Compound sea squirt

Didemnum vexillum

Other invertebrates
IUCN: Not evaluated

Usual depth35–102 m
Water temperature9–18 °C
Best monthsSeptember
How commonOccasional

Photo credit: no rights reserved, uploaded by Al Kordesch · CC0 1.0 · iNaturalist

About this species

Didemnum vexillum is a species of colonial tunicate in the family Didemnidae. It is commonly called sea vomit, marine vomit, pancake batter tunicate, or carpet sea squirt. It is thought to be native to Japan, but it has been reported as an invasive species in a number of places in Europe, North America and New Zealand. It is sometimes given the nickname "D. vex" because of the vexing way in which it dominates marine ecosystems when introduced into new locations; however, the species epithet vexillum actually derives from the Latin word for flag, and the species was so named because of the way colonies' long tendrils appear to wave in the water like a flag.

Text from the Wikipedia article “Didemnum vexillum”, licensed CC BY-SA 4.0. Read the article

Where and when

Where it has been recorded

Worldwide

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Best months

Worldwide (open data)

January: 321 records
February: 187 records
March: 197 records
April: 165 records
May: 287 records
June: 342 records
July: 498 records
August: 430 records
September: 1,081 records
October: 178 records
November: 346 records
December: 246 records

Depth and water temperature

Depth

Mostly recorded at 35–102 m · Deepest record: 117.9 m

0–10 m: 16 records
10–20 m: 10 records
20–30 m: 20 records
30–40 m: 109 records
40–50 m: 140 records
50–60 m: 35 records
60–70 m: 30 records
70–80 m: 115 records
80–90 m: 37 records
90–100 m: 61 records
100–110 m: 34 records
110–120 m: 38 records

Water temperature

Recorded in surface water of 9–18 °C

8–10 °C: 152 records
10–12 °C: 81 records
12–14 °C: 166 records
14–16 °C: 149 records
16–18 °C: 301 records

Photos

(c) Bernard Picton, some rights reserved (CC BY) · CC BY · iNaturalist
no rights reserved · CC0 1.0 · iNaturalist
(c) Libby Keatley, some rights reserved (CC BY) · CC BY · iNaturalist
no rights reserved · CC0 1.0 · iNaturalist
(c) Robbie, some rights reserved (CC BY) · CC BY · iNaturalist
no rights reserved · CC0 1.0 · iNaturalist
(c) Robbie, some rights reserved (CC BY) · CC BY · iNaturalist

Names and classification

English: Compound sea squirt, Carpet Sea Squirt, Carpet Sea Squirt, Marine Vomit, compound sea squirt, Compound Sea Squirt, Marine Vomit, Pancake Batter Tunicate, Sea Vomit, Sea Vomit Tunicate

Names in 1 more languages

French: Didemne étendard, Pâte à crêpe, Tunicier didemnum, Didemne étendard

Other scientific names: Didemnum vestitum, Didemnum vestum

Similar species

Northern white crust
Didemnum albidum
Green Barrel Sea Squirt
Didemnum molle
Didemnum jucundum
Moseley's Ascidian
Didemnum moseleyi
Colonial tunicate
Didemnum perlucidum
Ascidian
Didemnum psammatodes

Sources and credits

Names and taxonomy: WoRMS (CC BY 4.0) and the GBIF Backbone (CC BY 4.0). Photos: iNaturalist observers, each under the licence shown (CC0, CC BY or CC BY-SA).

Depth, temperature, months and maps: records from OBIS and GBIF under CC0 or CC BY.
Descriptions: Wikipedia, licensed CC BY-SA, each linked to its article.
Conservation status as published by GBIF (IUCN Red List).
4,314 open-data records from 1993 to 2025.
Species data updated November 2, 2026.

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