Exploring intraspecific morphological variations in Parvocalanus crassirostris (F. Dahl, 1894) (Copepoda: Paracalanidae) in the Gulf of Oman

In this study, morphological characters instability in adult females of Parvocalanus crassirostris (F. Dahl, 1894) is evaluated. This species shows differences in shape, segmentation, spine size, and presence or absence of spines on 5th legs and serration of outer edge of exopod 2 and 3 in legs 2–4. Accordingly, in female individuals of P. crassirostris more than 28 and five types were observed in P5 and ornamentation of P2–4, respectively. In this study, all observed morphs are described to provide informative data for evaluating diverse characters types. These variations seem to be density-dependent. Among state-of-the-art methods, the confocal laser scanning microscope was used to examine this unresolved phenotypic diversity and refer to the main patterns and hypotheses related to the factors affecting morphological traits inconsistencies in this species.