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| Cymbalcloeon sartorii Suttinun, Gattolliat & Boonsoong, 2020 |
Abstract
The genus Cymbalcloeon gen. nov. (Ephemeroptera: Baetidae) is established for a new species Cymbalcloeon sartorii sp. nov. from Thailand, based on larval stage. This genus is unique among all of the Baetidae by the presence of three pairs of single gills on segments V–VII, ventrally oriented to cover the sterna VI–IX. Cymbalcloeon sartorii gen. nov. et sp. nov. presents unique or rare morphological characters such as a deeply concave margin between the prostheca and mola, without setae; a very large subtriangular process of the left mandible; a maxillary palp segment II with scarce and very long setae; almost completely fused labial palp segments II and III with numerous very long setae; elongate tarsal claw with two rows of teeth; a shagreen surface of the terga and paraproct; and a very reduced body size. The gills of the new genus move very quickly during respiration and present a near-synchronous protraction. Due to the very derived larval morphological character and the unknown imaginal stage, the exact phylogenetic position of the genus remains unclear; it most certainly belongs to the concept of Anteropatellata and is possibly closely related to the genus Baetopus.
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| Fig 3. Cymbalcloeon sartorii gen. nov. et sp. nov. Larva habitus. (A) female larva, (B) male mature larva. |
Cymbalcloeon gen. nov.
Diagnosis: Labrum (Fig 4A) rectangular, almost without distal emargination, dorsally covered with abundant setae not arranged in a row. Mandibles (Fig 4B and 4D) with margin between prostheca and mola deeply incurved, without setae; right prostheca bifid (Fig 4C). Maxilla (Fig 4G) with highly developed 2-segmented palp, long and curvate teeth at apex galea-lacinia. Labium (Fig 4H) with crescent shaped glossae and paraglossae covered with stout setae, labial palp (Fig 4I) with segments II and III almost fused, crescent shaped, covered with numerous very long, thin setae. Foreleg (Fig 5A), femur dorsally with few clavate setae, femoral patch absent; tibia with patella-tibial suture, tarsal claw elongated with two rows of denticles ending with two enlarged denticles. Hindwing pads absent. Three pairs of single gills on segments V–VI, ventrally oriented (Fig 6A). Gonostyli bud (Fig 5C) Cloeon-type.
Etymology: The name of this genus is an arbitrary combination of the “Cymbal”–a musical instrument similar in appearance to the gill plate and gill mobility, and “Cloeon”–the most common and widespread genus of the subfamily. The gender is neutral.
Cymbalcloeon sartorii sp. nov.
Etymology: This species is dedicated to Dr. Michel Sartori (Museum of Zoology, Lausanne) for his outstanding contributions to the taxonomy of mayfly fauna worldwide and more recently in Thailand.
Biological aspects: The specimens were collected at altitudes from 265 m a.s.l. to 530 m a.s.l. in two small, shallow, slow headwater streams (Fig 8). Larvae were found in sandy and pebble bottom substrates, usually together with larvae of Nigrobaetis Novikova & Kluge, 1987 and Centroptella Braasch & Soldán, 1980.
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| Fig 8. Cymbalcloeon sartorii gen. nov. et sp. nov. Habitat. (A) sampling site, Huai Khayeng stream, Kanchanaburi province, Thailand, (B) microhabitat. |
Chanaporn Suttinun, Jean-Luc Gattolliat and Boonsatien Boonsoong. 2020. Cymbalcloeon gen. nov., An Incredible New Mayfly Genus (Ephemeroptera: Baetidae) from Thailand. PLoS ONE. 15(10): e0240635. DOI: 10.1371/journal.pone.0240635
