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Cephalopod Sex Determination and its Ancient Evolutionary Origin
Gabrielle C Coffing1, Silas Tittes1, Scott T Small1
1Department of Biology, University of Oregon.
Biorxiv : the Preprint Server for Biology
|March 11, 2024
Summary
Researchers sequenced the California two-spot octopus genome, revealing a unique sex chromosome system (ZO/ZZ) and providing the first genetic evidence for sex determination in cephalopods. This ancient chromosome has been conserved across cephalopod evolution.
Area of Science:
- Genomics
- Evolutionary Biology
- Marine Biology
Background:
- Coleoid cephalopods (octopuses, squids, cuttlefish) possess complex traits like advanced nervous systems and camouflage.
- Cephalopods represent a deeply diverged lineage, originating around 550 million years ago.
- Genomic insights are crucial for understanding the evolution of novel cephalopod traits.
Purpose of the Study:
- To establish a chromosome-scale reference genome for the California two-spot octopus (O. bimaculoides).
- To investigate the genomic basis of unique cephalopod characteristics, particularly sex determination.
- To reconstruct the evolutionary history of cephalopod sex chromosomes.
Main Methods:
- PacBio long-read sequencing of genomic DNA.
- IsoSeq full-length mRNA sequencing for gene annotation.
- Comparative genomics using whole genome alignments of multiple cephalopod species.
Main Results:
- A high-quality, chromosome-scale genome assembly and annotation for O. bimaculoides was generated.
- The study identified a single sex chromosome in females (ZO) and two in males (ZZ), confirming genetic sex determination.
- Phylogenetic analysis revealed the sex chromosome is ancient, predating cephalopod radiation (~480 million years ago) and highly conserved.
Conclusions:
- The genome assembly provides a valuable resource for cephalopod research.
- Genetic sex determination in cephalopods is confirmed, with a conserved, ancient sex chromosome.
- This finding offers new perspectives on the evolution of sex determination mechanisms in invertebrates.
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