Antranig Basman, Charlie Gibbs, Donna Gibbs, Elaine Humphrey, Andy Lamb, Andrew Simon
May 15th, 2023
Galiano Island’s arrow worm diversity
The name ‘Chaetognatha’ derives from the Greek χαίτη (khaítē), meaning “bristle”, and γνάθος (gnáthos), meaning “jaw”.
Chaetognatha (arrow worms) are a small phylum of predatory animals, all of which are marine, including 130 extant species in the class Sagittoidea. Though they are not diverse, arrow worms are extremely numerous, representing a major component of marine plankton worldwide. Of the six species of arrow worm known to the Northeast Pacific, four have been sampled in the waters off the coast of British Columbia. It is not possible to determine chaetognath reports in the Galiano Island record as they are based on dive observations, but studies indicate that, in all likelihood, these observations refer to Parasagitta elegans.
The arrow worm Parasagitta elegans – Photograph by Elaine Humphrey
Community science contributions
Since the Biodiversity Galiano project began in 2016, our community has not yet identified any arrow worms to species around Galiano Island, though arrow worms have been observed historically through the Pacific Marine Life Surveys. Parasagitta elegans is the most abundant species reported from the sheltered inland waters of the Salish Sea. Eukrohnia hamata is also known to occur infrequently in inland channels, as an oceanic species that is occasionally borne in by the intrusion of offshore waters. Sampling by use of plankton tows and microscopic analysis would help confirm the local fauna.