It’s always nice when you find out that something unusual is not an invasive species. With so many changes afoot in the Gulf of Maine, there have been some strange visitors in the water and along the shore. Blue crabs that typically frequent the Chesapeake area and black sea bass that are more common in New Jersey and places further south. This unusual find is native to both the northern Atlantic and Pacific oceans.

Chorda filum is not only found in a number of places but also is known by a number of different common names. As you might guess, it has a thread-like form, which gives it the lovely names mermaid’s tresses and sea-twine as well as the not-so-lovely names cat’s gut and dead man’s rope. It has a simple form — a long thread — but if you look more closely, you can see that it is hollow inside. This long thread can be more than 25 feet long!

It is a brown algae that is related to the common rockweeds that form the flopping mats that protect coastal tide pools and shares having a holdfast at the end that attaches it to a variety of surfaces like shells, rocks or other algal species. The holdfast is very small, though, and is often buried in the sand or mud. Chorda filum also has small, spiral-shaped gas floats at the end of its fronds similar to the floats found on rockweed that help it sway in the water and reach up towards the light to photosynthesize. The floats in mermaid’s tresses, however, often break off and all that you see is the simple thread. Also, there are tiny, translucent hairs that cover its surface, but these are impossible to see with the naked eye. Like rockweed, it is also found in shallow waters but is more limited in its habitat to the most protected shores.

The sample that I found was wrapped around my foot as I got out of the water. Its slippery texture was a little disconcerting at first, until I realized what it was. With the help of some colleagues at Maine Sea Grant, who helped me puzzle out its identity, I was delighted to find out that, while I hadn’t seen it before, this cat’s gut belonged here. It was a good reminder that as well as you think you know a place, there is always more to see.

There is a wonderful story about Samuel Scudder, a student of Louis Agassiz, a prominent natural history professor at Harvard. He wrote an essay, “Take this Fish and Look at It,” about the lesson Agassiz taught him about careful observation. Apparently, Agassiz gave Scudder a fish in a jar. He said, “Take this fish and look at it … by and by I will ask what you have seen.” Scudder recalled, “In the 10 minutes I had seen all that could be seen in that fish, and started in search of the professor.” After he shared his observations, Agassiz scolded, “You have not looked very carefully. You haven’t even seen one of the most conspicuous features of the animal, which is plainly before your eyes as the fish itself; look again, look again!” The entire essay is worth reading and is something I come back to repeatedly when I think I am familiar with something in the natural world or even otherwise. In a culture and time period where there is no shortage of things to see and experience and the content is designed to be quick and intense so that you can move on to the next new thing, Scudder’s lesson is worth putting into practice. Instead of moving on too quickly, “Look again! Look again!”

Susan Olcott is director of strategic initiatives for Maine Coast Fishermen’s Association.