The peculiar life of a Pacific sand dollar

Pacific sand dollars are a local species which belong to the same group as sea urchins. While alive, they are covered entirely by thousands of densely packed, short and slender spikes. (Photo courtesy of Louise Page)Pacific sand dollars are a local species which belong to the same group as sea urchins. While alive, they are covered entirely by thousands of densely packed, short and slender spikes. (Photo courtesy of Louise Page)
Pacific sand dollars are a local species which belong to the same group as sea urchins. While alive, they are covered entirely by thousands of densely packed, short and slender spikes. (Photo courtesy of Louise Page)Pacific sand dollars are a local species which belong to the same group as sea urchins. While alive, they are covered entirely by thousands of densely packed, short and slender spikes. (Photo courtesy of Louise Page)
A zoomed-in look at the spikes of a Pacific sand dollar, a local species which belong to the same group as sea urchins. While alive, they are covered entirely by thousands of densely packed, short and slender spines. (Photo courtesy of Louise Page)A zoomed-in look at the spikes of a Pacific sand dollar, a local species which belong to the same group as sea urchins. While alive, they are covered entirely by thousands of densely packed, short and slender spines. (Photo courtesy of Louise Page)

Sand dollar exoskeletons are often collected along the beaches of Vancouver Island, but one might not realize that prior to washing up on shore came an entire curious lifetime.

Pacific sand dollars are a local species which belong to the same group as sea urchins. While alive, they are covered by thousands of densely packed, short and slender spikes. Unlike their sharp, unapproachable, long-spiked sea urchin relatives, sand dollars have a more velvet-like covering.

“The entire surface of a sand dollar is covered by its skin, all of the spikes even have a very thin layer of skin,” said Louise Page, who teaches invertebrate biology and marine biology at the University of Victoria. “When they die, the skin decomposes, the muscles attaching the spines decompose and the spines fall off. So when you pick a dead sand dollar up on the beach, it’s a white disk and you can no longer see the little spikes.”

The spines of a sand dollar allow them to move, and bury themselves under sand and mud. The spines wave back and forth, which pulls their body in and out of the sand.

The beautiful flower-shaped pattern you see on a dead sand dollar, is a pattern revealing where specialized gills once attached.

“The flower pattern marks the point where specialized gills extend to the surface for gas exchange. It’s how they breathe,” said Page.

READ ALSO: Rare bird spotted at Vancouver Island backyard feeder

Sand dollars have a rather bland diet – in a human’s opinion – feeding primarily on, you may have guessed it… sand. To be more specific, they eat and digest grains of sand, but each grain is coated with a film of organic matter, which provides nourishment for their little bodies.

“An interesting thing about Pacific sand dollars, which is very unusual, is that they will also stand up… and then when water flows past them, they can capture small zooplankton in the water and feed on it,” noted Page.

Life out there as a larvae in the big ocean is risky, to say the least. The larvae of sand dollars don’t look anything like their adult self, said Page, and the time until metamorphosis generally takes about four to six weeks.

When it comes time to undergo metamorphosis, the larvae will settle on the sand, and from there, a sand dollar pops out of the left side of its juvenile body. The rest of the larvae body then degenerates.

Essentially, after being whisked around in the ocean for weeks, the fortunate larvae will smell adults of the same species, and then settle at that site.

“Where adult sand dollars are living is a great place for the juniors to recruit into. This is because there is a species of tube-dwelling crustaceans called ‘tanaids’ in the sand, which feed on newly metamorphosed sand dollars,” said Page.

“It turns out that the burrowing activity of adult sand dollars, who tend to live in beds, break up the tubs of these tanaids – and exclude the tanaids from that area. So now it’s a much safer place for little juvenile sand dollars to survive.”

READ ALSO: Kings Park advocates call on Saanich to extend fundraising deadline, contribute $1.75 million to save greenspace


Do you have a story tip? Email: vnc.editorial@blackpress.ca.

Follow us on Twitter and Instagram, and like us on Facebook.

West Shore

Just Posted

This conceptual rendering shows revisions to the proposed warehouse in Sidney on land under the authority of the Victoria Airport Authority. York Realty, which plans to build, then lease the building, said significant changes to the the massing and height of the building respond to community feedback. Additional feedback can be submitted until June 30. (Screencap/York Realty)
Sidney warehouse proposal lands Greater Victoria Chamber of Commerce endorsement

Public has until June 30 to submit additional comments after significant modifications

An eastern cottontail rabbit on the UVic campus. (Evert Lindquist/News Staff)
Wild rabbits persist at the University of Victoria

Feral rabbits are still absent, but another non-native species has arrived on campus

Staff will be reviewing public feedback from second-stage designs for cycling infrastructure in James Bay, part of the City of Victoria’s 32-kilometre network. (Black Press Media file photo)
Victoria sends James Bay bike lanes choice to next phase

Design modifications based on community input to be delivered to council this summer

Eric White’s roadside farm stand in Metchosin sits stocked with produce. (Photo courtesy of Eric White)
Fledgling Metchosin farmer frustrated by thefts from stand

Eric White said every dollar made at the roadside helps sustain his farm

Greater father involvement in the home leads to improved childhood development and increased marital satisfaction, says expert. (Black Press Media file photo)
University of Victoria researcher finds lack of father involvement a drag on gender equality

Working women still taking on most child and household duties in Canada

People line up to get their COVID-19 vaccine at a vaccination centre, Thursday, June 10, 2021 in Montreal. THE CANADIAN PRESS/Ryan Remiorz
Vaccines, low COVID case counts increase Father’s Day hope, but risk is still there

Expert says people will have to do their own risk calculus before popping in on Papa

(Black Press Media file photo)
POLL: When was the last time you visited the mainland?

The films are again lighting the screens at local theatres, the wine… Continue reading

Anyone with information on any of these individuals is asked to call 1-800-222-TIPS (8477) or visit the website victoriacrimestoppers.ca for more information.
Greater Victoria Crime Stoppers wanted list for the week of June 15

Greater Victoria Crime Stoppers is seeking the public’s help in locating the… Continue reading

The Co-op gas station at Whiskey Creek is burning after a camper van exploded while refueling just before 4 p.m. on Thursday, June 17, 2021. (FACEBOOK PHOTO)
Exploding camper van torches Highway 4 gas station between Qualicum Beach and Port Alberni

Highway traffic blocked after Whiskey Creek gas station erupts into flames

Helen Austin performing with Trent Freeman at the 2018 Vancouver Island MusicFest. Austin is one of the many performers listed for the 2021 event.
Vancouver Island MusicFest goes virtual for 2021

Black Press to stream 25 hours of programming July 9-11

FILE – A science class at L.A. Matheson Secondary in Surrey, B.C. on March 12, 2021. (Lauren Collins/Surrey Now Leader)
Teachers’ union wants more COVID transmission data as B.C. prepares for back-to-school

BCTF says that details will be important as province works on plan for September

Provincial health officer Dr. Bonnie Henry outlines B.C.’s COVID-19 restart plan, May 25, 2021, including larger gatherings and a possible easing of mandatory masks on July 1. (B.C. government photo)
B.C. records 120 new COVID-19 cases, second vaccines accelerating

Lower Pfizer deliveries for early July, Moderna shipments up

A Heffley Creek peacock caught not one - but two - lifts on a logging truck this month. (Photo submitted)
Heffley Creek-area peacock hops logging trucks in search of love

Peacock hitched two lifts in the past month

The Calgary skyline is seen on Friday, Sept. 15, 2017. THE CANADIAN PRESS/Jeff McIntosh
2 deaths from COVID-19 Delta variant in Alberta, 1 patient was fully immunized

Kerry Williamson with Alberta Health Services says the patients likely acquired the virus in the hospital

Most Read