Ephemerotoma, Potapov, Mikhail, Kahrarian, Morteza, Deharveng, Louis & Shayanmehr, Masoumeh, 2015

Potapov, Mikhail, Kahrarian, Morteza, Deharveng, Louis & Shayanmehr, Masoumeh, 2015, Taxonomy of the Proisotoma complex. V. Sexually dimorphic Ephemerotoma gen. nov. (Collembola: Isotomidae), Zootaxa 4052 (3), pp. 345-358 : 346-347

Ephemerotoma gen. nov.

Type species: Ephemerotoma skarzynskii sp. nov.

Diagnosis. Large Anurophorinae with all abdominal segments clearly separated and a Proisotoma -like furca: manubrium with few anterior chaetae (usually 1+1, more rarely 2+2); dens with posterior humps or crenulations, with few anterior and posterior chaetae; mucro clearly set off from dens, with 2 or 3 teeth. Ocelli 8+8. Simple maxillary palp and 4 sublobal hairs ( Fig. 2 ), considerably reduced number of guards on labial papilla E (3 e -guards absent, unknown for E. porcella ) ( Fig. 4 ), and only 2 prelabral chaetae ( Fig. 31 ). Complete set of microsens on tergites (11/111), macrosens of basic set (33/2224). Tergal macrosens on abdomen situated in front of p-row of chaetae. B-row of chaetae on tibiotarsi 1–2 complete (both B4 and B5 present). Four sens on Abd.V arranged in two rows, with 2 anterior and 2 posterior sens ( Figs 13 , 20 , 30 , 34 ). Abd.V polychaetotic, almost as long as Abd.IV, tegument on posterior part of Abd.V often modified: swollen and tuberous. Abd.VI small, partly hidden from dorsal view (cryptopygy). Ventral chaetae on Th.III present or absent. Often with sexual dimorphism.

Position in the Proisotoma complex. Potapov et al. (2006) keyed two members of the new genus to two incertae sedis forms: " Dimorphotoma " porcellus ( Ellis, 1976) and " Proisotoma " multituberculata ( Martynova, 1971) . Based on characters proposed by Fjellberg (1993) and Potapov et al. (2006) for the Proisotoma complex, Ephemerotoma gen. nov. is characterized by the simple maxillary palp, 2 prelabral chaetae, and the presence of chaetae on the anterior side of manubrium. In this combination the new genus is intermediate between Subisotoma and Scutisotoma . The simple maxillary palp and 2 prelabrals are shared with Subisotoma sensu Fjellberg, 1993 while the construction of the furca is very different. Characteristics of the furca, including the presence of anterior manubrial chaetae and shape of the mucro, indicate similarity with the genus Scutisotoma , which has 3 or 4 prelabral chaetae and usually a bifurcate (rarely simple) maxillary palp. The 'christianseni' and 'subarctica' groups of Scutisotoma ( Huang & Potapov 2012) also have simple maxillary palps (but not 2 prelabral chaetae), which suggests some affinity to Ephemerotoma gen. nov. The species of the 'christianseni' group bear an even closer resemblance to the new genus, sharing its large and polychaetotic Abd.V ( Huang & Potapov 2012). So far, the sexual dimorphism has not been found in 'christianseni' group species, contrary to Ephemerotoma gen. nov.

In the s -pattern of the body the new genus has the basic set of macro- and microsens (33/22224(s), 11/111(ms )) in all members. The s-chaetae of Abd.V are unusual: they form a 2 anterior + 2 posterior pattern, with the two anterior sens always longer and thicker than the two posterior ones. Such an arrangement is uncommon in the Proisotoma complex, in which all sens are usually arranged in one transverse row. This common "one transverse row" pattern exists in all taxa related to Ephemerotoma gen. nov. mentioned above ( Subisotoma , Scutisotoma 'christianseni' and 'subarctica' groups). The second unusual character of the new genus is the presence of only 4 e - guards at papilla E (3 e -guards are lost). Such strong reduction is very uncommon in related forms. For example, most species of Scutisotoma have a complete set consisting of 7 e -guards; Scutisotoma 'christianseni' group, 7; Scutisotoma 'subarctica' group, 6; Proisotoma s.str., 5; Subisotoma 'pusilla' group, 6; Subisotoma 'asiatica' group, 4 – 5. In the last taxon, Subisotoma cruda Potapov, Babenko, Fjellberg & Greenslade, 2009 has 4 e -guards but differs from Ephemerotoma gen. nov. in many significant characters.

Sexual dimorphism. Sexual dimorphism was described from adult individuals of two species of the new genus, E. porcella ( Ellis 1976) and E. huadongensis ( Chen 1985) . Ephemerotoma skarzynskii sp. nov. may also have well pronounced dimorphism, but reproductive males have not yet been found. Sexual dimorphism in E. multituberculata is also possible but more material is needed to make reliable conclusions (only one juvenile male seen by us). We suggest that sexual dimorphism is an obvious tendency in this new genus and reflects the unusual swarming ecology of its species, which has been also recorded in other genera of Proisotoma complex ( Chimitova & Potapov 2011).

Modification of tegument and remarks about Proctostephanus . Three members of Ephemerotoma gen. nov. have a modified dorsum of Abd.V, which seems to be a specific characteristic ( skarzynskii , porcella and multituberculata ), rather than being linked to ecomorphosis. In two species ( porcella and multituberculata ) rugosity is formed by a local group of elongated or roundish humps at the posterior edge of the segment ( Figs 40, 41 ). This group of humps resembles the corona-like wart of Proctostephanus Börner ( Figs 37, 38 ), but is less compact, regular and protruded. Proctostephanus is distributed mostly in the Mediterranean region and consists of six known species. Three species, P. stuckeni Börner (type species), P. sanctiaugustini Cassagnau and P. da l i i Arbea, are similar to Ephemerotoma in that their corona-like wart on Abd.V is not constricted at its base and consists of many irregular protuberances over its entire surface ( Figs 37 vs. 38). The detailed morphology of Proctostephanus is poorly known; Fjellberg (1999) indicated 4 e -guards in P. stuckeni , while Arbea (2003) found a simple maxillary palp in P. d al i i. Both these characters are shared with Ephemerotoma . For P. da l i i the "2 anterior + 2 posterior" s -pattern on Abd. V was identical to that of Ephemerotoma . We also studied P. c i d i ( France: Tarn: Larroque) and P. sanctiaugustini ( Algeria: Skikda: Collo massif, Hamra Kroua leg.); both species show the same s - pattern (33/22224(s), 11/111(ms), "2 + 2" s -pattern on Abd. V ( Figs 35, 36 ), simple maxillary palp, 2 prelabral chaetae, and only 4 e -guards.

The gap between Proctostephanus and Ephemerotoma becomes even narrower with the recently described Proisotoma anopolitana Schulz & Lymberakis, 2006 (Mediterranean: Crete). Provisionally, P. anopolitana was considered as an odd member of Proisotoma sensu lato but the simple maxillary palp, 2 prelabral chaetae, 4 e - labial guards, and s -pattern ( Fig. 32 ) all indicate either Ephemerotoma or Proctostephanus . We have transferred P. anopolitana to the latter genus due to the compact dorsal wart on Abd. V ( Figs 32 , 39 ). The taxonomic border between Proctostephanus and Ephemerotoma calls for further study.

Members of the genus. We place four species in Ephemerotoma gen. nov.: E. skarzynskii sp. nov. ( Iran), E. huadongensis comb. nov. ( China), E. multituberculata comb. nov. ( Tajikistan), and E. porcella comb. nov. (Mediterranean). Proisotoma papillosa Stach ( Bulgaria) is a possible member but the morphology is not well known.

Distribution and ecology. The genus is distributed in the Mediterranean and southern Asia. Species of Ephemerotoma are often recorded in remarkable mass aggregations that have been observed for all four species: E. skarzynskii (see below), E. porcella ( Ellis 1976) , E. multituberculata ( Martynova 1967) and E. huadongensis (see below).

Name derivation. The new genus is named after an ecological peculiarity—their occurrence in mass aggregations followed by a rapid disappearance.

Figures

FIGURES 1 – 10. Ephemerotoma skarzynskii sp. nov.: 1, chaetotaxy; 2, outer maxillary lobe; 3, antennal organ of Ant. 3; 4, labium; 5 – 7, sens of Ant. 1 in females (5) and two males (6,7); 8, furca, lateral view; 9, dens, anterior view; 10, distal part of leg 3. ls—lateral sens, is—inner sens, gs—guard sens.

FIGURES 29 – 33. Ephemerotoma multituberculata (29 – 31) and Proctostephanus anopolitanus (32 – 33): 29, 30, Abd. V, chaetotaxy (29) (granulation not shown) and granulation (30); 31, labrum; 32, Abd. V; 33, dens, posterior view.

FIGURES 11 – 14. Ephemerotoma skarzynskii sp. nov.: 11, 12, Furca, posterior (11) and anterior (12) view; 13, profile of Abd. V and VI; 14, chaetotaxy of Abd. V and VI.

FIGURES 20 – 21. Reproductive male of Ephemerotoma huadongensis: 20, Abd. IV – VI; 21, head and antennae, lateral view. msp—male spurs.

FIGURES 34 – 41. Posterior part of abdomen in genera Ephemerotoma and Proctostephanus: 34, E. porcella, Abd. V; 35, P. cidi, Abd. V, dorsal view, only sens shown; 36, posterior part of abdomen of P. sanctiaugustini, lateral view; 37 – 41, modification of posterior part of abdomen in Proctostephanus (37 – 39) and Ephemerotoma (40 – 41): P. c i di (37), P. stuckeni (38), P. anopolitanus (39), E. multituberculata (40), E. skarzynskii sp. nov. (41).