Procloeon (Oculogaster), Kluge, Nikita J., 2016

Kluge, Nikita J., 2016, A new subgenus Oculogaster subgen. n. for viviparous representatives of Procloeon s. l., with discussion about status of the generic name Austrocloeon Barnard 1932 and the species name africanum Esben-Petersen 1913 [Cloeon] (Ephemeroptera, Baetidae), Zootaxa 4107 (4), pp. 491-516 : 494-495

Subgenus Oculogaster subgen. n.

( Figs 1–79 )

Hierarchical name: Oculogaster /g(1)

= Austrocloeon /g(1): Kluge 2011: 362

Type species: Procloeon cylindroculum Kimmins 1956 .

Etymology. From oculus (Latin), eye, and γαστηρ (Greek) or gastrum (Latin), abdomen. The name refers to many black eyes and ocelli of embryos visible through integument of female imago inside its abdomen and other body parts ( Figs 38, 39, 41 , 76–79 ).

Diagnosis.

(1) Viviparous. Mature female imago is filled with embryos at such stage of development, when eyes and ocelli represent 5 black spots and mandibles have well sclerotized biting projections (incisor, kinetodontium and mola) ( Figs 38, 39, 42 ). These embryos are not covered with rigid egg chorion, so that their black eyes and ocelli are well visible through the mother's integument ( Figs 41 , 76–79 ). In mature female larvae, in female subimagoes and in young female imago reared in cage, eggs are small and soft, without embryos; probably, embryos are developed only in fertilized females. Among Ephemeroptera , besides Oculogaster, viviparity is known only for Cloeon s.str. and Callibaetis .

(2) Pterostigma with one vein only; this vein is always well-expressed, complete, oblique and non-branched ( Figs 32 , 67 ). Among more than 300 specimens examined, only 4 aberrant specimens of P. ( O.) cylindroculum were found: 2 male imagoes from Uganda and 2 female imagoes from Mali have 2 or 1½ veins in pterostigma of one wing and one vein in pterostigma of another wing. In all other mayfly taxa number of veins in pterostigma is more than one and varies individually.

(3) Larvae of both known species constantly have two or more enlarged spine-like setae on apex of femur ( Figs 20 , 56 ). In most other examined larvae of Procloeon s. l., apex of femur either lacks setae, or bears occasional seta(e) as small as setae on outer side of femur.

Distribution. Afrotropical and Oriental Regions.

Composition. Two species, P. ( O.) cylindroculum Kimmins 1956 and P. ( O.) album sp.n. Possibly, here belongs also the species described as Cloeon julia Gillies 1949 ; it is known as a single female imago from Malaya Peninsula; according to the original description, it has one vein in pterostigma and "might be placed in the genus Procloeon " ( Gillies 1949: 176).

Status of the name Austrocloeon . One of the species included to the subgenus Oculogaster, namely P. ( O.) cylindroculum , probably is conspecific with the species erroneously determined by Barnard (1932) as Cloeon africanum Esben-Petersen 1913 [see discussion under P. ( O.) cylindroculum ], which was designated as the type species of the generic name Austrocloeon Barnard 1932 .

Barnard (1932) established the genus Austrocloeon to comprise two species, Austrocloeon africanum (Esben- Petersen 1913) and Austrocloeon virgiliae Barnard 1932 . Subsequently Barnard (1940) designated A. africanum as the type species of Austrocloeon . The genus Austrocloeon was originally characterized as combining characters ascribed to the genera Cloeon and to Procloeon : (1) labial palp apically clavate (as in Procloeon , in contrast to Cloeon ), (2) maxillary palp 2-jointed (as in Procloeon , in contrast to Cloeon ), (3) tergalii with dorsal lamella (as in Cloeon , in contrast to Procloeon ). This comparison was based on the Bengtsson's (1914) diagnosis of the genus Procloeon (under the preoccupied name “ Pseudocloeon ”), which was based on a single species Procloeon bifidum ( Bengtsson 1912) . Actually, these characters are species-specific or even individual ones: among African species of Cloeon s.str., last segment of labial palp varies from narrow (i.g., in Cloeon perkinsi Barnard 1932 ) to wide (e.g., in Cloeon smaeleni Lestage1924b ) ( Gillies 1980 and my own observation); number of segments of maxillary palp can vary even individually (e.g., Kluge & Novikova 1992: Fig. 9 : 20–22); presence/absence of the additional dorsal lamella on tergalii varies among species of Procloeon and individually ( Kluge & Novikova 1992). The species virgiliae [ Austrocloeon ] belongs to Cloeon s. str. ( Gillies 1985), and the species determined by Barnard as africanum [ Cloeon ], belongs to Procloeon ( Kimmins 1956, Gillies 1997). Recently the generic name Austrocloeon is out of use, being either declared to be a junior subjective synonym of Cloeon ( Demoulin 1970) , or treated as a junior subjective synonym of Procloeon (e.g., Kimmins 1956, Gillies 1997). The question is, to which taxon in the new classification should be applied the genus-group name Austrocloeon .

As shown below, the species identified by Barnard (1932) as C. africanum , is not conspecific with the holotype of this species name, so the original description of Austrocloeon was based on misidentified type species. According to the Article 70.3 of the International Code of Zoological Nomenclature, “If an author discovers that a type species was misidentified ... the author may select, and thereby fix as type species, the species that will, in his or her judgment, best serve stability and universality, either (70.3.1.) the nominal species previously cited as type species [Arts. 68, 69], or (70.3.2.) the taxonomic species actually involved in the misidentification”. I regard that in this case fixation of the nominal species is preferable, because the taxon originally described under the generic name Austrocloeon had neither characters, nor formal composition common with the taxon recently proposed for P. ( O.) cylindroculum and P. ( O.) album . Thus, the type species of Austrocloeon Barnard 1932 is the species, to which belongs the holotype of Cloeon africanum Esben-Petersen 1913 , but not the species described by Barnard (1932) under this name. According to this type designation, Austrocloeon is not the senior synonym of Oculogaster subgen. n.

Figures

FIGURES 1 – 10. Procloeon (Oculogaster) cylindroculum, larva. 1 – 7, tergalii of I – VII pairs (specimen from Uganda); 8, 9, apices of left and right mandibles, dorsal view; 10, apex of right mandible, apical view. Abbreviations: in 1, in 2, in 3, in 4, denticles of incisor; in-V, ventral denticle of incisor; kd 1, kd 2, kd 3, denticles of kinetodontium.

FIGURES 11 – 20. Procloeon (Oculogaster) cylindroculum, larva. 11 – 17, tergalii of I – VII pairs (specimen from Zambia); 18, frontal suture; 19, claw; 20, fore leg, anterior view (fine setae not shown; dots show bases of fine setae forming regular rows on apical part of femur, proximal part of tibia and proximal part of tarsus).

FIGURES 21 – 29. Procloeon (Oculogaster) cylindroculum, larvae from Zambia. 21, cercus and paracercus; 22, distal part of cercus; 23 – 25, abdominal terga and sterna; 26, right half of pronotum and mesonotum; 27, subimaginal exuviae of right half of mesonotum; 28, maxilla; 29, labrum.

FIGURES 30 – 32. Procloeon (Oculogaster) cylindroculum from Zambia. 30, genitals of male imago (at left half gonovectal muscles shown by interrupted lines, hidden part of penis shown by interrupted line and dotted, gonostylar muscle not shown; at right half gonostylar muscle shown by interrupted lines, gonovectal muscles not shown; median styligeral muscle shown by interrupted lines, areas of anterior attachment of median paraproctal muscles shown by dotted lines). 31, exuviae of subimaginal genitals; 32, wing. Abbreviations: 1, 2, 3, segments of gonostylus; mIX-X, areas of anterior attachment of median paraproctal muscles (i. e., muscles going from sternum IX to common base of paraprocts); usg, unistyliger.

FIGURES 33 – 37. Procloeon (Oculogaster) cylindroculum. 33, 34, male imagoes; 35, subimaginal abdomen extracted from mature male larva; 36, subimaginal abdomen extracted from mature female larva; 37, subimaginal exuviae of postsubalar sclerite and lateropostnotal crest (33, 35 – 37, specimens from Zambia; 34, specimen from Uganda).

FIGURES 38 – 42. Procloeon (Oculogaster) cylindroculum, female imago. 38, head and prothorax in Canadian balsam with embryos visible inside; 39, enlarged embryo with focus on median ocellus and mandibles; 40, mature female imago free of embryos; 41, abdomen of female imago with embryos (black eyes and ocelli visible through integument); 42, embryo extracted from female imago (38, 39, 41, 42, from Uganda; 40, from Zambezi). Abbreviations: md, mandibles; oc, future facetted eye; ocl. l., lateral ocellus; ocl. m., median ocellus.

FIGURES 43 – 48. Procloeon (Oculogaster) album sp. n., larva. 43, labrum, 44, 45, apices of left and right mandibles; 46, maxilla, dorsal view; 47, half of labium, ventral view; 48, the same, dorsal view. Abbreviations: ds 1, ds 2, ds 3, dentisetae; in 1, in 2, in 3, in 4, denticles of incisor; in-V, ventral denticle of incisor; kd 1, kd 2, kd 3, denticles of kinetodontium.

FIGURES 49 – 58. Procloeon (Oculogaster) album sp. n., larva. 49 – 55, tergalii I – VII; 56, fore leg, anterior view (fine setae not shown; dots show bases of fine setae forming regular rows on apical part of femur, proximal part of tibia and proximal part of tarsus); 57, claw; 58, paraproct (49 – 52, 54 – 55, 58, holotype).

FIGURES 59 – 64. Procloeon (Oculogaster) album sp. n., larva. 59, paracercus and cercus (with subimaginal cercus inside); 60, distal part of cercus; 61, posterior margin of abdominal tergum X; 62, fragment of abdominal tergum III; 63, fragment of abdominal sternum VI; 64, tergalius VI (arrow shows additional middle rib) (59, 60, holotype).

FIGURES 65 – 67. Procloeon (Oculogaster) album sp. n. 65, genitals of male imago (at left half gonovectal muscles shown by interrupted lines, hidden part of penis shown by interrupted line and dotted, gonostylar muscle not shown; at right half gonostylar muscle shown by interrupted lines, gonovectal muscles not shown; median styligeral muscle shown by interrupted lines, areas of anterior attachment of median paraproctal muscles shown by dotted lines). 66, genitals of male subimago; 67, wing. Abbreviations: 1, 2, 3, segments of gonostylus; mIX-X, areas of anterior attachment of median paraproctal muscles (i. e., muscles going from sternum IX to common base of paraprocts); usg, unistyliger.

FIGURES 68 – 72. Procloeon (Oculogaster) album sp. n. 68, mature female larva (reddish paired hypodermal spots on abdominal terga IV, VII and VIII visible through cuticle); 69, subimaginal abdomen extracted from mature female larva (holotype); 70, mature male larva (reddish hypodermal markings on abdominal terga IV, VII and VIII visible through cuticle); 71, subimaginal abdomen extracted from this larva; 72, male imago.

FIGURES 73 – 75. Procloeon (Oculogaster) album sp. n., male imago. 73 – 74, the same specimen at different light; 75, head and thorax of another specimen.

FIGURES 76 – 79. Procloeon (Oculogaster) album sp. n., female imago. 76, 77, lateral and dorsal view; 78, 79, part of prothorax and part of abdomen with black eyes and ocelli of embryos visible through integument.