Doropygus Thorell, 1859

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 313

Genus Doropygus Thorell, 1859

Diagnosis. Body of female comprising cephalosome and inflated metasome consisting of 3 more-or-less well defined pedigerous somites plus fourth pedigerous somite, forming brood pouch and largely incorporating fifthpedigerous somite. Freeurosome 5-segmented in female and 6-segmented in male. Caudal ramus with 6 setae. Antennule typically 9-segmented. Antenna 4-segmented including coxa, basis and 2-segmented endopod; exopod represented by small knob bearing 1 or 2 setal vestiges, by minute seta on basis surface, or absent. Mandible consistingof coxa, basis, exopod and endopod; exopod typically armed with 5 setae; endopod with 3 or 4 and 9 or 10 setae on first and second segments, respectively. Maxillule armed with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, and 3 on basis; exopod with 3 or 4 setae, endopodwith 2 or 3 setae. Maxilla bearing 3 setal elements on basis, with distal element claw-like or setiform according to species. Maxilliped indistinctly segmented, although typically with partial suture dividing medial armature of 9 setae from apical part bearing 2 setae. Leg 1 with 3-segmented exopod and 2- or 3-segmented endopod. Legs 2–4 with 3-segmented exopods and 2-segmented endopods; exopods bearing setiform outer armature elements. Armature formula for legs 1–4 in type species ( D. pulex ) as follows:

	Coxa Basis Exopod			Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 4	0-1; 0-1; 1, 2, 3
Legs 2 & 30-1		1-0	1-1; 1-1; 3, 1, 5	0-1; 1, 3, 4
Leg 4	0-1	1-0	1-1; 1-1; 2, 1, 5	0-1; 1, 3, 3

Leg 5 typically consisting of protopod fused to pedigerous somite and elongate free exopodal segment armedwith 2 distal setation elements.

Type species: Doropygus pulex Thorell, 1859 , by original monotypy.

Remarks. Illg (1958) considered the diagnosis and composition of Doropygus at length. He tightened up the generic diagnosis and transferred several species to more appropriate genera; placing three former Doropygus species in a new genus, Pygodelphys Illg, 1958 , moving three more to Doropygella and another one to Doropygopsis . In addition, he by-passed the taxonomic paralysis caused largely by Hesse (1866a,b, 1869, 1871) who, over the course of five years had described no less than 21 new species from the coast of France, all inadequately. The treatment of these as species inquirenda allowed the study of Doropygus tomove forwards. Illg (1958) alsotreated Doropygus cylindriformis Schellenberg, 1922 as incertae sedis.

At the time of his revision Illg (1958) recognized 15 species as valid but since then a further 19 species have been added to the genus. Of these, we consider that D. apicatus Stock, 1967 and D. curvipes Gotto, 1975 are both junior synonyms of D. humilis Stock, 1967 (see discussion after redescription of D. humilis below). In addition, D. catalai Illg, 1970 is transferred to Chelipygus gen. nov. (see below) and D. pyurus Oldewage, 1994 is so inadequately described ( Oldewage, 1994) that its identity is unrecognizable, so it is here treated as a species inquirendum.

Doropygus is a large genus so for ease of navigating this species richness we have grouped species into loose artificial assemblages based on the setation of the exopod and endopod of the maxillule ( Table 6). These groupings are based on phenotype and we have not assessed their monophyletic status by analysis of their phylogenetic relationships. Therefore, we do not propose any formal taxonomic status for these groups.

Group A (maxillule with 4 setae on exopod and 3 setaeon endopod)