Blind life in the Baltic amber forests: description of an eyeless species of the ground beetle genus Trechus Clairville, 1806 (Coleoptera: Carabidae: Trechini)

Abstract

The first eyeless beetle known from Baltic amber, Trechus eoanophthalmus sp. n., is described and imaged using light microscopy and X-ray micro-computed tomography. Based on external characters, the new species is most similar to species of the Palaearctic Trechus sensu stricto clade and seems to be closely related to the Baltic amber fossil T. balticus Schmidt & Faille, 2015. Due to the poor conservation of the internal parts of the body, no information on the genital characters can be provided. Therefore, the systematic position of this fossil within the megadiverse genus Trechus remains dubious. The occurrence of the blind and flightless T. eoanophthalmus sp. n. in the Baltic amber forests supports a previous hypothesis that these forests were located in an area partly characterised by mountainous habitats with temperate climatic conditions.

X-ray microscopy reveals endophallic structures in a new species of the ground beetle genus Trechus Clairville, 1806 from Baltic amber (Coleoptera, Carabidae, Trechini)

“…All these species are obligatory wingless characterized by markedly shortened metepisternae and fully rounded humeri, and it can therefore be presumed that these Eocene species lived on the forest floor along mountain slopes, just as it is known for the huge number of wingless trechine beetles today (Schmidt et al 2016). This conclusion is in contradiction with the assumption of Alekseev and Alekseev (2016) that the amber forest was formed on a plain or slightly hilly area.…”

“…The methods and technology used were described in detail in a previous work by Schmidt et al (2016). Micro-CT scans were performed under phase contrast (40 KV, 8 W) using a 4× detector (10 s, 4.15 µm pixel size) and 10× detector (30 s, 1.89 µm pixel size).…”

“…Two additional Trechus fossils were described from the Eocene Baltic amber: Trechus balticus and Trechus eoanophthalmus (Schmidt and Faille 2015, Schmidt et al 2016). Trechus exhibitorius sp.…”

“…Both species were identified as representatives of Trechus sensu auctorum which, based on molecular data, is a non-monophyletic assemblage (see Faille et al 2010, 2011, 2013). Due to the absence of male genital characters (the type of Trechus balticus is a female; the type of Trechus eoanophthalmus is a male but insufficiently preserved) it was argued that the taxonomic position of both fossil species within Trechus sensu lato cannot be assessed with certainty (Schmidt and Faille 2015, Schmidt et al 2016). However, their striking similarity to extant species of the Trechus sensu stricto led the authors to conclude that the fossils are likely to be representatives of the stem lineage of the latter group.…”

Who’s that girl? A singular Tropiduchidae planthopper from the Eocene Baltic amber (Hemiptera: Fulgoromorpha)

“…(Archibald and Farrell, 2003;Archibald et al 2013;Szwedo, 2012;Szwedo and Kania, 2015;Wolfe et al, 2016). Palaeoclimatic and palaeoecological interpretations result in many questions regarding the variability of Baltic amber forest(s) habitats and environments (e.g., Alexeev and Alexeev, 2016;Perkovsky, 2016;Sadowski et al, 2016aSadowski et al, , 2016bSchmidt et al, 2016;Alexeev, 2017). However, it is probable that dry and open habitats, as e.g., sparse and open forests or low vegetation areas with a few resiniferous trees or at least on borderland with amber producing trees, were present in the area and at time of the Baltic amber deposit alimentation (Kohlmann-Adamska 2001; Szwedo, 2012;Szwedo and Drohojowska, 2015).…”