Nilotanypus Kieffer, 1923

Cranston, Peter S., Krosch, Matt N. & Tang, Hongqu, 2022, Verifying Australian Nilotanypus Kieffer (Chironomidae) In A Global Perspective: Molecular Phylogenetic And Temporal Analyses, New Species And Emended Generic Diagnoses, CHIRONOMUS Journal of Chironomidae Research 35, pp. 12-31 : 15-16

Nilotanypus Kieffer, 1923

Type-species: Nilotanypus remotissimus Kieffer, 1923 , by monotypy. = Pentaneura comata Freeman, 1953 , syn. nov.

The identity of the genotype, N. remotissimus Kieffer, 1923 , has been problematic. Freeman (1955: 34–35) could not find material matching the description by Kieffer of the wing as having surface hairs only at the tip (male) or sparse (female). Thus, essentially his concept for Nilotanypus (as a ‘group’ in Pentaneura ( Pentaneura )) was based on N. comatus ( Freeman, 1953) , leaving open the possibility that N. remotissimus and N. comatus might prove to be synonyms.

The genus has been recognised subsequently as having densely setose wings in both sexes of all species. Since all other features of N. remotissimus described by Kieffer (1923), especially the hairy eyes and attenuated radial sector of the wing, matched his material, Freeman (1955) speculated that the wings of Kieffer’s specimens may have been rubbed, but tempered this with “even then the hair pits should have been visible”. Observations on the wings of pharate and teneral males of N. comatus (Freeman) confirm the macrotrichia (hairs) are dense, long, and dark, as in all examined congeners. The pits on rubbed wings are distinctive along the veins, but much less so on the membrane, being very small (about 1 µm diameter) and visible only with phase contrast optics at high magnification (> 400×). Under regular illumination and optics, the pits are not visible. Males of the Australian species have (a) macrotrichia on the wing membrane and veins are easily lost and may appear absent, (b) the last marginal macrotrichia to remain are distal, and (c) sockets (hair pits) may not be visible under regular illumination, even at high magnification.

Freeman calculated from Kieffer’s description an AR of 0.3–0.4, notably lower than any values he obtained for his examined N. comatus . Problems include the segment or flagellomere count, as including the pedicel (as in a count of 15) distorts the calculated AR against a modern understanding of 14 flagellomeres, excluding the pedicel. Kieffer’s estimate actually derived from “14 e seulement égal au tiers de 2–13 réunis, 15 e conique, à peine aussi long que le13 e” [14th only equal to one third of 2–13 combined, 15th conical, barely as long as 13th]. The pedicel was included as segment 1, as did Freeman who diagnosed 15 antennal segments for all males in the entire subfamily ( Freeman 1955: 19). Inclusion or exclusion of the terminal 15th and inexactitude of ‘one third’ render doubtful Freeman’s calculated value of 0.3 as too low. Furthermore, the accuracy of Freeman’s own calculations is in doubt, appearing to derive from pinned dry specimens (Duncan Sivell, NHM, personal communication 2022). Thus, these values may not differentiate between N. remotissimus Kieffer and his N. comatus .

Actually, it is the value Freeman cited of ‘about 1’ for the upper end of the AR range in N. comatus that has not been verified subsequently, whereas his lower values of 0.4 and 0.6 have been confirmed. Lehmann (1979) redescribed N. comatus from Kivu, Zaire [= DRC], with the male ‘Antenna 15 segmented; AR = 0.6’. Harrison (1991) also added description of the species from Zimbabwe and Ethiopia but did not emend previous measurements. Two pharate males from the Western Cape ( South Africa) provide AR values of 0.4 and 0.53. Clearly in this widespread species ( Ethiopia to the southernmost Cape) the absolute size of the adult male body varies as does the antennal ratio, and although no AR value as high as 1 (Freeman) has been observed since, it may derive in part from measurements of dry material by Freeman those of 0.4–0.6. Features suggestive of a second African species are the relative lengths of the gonostylar megaseta, the state of the L 3 seta on segment VII and the transverse spinule row on VIII in the pupa. Although the relative length of the megaseta is high (ratio to gonostylus length = 0.3–0.4), it is nearly impossible to determine as variable orientation of the gonostylus and megaseta prevents accuracy. Regarding the condition of the L 3 on VII all available material shows the seta is semitaeniate, and this does not distinguish two pupal types. Finally, the posterior margin on SVIII varies from quite robust, few very fine ones or absence of any such spinules. In female exuviae, the row(s) are separated medially by broad, spine-free area. Evidence of high variability derives from these variants as all occur in contemporaneous exuvial collections in similar streams of the western Cape.

The above indicates that Nilotanypus remotissimus Kieffer can be reconciled with N. comatus (Freeman) . Uncertainty about the genotype would be resolved by synonymy, even in the absence of original type material for N. remotissimus . Given assurance that there is a single species of Nilotanypus in sub-Saharan Africa, we confidently assert conspecificity of N. comatus with N. remotissimus and propose the formal synonym here.