Maternal care by Early Cretaceous cockroaches

Abstract

Most cockroaches produce a special capsular structure, the ootheca, to enclose eggs for protection and maternal brood care. However, the origin and early evolution of the cockroach ootheca is poorly known, attributable to a lack of fossil evidence from the Mesozoic. Here, we report the earliest known cockroach fossil possessing an internally partitioned ootheca: Piniblattella yixianensis Gao, Shih & Ren sp. nov. is described from the mid Early Cretaceous Yixian Formation of China. The ootheca of this species measures 46–62% of its body length, contains 60–70 eggs, and exhibits the oviparity B reproduction mode, similar to that of the extant ectobiid and blattid cockroaches. In conjunction with several isolated ootheca specimens preserved in the mid-Cretaceous Myanmar amber (Burmite), we infer that the cockroach reproductive mode using the complete oothecate structure occurred during or before the mid Early Cretaceous. Maternal care associated with the oothecate condition in these Cretaceous cockroaches added a unique and major life-history trait, later resulting in true viviparity. This new life-history trait providing maternal protection and care may have been a key factor in the subsequent evolutionary diversification and ecological expansion of modern cockroach lineages.

http://zoobank.org/urn:lsid:zoobank.org:pub:588C91F4-FB8D-43E5-8C2D-86D50393B851

Keywords:

• oviparity
• Dictyoptera
• Blattaria
• Isoptera
• Mantodea
• Piniblattella

Acknowledgements

We are grateful to Dr Alexandr P. Rasnitsyn (Russian Academy of Sciences) and Dr Christine Nalepa (North Carolina State University, USA) for their comments and suggestions in improving this manuscript. We thank Dandan Wei who provided suggestions and discussion, and Dr Chen Wang who completed the reconstruction artwork for Figure 3F. We express our gratitude to Dr Andrew Ross (National Museum of Scotland) and Dr Peter Vršanský (Slovak Academy of Sciences) for their critical but valuable reviews of the manuscript. DR was supported by grants from the National Natural Science Foundation of China (grant numbers 31730087, 41688103 and 31672323), the Program for Changjiang Scholars and Innovative Research Team in University (grant number IRT-17R75), and Support Project of High-level Teachers in Beijing Municipal Universities in the Period of 13th Five-year Plan (grant number IDHT20180518). TPG was supported by the Young Elite Scientist Sponsorship Program by CAST (YESS), the Natural Science Foundation of Beijing, China (grant number 5182004) and the Science and Technology Development Program of Beijing Municipal Commission of Education (grant number KM201610028009). This is contribution 315 of the Evolution of Terrestrial Ecosystems consortium at the National Museum of Natural History, Washington DC.

Additional information

Funding

DR was supported by grants from the National Natural Science Foundation of China (grant numbers 31730087, 41688103 and 31672323), the Program for Changjiang Scholars and Innovative Research Team in University (grant number IRT-17R75), and Support Project of High-level Teachers in Beijing Municipal Universities in the Period of 13th Five-year Plan (grant number IDHT20180518). TPG was supported by the Young Elite Scientist Sponsorship Program by CAST (YESS), the Natural Science Foundation of Beijing, China (grant number 5182004) and the Science and Technology Development Program of Beijing Municipal Commission of Education (grant number KM201610028009). This is contribution 315 of the Evolution of Terrestrial Ecosystems consortium at the National Museum of Natural History, Washington DC.