Understanding Our Coast: A Guide to Southern California Marine Pillbugs

A review of nearly 200 marine pillbugs, or underwater roly-polies, will improve ocean monitoring off the coast of Southern California.

Los Angeles, CA (May 16, 2023)—A 167-page summary of knowledge of marine pillbugs local to the Southern California coast was recently published in the open access journal ZooKeys, where it will serve as a critical guide for comprehensive ocean monitoring.

“This publication is the only review and guide that compiles current biodiversity data for this important group of animals in this region,” said Dr. Regina Wetzer, curator and director of the Marine Biodiversity Center at the Natural History Museum of L.A. County (NHM).

Synidotea magnifica_lateral isopod
A lateral view of Synidotea magnifica shows the sculpturing better than a dorsal view would.
Photo by Tim Stebbins

NHM researcher and marine pillbug expert, Dr. Wetzer and her colleague, NHM Research Associate Dr. Tim Stebbins, created this extensive review to improve ocean monitoring of the Southern California Bight (SCB), a 430-mile section of coastline running along the west coast of Mexico and the United States. The SCB region is an important ecological and economic resource because of its diverse and productive coastal ecosystems. It is also a region densely populated by humans and therefore is in close proximity to various pollutants, which makes the SCB the focus of some of the largest and most comprehensive ocean monitoring programs in the world.

Southern-California-Bight-region-from-Point-Conception-California-USA-to-Punta-Colonet
The Southern California Bight region from Point Conception, California, USA to Cabo Colonet, Baja California, Mexico.
Imagery © 2023 TerraMetrics, Map data © 2023 Google, INEGI

“A key component of those programs is documenting changes in marine animal communities that live on the seafloor, including pillbug populations,” said Dr. Stebbins.

Pillbugs, also known as isopods, are a group of invertebrates (animals without backbones) related to crabs, shrimp, and lobsters. There are over 10,600 described species of pillbugs worldwide that live in diverse habitats, from rocky mountains, to dry deserts, to the deep sea. 

Colidotea rostrata_dorsal
Colidotea rostrata, a commensal species of isopod that lives only amongst the spines of sea urchins. Commensalism is a relationship between two organisms where one benefits while the other neither benefits nor derives harm. 
Photo by Tim Stebbins

About half of known pillbugs live in the ocean, including the SCB, residing in nearly every kind of marine habitat from rocky shores to sandy beaches, shallow bays, and even deep beneath the surface of the ocean on the seafloor. Marine pillbugs are also found in smaller microhabitats amongst rocks, sponges, and algae. “Until this publication, most information on these species has been scattered amongst a vast scientific literature published over the past 100 years,” Dr. Stebbins said. 

exosphaeroma pentcheffi isopod on black
Exosphaeroma pentcheffi, an isopod that was discovered near the Port of Los Angeles.
Photo by Adam Wall

This paper is scientists’ best attempt to bring together the morphological, habitat, and distributional data of the 190 known species of marine pillbugs in the SCB. It includes ten keys to help researchers identify the species in this guide. Dr. Stebbins and Dr. Wetzer hope that future versions of this guide will function as a direct entry point to all available data and research relevant to this region’s taxonomy and biogeography. 

This review was made possible thanks to the generous support of the Southern California Association of Marine Invertebrate Taxonomists and the Natural History Museum of Los Angeles County.  
         
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