Cloeon Leach, 1815

Gattolliat, Jean-Luc, Samraoui, Boudjema, Benhadji, Nadhira, Kechemir, Lina, Zrelli, Sonia, El Yaagoubi, Sara, El Moutaouakil, Majida El Alami & Sartori, Michel, 2023, Baetidae (Baetidae, Ephemeroptera) in the Maghreb: state of the art, key, and perspectives, ZooKeys 1139, pp. 137-163 : 137

6. Cloeon Leach, 1815

Diagnosis.

1) Gills I-VI with double lamellae, upper lamellae similar in shape to lower ones and only slightly smaller; 2) legs elongated, claw elongated with two rows of abundant small to medium denticles; 3) labial palp conical and truncated; 4) maxillary palp 3-segmented; 5) paracercus subequal in length to cerci.

Remarks.

Cloeon is the most common and most abundant mayfly genus in still and standing waters all over the world (except in America). It can survive in conditions with high temperature and very low oxygen level. Cloeon gr. dipterum is a complex of very similar species. In Maghrebian ecological and faunistic surveys, it is generally referred as Cloeon dipterum (Linneaus, 1761) or Cloeon cognatum Stephens, 1835 ( Boumaiza and Thomas 1995; Thomas 1998; Mabrouki et al. 2017; El Alami et al. 2022a). Recent molecular studies support the presence of six lineages in the West Palearctic and at least one of them is present in the Maghreb ( Rutschmann et al. 2014, 2017). This lineage corresponds to Cloeon peregrinator Gattolliat & Sartori, 2008 (Fig. 4E ), a species originally thought to be endemic to Macaronesian archipelago but reported later from Algeria ( Gattolliat et al. 2008; Benhadji et al. 2020). Cloeon gr. dipterum is known to present high plasticity; for example the size of the gills is directly adapted to the concentration of dissolved oxygen ( Sweeney et al. 2018). Therefore, for the moment, identification to the species level can only be securely made based on molecular evidence (CO1 barcoding).

Besides Cloeon gr dipterum , another species, Cloeon saharense Soldán & Thomas, 1983, was reported from different localities in intermittent brooks and pools in arid and subarid zones of Algeria ( Soldán and Thomas 1983a). This species should be easily separated from C. gr. dipterum by the absence of spines on the lateral side of abdominal segments, a character which is unique among Cloeon . Forewing of female imagoes are hyaline while those of C. gr. dipterum have costal and subcostal areas with dark brown pattern ( Soldán and Thomas 1983a). Although this species is supposed to be morphologically easily recognisable, C. saharense has never been reported from the Maghreb since its original description.

Figures

Figure 4. Baetidae: larvae in toto in dorsal view A Baetis (Rhodobaetis) atlanticus B Centroptilum alamiae C Cheleocloeon dimorphicum D Cheleocloeon dimorphicum (ready to molt specimen) E Cloeon peregrinator F Labiobaetis cf. neglectus.