Study on the Korean monstrilloids (Copeopda: Monstrilloida: Monstrillidae) integrating morphological, molecular phylogenetic and ecological evidence

Abstract

Research on monstrilloid copepods has been performed very rarely by a limited number of researchers worldwide. This low rate of research activity can result from their very unusual morphological features and little known ecological knowledge. In addition, the incomplete early studies on this animal group and the definitions of the present genus/species based on these earlier knowledge have also become a big obstacle to the study of monstrilloid taxonomy. Despite this situation, most of studies on these taxa have been still focused on the morphological descriptions and following designations of new or unrecorded species, based only on the adult specimens. However, there is still a relative lack of considerations for somewhat unsettled genus/species diagnoses or for their true diversity. In this study, I tried to prove the relationship between the Korean monstrilloids by using molecular and ecological approaches as well as morphological analysis. As a result, it provided detailed morphological information on six species of monstrilloids that emerged in Korea, and furthermore, the establishment of a new genus Caromiobenella for the four species that exhibit unusual morphological character set. The formation of this new group has resulted in an emphasis on the importance of some features that were not previously considered important in the genus-level classification. Two other species have been identified as the species of Monstrillopsis, but still exhibit very strange features to the generic diagnosis of Monstrillopsis. These features, on the contrary, suggested the necessity of reconsidering the features that were considered important to differentiate the monstrilloid genera. The validity of the above results from the morphological investigation was verified again based on molecular phylogenetic results obtained in this study. The conventional morphological classification was found to be in general agreement with the current molecular results. The results also supported the clear separation of Caromiobenella from Monstrilla. It additionally showed the possibility that the genus Cymbasoma could be divided into at least two different subgroups. Based on the results derived from both morphological and molecular integration, their ecological behavior and subsequent adaptation as well as the morphological features prepared for those were also discussed. The assessment of the relation between specific morphology and ecology proposed in this study still remains speculative due to the limited ecological knowledge available, nonetheless it is worth considering for a better understanding of this group.