''Nemopsis bachei'' is a species of relatively small gelatinous

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

hydrozoa Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specializ ...

found in both marine and

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

environments. This particular species was first found and described by

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he rec ...

in 1849 from samples that were taken from the coast of

Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət'' English: , ), officially the Commonwealth of Massachusetts, is the most populous U.S. state, state in the New England ...

. It was also noted and described in 1857 by another name off the coast of

South Carolina )''Animis opibusque parati'' ( for, , Latin, Prepared in mind and resources, links=no) , anthem = " Carolina";" South Carolina On My Mind" , Former = Province of South Carolina , seat = Columbia , LargestCity = Charleston , LargestMetro = ...

.Moore, D.R. “Occurrence and distribution of Nemopsis bachei Agassiz (Hydrozoa) in the Northern Gulf of Mexico”. ''Bulletin of Marine Science of the Gulf and Caribbean'' (1962) As part of the phylum

Cnidaria Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that th ...

they are mainly gelatinous with their most identifying characteristic being the

gonads A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sperm ...

which, viewed from above, look like an X and then continue down the sides lining up with the radial canals. As a part of the zooplankton, it is incapable of sustained horizontal movement and relies on its tentacles to encounter and capture smaller organisms for food (feeds mainly on copepedites, selecting against naupilar stages).Purcell, J.E., Nemazie, D.A. “Quantitative Feeding Ecology of the Hydromedusan Nemopsis-Bachei in Chesapeake Bay”. ''Marine Biology'' 113:2 (1992): 305-311. Like most living organisms, ''N. bachei'' has communities of

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

that associate with it. The most often found groups include ''

Vibrio ''Vibrio'' is a genus of Gram-negative bacteria, possessing a curved-rod (comma) shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Being highly salt tolerant and unable to survive ...

'' spp. and ''

Photobacterium ''Photobacterium'' is a genus of gram-negative, oxidase positive and catalase positive bacteria in the family ''Vibrionaceae''. Members of the genus are bioluminescent, that is they have the ability to emit light. Many species, including '' Pho ...

'' spp.Daley, M.C., Urban-Rich, J., Moisander, P.H. “Bacterial associations with the hydromedusa Nemopsis bachei and scyphomedusa Aurelia aurita from the North Atlantic Ocean”. ''Marine Biology Research'' 12:10 (2016): 1088-1100. According to genetic analysis, researchers have found that ''N. bachei'' is closely related to a species of "immortal jellyfish", ''

Turritopsis nutricula ''Turritopsis nutricula'' is a small hydrozoan that once reaching adulthood, can transfer its cells back to childhood. This adaptive trait likely evolved in order to extend the life of the individual. Several different species of the genus ''Tur ...

'' based on analysis of the COX1 gene.Devarapalli, P., Kumavath, R.N., Barh, D., Azevedo, V. “The conserved mitochondrial gene distribution in relatives of ''Turritopsis nutricula'', an immortal jellyfish”. ''Bioinformation'' 10:9 (2014): 586-591.

Description

Like many other medusa, it moves by a pulsing movement in the bell and ''N. bachei'' has been described as “fast-swimming” due to a greater value than others found in engineering studies.Dabiri, J.O., Colin, S.P., Costello, J.H. “Fast-swimming hydromedusae exploit velar kinematics to form an optimal vortex wake”. ''Journal of Experimental Biology'' 209:11 (2006): 2025-2033. It has a rounded, cube-like bell ranging from 0.4 to 12 mm.Johnson, William S., et al. ''Zooplankton of the Atlantic and Gulf Coasts: a Guide to Their Identification and Ecology''. The Johns Hopkins University Press, 2012. Its most notable characteristic are the 4 ribbon-shaped gonads which extend down the bell along the radial canals at times all the way down to the base. They also have two short, distinct, club-like

tentacles In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

extending from each of their 4 marginal bulbs. These marginal bulbs also contain

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

or light sensing organs. On each of the marginal bulbs they have 14-18 longer thin tentacles that extend downward.

Feeding

Cnidaria are often studied to investigate their grazing rates in terms to smaller zooplankton because cnidarian's are subject to large blooms. While they do consume a substantial amount of zooplankton when at peak abundance, due to the regeneration rate of copepidite stocks, ''N. bachei'' were not found to have a lasting effect on the overall population. They do display some amount of predatory behavior, in studies they have been shown to seek out new areas of prey when the rate at which they encounter prey starts to get decrease.Frost, J.R., Jacoby, C.A., Youngbluth, M.J. “Behavior of Nemopsis bachei L. Agassiz, 1849 medusae in the presence of physical gradients and biological thin layers”. ''Hydrobiologia'' 645:1 (2012): 97-111.

Distribution

In the southeast, these organisms are found typically in the colder months ranging from November–February. Other reports indicate they may also during the spring-summer months in the North Atlantic.Marshalonis, D., Pinckney, J.L. “Grazing and assimilation rate estimates of hydromedusae from a temperate tidal creek system”. ''Hydrobiologia''. (2008) 606:203- 211. It has been documented as native to the eastern coast of the US and the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

and recently has been found to an invasive species in the coastal waters of

Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe Northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other g ...

. Additionally, it can be found in waters of variable salinity in Germany and was likely transported there by ships.Laakmann, S., Holst, S. “Emphasizing the diversity of North Sea hydromedusae by combined morphological and molecular methods”. ''Journal of Plankton Research'' 36:1 (2014): 64-76. In general, they can be found in waters ranging from sub-tropical to cold-temperate in both the Atlantic and Pacific oceans typically in

euryhaline Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly (''Poecilia sphenops'') which can live in fresh water, brackish water, or salt water. The green crab (''Carcinus maenas'') is an e ...

waters ~14-26 degrees C and in salinities ranging from 5-30 ppt.Nowaczyk, A., David, V., Lapage, M., Goarant, A., De Oliveira, E., Sautour, B. “Spatial and temporal patterns of occurrence of three alien hydromedusae, Blackfordia virginica (Mayer, 1910), Nemopsis bachei (Agassiz, 1849) and Maeotias marginata (Modeer, 1791) in the Gironde Estuary (France)”. ''Aquatic Invasions'' 11:4 (2016): 397-409.Cronin, L.E., Daiber, J.C., Hulbert, E.M. “Quantitative seasonal aspects of zooplankton in the Delaware River estuary”. ''Chesapeake Science'' 3:2 (1962): 63-93.Mendoza-Becerril, M.D., Marques, A.C. “Synopsis of the knowledge and distribution of the family Bougainvilliidae (Hydrozoa, Hydroidolina)”. ''Latin American Journal of Aquatic Research'' 41:5 (2013): 908-924.

References

{{Taxonbar, from=Q2867860 Animals described in 1849 Bougainvilliidae Taxa named by Louis Agassiz