Demoulinia, Gillies, 1990

Kluge, Nikita J., 2020, Demoulinia Gillies 1990 and two unnamed genera of the plesiomorphon Protopatellata (Ephemeroptera, Baetidae) from South Africa, Zootaxa 4820 (3), pp. 438-464 : 439-441

Autapomorphies of Demoulinia .

(1) In male imago, the terminal (3rd) segment of gonostylus has unique structure: it is hooked and pointed; cuticle of its outer side (directed caudally) is thick, rigid, smooth and sharply convex, while cuticle of its other sides is thin and rugose ( Figs 60–61 ). In subimago, the terminal segment of gonostylus is also pointed, with larger outer side and smaller inner side ( Fig. 66 ), but its subimaginal cuticle is entirely thin and covered with microtrichia, as are other gonostylar segments and most of other body parts. This shape of the terminal gonostylar segment is already expressed in subimaginal gonostyli which are crumpled under larval cuticle before moult to subimago ( Figs 57–58 , 65 ).

Male imagines are known for D. crassi only. Conclusion that another species, D. insularis (= D. assimilis ) has the same structure of the terminal gonostylar segment, is based on the fact that the same shape occurs in subimaginal gonostyli located under larval cuticle of a paratype of D. assimilis ( Fig. 57 ). Among the type specimens of D. assimilis , only one male larva is mature enough to examine this character (Gattolliat, personal communication); the description of D. insularis was based on the single female larva (see below); no other specimens of D. insularis (= D. assimilis ) are known.

(2) Larva has unique shape of labial palp (which retains all 3 segments and muscle moving 3rd segment): its 2nd segment bears a large distal-medial projection of nearly quadrate form; more distal angle of this projection is rounded, and more proximal angle bears a small sclerotized point; distal margin of the projection of 2nd palpomere and apex of 3rd palpomere bear heavy spine-like setae ( Figs 29, 31 ; Wuillot & Gillies 1993: fig. 21; Gattolliat 2003: fig. 6). Shape and setation of other parts of labium are also unusual [see (9)].

(3) Tibiae of all larval legs lack patella-tibial suture. Row of long hairs on outer-anterior side (at the place corresponding to the outer-proximal end of the patella-tibial suture, had it been present) is stretched along tibia and curved S-shaped ( Fig. 34 ).

Unlike larvae, subimago and imago of both sexes have patella-tibial suture on middle and hind legs, but not on fore leg ( Figs 69–70 ). Absence of this suture on fore legs of female subimago and imago testifies that Demoulinia belongs to the plesiomorphon Protopatellata Kluge & Novikova 2011, while the larval structure is derived. Among Baetidae , the patella-tibial suture is smoothed out or lost in some taxa whose larvae have strengthened legs and are adapted for inhabiting rapidly flowing streams, such as Centroptiloides Lestage 1918 and Dicentroptilum Wuillot & Gillies 1994 among Protopatellata or Moribaetis Waltz & McCafferty 1985 among Anteropatellata ( Kluge & Bernal Vega 2018: figs 25–27). The complete loss of patella-tibial suture on slender legs of the « Cloeon »- type » [see (4)] is a unique feature of Demoulinia , not found in other Baetidae .

Other characters of Demoulinia .

(4) Larva of the « Cloeon - type », adapted for inhabiting stagnant water ( Fig. 1 ): abdomen is relatively long, cerci and paracercus are subequal, with dense and long primary swimming setae ( Figs 41–42 ) (that is the siphlonuroid swimming specialization initial for Ephemeroptera ); legs are long and slender, with slender femora [see (11)] and long claws [see (13)]; tergalii are large and adopted for effective respiratory movements [see (14)].

(5) Labrum with long setae irregularly scattered on outer surface, i.e. without constant submedian pair and without pair of regular submarginal setal rows ( Figs 7–11 ). This is also seen in some other baetid taxa.

Within one population of D. crassi , some individuals have long setae more or less evenly scattered over whole outer surface ( Fig. 11 ), in some others long setae form a pair of irregular rows parallel to distal margin ( Fig. 9 ). The same variability occurs in D. insularis (= D. assimilis ) (see discussion below).

(6) Mandibles of the « Centroptilum - type ». In most Baetidae the kinetodontium is fused with the incisor; in this case the left prostheca is wide, terminated with 3–6 blunt denticles and 2–4 pointed denticles; all denticles of incisor, kinetodontium, prostheca and mola are visible in one view ( Kluge 2004: fig. 29B); this structure of mandibles can be termed « Baetis - type ». In some non-related taxa, mandibles have a modified structure, which can be termed « Centroptilum - type »: kinetodontium is separated from incisor (but remains to be immovable) and rotated perpendicular to the plane of mandible, so that its denticles hide one another in dorsal or ventral view; left prostheca is bifurcate and rotated in the same manner ( Figs 14–15 ). This « Centroptilum - type » of mandibles occurs in the unrelated taxa Demoulinia , Centroptilum , Anafroptilum Kluge 2012a ( Kluge & Novikova 2017: figs 13–14, 38–39), Pseudocentroptiloides Jacob (in Jacob & Glazaczow) 1987 , Securiops Jacobus et al. 2006 , Monilistylus Kluge 2020 ( Kluge 2020a: figs 18–25), Callibaetis Eaton 1881 , Paracloeodes Day 1955 , Apobaetis Day 1955 , Waltzoyphius Lugo-Ortiz & McCafferty 1995 and some other taxa (e.g., see Protopatellata gen. sp. 1 below); among them, Securiops , Pseudocentroptiloides and Monilistylus belong to the holophyletic taxon Procloeon /g1 within Cloeon /fg1 ( Kluge 2020a), while Paracloeodes , Apobaetis , Callibaetis and Waltzoyphius belong to the holophyletic taxon Baetovectata ( Kluge & Novikova 2011). Most other representatives of Cloeon /fg1 and Baetovectata have mandibles of the « Baetis - type », that testifies to multiple independent transformations of mandibles from the « Baetis - type » to the « Centroptilum - type ».

(7) Maxilla with a regular row of long setae on apico-ventral side just laterad of canines ( Fig. 21 ; Gattolliat 2003: fig. 5). All three maxillary canines and all three dentisetae are long, slender and bent in one direction (the « Cloeon - type » of maxilla).

(8) Maxillary palp is 3-segmented, with 3rd segment short and separated from 2nd segment by integral ring groove ( Fig. 21 ). In most other mayflies maxillary palp varies between 3-segmented and 2-segmented, often with 2nd and 3rd segments incompletely separated; 3rd segment never has muscle attached to its base.

In the original descriptions of D. crassi and D. insularis the maxillary palp was described and figured as 2segmented ( Crass 1947: 88, fig. 27e; Lugo-Ortiz & McCafferty 1998: 360, fig. 15). However, in the specimens of D. crassi examined from South Africa, the maxillary palp is 3-segmented ( Fig. 21 ). The holotype of D. insularis has one maxillary palp broken off, and another one clearly 3-segmented ( Fig. 24 ). In the original description of D. assimilis the maxillary palp was correctly described and figured as 3-segmented ( Gattolliat 2003: 4, fig. 5).

(9) Labium has unusual structure of glossae and paraglossae ( Figs 26, 28, 30 ; Gattolliat 2003: fig. 7). Glossa is widened, wider than paraglossa, semicircular; two glossae are closely contiguous medially; spine-like setae of median row are few and shifted on dorsal side of glossa. Ventral side of glossa is entirely covered with numerous irregularly situated long hair-like setae. Dorsal side of glossa, in addition to setae of median row and a regular dorsolateral row, has irregularly situated setae in distal half. Paraglossa with concavity on median side, which allows overlap with glossa not only laterally, but partly ventrally; setae of latero-apical and ventro-median longitudinal rows are long and situated irregularly, not forming regular rows; only dorso-median row is regular. Labial palp has peculiar structure [see (2)].

(10) Hind wings are absent. Larval metanotum without vestiges of hind protoptera. Hind wings are lost in many other Baetidae ; among Protopatellata, these are Potamocloeon , Indocloeon , part of Anafroptilum , part of Rhithrocloeoninae and Protopatellata gen. sp. 1 described below.

(11) Femora of larval legs are slender, parallel-sided; spine-like setae are pointed, irregularly situated and equally small on outer and inner sides of femur ( Fig. 32 ). As in most other Baetidae , two stout apical setae are present ( Fig. 34 ) (on individual legs number of stout apical setae is 3 or 1).

(12) Larval tibiae of all legs without outer-apical stout seta (in contrast to many other Baetidae ). Tibia [lacking patella-tibial suture – see (3)] with small pointed spine-like setae on outer side and longer spine-like setae on inner side ( Fig. 32 ).

(13) Larval claw is long and slender, with 2 rows of small denticles on proximal part ( Figs 35–38 ). For D. crassi fine pectination of claw was reported and figured in the original description ( Crass 1947: 88, fig. 27c). The claws of D. insularis and D. assimilis were originally described and figured as edentate ( Lugo-Ortiz & McCafferty 1998: 360, fig. 17; Gattolliat 2003: 4, fig. 9). Actually, the holotype of D. insularis has very small denticles on claws ( Fig. 38 ). The same is true for the paratypes of D. assimilis (Gattolliat, personal communication).

(14) Tergalii of all pairs I–VII are wide, with anal rib poorly developed or absent ( Figs 5 , 45–51 ). Tergalii are capable of for rhythmical respiratory movements, that allows larva to inhabit places with stagnant water (observed for D. crassi ).

Species composition of Demoulinia . Two species: Demoulinia crassi (Demoulin 1971) distributed in South Africa and Demoulinia insularis Lugo-Ortiz & McCafferty 1998 (= Demoulinia assimilis Gattolliat 2003 syn. n.) distributed in Madagascar. Synonymy of D. insularis and D. assimilis is argued below. Larvae of D. crassi and D. insularis can be distinguished by paraproct structure ( Figs 43 and 44 ) and by denticles on claws, which are distinct in D. crassi ( Figs 35–37 ) and poorly expressed or absent in D. insularis ( Fig. 38 ). Imagines and eggs are known for D. crassi only.

Figures

FIGURES 57–61. Male genitalia of Demoulinia spp. 57, D. insularis (paratype of D. assimilis), subimaginal gonostyli under larval cuticle. 58–61, D. crassi: 58, subimaginal gonostyli extracted from larva; 59, imaginal genitalia; 60–61, apex of imaginal gonostylus.

FIGURES 62–66. Male genitalia of Demoulinia crassi. 62, penis, ventral view (left muscles not shown); 63, genitalia, ventral view (penis dotted; left gonovectal muscle and right styligeral muscle not shown); 64, penis (dotted), posterior view (left muscle not shown); 65, subimaginal gonostyli crumpled under larval cuticle; 66, exuviae subimaginal of gonostyli (gd, gonoduct; gs1, gs2, gs3, segments of gonostylus; m.gv, gonovectal-sternal muscle; m.g-t, gonovectal-tergal muscle; m.pp, paces of attachment of muscles going to paraprocts; m.sg, sterno-styligeral muscle; usg, unistyliger).

FIGURES 26–31. Labium of Demoulinia crassi. 26, cross section of glossae and paraglossae; 27, labium and maxilla; 28–31, exuviae of glossae, paraglossae and labial palp: 28–29, with focus on ventral side; 30–31, with focus on dorsal side (gl:dl, dorsolateral row of stout setae on glossa; gl:m, median row of stout setae on glossa; gl:vm, setae corresponding to ventro-median row of glossa; pg:dm, dorso-median row of long setae on paraglossa; pg:la, latero-apical long setae of paraglossa; pg:vm, long setae corresponding to ventro-median row of paraglossa).

FIGURES 32–38. Larval legs of Demoulinia spp. 32–37, D. crassi: 32, exuviae of hind leg; 33, inner side of fore tarsus; 34, femoral-tibial of hind leg, focus on anterior side; 35–37, claws. 38, D. insularis (holotype), fragment of claw with subimaginal claws inside (arrow shows row of vestigial denticles on inner side).

FIGURES 67–70. Females of Demoulinia crassi. 67–68, female imago; 69–70, subimaginal exuviae of tibia and tarsus: 69, middle leg; 70, fore leg.

FIGURES 1–5. Larva of Demoulinia crassi. 1, Female larva of last instar; 2–3, exuviae of male larvae: 2, left half of prothorax and mesothorax; 3, abdomen; 4, abdomen of male subimago extracted from mature larva (to show hypodermal larval coloration); 5, tergalius III.

FIGURES 39–44. Exuviae of larval abdomen of Demoulinia spp. 39–43, D. crassi: 39, lateral and posterior area of abdominal tergum VII; 40, anterior-lateral area of abdominal sternum VI; 41, caudalii; 42, fragment of cercus; 43, paraproct. 44, D. insularis (holotype), median margin of paraproct (scale bar refers to Figs 39, 40, 42, 43).

FIGURES 6–12. Labrum of Demoulinia spp., dorsal view. 6–7, D. insularis (holotype). 8–12, D. crassi.

FIGURES 13–20. Mandibles of Demoulinia crassi. 13, 16, 19, left mandible; 14, 17, 20, right mandible; 15, apex of right mandible, proximal view (inc, incisor; kd, kinetodontium; prs, prostheca).

FIGURES 21–25. Demoulinia spp. 21–23, D. crassi; 24–25, D. insularis (holotype); 21, 22, 24, maxilla (21, with focus on ventral side; 22, with focus on dorsal side; d1, d2, d3, dentisetae; p1, p2, p3, segments of maxillary palp); 23, 25, hypopharynx and superlingua.

FIGURES 45–51. Demoulinia crassi, tergalii I–VII.