Copepoda note details

Taxonomic remark
This review of Pennella suggests that 15 of 44 reported species exhibit unique and distinct characteristics and are substantiated, or are potentially valid members of the genus. Six species (P. elegans, P. longicauda, P. platycephalus, P. robusta) described from single specimens on flyingfish (Gnanamuthu 1957), P. selaris from trevally (Kirtisinghe 1964) described from two specimens (one immature and one apparent adult) and P. remorae (also described from a single specimen), are now included in this group although no type material, or any other specimens exist. We have only the original descriptions and figures, which indicate that the mature parasites exhibited unique characters, to consider the species as valid. Additional specimens of these six species are required to discover the true nature of each. One objective of this present review has been to define a set of characters which can be effectively used to differentiate species of Pennella. Wilson (1917) had previously indicated in his discussion on the taxonomy of Pennella: “scarcely any two authors have described their species similarly”. If species of previously documented Pennella had been treated in a similar manner, with descriptions based on a consistent set of differentiating characters, the confusion in the taxonomy of the genus would be much reduced. It would be useful to incorporate those characters which are now suggested for distinguishing species into any future descriptions of new Pennella. The salient morphological features useful for differentiating species are the parasite size, cephalothoracic papillae shape and configuration, segmentation of the first and second antenna, holdfast horn number and arrangement, and abdominal plume structure. The non-morphological character based on host type is also useful. For Pennella, the key to confident assessment of any species is the application of defined character states to multiple specimens. In the present review, the alignment of species groups by size is amended from previous assessments, there are four large species (>100 mm): P. balaenoptera, P. benzi sp. nov., P. filosa and P. instructa; 3 species are intermediate in size (50–100 mm): P. hawaiiensis, P. remorae and P. robusta and eight are small species (<50mm): P. diodontis, P. elegans, P. exocoeti, P. longicauda, P. makaira , P. platycephalus, P. sagitta, and P. selaris. Species grouping and diversity based on the host type is evident: P. balaenoptera is parasitic on marine mammals, P. filosa is a parasite of large pelagic fish (billfish, tunas, ocean sunfish, amberjack, and dolphinfish), P. benzi sp. nov. occurs on escolars, P. hawaiiensis occurs on boarfish, P. instructa is found on swordfish and sailfish, P. remorae parasitizes remoras, P. exocoeti, P. elegans, P. longicauda, P. elegans and P. platycephalus are parasites of several species of flyingfish, Pennella makaira is found on blue marlin, P. diodontis is found on porcupine fish, P. selaris parasitizes the blackfin trevally and P. sagitta infests frogfish. Species richness and diversity of the genus is re-affirmed; based on this current review using external morphology and phenotypic characters to define species, it is suggested that there are a variety of Pennella species which exhibit a wide range of shapes and sizes, and type of hosts infested. If Pennella was subjected to molecular phylogenetic analysis some confusion as to what defines a legitimate species could be eliminated. Castro-Romero et al. (2016) documented morphological variability in cephalothorax and holdfast structures between specimens of single species of three pennellid genera (Peniculus Nordmann, 1832, Metapeniculus Castro-Romero & Baeza-Kuroki, 1985, and Trifur Wilson, 1917) based on DNA barcoding; this method when applied to Pennella may show similar results. It would be very useful to determine the polyphyletic distribution within Pennella based on host designation as this could indicate if there are
Hogans, W.E. (2017). Review of Pennella Oken, 1816 ( Copepoda: Pennellidae) with a description of Pennella benzi sp nov., a parasite of Escolar, Lepidocybium flavobrunneum (Pisces) in the northwest Atlantic Ocean. Zootaxa, 4244(1):1-38. Available for editors  PDF available
2019-12-27 02:53:12Z