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Dolphinitely a gray area

The Risso’s dolphin, Grampus griseus, sets some impressive #travelgoals. Some estimates say that the Risso’s dolphin may spend as much as 77% of their lives traveling [1]! Their geographical range is spread across the world, although they prefer deeper waters over the coast. From temperate to tropical waters, the Risso’s dolphin can be found in pods of 10-30 individuals [2].

Sometimes called the gray dolphin, the coloring of this species changes with age. Risso’s dolphins start their lives as black or dark gray in color and then lighten to a gray/white as they mature. The skin of this species is often marked by many scars, usually caused by teeth raking from other dolphins [3].

Unlike most cetaceans, the Risso’s dolphin lacks any upper teeth but instead can have several rows of peg-like teeth on their lower jaw. These teeth are useful in catching their preferred prey the cephalopods and also may play a role in mating behavior [4].

Risso's Dolphin, Grampus griseus by Robin Agarwal, [CC BY-NC 2.0], via

Today, we share the chromosome-length assembly for the Risso’s dolphin. This is a $1K de novo genome assembly with a contig N50 = 62 Kb and a scaffold N50 = 93 Mb. See Dudchenko et al., 2018 for details on the assembly procedure.

The sample for this genome assembly was provided to us by Barbie Halaska, Necropsy Manager at The Marine Mammal Center in Sausalito, California. As the world’s largest marine mammal hospital, the Center prides itself on gathering and providing open research data that is free to access, reuse, repurpose and redistribute in service to ocean conservation and marine mammal health.

This sample was collected by The Marine Mammal Center under the Marine Mammal Health and Stranding Program (MMHSPR) Permit No. 18786-04 issued by the National Marine Fisheries Service (NMFS) in accordance with the Marine Mammal Protection Act (MMPA) and Endangered Species Act (ESA). The work at DNA Zoo was performed under Marine Mammal Health and Stranding Response Program (MMHSRP) Permit No. 18786-03.

Want to compare this genome against other members of the Delphinidae family? You’re in luck as this is the DNAZoo’s 8th genome assembly of a dolphin species! Check out the assembly pages for the bottlenose dolphin and the Commerson’s dolphin.

We thank Barbie Halaska, Laura Sherr, Giancarlo Rulli and Ben Neely for their help with this genome assembly!

Learn more about the impact of The Marine Mammal Center’s scientific research by visiting the TMMC website at


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