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Cephalopod sex determination and its ancient evolutionary origin.
Gabrielle C Coffing1, Silas Tittes1, Scott T Small1
1Institute of Ecology and Evolution, University of Oregon, 1585 E 13th Ave, Eugene, OR 97403, USA.
Current Biology : CB
|February 4, 2025
Summary
Researchers sequenced the California two-spot octopus genome, revealing a unique sex determination system. This finding provides the first genetic evidence for sex chromosomes in cephalopods, dating back millions of years.
Area of Science:
- Cephalopod Genomics
- Evolutionary Biology
- Invertebrate Zoology
Background:
- Coleoid cephalopods (octopuses, squids, cuttlefish) display complex behaviors and novel traits.
- Cephalopods possess the most complex invertebrate nervous system and advanced camera-type eyes.
- This lineage diverged from other mollusks approximately 550 million years ago.
Purpose of the Study:
- To explore the genomic underpinnings of cephalopod novelties.
- To establish a chromosome-scale reference genome for the California two-spot octopus (O. bimaculoides).
- To investigate the evolutionary origins of cephalopod traits.
Main Methods:
- PacBio long-read sequencing of genomic DNA.
- Iso-Seq full-length mRNA sequencing.
- Whole-genome alignments of multiple cephalopod species.
Main Results:
- A chromosome-scale reference genome and annotation for a female O. bimaculoides was generated.
- The study identified a single sex chromosome in females (ZO) and two in males (ZZ), indicating genetic sex determination.
- The cephalopod sex chromosome is ancient, predating the radiation of extant species ~480 million years ago.
Conclusions:
- This research provides the first genetic evidence for sex determination in cephalopods.
- The identified sex chromosome has been conserved across cephalopod evolution.
- The genome assembly offers a foundation for future studies on cephalopod biology and evolution.
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