Hydaticus tuyuensis Trémouilles (Coleoptera: Dytiscidae): Larval Morphology and Phylogenetic Relationships within Dytiscinae |
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Authors: | Mariano C Michat Patricia L M Torres |
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Institution: | (1) Laboratorio de Entomología, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Av. Int. Güiraldes s/n, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina |
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Abstract: | The three larval instars of Hydaticus (Guignotites) tuyuensis Trémouilles are described and illustrated for the first time, emphasizing the morphometry and chaetotaxy. Second- and third-instar
larvae of the known species of the subgenus Guignotites Brinck are characterized by a trilobate median process of prementum. All larval instars of H. tuyuensis, however, have a bilobate process, similar to that present in the known species of the subgenus Hydaticus Leach. This implies that a trilobate process cannot be used as a diagnostic character for Guignotites. Alternatively, Guignotites as presently defined may not represent a natural group. A cladistic analysis of 57 larval characters suggests that the genus
Hydaticus shares a common origin with the clade composed of the genera Eretes Laporte and Thermonectus Dejean, based on the following synapomorphies: (i) abdominal segment VII almost completely sclerotized ventrally; the absence
of (ii) additional ventroapical pores on the third antennomere, (iii) setae FE4 and FE6, (iv) additional setae on the femur
and (v) additional setae on the tibia; and the presence of (vi) setae on the median process of prementum and (vii) spinulae
on the second labial palpomere. A bilobate or trilobate median process of the prementum and the submedial insertion of seta
AN3 distinguish Hydaticus from the remaining genera of Dytiscinae studied. |
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Keywords: | Hydaticini Hydaticus larvae chaetotaxy phylogeny |
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