Research Article |
Corresponding author: Thomas Kaltenbach ( thomas.kaltenbach@bluewin.ch ) Academic editor: Burgert Muller
© 2021 Thomas Kaltenbach, Jean-Luc Gattolliat.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Kaltenbach T, Gattolliat J-L (2021) A new genus from Madagascar with strongly enlarged labium (Ephemeroptera, Baetidae). African Invertebrates 62(2): 465-484. https://doi.org/10.3897/afrinvertebr.62.73911
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A new genus of Baetidae, Megalabiops gen. nov., and a new species, M. madagasikara sp. nov., are described from Madagascar based on nymphs. The new genus is characterized by having a strongly enlarged mentum; pedicelli with many long, stout, pointed setae; a brush of dense, short setae between prostheca and mola of both mandibles; an apically pointed maxillary palp with a stout seta at the tip; and a labium with many long, simple setae ventrally on glossae. The patellotibial suture is absent on the fore tibia and present on middle and hind tibiae. The claw is strongly elongated with two rows of denticles. The imago remains unknown and the relationships with other African genera of Baetidae are tentative. Despite being easily identifiable, only two nymphs were found in two highly sampled localities in Madagascar.
Afrotropical, mayflies, morphology, Protopatellata, systematics
With nearly one third of all mayfly species worldwide (ca. 1,100 species in 114 genera), the family Baetidae has the highest species diversity among mayflies (updated from
Madagascar is the fourth-largest island in the world with ca. 581,500 km2, situated ca. 400 km east of Africa in the Indian Ocean. Some 160 million years ago, the supercontinent Gondwana started to break apart and the eastern section of this land mass, incl. today’s Madagascar, drifted eastwards. Approximately 140 million years ago, the landmass composed of Madagascar and the Indian subcontinent was completely separated from the African landmass, without subsequent land connection. Finally, around 80 million years ago, Madagascar split from the Indian subcontinent and stayed isolated until today. This long-term isolation in combination with a high topographic and geological complexity, supporting speciation on the island, is responsible for the outstanding biological richness and the high level of endemism in Madagascar (
Until 1990, the Malagasy mayflies, as other aquatic insects, remained very poorly known. Only a few reports were made based on a limited number of specimens and localities (
The present study is based on two nymphs collected in 2001 and 2003 in two different locations in Madagascar. The type-locality was sampled fourteen times during biodiversity assessments of Malagasy streams between 1993 and 2003 by teams of the French ORSTOM (Office de la recherche scientifique et technique outre-mer) and the Museum of Zoology, Lausanne (MZL) (
The specimens were collected in 2001 and 2003 from two different locations in the same area of Madagascar. Specimens were preserved in 70%-80% ethanol. Nymphs were dissected in Cellosolve (2-Ethoxyethanol) with subsequent mounting on slides in Euparal medium, using an Olympus SZX7 stereomicroscope.
The DNA of one specimen was extracted using non-destructive methods allowing subsequent morphological analysis (see
Drawings were made using an Olympus BX43 microscope. Photographs of nymphs were taken with a Canon EOS 6D camera and processed with Adobe Photoshop Lightroom (https://adobe.com/ch_de/products/photoshop-lightroom) and Helicon Focus version 5.3 (http://www.heliconsoft.com). Photographs were subsequently enhanced with Adobe Photoshop Elements 13 (https://adobe.com/ch_de/products/photoshop).
Distribution maps were generated with SimpleMappr (https://simplemappr.net,
The terminology used in the manuscript follows
The new species is established based on morphological characters.
MZL Museum of Zoology Lausanne (Switzerland).
Megalabiops madagasikara gen. et sp. nov., by present designation.
Nymph. This new genus is distinguished by the combination of the following characters: A) body rather short and stocky (Fig.
Megalabiops is an arbitrary combination of letters with allusion to the Greek words mega and iops, and the Latin word labium. Megalab- is with reference to the strongly enlarged labium and -iops with reference to the Baetidae which look and move like small fishes. The gender is feminine.
Nymph. (Figs
Body. Short and stocky (Figs
Head. Antenna (Figs
Labrum
(Fig.
Right mandible
(Fig.
Left mandible
(Fig.
Hypopharynx
(Fig.
Maxilla
(Fig.
Labium
(Figs
Thorax. Hind protoptera well developed.
Foreleg
(Fig.
Middle and hind legs
(Fig.
Abdomen. Tergites (Fig.
Gills
(Fig.
Paraproct
(Fig.
Caudal filaments
(Fig.
Imagines. Unknown.
Nymph. See genus diagnosis. Otherwise, if more species are discovered, specific differences in shape of labial and maxillary palps, and in setation of the legs are expected. Species with less derived characters (setation of pedicellus, shape of mentum) may also be expected.
Madagasikara is the Malagasy name of Madagascar.
Holotype. Madagascar • female nymph; Bas. Rianila, Riv. Affluent non nommé, Loc. Camp: route vers Lakato; 19°03'30"S, 48°21'50"E; 25.04.2003; leg. Mission MZL and M. Monaghan; on slides; GBIFCH00592692, GBIFCH00592693, GBIFCH00592728; GenBank OK510778; MZL. Paratype. Madagascar • nymph; Andasibe National Park, Antanambotsira; 18°56'09"S, 48°24'52"E; 30.11.2001; on slide; GBIFCH00592729; leg. R. Oliarinony; MZL.
Nymph. (Figs
Colouration
(Fig.
Head. Antenna (Fig.
Labrum
(Fig.
Right mandible
(Fig.
Left mandible
(Fig.
Both mandibles with lateral margins convex. Basal half laterally with short, fine, simple setae.
Hypopharynx and superlinguae
(Fig.
Maxilla
(Fig.
Labium
(Figs
Thorax. Hind protoptera well developed.
Foreleg
(Fig.
Middle leg. Ratio of middle leg segments 1.7: 1.0: 1.0: 0.5. Femur. Length 3.4× maximum width. With similar setation as foreleg; femoral patch absent. Tibia as hind leg; dorsal margin almost bare; ventral margin with row of short, spine-like setae. Patellotibial suture present on basal 1/3 area. Tarsus as hind leg; dorsal margin bare; ventral margin with row of short, spine-like setae. Claw as foreleg.
Hind leg
(Fig.
Abdomen. Tergites (Fig.
Gills
(Fig.
Paraproct
(Fig.
(Fig.
Larvae were collected in two pristine streams running in relatively preserved natural tropical rain forests. Environmental parameters of the type-locality: width 2–3m, depth 0.1–0.2m, velocity 0.6–0.8 m/s, temperature 16–18 °C. The riverbed was a mix of sand, gravel and rocks with a few small waterfalls and very limited riparian vegetation. Mayfly fauna is very diversified with around twenty species of Baetidae, including four carnivorous species (Nesoptiloides electroptera (Demoulin, 1966), Herbrossus christinae Gattolliat & Sartori, 1998, Herbrossus edmundsorum McCafferty & Lugo-Ortiz, 1998, and Guloptiloides gargantua Gattolliat & Sartori, 2000), scrapers (Dicentroptilum merina Lugo-Ortiz & McCafferty, 1998, Xyrodromeus spp.), and species adapted to fast flow (Afroptiloides delphinae Gattolliat, 2000). Besides Baetidae, Caenidae and Tricorythidae were the most abundant families; larvae of the huge borrowing mayfly, Proboscidoplocia sp. (Euthyplociidae), were also collected in abundance. Both larvae were still in middle instar in April (end of rainy season) and November (beginning of rainy season); we hypothesize that Megalabiops madagasikara sp. nov has a long flight period as most of the Malagasy species of Baetidae.
Megalabiops gen. nov. clearly belongs to the family Baetidae based on the pisciform body shape (Fig.
African genera of Protopatellata were previously assigned either to the Centroptiloides complex (
The following characters differentiate Megalabiops gen. nov. from all other genera of Protopatellata and even of Baetidae in general: antennae with many long, slightly lanceolate setae on pedicelli (Fig.
Pedicelliops Kaltenbach & Gattolliat, 2020, another genus of Protopatellata, also has two rows of setae of different length ventrally on and close to the margin of the glossae and similar stout, curved setae at their apex (
Elongated claws with two rows of numerous denticles increasing in length toward the apex are also typical for species of Bugilliesia Lugo-Ortiz & McCafferty, 1996. However, the legs are generally very slender and there is no tight connection between tibia and tarsus. Additionally, the maxillary palp has a small third segment, the glossae are without rows of long setae, the labial palp segment II has a distomedial protuberance, and the submarginal arc of setae on dorsal surface of the labrum is composed of lanceolate setae (
The legs of Megalabiops gen. nov. are similar to Delouardus djabala Lugo-Ortiz & McCafferty, 1999: the tibia is slightly shorter than the tarsus, with a tight connection between them; the claws are elongated with two rows of denticles; and the setation is similar. Further, there are some long, simple setae on the pedicellus (but not stout, slightly lanceolate setae as in Megalabiops gen. nov.) and both mandibles have a brush of fine, simple setae between prostheca and mola. The claws of Megalabiops gen. nov. and the tight connection between tibia and tarsus are also similar to Cheleocloeon Wuillot & Gillies, 1993. However, Delouardus and Cheleocloeon are different in other characters from Megalabiops gen. nov., e.g. the labium without long setae on the glossae and the labial palp segment II with a large distomedial protuberance. The sister genera Delouardus and Cheleocloeon belong to the Anteropatellata according to the rank free system of Kluge (
The labrum with straight lateral margins and a largely V-shaped distal margin is also rather unusual among Baetidae. All other genera presenting a similar labrum (Callibaetis Eaton, 1881; Callibaetoides Cruz, Salles & Hamada, 2013; Demoulinia Gillies, 1990; Waltzoyphius Lugo-Ortiz & McCafferty, 1995 and Australian species provisionally assigned to Centroptilum Eaton, 1869) have a patellotibial suture on all legs of the nymph, belonging to the Anteropatellata (
A remarkable setation on the antennal base is also present in two Neotropical Anteropatellata: Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998 has many long, robust, simple setae on scape and pedicellus and Spiritiops silvudus Lugo-Ortiz & McCafferty, 1998 has many minute, fine, simple setae scattered over surface of scape and pedicellus (
As a conclusion, the relationship of Megalabiops gen. nov. with other genera remains unresolved and knowledge of the imaginal stage, especially of the male genitalia and the number of intercalary veins of the wings is of major importance to confirm the possible relationship with the Centroptiloides complex or Rhithrocloeoninae (sensu
The description of Megalabiops gen. nov. is based on only two nymphs. Remarkably, these nymphs were found in two frequently sampled localities, where different field trips of the ORSTOM and MZL teams (
The number of localities and different habitats sampled in Madagascar are relatively high, but there are still areas where no collection activities have occurred (especially in the Northeast of the island including the Masoala Peninsula). Taking into account the obvious biological richness of this island, it would be prudent to assume that the number of genera and species of Baetidae will continue to increase with further fieldwork and collections in Madagascar.
We sincerely thank Ranalison Oliarinony (Antananarivo, Madagascar), and the participants of the mission in 2003 (Michel Sartori, Olivier Glaizot (MZL), Jean-Marc Elouard and Michael Monaghan (Leibniz-IGB and Freie Universität Berlin)) for the collection of these precious nymphs. We are also grateful to Michel Sartori (MZL) for his constant interest and support for our projects and to Marion Podolak (MZL) for her support with lab work and preparation of the COI barcodes. Finally, we are thankful to the reviewers of our manuscript for their valuable comments.