Evolutionary history of sloth moths and their relatives (Insecta: Lepidoptera: Pyralidae)
(2025) BION03 20242Degree Projects in Molecular Biology
- Abstract
- Sloth moths are highly-specialized for a life in a very close relationship with sloths – the adults live in the sloth fur and the larvae feed on the sloth faeces. They belong to the pyralid subfamily Chrysauginae (Insecta: Lepidoptera: Pyralidae). Although Pyralidae have been a focus of several molecular phylogenetic studies, including a few Chrysauginae genera, so far none of the three sloth moth genera have been sampled. This master’s thesis aimed to understand the phylogenetic relationships of Chrysauginae, and answer whether Chrysauginae and sloth moths are monophyletic groups. This was done using museomics methods. We have obtained samples from 45 genera and have sequenced their whole genomes. Combining our data with the DNA sequences... (More)
- Sloth moths are highly-specialized for a life in a very close relationship with sloths – the adults live in the sloth fur and the larvae feed on the sloth faeces. They belong to the pyralid subfamily Chrysauginae (Insecta: Lepidoptera: Pyralidae). Although Pyralidae have been a focus of several molecular phylogenetic studies, including a few Chrysauginae genera, so far none of the three sloth moth genera have been sampled. This master’s thesis aimed to understand the phylogenetic relationships of Chrysauginae, and answer whether Chrysauginae and sloth moths are monophyletic groups. This was done using museomics methods. We have obtained samples from 45 genera and have sequenced their whole genomes. Combining our data with the DNA sequences from public databases, we inferred the first molecular phylogeny of Chrysauginae, including 45% of the genera. Our mitochondrial and BUSCO trees (as well as other nuclear datasets) showed that Chrysauginae are monophyletic, and sister to the subfamily Galleriinae. The sloth moths are within Chrysauginae, and also monophyletic. The closest non-sloth moth relative is the species Basacallis tarachodes. This is the first in-depth phylogenetic study for this group, and is thus a stepping stone to further our understanding of the evolutionary history of Chrysauginae, with a special focus on the sloth moth genera. (Less)
- Popular Abstract
- The ever-elusive sloth moths
Sloth moths, though unpopular and understudied, are a fascinating group of pyralid moths. Named after their lifestyle, they are known for their symbiotic relationship with sloths. The larvae feed exclusively on sloth faeces and as adults, the sloth moths find refuge and mates in the sloths’ fur.
The entire lifecycle of sloth moths is dependent on the sloths. We are not certain of how this relationship developed and evolved, or even if this relationship is of any benefit to sloths. Sloths are enigmatic when it comes to their symbiotic relationships—they have many other types of organisms in their fur such as beetles and algae, and these symbiotic relationships are also not well understood. We decided to... (More) - The ever-elusive sloth moths
Sloth moths, though unpopular and understudied, are a fascinating group of pyralid moths. Named after their lifestyle, they are known for their symbiotic relationship with sloths. The larvae feed exclusively on sloth faeces and as adults, the sloth moths find refuge and mates in the sloths’ fur.
The entire lifecycle of sloth moths is dependent on the sloths. We are not certain of how this relationship developed and evolved, or even if this relationship is of any benefit to sloths. Sloths are enigmatic when it comes to their symbiotic relationships—they have many other types of organisms in their fur such as beetles and algae, and these symbiotic relationships are also not well understood. We decided to answer one central question: are all sloth moths closely related to each other? This would let us know if this sloth-related lifestyle evolved just once, or multiple times and it would be a first step in unraveling the complicated relationships of sloths with their other symbionts.
We looked at the evolutionary relationships between sloth moths by studying the moth subfamily in which they are classified, Chrysauginae. The relationships were studied using phylogenetic methods, using both mitochondrial and nuclear DNA sequences. The results were visualised as phylogenetic trees, which are similar to family trees.
What did we learn?
Our family trees showed that the sloth moths are very closely related to each other, arising from one common ancestor! It also showed that the subfamily to which sloth moths belong, Chrysauginae, a natural group, meaning that they also all descend from one common ancestor. This is a breakthrough as we have never had a phylogenetic tree looking at so many Chrysauginae species, and we can now begin to understand how the different chrysaugine groups are related to each other within the subfamily.
There are other very exciting aspects of our results. The sloth moths consist of three genera: Bradypodicola, Bradypophila and Cryptoses. Interestingly, one of the Cryptoses species seems to be more closely related to the Bradypodicola species. Since Bradypodicola is the older name, it is very likely that the three Cryptoses species will have to instead be named under Bradypodicola so as to keep a natural classification.
Finally, one of the goals of the study was to try to understand how such a strange lifestyle evolved and we wanted to identify which group is the closest relative to sloth moths, as well as what kind of a lifestyle they have. This turned out to be Basacallis tarachodes. Not much is known about it, but this species may have larvae feeding on decayed organic matter, occasionally consuming faeces.
Master’s Degree Project in Biology|60 credits 2025
Department of Biology, Lund University
Advisors: Jadranka Rota (Biological Museum), Niklas Wahlberg, and Etka Yapar (Biodiversity and Evolution Unit) (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9214983
- author
- Mukherjee, Mahika
- supervisor
-
- Jadranka Rota LU
- Niklas Wahlberg LU
- Etka Yapar LU
- organization
- course
- BION03 20242
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9214983
- date added to LUP
- 2025-11-06 09:43:00
- date last changed
- 2025-11-06 09:43:00
@misc{9214983,
abstract = {{Sloth moths are highly-specialized for a life in a very close relationship with sloths – the adults live in the sloth fur and the larvae feed on the sloth faeces. They belong to the pyralid subfamily Chrysauginae (Insecta: Lepidoptera: Pyralidae). Although Pyralidae have been a focus of several molecular phylogenetic studies, including a few Chrysauginae genera, so far none of the three sloth moth genera have been sampled. This master’s thesis aimed to understand the phylogenetic relationships of Chrysauginae, and answer whether Chrysauginae and sloth moths are monophyletic groups. This was done using museomics methods. We have obtained samples from 45 genera and have sequenced their whole genomes. Combining our data with the DNA sequences from public databases, we inferred the first molecular phylogeny of Chrysauginae, including 45% of the genera. Our mitochondrial and BUSCO trees (as well as other nuclear datasets) showed that Chrysauginae are monophyletic, and sister to the subfamily Galleriinae. The sloth moths are within Chrysauginae, and also monophyletic. The closest non-sloth moth relative is the species Basacallis tarachodes. This is the first in-depth phylogenetic study for this group, and is thus a stepping stone to further our understanding of the evolutionary history of Chrysauginae, with a special focus on the sloth moth genera.}},
author = {{Mukherjee, Mahika}},
language = {{eng}},
note = {{Student Paper}},
title = {{Evolutionary history of sloth moths and their relatives (Insecta: Lepidoptera: Pyralidae)}},
year = {{2025}},
}