As we continue our series on marine life in the Gulf of Mexico, we also continue our articles on marine worms. Worms are not the most charismatic creatures in the Gulf, but they are very common and play a large role on how life functions in this environment. Roundworms are VERY common. There are at least three phyla of them but here we will focus on one – the nematodes.

Most nematodes are microscopic, a large one would be about 2 inches, and some beach samples have found as many as 2 million worms in 10 ft² of sand. So, what do we know about them? What role, or function, do they play in the ecology of the Gulf of Mexico?

Well first, they are long and round – cylinder shaped. There is a head end, but it is hard to tell which end is the head. Round is considered a step up from being flat in that it can allow for an internal body cavity. An internal body cavity can allow for the development of internal body organs. Internal body organs can move large amounts of nutrients, blood, oxygen, and hormones around the body allowing the animal to become larger. Some argue that a larger body can have advantages over smaller ones. Some say the opposite, but either way – a large body has been successful for some creatures and an internal body cavity is needed for this.

That said, the nematodes do not have a complete internal body cavity. So, they do not have a complete assortment of internal organs. Being round reduces your efficiency in absorbing enough needed nutrients, oxygen, etc. through your skin alone and this MAY be a reason they are small. They are very small.

There are free living and parasitic forms in this group. There are at least 10,000 species of them, and they can be found not only in the marine environment, but also in freshwater and in the soil found on land. They have played a role in the success of agriculture, infesting both crops and livestock. Nematodes can be a big concern for farmers and gardeners.

The free-living forms are known to be carnivorous, feeding on smaller microscopic creatures. They have toothed lips, and some have a sharp stylet to grab or stab their prey. Some stylets are hollow and can “suck” their prey in. Moving through the environment, they can consume algae, fungi, and diatoms. Some are deposit feeders and others are decomposers. On our farms and in our gardens, they are known to enter plants via the roots and can be found in the fruit.

The parasitic version of nematodes has been a problem for some species. In humans we have the hookworms and pinworms. Dogs have their heart worms. An interesting twist on the parasitic nematode way of life, compared to flatworms like tapeworms, is their lack of a secondary (or intermediate host). The entire life cycle can take place in the same animal.

Females are larger than males and fertilizations is internal. Males are usually “hooked” at the tail end and hold on to the females during mating. About 50 eggs will be produced and released into the digestive tract, where they exit the animal in the feces and find new hosts either by the feces being consumed or drifting in the water column.

There multiple forms of parasitism in nematodes.

– Some are ectoparasites (outside of the body) on plants.

– Some are endoparasites in plants – some forming galls on the leaves.

– Some infest animals but only as juveniles.

– Some live-in plants as juveniles and animals as adults.

– Some live-in animals as juveniles and plants as adults.

It would be fair to say that many forms of marine creatures have nematodes living either within them, or on them. Some can be problematic and cause disease; some diseases can be quite serious. Others play an important role in “cleaning” the ocean, filtering the sand of organic debris. Many have heard of nematodes but know little about them. Either good or bad, they do play roles in the ecology of the Gulf of Mexico.

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