Centroptilum nana Bogoescu 1951

Kluge, Nikita J., 2025, Contribution to the knowledge of psammophylous representatives of Procloeon Bengtsson 1915 - Psammonella Glazaczow 1987 and Pseudocentroptiloides Jacob 1987 (Ephemeroptera: Baetidae), Zootaxa 5691 (3), pp. 449-494 : 488-491

Status of the species name Centroptilum nana Bogoescu 1951

The species under the name « Centroptilum nana » was described by Bogoescu (1951) based on male and female imagines collected in Ţugureşti ( Dolj) near bank of Jiului in Romania. A list of specimens examined was not given, holotype was not designated, and place of material deposition was not reported. The type specimens are probably lost (Glazaczow & Klonowska-Olejnik 2009: 150). Assumption that the male and the female belong to one and the same species, was based on nothing.

Species name. Judging by the fact that earlier this author introduced the binomen Centroptilum romanicum Bogoescu 1949 with the species name « romanicum » as adjective neutral with ending «- um », the species name « nana » is not an adjective, but a noun with non-changeable ending. In spite of this, some authors adopted it as adjective neutral—either as « Centroptilum nanum » ( Keffermüller 1967) , or « Cloeoptilum nanum » ( Kazlauskas 1972), or « Procloeon nanum » ( Jacob 1991) , or « Pseudocentroptilum nanum » ( Kovacs et al. 1998) .

Identity of male imago. Figure of male genitalia ( Bogoescu 1951: fig. 2) suggests that the male imago originally described as Centroptilum nana , is conspecific either with Procloeon ( Pseudocentroptiloides) shadini , or with Procloeon macronyx . Male imagines of these two species have no reliable difference in structure of genitalia and hind wings ( Kluge & Novikova 1992: figs 1, 2, 5, 11, 12, 14; Glazaczow & Klonowska-Olejnik 2009: figs 29– 30, 36–37), but can be distinguished by coloration of abdomen. In the both male imaginal individuals of P. shadini reared by me from larvae collected in the river Neris in Lithuania, coloration of abdominal terga is differentiated as the following: terga II– III and V – VI have red-brown markings, which are absent on tergum IV ( Figs 207–208 ; Kluge & Novikova 1992: fig. 13 and p. 80). Among three male individuals reared by Keffermüller from larvae collected in river Warta in Poland, one individual has the same differentiation of abdominal terga: «po bokach, wzdłuż tylnej krawędzi oraz w środku segmentów (zwłaszcza II, III, V i VI) rdzawy nalot, wyraźny tylko u jednego z okazów» ( Keffermüller 1967: 18). In contrast to this, all 15 male imagines of P. macronyx reared by me from larvae collected in the river Neris in Lithuania, had uniform red-brown markings on abdominal terga II– VI; tergum IV is not lighter than others, but, vice verse, with a pair of darker lateral markings ( Fig. 211 ; Kluge & Novikova 1992: fig. 3 and p. 77). All 15 male imagines of P. macronyx reared by me from larvae collected in the river Chu in Kazakhstan, also had uniform markings on abdominal terga II– VI, but less extensive than in the specimens from Lithuania ( Fig. 210 ). After preservation in alcohol since 1986 and 1988 till 2025, these specimens lost their red-brown markings of abdominal terga; the coloration is preserved in the specimens mounted on slides in Canadian balsam.

According to the original description of Centroptilum nana , «Abdomenul are tergitele 1, 2, 7 si 8 pigmentate mult in brun inchis, tergitele 3–6 colorate foarte slab, iar 9 si 10 de coloare galben-brun» (The abdomen has tergites 1, 2, 7 and 8 highly pigmented in dark brown, tergites 3–6 very weakly colored, and 9 and 10 yellow-brown) ( Bogoescu 1951: 2). In Baetidae , the first abdominal tergum of male imago is mostly substituted by metanotum, so terga «1, 2» could be confused with terga II and III. We ( Kluge & Novikova 1992) synonymized P. shadini with P. nana based on this assumption and on the fact that abdominal terga have differentiated color pattern in P. shadini and uniform color pattern in P. maronyx .

Identity of female imago. Eggs extracted from female imago of Centroptilum nana , were characterized as «Oul arc corionul înconjurat de un brâu reticulat ingrosat, alcătuit din 7 rânduri» (The egg chorion is surrounded by a thickened reticulate girdle, made up of 7 rows), and illustrated by a drawing ( Bogoescu 1951: 3, fig. 4). According to this drawing, the egg is ellipsoid («spindle-shape» according to Glazaczow & Klonowska-Olejnik 2009), i.e. gradually narrowing toward poles, and its girdle consists of cells projected above other cells of the egg surface. In another publication by this author, optic section of egg chorion is shown ( Bogoescu 1958: fig. 77C), which demonstrates that inner margin of the girdle is straight, and its outer margin is convex. Such egg structure occurs in P. shadini ( Figs 215–216 ).

In contrast to this, egg of P. macronyx ( Figs 218–219 ) has hemispheric polar areas («oval shaped» according to Glazaczow & Klonowska-Olejnik 2009) and a concave equatorial area, with a girdle inserted into this concavity; papillae of the girdle are terminated not by concavities, but by convexities, so they do not form cells of a reticulum, but form hemispheric projections located in the same plane as the cells of other egg surface ( Fig. 217 ). In optic section, inner margin of the girdle is concave, and its outer margin is straight ( Fig. 219 ).

Number of rows forming the girdle is reported and figured as 7 for Centroptilum nana . Eggs of P. macronyx examined by me have 5–11 rows, and eggs of P. shadini examined by me have 11–15 rows. Based on the rows number only, Glazaczow & Klonowska-Olejnik (2009), concluded that Centroptilum nana is conspecific with P. macronyx . Concerning other features of the egg structure, they wrote: «It is difficult to state exactly what was seen by Bogoescu through the microscopes from the middle of the last century». However, it is clear that Bogoescu used translucent light microscopy and saw optic sections of eggs, as well as surfaces of eggs, and draw a combination of these views, as in the photos on my Figs 216 and 219 . Judging by his figures and descriptions, at that time he did not see eggs of P. macronyx , and the female described by him as Centroptilum nana is not conspecific with P. macronyx .

In another publication ( Bogoescu & Tabacaru 1966), Centroptilum nana was included in a key for female imagines, and its egg was characterized as «Die Äquatorialzone des Chorions mit 5–7 Warzenreihen» (the equatorial zone of chorion with 5–7 rows of warts). This wordily characteristics agrees with P. macronyx , but figure was not given, and material examined was not reported.

Figures

FIGURES 207–212. Imaginal abdomen. 207–209, Procloeon (Pseudocentroptiloides) shadini from Lithuania (207–208, males; 209, female); 210–212, Procloeon macronyx (210, male from Kazakhstan; 211, male from Lithuania; 212, female from Lithuania).

FIGURES 213–216. Eggs of Procloeon (Pseudocentroptiloides) shadini. 213–215, under scan electronic microscope (213–214, fragments of destroyed girdle); 216, in transmitted light, slide in Canadian balsam (optic section and surface view combined).

FIGURES 217–219. Eggs of Procloeon macronyx. 217–218, under scan electronic microscope (217, fragments of destroyed girdle); 219, in transmitted light, slide in lactic acid (optic section and surface view combined).