1. Ecology
  2. Evolutionary Biology
Download icon

Palaeobiology: Unearthing the secrets of ancient immature insects

  1. Enrique Peñalver  Is a corresponding author
  2. Ricardo Pérez-de la Fuente  Is a corresponding author
  1. Instituto Geológico y Minero de España, Spain
  2. Harvard University, United States
Insight
  • Cited 5
  • Views 1,235
  • Annotations
Cite this article as: eLife 2014;3:e03443 doi: 10.7554/eLife.03443

Abstract

Jurassic fossils of a bizarre fly larva that lived in water as a blood-sucking parasite highlight how much can be learnt from the study of the fossils of immature insects.

Main text

Insects are a highly diverse group of organisms, ranging from tiny fleas to creatures as large as some butterflies and moths. However, these very different insects have much in common. In particular, in around 80% of insect species, the egg hatches to become a soft-bodied larva that does not have wings, which then becomes a pupa, which finally becomes an adult insect. It has been suggested that the emergence of the larval stage was a hugely important innovation in the evolution of insects because, for example, larvae are able to exploit resources that are not used by adult insects (Grimaldi and Engel, 2005). However, the degree to which this so-called 'complete' form of metamorphosis explains the success of these insects is still unknown.

Insect larvae are very rarely found in the fossil record as body remains, partly because they contain relatively few hardened structures. Instead, traces of their activity fossilize more often, such as feeding marks on leaves or larval cases. Moreover, when found, body fossils of insect larvae are also challenging to study because insects tend to exhibit fewer traits during the larval and pupal stages of their life cycle than they do when they are adults.

But can the fossils of insect larvae provide us with novel insights into insect evolution and palaeobiology? Now, in eLife, Jun Chen, Bo Wang, Michael Engel and co-workers demonstrate that the answer to this question is “yes” by reporting the discovery of five exquisitely preserved, virtually complete, larval specimens all belonging to the same fly species (Chen et al., 2014). The specimens were found in Chinese fossil deposits that date back to the Middle Jurassic Epoch. Chen et al. were able to completely reconstruct the morphology of the larvae to reveal how they were uniquely, and somewhat bizarrely, adapted to life as aquatic ectoparasites. The name chosen for the new species—Qiya jurassica—reflects its unusual characteristics ('qiya' means bizarre in Chinese).

So what was Qiya jurassica like? Imagine a worm-shaped creature that has a tiny head equipped with heavily hardened mandibles, a thorax that bears a large ventral sucker armed with radially arranged 'teeth', short legs with bunches of spines on the back, and tentacle-like extensions on its rear end… Such a larval morphology is bizarre, even for insects!

Chen et al. demonstrate that Qiya jurassica larvae were aquatic and are related to water snipe flies (family Athericidae). This small group of flies, with about 100 known species, is related to horse flies, and the adults of both groups are infamous for their painful bites as they feed on blood (a habit that is known as hematophagy). However, unlike modern athericid larvae, the fossil larvae exhibit a combination of traits adapted to hematophagy and ectoparasitism (which involves an organism spending a significant part of its life cycle on its host; Balashov, 2006). These adaptions include the thoracic sucker and legs with spines for anchoring to its host, and piercing-sucking mandibles for fluid feeding.

It is clear that feeding on blood as an ectoparasite evolved several times in insects (Figure 1). Ectoparasites not only feed on blood but also on other animal substances, such as gland secretions, and keratin from feathers, hair or skin. Although insects that are both ectoparasites and blood-feeders are very unusual in the fossil record, 'free-living' insects that feed on blood, such as mosquitoes, are relatively abundant (Lukashevich and Mostovski, 2003). The most striking example of the latter is the fossil of a 46-million-year-old female mosquito in which its blood meal is preserved (Greenwalt et al., 2013).

A timeline of the insect lineages that are ectoparasitic and feed on blood.

The groups to which they belong are shown on the right. Temporal ranges (shown in red) are based on the fossil record: grey dots represent fossils found in compression (rock) deposits, orange dots those found in amber; temporal ranges not supported by fossil evidence are denoted by a broken red line. The new fossil fly larva reported by Chen et al. is shown as a star-shaped grey dot. Insect outlines to the right depict living forms, those on the left extinct forms. The question mark denotes a fossil with unclear affiliations and life habits. Quaternary records (for the last 2.5 million years) are not shown. Sources: Lukashevich and Mostovski, 2003; Grimaldi and Engel, 2005; Grimaldi and Engel, 2006; Engel, 2008; Huang et al., 2012.

By taking into account other fossils found in the same outcrop where the Qiya jurassica specimens were collected, Chen and co-workers—who are based at Linyi University, the University of Bonn, the Chinese Academy of Science, the University of Kansas and the Natural History Museum—conclude that a likely host of Q. jurassica larvae were aquatic salamanders.

Although no blood-sucking ectoparasites are known for extant reptiles or amphibians (Grimaldi and Engel, 2005), it was recently discovered—also from Chinese deposits—that Mesozoic reptiles were most likely ectoparasitized by giant fleas (Huang et al., 2012; Figure 1). Thus, the findings of Chen et al. lead to the novel idea that amphibians could have been ectoparasitized by blood-sucking insects in the past.

The evolution of larval stages is one of the most overlooked topics in insect palaeontology. The research of Chen et al. highlights what can be discovered from studying larval fossils. As insect palaeontology, despite its remarkable progress in the past decades, remains strongly biased towards the study of adult forms, there is a clear need to train new researchers to recognize and study the fossils of immature insect stages. Such an undertaking will help us to understand the role played by the larval and pupal stages through evolutionary time, and learn more about the most ecologically dominant animal lineage on land.

References

    1. Engel MS
    (2008)
    A stem-group cimicid in mid-Cretaceous amber from Myanmar (Hemiptera: Cimicoidea)
    Alavesia 2:233–237.
  1. Book
    1. Grimaldi D
    2. Engel MS
    (2005)
    Evolution of the insects
    New York: Cambridge University Press.
    1. Lukashevich ED
    2. Mostovski MB
    (2003)
    Hematophagous insects in the fossil record
    Journal of Paleontology 37:48–56.

Article and author information

Author details

  1. Enrique Peñalver

    Museo Geominero, Instituto Geológico y Minero de España, Madrid, Spain
    For correspondence
    e.penalver@igme.es
    Competing interests
    The authors declare that no competing interests exist.
  2. Ricardo Pérez-de la Fuente

    Museum of Comparative Zoology, Harvard University, Cambridge, United States
    For correspondence
    perezdelafuente@fas.harvard.edu
    Competing interests
    The authors declare that no competing interests exist.

Publication history

  1. Version of Record published: June 24, 2014 (version 1)

Copyright

© 2014, Peñalver and Pérez-de la Fuente

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 1,235
    Page views
  • 93
    Downloads
  • 5
    Citations

Article citation count generated by polling the highest count across the following sources: Crossref, Scopus, PubMed Central.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Download citations (links to download the citations from this article in formats compatible with various reference manager tools)

Open citations (links to open the citations from this article in various online reference manager services)

Further reading

    1. Ecology
    2. Evolutionary Biology
    Motoko Iwashita, Masato Yoshizawa
    Research Article

    Social behaviour is a hallmark of complex animal systems; however, some species appear to have secondarily lost this social ability. In these non-social species, whether social abilities are permanently lost or suppressed is unclear. The blind cavefish Astyanax mexicanus is known to be asocial. Here, we reveal that cavefish exhibited social-like interactions in familiar environments but suppressed these interactions in stress-associated unfamiliar environments. Furthermore, the level of suppression in sociality was positively correlated with that of stereotypic repetitive behaviour, as seen in mammals. Treatment with a human antipsychotic drug targeting the dopaminergic system induced social-like interactions in cavefish, even in unfamiliar environments, while reducing repetitive behaviour. Overall, these results suggest that the antagonistic association between repetitive and social-like behaviours is deeply shared from teleosts through mammals.

    1. Ecology
    2. Epidemiology and Global Health
    David R M Smith et al.
    Research Article

    The human microbiome can protect against colonization with pathogenic antibiotic-resistant bacteria (ARB), but its impacts on the spread of antibiotic resistance are poorly understood. We propose a mathematical modelling framework for ARB epidemiology formalizing within-host ARB-microbiome competition, and impacts of antibiotic consumption on microbiome function. Applied to the healthcare setting, we demonstrate a trade-off whereby antibiotics simultaneously clear bacterial pathogens and increase host susceptibility to their colonization, and compare this framework with a traditional strain-based approach. At the population level, microbiome interactions drive ARB incidence, but not resistance rates, reflecting distinct epidemiological relevance of different forces of competition. Simulating a range of public health interventions (contact precautions, antibiotic stewardship, microbiome recovery therapy) and pathogens (Clostridioides difficile, methicillin-resistant Staphylococcus aureus, multidrug-resistant Enterobacteriaceae) highlights how species-specific within-host ecological interactions drive intervention efficacy. We find limited impact of contact precautions for Enterobacteriaceae prevention, and a promising role for microbiome-targeted interventions to limit ARB spread.