Paraleptophlebia moerens ( McDunnough, 1924: 94 )

Burian, Steven K., 2024, Nymphs of the Northeastern Nearctic Species of Neoleptophlebia Kluge, 1997 and Paraleptophlebia Lestage, 1917 (Ephemeroptera: Leptophlebiidae), Zootaxa 5521 (1), pp. 1-65 : 14

Paraleptophlebia moerens ( McDunnough, 1924: 94)

Leptophelebia moerens McDunnough, 1924 (original description)

Description of Nymph: Gordon 1933: 127

Nymphs of P.moerens can be recognized from other members of the northeast Paraleptophlebia that have posterolateral projections of abdominal segments VIII and IX (as in Figs. 3b–d ) by the deeply forked abdominal gills lacking long, hair-like marginal setae ( Fig. 22a ), legs uniform light brown without bands ( Figs. 23a,b ), ventral edge of femora with only a few short hair-like setae, lateral margins of abdominal sternites lacking distinct longitudinal brown bands ( Figs. 39a,b ), first segment of maxillary palp long, with apex reaching beyond outer corner of galea-lacinia and with only few setae on ventral surface ( Figs. 28a,b ), posterolateral projections on segments VIII and IX about equal in length ( Fig. 3d ), color pattern of abdominal tergites brown with large median pale spots mostly restricted to tergites VI–X ( Figs. 40a,b ) with a distinctive u-shaped spot on VII and pale lateral margins, and abdominal gills with the clear membranous portion of gill filaments tapering symmetrically to the tip of gill filaments ( Figs. 22a , 40a,b ). Most characters seem consistent on nymphs from mid-development to the final instar. Abdominal gills may appear to lack marginal setae or have a few short, widely spaced marginal setae, which are quite different from the alternate condition shown in Fig. 17 . Legs are uniform light brown except for pale areas near apex of femora ( Figs. 23a,b ), which are most distinctive on live or freshly preserved specimens. The rounded apical corner of the femur is slightly darker than the rest of the segment ( Fig. 23b ) and when this corner overlaps the basal edge of the tibia the zone of overlap can appear as a darker brown mark or diffuse band at this junction. On live specimens, pale areas near the apices of femora punctuate the overall uniform color of legs almost appearing as pale bands on these segments, but after preservation this distinctive condition rapidly fades. The ventral edge of the femora has only a few short, hair-like setae that are dispersed along the edge, with most occurring close to the base of the edge ( Fig. 25c ). Segment 1 of the maxillary palp is long with its tip well above the outer corner of the galea-lacinia reaching to about the halfway point of the longest crown setae ( Fig. 28a,b ). The ventral surface of segment 1 with only a few scattered hair-like setae and one or two small spine-like setae ( Fig. 28b ). The color pattern of abdominal tergites is distinctive and similar between male and female nymphs, especially regarding the u-shaped spot on tergite VII ( Figs. 40a,b ), but there are some differences. On male nymphs tergites I–VI are mostly brown with small paired medial pale spots and almost no evidence of a pale median streak ( Fig. 40a ). All tergites have pale lateral margins and dark brown (almost black) marks adjacent to their posterolateral corners, on gill bearing segments these occur above the gill insertions. The most distinctive pale spots occur on tergites VII–X ( Fig. 40a ). On tergite VII paired pale longitudinal spots merge along the posterior margin producing a pale u-shaped pattern and laterally dark brown extends longitudinally spanning from dark mark on the posterior margin almost to the anterior margin. On tergite VIII smaller paired pale spots meet only the anterior margin where they appear to join the base of the u-shaped spot on tergite VII, and lateral dark brown bands are well developed spanning the length of the tergite. The pattern on tergites IX and X are smaller versions of the pattern that occurs on tergite VIII. On female nymphs tergites I–VI may or may not have small pale paired medial spots and usually have some evidence of a pale medial streak that is usually flanked with dark brown ( Fig. 40b ). All tergites have more extensive pale margins and usually a portion of each pale marginal spot extends into the brown medial area of tergites. Dark brown (almost black) marks occur adjacent to their posterolateral corners of all tergites and on gill bearing segments marks these occur above the gill insertions. The dark lateral marks on tergites VII–X often don’t become longitudinal dark bands as described for male nymphs. Large pale spots on tergites VII–X are like those described for male nymphs, but additional rectangular pale spots occur medially on the posterior margins of tergites V and VI at the base of the faint pale median streak. The pronotum has two pale spots laterally that are distinctive on live or recently preserved specimens ( Fig. 41 ), but can fade after long term preservation. In addition, two to three small spine-like setae occur at the anterior corners of the pronotum. This character may be useful in separating early instar nymphs from those of P. praepedita , which seem to have several large spine-like setae on the anterior corners of the pronotum.

Paraleptophlebia moerens has been sporadically recorded across the northeast Nearctic region with records in 7 of the 14 states and provinces ( Table 2). It has yet to be recorded from NB, NL-I, NL-Lab, NH, RI, VT, and PE. The occurrence of P. moerens in areas which border those with no records suggests that P. moerens should occur in most, if not all, of the states and provinces of the northeast Nearctic region. The lack of records for all mainland areas is likely the result of sampling effort. The lack of records from major islands (NL-I and PE) may reflect actual absences because of the difficulty of dispersal to islands across straits. Among all the species treated here P. moerens has the greatest continental range extending from the southeastern U.S. ( McCafferty et al. 2010) to above the Arctic Circle ( Harper & Harper 1981). Although the widespread distribution of P. moerens is indicative of its broad habitat and environmental tolerances, in the northeast Nearctic region it seems to prefer smaller sized streams. In CT ( Burian & Bednarik 1994), ME ( Burian & Gibbs 1991), PA ( Grant et al. 1997), and NY ( Gordon 1933) all records are from first to third order stream channels. In CT it was reared from a small, first order stream that was the outlet of a small spring-fed pond in the southwestern part of the state (all CT records are from this same area). In the early spring, nymphs were particularly abundant in leaf packs and loose CPOM trapped under tree roots or under debris dams in shallow riffles or at the outlet of small pools. Currently most of the habitat information reported for records in CT, NY, and PA associates this species with small, cool, spring-fed stream systems. In Kentucky, P. moerens was also associated with a similar habitat ( Minshall 1968). If these first and second order spring-fed systems are the primary habitats for this species, then this species may be vulnerable to climate change induced habitat disruption because spring-fed aquatic habitats are particularly vulnerable to changes in precipitation patterns predicted as part of a climate modified regional hydrology ( Hicke et al. 2022; Richardson 2019). Although P. moerens may be vulnerable to habitat disruption, its occurrence both far to the south and north of the study area suggests that it is capable of dispersing widely and tolerating conditions that vary from the Arctic to the temperate southeastern U.S. Being able to occupy such a wide latitudinal range of conditions may provide P. moerens a hedge against the potential problems of climate induced habitat disruption. However, because our knowledge of the distribution and habitats of this species is incomplete it’s not possible to comment on how secure it may be in the northeast Nearctic region.

Figures

FIGS. 1–4: gills and abdominal tergites VIII–X of Neoleptophlebia and Paraleptophlebia nymphs. 1. N. adoptiva gill 4, 2. P. praepedita gill 4, 3a. N. assimilis tergites VIII–X, 3b P. praepedita tergites VIII–X, 3c. P. volitans tergites VIII–X, 3d. P. moerens tergites VIII–X, 4a. N. adoptiva tergites VIII–X, 4b. P. guttata tergites VIII–X.

FIGS. 22–24: gills and legs of Paraleptophlebia nymphs. 22a. dorsal view of lateral gills of P. moerens with gill margins lacking long, hair-like setae, 22b. lateral view of gills of P. debilis with gill margins lacking long, hair-like setae, 23a dorsal view of legs of live P. moerens nymph showing typical brown color pattern without distinct bands, 23b. close-up of foreleg of preserved P. moerens nymph showing uniform brown color, pale areas visible on live nymphs are much less distinct after being preserved, 24a. lateral view of legs of P. debilis showing distinct bands on all leg segments, 24b. lateral view of legs of P. ontario showing partial brown band near apex of femora and dark brown mark on tibiae at joint with femora; dark brown on femora is often diffuse and usually does not encircle the segment.

FIGS. 38–39: nymphs of Paraleptophlebia. 38. lateral view of the abdomen gills of P. praepedita with arrow indicating distinct transition point of the clear membranous portion of gill filaments past which the clear membrane surrounding the medial trachea is much reduced, 39a. ventral view of the abdomens of female nymphs of P. moerens, arrow indicates dark lateral shading on sternites VIII and IX, 39b. ventral view of the abdomens of male nymphs of P. moerens, arrow indicates depressions along edges of sternites and dark lateral shading on sternites VIII and IX.

FIGS. 28–29: mouthparts and legs of Paraleptophlebia nymphs. 28a. right maxilla of P. moerens (dorsal view), 28b. close-up of segment 1 of maxillary palp (ventral surface) of P. moerens, 29a. foreleg of P. ontario nymphal exuviae from reared specimen with residual dark brown shading visible on femur from partial apical band, arrow indicates dark brown mark at base of tibia adjacent to joint with femur, some brown shading around mark extends along the sides of tibia, but doesn’t completely encircle the leg segment, 29b. lateral view of legs of P. ontario nymph intact showing coloration, arrow indicates dark brown mark at apex of tibia adjacent to joint with femur.

FIGS. 40a–b: nymphs of Paraleptophlebia moerens. 40a. dorsal view of abdominal color pattern of male nymph with distinct larger pale spots on tergites VII–X and pale spots along the lateral margins, 40b. dorsal view of abdominal color pattern of two female nymphs with median pale spots on tergites VII–X similar to those of the male nymphs, but with additional smaller pale spots on the medial posterior margins of tergites IV–VI and more distinct pale lateral margins of all tergites, also dark brown shading often occurs along edges of the short pale medial streak that occurs on tergites I–IX.

FIGS. 17–18: legs, and gills of Paraleptophlebia volitans. 17. dorsal view of abdominal gills with arrow indicating long, hairlike setae along edges of gill filaments, 18a. view of all legs showing presence of distinct bands, 18b close-up of foreleg (dorsal view) showing bands on each leg segment.

FIGS. 25a–c: forefemora of Paraleptophlebia nymphs. 25a. close-up of ventral edge of forefemur of P. ontario showing few short, hair-like setae and stout setae, 25b. close-up of ventral edge of forefemur of P. debilis showing few short, hair-like setae and stout setae, 25c close-up of ventral edge of forefemur of P. moerens showing few short, hair-like setae and stout setae.

FIG. 41: nymph of Paraleptophlebia moerens. dorsal view of head and pronotum of live female nymph showing large paired pale median spots with diagonal gray streaks that divide each spot into two and less distinct lateral somewhat crescent shaped pale spots, which may also have gray streaks.