Euplokamididae

''Euplokamis'' is a genus of ctenophores, or comb jellies, belonging to the monotypic family Euplokamididae. Despite living for hundreds of millions of years in marine environments, there is minimal research regarding ''Euplokamis'', primarily due to their body structure. Research on the evolution of the basic body structures of diploblastic metazoans revealed that there are four major phyla, including the Ctenophores. Although the morphology of ''Euplokamis'' often resembles the medusa stage of Cnidarians, their eight rows of combs are one distinguishing feature that led to the official classification of Ctenophores. After being originally described by Chun (1879), the family '' Euplokamididae'' was expanded by Mills (1987) due to the discovery of a new species, ''Euplokamis dunlapae''. Further research indicated that ''Euplokamis'' should be identified from Mertensiidae due to the rows of combs and some compression. They may also be distinguished from the genus ''Pleurobrachia'' due to their more elongated shape. Additionally, various adaptations of ''Euplokamis'' have been observed such as the use of tentacles for movement/feeding, a complex nervous system, and bioluminescent capabilities. Other characteristics including a defined mesoderm, lack of stinging cells, developmental differences, and symmetry supported the reclassification of these organisms.

Distribution & Habitat

''Euplokamis'' have been found in fossil records dating back to the Cambrian period, part of the Paleozoic Era, and it is estimated that some species may have evolved before this period. Originally, Cnidarians and Ctenophores were classified under the same phyla, Coelenterata. Ctenophore bodies are made up of a gelatin substance, similar to Cnidarians, but the multiple rows of combs present in fossil records are unique to ctenophores. Records of ''Euplokamis'' sp. indicate they are distributed widely around the world, but are most often found in warm coastal waters. ''Euplokamis'' prefer marine, or saltwater, environments and are classified as free swimmers, due to their ability to move through the water column. They have been identified in the Mediterranean Sea, the North Pacific, the Gulf of Maine, and off the coast of Sweden. However, since this genus was originally grouped in the family Pleurobrachiidae, there is limited information regarding their actual distribution and habitat.

Anatomy & Morphology

Ctenophores are divided into two classes based on either the presence(Tentaculat)) or the lack (Nuda) of tentacles. Within each class, there are multiple orders to further distinguish their structures and characteristics. The class Tentaculata contains the following orders: Cydippida, Lobata, and Cestida. The genus ''Euplokamis'' is part of the class tentaculate, which indicates that tentacles are present. They are also part of the order Cydippida, distinguished by their tentacles and their round body shape. These tentacles are long, may display branching, and have a sheath allowing them to be retractile. The branching tentacles are known as tentilla, which are held tightly in coils. Further, the widely spaced tentillia droplets allow for organisms to be classified to the genus level and are one of the only examples of striated muscle found in ctenophores.

Additionally, these organisms have bi-radial symmetry with a mouth on their front end and a statocyst, or sense organ, at the other end. The sides of their stomachs are lined with distinct bulbs, shaped like tadpoles, and unlike other well-known jellyfish, ''Euplokamis'' do not have any nematocytes, known as stinging cells. The mouth is connected to the digestive tract via the pharynx. The digestive system, or gastrovascular cavity, is made up of intricate canals that allow for both digestion and circulation to occur. They also lack an anus but are able to excrete some waste through pores on the adoral