This page last revised: 4-11-2020
Click on photos to enlarge.
Mollusks
Aberrations, Mutations & Twins
of Marine Life on the West Coast of North America
Bivalves
Zirfaea pilsbryi - Rough Piddocktwinned exhalent siphon
all photographed in Rich Passage, Puget Sound, WA - 2012, 2012 & 2013 respectively
Tresus sp. - Horse Clamtwinned inhalent siphon
Rockaway Beach, Bainbridge Is., WA, 2007
Tresus sp. - Horse Clamtwinned inhalent siphon
Langley Tire Reef, Whidbey Is., WA, 2006
Zirfaea pilsbryi - Rough Piddocktwinned inhalent siphon
Rich Passage, Puget Sound, WA, 2012
Flabellina verrucosa
Red-gilled Nudibranchmerged rhinophore with two tips instead of two separate rhinophores
Rich Passage, Puget Sound, WA, 2013
Nudibranchs
Anemones
Chitons
Metridium farcimen - Giant Plumose Anemonetwinsleft - Langley Harbor, Whidbey Island WA, 2008right - Seahurst Park, Burien, WA, 2007
Neah Bay, WA, 1982 Sitka, AK, 1983
Lepidozona mertensii Merten's Chiton
7 plates instead of 8
Metridium senile Short Plumose AnemonetwinPenrose Point State Park, Puget Sound, WA, 2014
Stomphia didemon Swimming AnemonetwinFlagpole Point, Hood Canal, WA, 2012
Lepidozona pectinulata 9 plates instead of 8
Palos Verdes, CA, 1999
Cyanoplax hartwegii6 plates instead of 8Puerto Santo Tomas, Baja Norte, 1982
Chaetopleura lanuginosa6 plates instead of 8
Punta Banda, Baja Norte, 1982
Nuttallina californica California Nuttall's Chiton9 plates instead of 8La Jolla, CA, 1934
Tonicella lineata (Wood, 1815)Lined Chiton9 plates instead of 8Adak, Is., AK, 1966
Seastars
Dermasterias imbricata
Leather Star 4 limbs instead of 5, replaced only one when two were lost or only started with four
Point Hudson, Port Townsend, WA, 2013
Anthopleura elegantissima
Aggregating Anemone
twin
Freshwater Bay, WA, 2015
Mopalia ferreirai
7 plates instead of 8
Metlakatla, AK, 1990
Seastars will regrow limbs lost to predator attacks, but sometimes they regrow them in unusual ways.
Mopalia spectabilis
Red-Flecked Mopalia
7 plates instead of 8
San Francisco, CA, 1982
Mopalia swaniiSwan's Mopalia7 plates instead of 8Tacoma, WA, 1965
Dermasterias imbricata
Leather Star7 limbs instead of 5Twanoh State Park, Hood Canal, WA, 2011
Henricia leviuscula - Blood Star4 limbs instead of 5Freshwater Bay, Strait of Juan de Fuca, WA, 2014
Henricia pumila
Dwarf Mottled Henricia6 limbs instead of 5
Deception Pass State Park, WA, 2008
Dermasterias imbricata Leather Star6 limbs instead of 5
Ed's Fault, Discovery Bay, WA, 2015
Crabs
Mediaster aequalis
Vermilion Star4 limbs instead of 5
Pulali Point, Hood Canal, WA, 2015
Dermasterias imbricataLeather Starone limb split at the end, likely after an injury
Green Point, east of Port Angeles, WA, 2017
Henricia leviusculaBlood Starone limb split at end
Rich Passage, WA, 2020
Henricia leviuscula - Blood Star
6 limbs instead of 5
Klas Rocks, near Mats Mats Bay, WA, 2015
Pteraster tesselatus
Cushion Star6 limbs instead of 5
Rich Passage, WA, 2010
Zirfaea pilsbryi - Rough Piddock twin inhalent & exhalent siphons
Rich Passage, Puget Sound, WA, 2019
Cancer magisterDungeness Crabtwinned claw
photographed at the University of Washington, no data available
Henricia leviuscula - Blood Star6 limbs instead of 5Freshwater Bay, Strait of Juan de Fuca, WA, 2014
Tresus sp. - Horse Clamtwinned inhalent siphon
Freshwater Bay, Strait of Juan de Fuca,
WA, 2014
