Perinereis nuntia species complex

Elgetany, Asmaa Haris, Struck, Torsten H. & Glasby, Christopher J., 2022, Three new species of the genus Perinereis (Annelida, Nereididae) from Egyptian coasts, ZooKeys 1132, pp. 163-188 : 163

Perinereis nuntia species complex

Perinereis nuntia species complex Wilson & Glasby, 1993: 259. - Glasby and Hsieh 2006: 558. - Villalobos-Guerrero 2019: 468.

Diagnosis.

Perinereis species having conical paragnaths on all areas (rarely absent on area V), except area VI with long bars, which can be shield-shaped or pyramidal paragnaths, arranged in a single-arched row; area V with paragnaths displaced posteriorly (on everted proboscis) to those on area VI; area IV rarely with merged paragnaths.

Remarks.

We have restricted the diagnosis of the species complex to include only unique diagnostic features. Some new characters introduced by Villalobos-Guerrero (2019) describing the faint ridges and furrows of the dorsal oral ring may prove to be useful when broader comparisons can be made. However, at this stage we consider that the form of the pharyngeal ridges and furrows is too closely allied to underlying musculature, and therefore could be unduly influenced by the fixation process and length of time in preservative. Similarly, the form (and length) of the deeply embedded paired nuchal organs may prove to be useful when more comparative data are available. However, observation of that character depends heavily on state of preservation (e.g., they are seen more clearly in specimens relaxed before preservation); in the present specimens the nuchal organs were hidden under the anterior edge of the apodous segment and thus not visible externally. Pharyngeal morphologies are reported herein by describing the form and arrangement of paragnaths on the ridges and in the furrows of the pharynx. The form and arrangement of paragnaths on area VI is unique to the genus (and family) and serves as the easiest way to recognize a member of the species complex. However, Tosuji et al. (2019) have demonstrated that in at least two East Asian species of the complex, the number of bars increases with the growth of individuals (fragmentation of the long bars produces multiple shorter bars (= shield-shaped paragnaths)). Therefore, this character should be used cautiously for species identification across the group, and comparisons are best made between individuals of similar size until we have a better understanding of the processes involved.