Adventures of a sea squirt sleuth: unraveling the identity of Didemnum vexillum, a global ascidian invader

By G. Lambert. 2009

165 citations recorded by the source corpus.

The magnitude of the worldwide invasions of Didemnum vexillum Kott, 2002 has taken a number of years to be comprehended. During the past 15 years, it has been identified as different species depending on its location—D. carnulentum on the U.S. west coast, D. lutarium or D. vestum in New England, D. lahillei or D. helgolandicum in France and the Netherlands, D. vexillum in New Zealand, D. pardum or D. moseleyi in Japan. A number of recent publications refer to it as Didemnum sp. or Didemnum sp. A. This paper presents a chronology of the steps in the development of our awareness and understanding of this species based on comparative morphology and genetics, and lists invaded regions and the approximate minimum length of time it has been known in each area. Evidence is presented that D. vexillum may have originated in Japan. The importation of vast quantities of Japanese oysters and spat into many countries prior to the 1960s is discussed but eliminated as a likely vector because there are no reports of a sudden didemnid ascidian appearance prior to the 1970s. Introductions (including to the type locality in New Zealand) are very likely due to shipping (either via hull or sea chest fouling), with subsequent local spreading by fouled recreational craft, barges, etc., drifting and reattachment of dislodged fragments, and movements of fouled aquaculture stock and gear. Based on morphological and genetic comparisons of hundreds of world-wide samples, museum type specimens, and anecdotal information on the presence of this species in various locations over several or many decades, the valid name is concluded to be Didemnum vexillum Kott, 2002 due to the lack of any pre-existing published description. D. vestum Kott, 2004 is synonymized under D. vexillum.

Subfields: Ecology, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/1c8a6119f3b93455d0aa503faa24a42dd14ba11f

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In Ecology

1. T. Therriault
2. I. Davidson
3. C. Simkanin
4. G. Jamieson
5. J. Dower
6. G. Lambert
7. Aibin Zhan
8. H. MacIsaac

In Global and Planetary Change

1. G. Lambert
2. T. Therriault
3. C. Simkanin
4. I. Davidson
5. J. Dower
6. G. Jamieson
7. H. MacIsaac
8. Sara Ghabooli

Citations in the corpus

• Ascidians as models for studying invasion success (2015, background): “Coupled with morphological evidence, D. vexillum seems to be the most appropriate name for this ascidian species (Lambert 2009; Stefaniak et al. 2009).”
• Anthropogenic structures and the infiltration of natural benthos by invasive ascidians (2012, background): “Since the identity of Didemnum vexillum only recently has been determined (see Lambert 2009; Stefaniak et al. 2009) we searched for both Didemnum sp. and Didemnum vexillum.”
• Genetic conspecificity of the worldwide populations of Didemnum vexillum Kott, 2002. (2009, background): “…non-feeding larvae that could limit gene flow, to have a low genetic variation (based on coI) on a global scale, the most likely explanation is recent invasion in multiple regions, an explanation that is supported by the timeline of discovery of D. vexillum populations world wide (Lambert 2009).”