distally six setae: four terminal setae (St), one on the inner apical margin (Si) and one on the outer margin (Se).

The thinness of the cuticle allows observation of various internal organs (fig. G1B).

Fig. G1B: Calanus sp. (female) (schematic internal lateral view)

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