Narcomedusae

Narcomedusae is an order of hydrozoans in the subclass Trachylinae.[1] Members of this order do not normally have a polyp stage. The medusa has a dome-shaped bell with thin sides. The tentacles are attached above the lobed margin of the bell with usually a gastric pouch above each. There are no bulbs on the tentacles and no radial canals. Narcomedusans are mostly inhabitants of the open sea and deep waters. They can be found in the Mediterranean in large numbers.[2] Narcomedusae are essential to the ecosystem as they are top-down regulators for the midwater environment.[3]

## Contents

* 1 Feeding behavior
* 2 Reproductive features
* 3 Anatomy
* 4 Gallery
* 5 References

## Feeding behavior

Narcomedusae use their tentacles to catch large, fast-moving prey. They do this by holding their tentacles perpendicular to the direction they are swimming to cover a larger area. If something is caught they bend the tentacle inwards and coil them at the tips to their mouths.[4][5]

## Reproductive features

Narcomedusae are hermaphroditic, meaning that they have both male and female reproductive organs. As a result they release their eggs and sperm into the water which is also where fertilization happens.[6] Once the eggs are fertilized they then develop into a stage called planula which can be defined as a larval stage and it then lives in the seafloor. These jellyfish are capable of reproducing all year round, although this depends on their reproductive cycle and patterns as they fluctuate depending on factors such as environmental conditions and food availability.

## Anatomy

Narcomedusae lack radial canals and have an umbrella that is rather flat. It has a quadratic dome that has a diameter of 4 to 11 mm. Narcomedusae have four tentacles that leave the umbrella near the level of the stomach. They have a stomach that is broad and circular and do not have a pouch. These jellyfish have tentacles that are solid that curve upwards into the mesoglea above the stomach.[7]

## Gallery

* Aeginura grimaldii by Ernst Haeckel

## References

1. ↑ Schuchert, Peter; Ville-ge.ch (2005). "Hydrozoan Phylogeny and Classification". http://www.ville-ge.ch/mhng/hydrozoa/intro/phylogeny.htm. Retrieved 24 February 2010.
2. ↑ Order Narcomedusae – Haeckel, 1879 The Hydrozoa Directory. Retrieved 6 November 2011.
3. ↑ Verhaegen, Gerlien; Sangekar, Mehul; Bentlage, Bastian; Hoving, Henk-Jan; Collins, Allen; Lindsay, Dhugal (1 August 2023). "Drivers behind the diversity and distribution of a widespread Midwater Narcomedusa". Association for the Sciences of Limnology and Oceanography 68 (9): 2088–2107. doi:10.1002/lno.12408. Bibcode: 2023LimOc..68.2088V.
4. ↑ Raskoff, .K. Foraging, prey capture, and gut contents of the mesopelagic narcomedusa Solmissus spp. (Cnidaria: Hydrozoa). Marine Biology 141, 1099–1107 (2002). https://rdcu.be/cJjXC. Retrieved 3 March 2022
5. ↑ Larson, Ronald J.; Mills, Claudia E.; Harbison, G. Richard (1989). "In Situ Foraging and Feeding Behaviour of Narcomedusae (Cnidaria: Hydrozoa)". Journal of the Marine Biological Association of the United Kingdom 69 (4): 785–794. doi:10.1017/s002531540003215x. ISSN 0025-3154. Bibcode: 1989JMBUK..69..785L.
6. ↑ Lucas, Cathy H.; Reed, Adam J. (February 2009). "Observations on the life histories of the narcomedusae Aeginura grimaldii, Cunina peregrina and Solmissus incisa from the western North Atlantic" (in en). Marine Biology 156 (3): 373–379. doi:10.1007/s00227-008-1089-6. ISSN 0025-3162. Bibcode: 2009MarBi.156..373L. http://link.springer.com/10.1007/s00227-008-1089-6.
7. ↑ Arai, M (2000). "Morphology and distribution of a deep-water Narcomedusa (Solmarisidae) from the northeast Pacific". Scientia Marina 1 (1): 57–60. doi:10.3989/scimar.2000.64s155. Bibcode: 2000ScMar..64S..55N. https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/792/829.

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