Neoleptophlebia assimilis ( Banks, 1914: 614 )

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 : 9

Neoleptophlebia assimilis ( Banks, 1914: 614)

Leptophlebia assimilis Banks, 1914 (original description)

Paraleptophlebia assimilis ( Banks, 1914) (combination)

Description of Nymph: Randolph and McCafferty 1996: 225

Nymphs of N. assimilis are recognized from other northeast members of this genus by the presence of sharp posterolateral projections on abdominal segments VIII and IX ( Fig. 3 ). Posterolateral projections on segment VIII are almost as long as those on segment IX. Nymphs are smaller, lighter colored, and more delicate compared to those of other northeast Neoleptophlebia , but they do have a large pale spot on the frons of the head capsule that is similar to the one on N. adoptiva nymphs.

Currently N. assimilis is rare in the northeast Nearctic region with occurrences recorded only from CT and PA. In CT, N. assimilis has only been found in one small spring-fed, first order stream (Burnhams Brook) and its receiving small second order river (Eightmile River) upstream from their confluence. In these habitats nymphs were found in deposits of small gravel and CPOM in riffles and at the outlets of small pools. In PA, N. assimilis was reported by Markarian (1980) from a small, spring-fed first order stream on the western edge of the Ridge and Valley physiographic region. The work of Markarian (1980) is the only detailed analysis of this species concerning the effects of stream water temperatures on nymphal growth. With so few documented occurrences, the distribution of this species in the northeast Nearctic region is poorly known. However, because the stream habitats of the two known occurrences are so similar, it seems clear that this species is restricted to small, cool headwater streams with primary groundwater sources in forested watersheds. This type of lotic habitat is poorly documented and highly vulnerable to disturbance from changes in regional precipitation patterns that are expected to occur because of climate change ( Hicke et al. 2022; Richardson 2019). In addition, because these small streams often have seasonally interrupted flow, resulting from variation in groundwater elevation, they are poorly documented on maps and often lack the regulatory protection afforded permanently flowing streams concerning land use activities such as logging, mineral extraction, agriculture, and commercial/residential development. Any event, or activity, that adversely affects flow and/or chemical composition of source water or reduces riparian forest cover poses a serious threat to these vulnerable small spring-fed streams and species that depend on them. Because N. assimilis is only known from a highly vulnerable aquatic habitat it must be considered extremely vulnerable (possibly at risk of local extirpation) with regards to the predicted effects of climate change on regional hydrology.

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.