Does Alella Leigh-Sharpe, 1925 (Siphonostomatoida: Lernaeopodidae) really consist of seven species?

Alella Leigh-Sharpe, 1925 (Lernaeopodidae) consists of seven species, namely A. pagelli (Krøyer, 1863), A. canthari (Heller, 1865), A. macrotrachelus (Brian, 1906), A. ditrematis (Yamaguti, 1939), A. pterobrachiata (Kabata, 1968), A. tarakihi Hewitt & Blackwell, 1987 and A. gibbosa van Niekerk & Olivier, 1995. Specimens of Alella collected from Rhabdosargus sarba (Forsskål), R. holubi (Steindachner), R. globiceps (Valenciennes) and Acanthopagrus berda (Forsskål) (Sparidae) from South African waters were examined. The specimens from R. sarba are from the same host individuals that A. gibbosa were described. However, comparing the armature of the appendages, no consistent and conclusive differences were found between the examined specimens and the other congeners. Additionally, a comparison of the morphology of the appendages and their armature of the examined specimens and those described and illustrated for the known species also revealed limited differences which may be due to regional or intraspecific variation and inconsistent observations rather than distinguishing characteristics of different species. Therefore it is proposed that Alella only has one valid species namely A. pagelli.