Caenis reissi Malzacher, 1986

Lima, Lucas R. C. & Boldrini, Rafael, 2017, New distributional records and life stage description of Caenis species (Ephemeroptera: Caenidae) from Brazil, Zootaxa 4276 (2), pp. 285-292 : 288-291

Caenis reissi Malzacher, 1986

( Fig. 6–16 )

Caenis reissi Malzacher, 1986: 95 (male and female imagos, egg); Lima & Boldrini, 2016: 4 (male imago).

Egg. Length: 102–123µm; width: 55–65µm. Coloration light yellow. Oval shaped with length 1.8–2.1 maximum width. Chorion densely punctured. Two hood-like polar caps each on an egg pole ( Fig. 6 ). Micropyle funnelshaped, narrow and long, with a small sperm guide ( Fig. 7 ).

Nymph. Length of male: body, 2.4 mm; cercus, broken. Length of female: body, 3.1–3.2 mm; cercus, 2.8 mm.

Ratios. Mouthparts: width of maxillary palp segment I 1.9 times the width of segment II; length of maxillary palp segment I 1.6 times the length of segment II; length of maxillary palp segment I 0.9 times the length of segment III. Leg: length of fore femur 2.4 its maximum width.

Coloration ( Fig. 8 ). Head: light brown; occiput and mouthparts paler, grayish markings on posterior margin of occiput; also shaded gray behind eyes. Antenna: scape, pedicel and flagellum hyaline.

Thorax. Nota light with black sutures. Pronotum shaded with black in the males, with anterolateral corners translucent, and blackish paramedian spots. Mesonotum with pair of medial blackish lines in females. Legs yellowish, with blackish banding present on subapical zones of femora, the majority of the central portion of the tibiae and tarsi. Thoracic sterna paler.

Abdomen. Terga yellowish; segments I–II shaded with gray; segments III–VIII, paler medially and with blackish marks laterally. Operculate gills translucent yellow, almost completely shaded with black and with 2–4 blackish spots in male and 6–9 in female nymphs. Abdominal sterna much paler, with only small grayish sublateral marks. Caudal filaments yellowish.

Morphology. Head: hind margin without setae. Mouthparts: lateral margins of labrum slightly rounded, with long subapical setae on dorsal surface ( Figs. 11, 11 a); mandibles with dorso-lateral row of pectinate setae; lingua of hypopharynx with fore margin almost straight ( Fig. 12 ); maxilla as in Fig. 13 .

Thorax. Pronotum with anterolateral margins rounded and directed anteriorly; lateral margins smooth. Legs: meso and –metacoxal process semicircular, weakly projected and with smooth margins ( Fig. 15 a). Fore femur with submarginal row of short and long setae ( Fig. 14 ); middle and hind femora each with long robust setae on dorsal margin ( Figs. 15–16 ); transverse rows of spatulate setae of forefemur reduced, only with six robust setae apically frayed ( Fig. 14 ). Tibiae of all legs with longitudinal row of long and slender setae, except pectinate and robust spine-like setae at apex. Fore tarsus with one marginal row of simple spine-like setae near to apex ( Fig. 14 ); middle tarsus with one marginal row of serrated setae, and hind tarsus with two rows of setae ( Figs. 15, 16 ): one simple and one serrated. Claws: tarsal claws I and II slender without denticles ( Figs. 14 a, 15b); tarsal claw III curved with 10 minute denticles ( Fig. 16 a).

Abdomen. Tergum II with small projection, wide at base and posteriorly curved. Operculate gills with submarginal ventral row of frayed, subtriangular microtrichia ( Fig. 9 ); Y-ridge complete and well developed; dorsal surface smooth with long, simple setae ( Fig. 9 ). Posterolateral projections on abdominal segments V–VIII short and pointed, not reaching the basal half of following tergum. Sternum IX with broadly rounded hind margin, laterally posteriorly with long simple setae ( Fig. 10 ).

Distribution. Brazil: States of Pará and Roraima.

Material examined. One nymhal exuvium, Brazil, Roraima State, Amajari , Rio Amajari , 3°39’51” N / 61°21’32” W, 16-18.ii.2016, Lima, L.R.C. and Boldrini, R. cols.; same data as preceding except one female imago with its respective exuvium (reared) ; same data as preceding except three nymphs, 30.iii.2016, Boldrini, R. coll. One nymph, Brazil, Roraima State, Amajari, Igarapé Pau Barú , 3°37’07” N / 61°35’44” W, 17.ii.2016, Lima, L.R.C. and Boldrini, R. cols.

Comments. The nymphal stage of Caenis reissi shares the characters of the absence of denticles on fore and median tarsal claws with the nymphs of C. elidioi Lima, Molineri, Pinheiro & Salles, 2016 , C. chamie Alba Tercedor & Mosquera, 1999 , and C. pflugfelderi Malzacher, 1990 . This species differs from C. pflugfelderi by present coxal processes small and weakly projected ( Figs. 15 b) (in C. pflugfelderi it is longer and with marginal teeth. C. reissi can be distinguished from the nymphal stages of all three species by the number and size of denticles on hind claw with about 10 minutes denticles ( Fig. 16 a) rather than about 20–30 longer and slender denticles in the others. Besides that, the middle and hind claws are strongly curved ( Figs. 15 b, 16a) instead of slender and only slightly curved in the other species. The sternum IX has the hind margin broadly rounded ( Fig. 10 ) which differs from truncate margin in C. pflugfelderi and the medially excavated margin of C. chamie .

Figures

FIGURES 4 – 7. Caenis spp., eggs. 4 - 5, C. cuniana: 4, detail of surface (c = chorion; mc = micropylar canal; pc = polar cap); 5, detail of polar cap. 6 - 7, C. reissi: 6, detail of surface (c; chorion; mc = micropylar canal; pc = polar cap); 7, detail of micropyle.

FIGURES 8 – 10. Caenis reissi, nymph. 8, dorsal view. 9, opercular gill. 10, detail of IX sternum (ventral view).

FIGURES 11 – 16. Caenis reissi, nymph. 11, labrum. 11 a, detail of anterior margin of labrum. 12, hypopharynx. 13, maxilla. 14, foreleg. 14 a, detail of foreleg. claw, 15, mid leg. 15 a, metacoxal process. 15 b, detail of mid leg claw. 16, hind leg. 16 a, detail of hind leg claw.