Sagum Wilson, 1913

Boxshall, Geoff A., Bernot, James P., Barton, Diane P., Diggles, Ben K., Q-Y, Russell, Atkinson-Coyle, Toby & Hutson, Kate S., 2020, Parasitic copepods of the family Lernanthropidae Kabata, 1979 (Copepoda: Siphonostomatoida) from Australian fishes, with descriptions of seven new species, Zootaxa 4736 (1), pp. 1-103 : 82

Genus Sagum Wilson, 1913

Remarks: The genus Sagum was established by Wilson (1913) to accommodate a new species, S. flagellatum Wilson, 1913 , found on the gills of a serranid Epinephelus adscensionis (Osbeck, 1765) caught off Jamaica. The new genus was distinguished from Lernanthropus by “the rostrum and wings of the cephalothorax, by the long endopods of the third legs, and by the lash-like tips of the fourth legs.” The two female syntypes of S. flagellatum lacked egg sacs, so the form of the egg sacs was not included in the original generic diagnosis. In his revision of the North American Dichelesthiidae, Wilson (1922) transferred Lernanthropus angulatus Krøyer, 1863 into Sagum as S. angulatum and gave a revised generic diagnosis which included as a key feature, the possession of coiled egg sacs entirely contained within the space enclosed between the dorsal trunk plate and the third and fourth legs.

In their phylogenetic analysis of the lernanthropid genera, Ho & Do (1985) grouped Aethon , Norion and Sagum together on the basis of the possession of coiled egg sacs. They distinguished Aethon by its highly modified second legs and grouped Sagum and Norion by the shared possession of bilobate fourth legs with lobes that are lamellate proximally and flagellate distally. Although used by Wilson (1922) is his original diagnosis of the genus, this latter character is not robust since at least half of Sagum species (see Table 4 ) have tapering bilobate fourth legs rather than legs with flagellate tips on the exopodal and endopodal lobes. The loss of leg 2 was used to characterize Norion species whereas the form of leg 3, described as “divided into 3 branches; lamelliform or cylindrical”, was used to diagnose the Sagum branch. This latter character is also not robust, applying only to a minority of species. Given the difficulty in using some of these traditional characters, it is clear that the relationships between the currently recognized lernanthropid genera need to be reassessed using a wider range of characters from both sexes.