Variation of Von Vaupel Klein's organ among genera of the Calanidae and Megacalanidae (Copepoda, Calanoida)

Von Vaupel Klein's organ (VVKO), an association of the basal seta and proximal segment on the endopod of swimming leg 1 on many gymnoplean copepods, is surveyed on one species each of eight genera of calanids, viz., Calanoides acutus Giesbrecht, 1902, Calanus finmarchicus (Gunnerus, 1770), Canthocalanus pauper (Giesbrecht, 1888), Cosmocalanus caroli (Giesbrecht, 1888), Mesocalanus lighti (Bowman, 1955), Nannocalanus minor (Claus, 1863), Neocalanus robustior (Giesbrecht, 1888) and Undinula vulgaris (Dana, 1849), and three of megacalanids, viz., Bathycalanus richardi Sars, 1905, Bradycalanus typicus Sewell, 1947 and Megacalanus longicornis Sars, 1905. In this exploratory survey, VVKO shows significant variability among the eleven species in the shape of the distodorsal corner of the proximal endopodal segment, presence and location of denticles on the anterior face of the segment, presence and size of denticles along the distal margin of the segment, number of pores on the segment, shape of the seta that originates on the basis, and the nature of the basis at the origin of the seta.