Research Article |
Corresponding author: Changfa Zhou ( zhouchangfa@njnu.edu.cn ) Academic editor: Lyndall Pereira-da-Conceicoa
© 2016 Yi-Ke Han, Wei Zhang, Ze Hu, Changfa Zhou.
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:
Han Y-K, Zhang W, Hu Z, Zhou C-F (2016) The nymph and imago of Chinese mayfly Siphlonurus davidi (Navás, 1932). ZooKeys 607: 37-48. https://doi.org/10.3897/zookeys.607.9159
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The imagos and nymphs of Siphlonurus davidi (Navás, 1932) are described for the first time. The adult has colourful wings and cross veins, the MP is forked asymmetrically at its base, a long cubital area is present with more intercalaries, and it has a relatively simpler penis and larger hindwings compared to its congeners. The venation and genitalia show that it is a plesiomorphic species in the genus. A key to the Asian species of Siphlonurus with coloured wings is provided in conclusion.
China, evolution, mayfly, Siphlonurus , wing
The species Siphlonurus davidi (Navás, 1932), which was based on a single male subimago, was re-described by
In 2013, a Chinese professor working on aquatic insects collected within a national park in Sichuan province (southwestern China), the same province where the type of Siphlonurus davidi was originally found. Among his mayfly collection, some Siphlonurus nymphs and imagos were present: the imago wings had distinct pigmented spots and markings. After careful examination and comparison with the good quality photographs in
1♂2♂♂subimagos, 4♀♀subimagos and 25 nymphs, Jing Hai (Mirror pool or lake, alt. 2398m), 2013-VII-6; 2♀♀5 nymphs, Xi-Niu Hai (rhinoceros pool, alt. 2348 m), 2013-VII-7, leg. Beixing Wang; 1♀ and 36 nymphs, Lao-Hu Hai (tiger pool, alt. 2439 m), 2013-VII-7, leg. Hun He and Guangba Li; 50 nymphs, Jia-zu Hai (bamboo pool, alt. 2744 m), 2013-VII-6, leg. Yong Cao.
All specimens were collected at Jiu-Zhai-Guo (Jiuzhai Valley), Sichuan Province, China, and now are deposited in Mayfly Collection, College of Life Sciences, Nanjing Normal University, China. The nymphs were sampled from pools or lakes and imaginal materials were attracted to and collected by lights.
Siphluriscus? davidi Navás, 1932: 929, fig. 46, male subimago. Type: male subimago, from China (Sichuan=Se-Tchouen).
Siphluriscus? davidi [sic.]: Ulmer, 1936: 215.
Siphluriscus davidi : Wu, 1935: 251; Gui, 1985: 80.
Siphlonurus davidi : Zhou & Peters, 2003: 346 (tentatively); Sartori & Peters, 2004: 2, figs 1–7 (redescription on type and transfer).
China (Sichuan).
NYMPH (in alcohol, Figs
Body length 15.0–20.0 mm, caudal filament 6.0–7.0 mm, yellowish brown; head mostly obscured by compound eyes, hypognathous, length of antenna subequal to width of head, surface of antennae with very sparse tiny setae (Fig.
Thorax: all legs similar, femora with broad median marking bands, tibiae pale, tarsus with basal and apical colour rings, the latter one darker; length of femora: tibiae: tarsus ca. 1.8: 1.0: 1.5, surface with very short sparse spines and setae; mid- and hind-legs with clear patellar-tibial suture. Claws relatively slim and simple, without teeth (Fig.
Abdomen: Each tergite with three pairs of stripes dorsally; one pair parallel near median line, one at lateral margin, one oblique pair between them. Colour of tergites 3, 6, 9 slight darker than others; each tergite with a pair of short median stripes. Posterolateral corner of each tergite extended into sharp spines, progressively larger and wider from anterior to posterior (Fig.
MALE (in alcohol, Figs
General colouration reddish brown, with pale sutures and grooves on body (Fig.
FEMALE (in alcohol, Fig.
Body length 12.0–13.0 mm, forewing 12.0–13.0 mm, hindwing 6.0–7.0 mm, cerci 15 mm; body colour pattern similar to male imago (Fig.
MALE SUBIMAGO (in alcohol, Fig.
Similar to male but duller. Femora: ratio of tibiae: tarsus of foreleg = 1.0: 0.6: 1.2, that of mid- and hind-legs 1.0: 0.6: 0.9. Colour pattern of abdominal terga and sterna similar to male but clearer (Fig.
FEMALE SUBIMAGO (in alcohol).
Similar to female imago in colour pattern but opaque. Ratio of femora: tibiae: tarsus of legs = 1.0: 0.6: 1.0.
EGGS (Fig.
Generally oval but one pole larger than the other, approximately 150 µm in length and 100 µm in width, without polar cap. Exochorionic surface uniform, consisting of irregular ridges or rims.
1 | Ventral lobe of penes with teeth | 2 |
– | Ventral lobe of penes without teeth | Siphlonurus davidi |
2 | All cross veins of forewing pigmented, fore- and hindwings with colourful stripes and spots | Siphlonurus palaearcticus |
– | Cross veins of wings without pigment, hindwing may with central spot but without stripe | Siphlonurus binotatus |
1 | All cross veins of forewing pigmented, fore- and hindwings with colourful stripes and spots | 2 |
– | Cross veins of wings without pigment, hindwing may with central spot but without stripe | Siphlonurus binotatus |
2 | Cross veins between C to Rs of forewing clearly surrounded with colourful pigments; distal half of hindwing with colour, semi-transparent | Siphlonurus davidi |
– | Cross veins of whole forewing surrounded with pigments; hindwings wing pigments surrounding cross veins, other parts transparent | Siphlonurus palaearcticus |
1 | Abdomen with clear, obvious, relatively wide trachea or thread-like markings | Siphlonurus binotatus |
– | Abdomen maybe with various markings but without distinct above colour pattern | 2 |
2 | Obvious posterolateral spines present on terga 1–9 | Siphlonurus davidi |
– | Obvious posterolateral spines present on terga 3–9 | Siphlonurus palaearcticus |
Approximately 40 Siphlonurus species have been reported from the Nearctic and Palaearctic realms, Eurasia hosting half of them (Kluge, 2004). Just as
1) The forewing of S. davidi has more pigmented patches than that of S. binotatus but fewer than S. palaearcticus. According to
2) Compared to S. binotatus and S. palaearcticus, the MP on forewing of S. davidi forks more basally, CuP more curved and cubital area is longer.
3) Unlike S. binotatus and S. palaearcticus, the hindwings of S. davidi are more colourful. They have two obvious dark patches and half of the hindwing is pigmented and semi-transparent. On the contrary, S. binotatus has only one clear stripe or patch near the centre, the other part of hindwing has no colour and is totally hyaline. The cross veins in the hindwing of S. palaearcticus are pigmented but the patches are separated.
4) The penis of S. davidi has only ventral membranous lobe, but the lobe of S. binotatus and S. palaearcticus have teeth on its apex.
In nymphs, the terga of S. davidi and S. binotatus have three pairs of stripes while that of S. palaearcticus has only one pair. Similarly, all abdominal terga of S. davidi and S. binotatus nymph have distinct posterolateral spines, while the spines of S. palaearcticus are only on segments 3–9 and much smaller. Siphlonurus binotatus, on the other hand, has obvious tracheae-like markings on the abdomen and obvious dark spots near the lateral margins of terga, which are not found in S. davidi or S. palaearcticus. The latter two species have different colour patterns on nymphal legs. The median half of femora of S. davidi is washed with brown pigments, but that of S. palaearcticus is paler. Both species have two brown rings on the tarsal base and apex respectively, while the apical one of S. davidi is much darker than that of S. palaearcticus The gill figures provided by
Based on the double gills 1–2, coxae and mouthparts without gills, simple claws of nymphs and colourful wings, the distal fork MA of hindwing, the fused subgenital plate, and complex penes of imagos, S. davidi is definitely a species which belongs in the Siphlonuridae. However, at least three characteristics show it is older than other species in the genus Siphlonurus. The first one is the forking point of MP which is sub-equal to that of fusion point of MA and Rs. In other Siphlonurus species, as far as we know, like in S. palaearcticus, this point is more distal. The second character is the cubital area which is longer and with more intercalaries between CuA and the posterior margin of wing. The third structure mentioned here is the hindwings of S. davidi, which are approximately half the length of forewings, longer than in other Siphlonurus species (less than half). It should be pointed out that these three characters of S. davidi are also found in Siphluruscus chinensis (Siphluriscidae), which is clearly a basal clade of Ephemeroptera; therefore, these characters are considered as plesiomorphic.
The MP vein in forewing of S. davidi is somewhat unique. It forks asymmetrically at the base, then MP2 bends backwards strongly near to CuA. This condition is common in Ephemeridae and Potamanthidae, and is similar to Siphluruscus chinensis, but it seems that it is not found in other siphlonurids.
We are very grateful to Mrs. Janice Peters (Entomology, Florida A&M University, USA) for her improvements to our manuscript, to Dr. Koji Tojo (Department of Biology, Shinshu University, Matsumoto, Japan) for his help in checking some Japanese specimens and pictures. This work was supported by the National Natural Science Foundation of China (Grant 31172124 and 31472023), funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and supported by key projects of science-technology basic condition platform from The Ministry of Science and Technology of the People’s Republic of China (Grant No. 2005DKA21402). Some data in this research is derived from the database of National Digital-Museum of Animal Specimens (http://museum.ioz.ac.cn).