The lunule of caligid copepods: an evolutionarily novel structure

SUMMARY Nearly half of the genera of the family Caligidae possess an evolutionarily novel structure called the “lunule” on the ventral surface of the frontal plate. Lunules are paired cup‐like suckers that assist in securing attachment of the copepod parasite to its host. Although present in genera...

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Bibliographic Details
Published in:	Evolution & development Vol. 14; no. 6; pp. 465 - 475
Main Authors:	Kaji, Tomonari, Venmathi Maran, B. A., Kondoh, Yuusuke, Ohtsuka, Susumu, Boxshall, Geoff A., Tsukagoshi, Akira
Format:	Journal Article
Language:	English
Published:	United States Blackwell Publishing Ltd 01-11-2012
Subjects:	Animals Biological Evolution Copepoda - anatomy & histology Copepoda - genetics Copepoda - growth & development Developmental biology Evolution & development Female Host-Parasite Interactions Japan Male Microscopy, Confocal Microscopy, Electron, Scanning Microscopy, Electron, Transmission New Caledonia Parasites Perciformes - parasitology Takifugu - parasitology Tetraodontiformes - parasitology Japan New Caledonia
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Summary:	SUMMARY Nearly half of the genera of the family Caligidae possess an evolutionarily novel structure called the “lunule” on the ventral surface of the frontal plate. Lunules are paired cup‐like suckers that assist in securing attachment of the copepod parasite to its host. Although present in genera such as Caligus and Pseudocaligus, lunules are absent in other caligid genera such as Lepeophtheirus as well as in more primitive caligiforms such as members of the families Trebiidae and Dissonidae. We compared the morphology and development of the anterior margin of the frontal plates between two caligids, Pseudocaligus fugu and Lepeophtheirus sekii, and a more basal caligiform, Dissonus heronensis (a dissonid), using scanning electron, transmission electron, and laser confocal microscopes. Our observations suggest that the lunules originated as a modification of the marginal membranes of the ancestral frontal plates. We also demonstrated the presence of an anlagen cell population for the lunule and marginal membrane in the developing frontal plate. These primordial cells can be detected as early as the first stage of the chalimus phase. Based on these observations, an evolutionary scenario for the lunule is proposed based on cytological evidence. This case study enhances our understanding of “evolutionary novelty,” which is a main focus of contemporary evolutionary developmental biology.
Bibliography:	ArticleID:EDE12000 ark:/67375/WNG-3KC8JV1S-P istex:0305BC50B944F3499AB5A6985BFB6D84B90A27BC Japan Society of the Promotion of Science - No. 20380110 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1520-541X 1525-142X
DOI:	10.1111/ede.12000