Tentaculata

LightRefractsOf comb-rows of ctenophore Mertensia ovum

Tentaculata is a subphylum of aquatic invertebrates belonging to the phylum Ctenophora, commonly known as comb jellies. The members of this subphylum are characterized by the presence of two long tentacles, which are used for capturing prey. Unlike their ctenophore relatives, which primarily use cilia arranged in rows (combs) for locomotion, Tentaculata species rely on their tentacles for both movement and feeding. This group includes a variety of species, ranging from the well-known sea gooseberry to the more obscure deep-sea dwellers.

Characteristics

Tentaculata species are distinguished by their two tentacles, which are often retractable and can be adorned with specialized cells called colloblasts or lasso cells. These cells secrete a sticky substance that adheres to prey, facilitating capture. The body of a Tentaculata is typically globular or cylindrical, with an outer layer known as the epidermis and an inner layer called the gastrodermis. Between these layers is the mesoglea, a gelatinous substance that helps maintain the body's shape.

The digestive system of Tentaculata is simple, with a mouth leading to a gastrovascular cavity that serves both digestive and circulatory functions. Some species possess a pair of anal pores for excretion, although this is not universal across the subphylum.

Habitat and Distribution

Tentaculata species are found in a variety of marine environments, from shallow coastal waters to the deep sea. They are distributed globally, from the Arctic to tropical regions. Their ability to inhabit a wide range of depths and conditions is a testament to their adaptability and the diversity of the subphylum.

Ecology and Behavior

Tentaculata play a significant role in marine ecosystems, primarily as predators of small planktonic organisms. Their tentacles allow them to capture prey with precision, and their diet can include anything from small copepods to larvae of various marine species. Some Tentaculata are known to exhibit bioluminescence, producing light through biochemical reactions. This ability can be used for attracting prey or as a means of defense against predators.

Reproduction

Reproduction in Tentaculata can be both sexual and asexual, depending on the species. Sexual reproduction involves the release of eggs and sperm into the water, where fertilization occurs externally. Many species are hermaphroditic, possessing both male and female reproductive organs. Asexual reproduction, when it occurs, is typically through a process known as budding, where a new individual grows from the body of an existing one.

Conservation

While many Tentaculata species are not currently considered to be at risk, their populations can be affected by changes in marine environments, such as pollution, overfishing, and climate change. The impact of these factors on Tentaculata populations is an area of ongoing research.

See Also

• Ctenophora
• Invertebrate
• Marine biology
• Bioluminescence