Oogenesis in calanoid copepods

• Published in: Invertebrate reproduction & development Vol. 47; no. 3; pp. 167 - 181
• Main Authors: ECKELBARGER, KEVIN J., BLADES-ECKELBARGER, PAMELA I.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 2005
• Subjects: Acartia tonsa; annulate lamellae; Calanus finmarchicus; Calanus glacialis; Calanus hyperboreus; Centropages furcatus; Centropages velificatus; Crustaceans; Euchaeta marina; Labidocera aestiva; Marine; Pleurommama xiphias; Undinula vulgaris; vitellogenesis
• ISSN: 0792-4259; 0168-8170; 2157-0272
• DOI: 10.1080/07924259.2005.9652157

An ultrastructural investigation of ovary structure and oogenesis was conducted on ten species of cold and warm water calanoid copepods from six families with broad distributions ranging from coastal to mesopelagic habitats. They include Calanus finmarchicus, C. hyperboreus, C. glacialis, Euchaeta marina, Centropages furcatus, C. velificatus, Labidocera aestiva, Acartia tonsa, Pleurommama xiphias, and Undinula vulgaris. All ten species show similarities with respect to ovarian morphology and oogenesis. Oogenesis is asynchronous with all stages of oocytes present within each sexually mature female. The oocytes differentiate to diplotene of the first meiotic division and undergo a growth phase within the ovary before initiating vitellogenesis within the diverticulae. Vitellogenesis involves both an autosynthetic (endogenous) and a heterosynthetic (exogenous) process resulting in the deposition of two different types of yolk bodies. Endogenous yolk formation is initiated by the proliferation of vesicular endoplasmic reticulum (ER) through the blebbing of the outer lamina of the nuclear envelope. These ER vesicles contain a variable number of granules that arise before the vesicles detach from the nuclear envelope. Parallel arrays of annulate lamellae (AL) also appear in this region and their swollen, distal cisternae release ER vesicles into the surrounding ooplasm that are indistinguishable from those generated by the nuclear envelope. Golgi complexes proliferate and produce secretory products that fuse with both the ER cisternae and newly formed yolk bodies. Simultaneous biosynthetic activity of the ER, AL, and Golgi results in the formation of Type I yolk bodies, and primary and secondary cortical vesicles that likely participate in the formation of the egg envelope. In the later stages of vitellogenesis, extraoocytic yolk precursors originating in the hemocoel pass through the follicle cells that encompass the oocytes in an endocytotic process that releases precursors into the pervitelline space. Oocytes then incorporate these precursors endocytotically resulting in the gradual assembly of Type II yolk bodies. To our knowledge, this is the first ultrastructural study to describe the biosynthesis of specific products (yolk bodies and cortical granules) by annulate lamellae in any metazoan oocyte. Vitellogenesis in calanoid coperpods is significantly different from that described in any other crustacean group. Further investiation of this process in related crustaceans might provide useful phylogenetic insights.