GUT WEED – Ulva intestinalis Linnaeus, 1753

Closer view of the Gut weed Ulva intestinalis

Gut weed (Ulva instestinalis) also called as grass kelp is a common species of green alga (Chlorophyta) found along the east and west coasts of India. Many research works may refer the scientific name as Enteromorpha instestinalis but, after genetic work carried out in the early 2003*, the genus name has been given as Ulva (contains algae commonly called sea lettuce).

Gut weed prefer to grow on gravel, rocky bottoms or even in muddy substrata (as seen in the image). They are also found in estuaries and salt marshes where the salinity is lower due to freshwater mixing. During low tides, they are exposed forming long mat-like chains. The shoots grow tubular and long, and are filled with gas (aids in floating when water levels are high). Through water current movements or tidal surges, they are washed ashore in large quantities. They attach to the substrate with minute disc-shaped hold fasts (also called as basal rhizoidal cell).

Gut weed exposed during low tide in Pulicat Lake near Chennai, Tamil Nadu, India

The shoots of Gut weed are pale green in colouration growing 20-40 cms in length and thrive up to depths of 7 meters (21 feet). Occasionally they might be bleached white because of long duration of exposure to sun. This green algae alternate between asexual and sexual life stages (referred to as alternation of generation). For the sexual phase, the gametes and zoospores are released from the tip of the fronds and when fertile the tips become orange-yellow coloured in males and yellow-green in females.

Gut weeds are sold as foodstuff in many parts of the world. Gut weeds have been recorded from Goa, Malvan, Ratnagiri, Karwar, Honawar, Lakshadweep, Gulf of Mannar, Palk Bay, Chennai and Andhra coasts. In Pulicat Lake, they are found to be thriving well along with seagrass in shallow waters.

Taxonomic position

Kingdom: Plantae

Phylum: Chlorophyta

Class: Ulvophyceae

Order: Ulvales

Family: Ulvaceae

Genus: Ulva

Species: U.intestinalis

Author: Linnaeus, 1753

IUCN Status

Not Assessed

* Hayden, H.S., Blomster, J., Maggs, C.A., Silva, P.C., Stanhope, M.J. & Waaland, J.R. (2003). Linnaeus was right all along: Ulva and Enteromorpha are not distinct genera. European Journal of Phycology 38: 277-294.

Identifier: Dr. C. Parthiban

©Deepak Samuel, May 2014