Physalia
| Physalia | |
|---|---|
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| Physalia physalis | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hydrozoa |
| Order: | Siphonophorae |
| Suborder: | Cystonectae |
| Family: | Physaliidae Brandt, 1835 |
| Genus: | Physalia Lamarck, 1801 [1] |
| Species | |
Physalia is a genus of the order Siphonophorae, colonies of four specialized polyps and medusoids that drift on the surface of the Atlantic, Indian and Pacific oceans. Although these organisms look like a single multicellular organism, each specimen is actually a colony of minute organisms called zooids that have to work together for survival. A gas-filled bladder resembling a blue bottle provides buoyancy, and long tentacles of venomous cnidocytes provide a means of capturing prey. A sail on the float, which may be left or right-handed, propels Physalia about the sea, often in groups. These siphonophores sometimes become stranded on beaches, where their toxic nematocysts can remain potent for weeks or months in moist conditions. Both species of this siphonophore resemble a jellyfish in appearance, with their gas-filled float and cluster of polyps beneath, which can hang up to 30 or 165 ft (9 to 50 m) below the surface of the sea.
Because it frequently washes up on beaches on the coast of the Atlantic, Indian and Pacific Oceans and is seen in the open ocean, Physalia is the best-known genus of siphonophore, as nearly all siphonophores live in the cold, dark ocean depths where they can only be observed in their natural habitat by a submersible or ROV.
The genus was first described by Jean-Baptiste Lamarck in 1801.[1]
Diversity
[edit]The family Physaliidae is monotypic, consisting of only one genus, Physalia.[2] The genus is also monotypic, containing only P. physalis.[1][3] There is a long history of the genus being described with multiple species, such as the Pacific man o' war (P. utriculus), however most of these species are now considered synonyms for P. physalis.[4]
Distribution
[edit]Physalia are found globally in a wide range of oceanic conditions due to their pleustonic nature,[5] allowing their involuntary locomotion to be determined only by currents and wind.
According to data recorded from beachings, dispersal of Physalia is suggested to be highly influenced by wind over temperature. Although a higher rate of Australian beachings are recorded in summer than any other season, research reveals that this is likely due to the seasonality of high and low pressure winds acting on the organism's sail, since species density has been shown to be unaffected by colder temperatures.[6]
Drifting
[edit]Physalia drifting is mainly determined by wind, similar to drift migration seen in migrating birds. Which direction they drift from wind influence is determined by their dimorphism. Physalia have two forms of their enlarged pneumatophores that affect drift; left-handed, which shifts to the right of the downwind direction and right-handed, which moves to the left of the downwind.[7] In strong winds, Physalia drift with its float oriented in the same direction of the wind.[7]
It is thought that this drifting, controlled by the direct influence of wind drag, is what leads mass amounts of Physalia to wash up on beaches. Moderately strong winds, around 5 m/s, produce drifting velocities significantly higher than the typical speed of ocean currents. When Physalia get closer to the coast, they start to experience the influence of the slope-shelf currents, which are strong even in light winds.[8] Because of the Physalia's long tentacles, these currents can overtake the wind drift and wash them ashore.[8]
Differentiation from Rhizophysidae
[edit]Physalia (family Physaliidae) shares the suborder Cystonectae with the family Rhizophysidae.[9]
The differences between these families are apparent when comparing morphologies. Physalia possess larger pneumatophores and trailing tentacles instead of a stem. The stem of Rhizophysidae species and other Siphonophores contain segmented colonial polyps along its length which carry out specific functions such as feeding and reproduction.[10] In Physalia, these structures, such as the gastrozooid, are concentrated on the ventral side of the pneumatophore.[11]
These families also differ in the ocean water column zones they inhabit. Physalia exist strictly on the surface of the water while members of the Rhizophysidae family are found in the epipelagic and bathypelagic zones.[10]
References
[edit]- ^ a b c "Physalia Lamarck, 1801". Integrated Taxonomic Information System.
- ^ "WoRMS - World Register of Marine Species - Physaliidae Brandt, 1835". www.marinespecies.org. Retrieved 2024-11-01.
- ^ "WoRMS - World Register of Marine Species - Physalia Lamarck, 1801". www.marinespecies.org. Retrieved 2024-11-01.
- ^ Bardi, Juliana; Marques, Antonio C (2007). "Taxonomic redescription of the Portuguese man-of-war, Physalia physalis (Cnidaria, Hydrozoa, Siphonophorae, Cystonectae) from Brazil". Iheringia. Série Zoologia. 97 (4): 425–433. doi:10.1590/S0073-47212007000400011.
- ^ Munro, Catriona; Vue, Zer; Behringer, Richard R.; Dunn, Casey W. (2019-10-29). "Morphology and development of the Portuguese man of war, Physalia physalis". Scientific Reports. 9 (1): 15522. Bibcode:2019NatSR...915522M. doi:10.1038/s41598-019-51842-1. ISSN 2045-2322. PMC 6820529. PMID 31664071.
- ^ Bourg, Natacha; Schaeffer, Amandine; Cetina-Heredia, Paulina; Lawes, Jasmin C.; Lee, Daniel (2022-03-17). "Driving the blue fleet: Temporal variability and drivers behind bluebottle (Physalia physalis) beachings off Sydney, Australia". PLOS ONE. 17 (3): e0265593. Bibcode:2022PLoSO..1765593B. doi:10.1371/journal.pone.0265593. ISSN 1932-6203. PMC 8929625. PMID 35299230.
- ^ a b Ferrer, Luis; González, Manuel (2021-01-01). "Relationship between dimorphism and drift in the Portuguese man-of-war". Continental Shelf Research. 212: 104269. Bibcode:2021CSR...21204269F. doi:10.1016/j.csr.2020.104269. ISSN 0278-4343.
- ^ a b Prieto, L.; MacÍas, D.; Peliz, A.; Ruiz, J. (2015). "Portuguese Man-of-War (Physalia physalis) in the Mediterranean: A permanent invasion or a casual appearance?". Scientific Reports. 5: 11545. Bibcode:2015NatSR...511545P. doi:10.1038/srep11545. PMC 4480229. PMID 26108978.
- ^ "WoRMS - World Register of Marine Species - Rhizophysidae Brandt, 1835". www.marinespecies.org. Retrieved 2025-03-23.
- ^ a b Mapstone, Gillian M.; Landschoff, Jannes (2024-12-10). "The rare siphonophore Rhizophysa eysenhardtii Gegenbaur, 1859 (Hydrozoa, Siphonophora, Cystonectae) from False Bay, South Africa". African Invertebrates. 65 (2): 213–221. Bibcode:2024AfrIn..65..213M. doi:10.3897/AfrInvertebr.65.136267. ISSN 2305-2562.
- ^ Munro, Catriona; Vue, Zer; Behringer, Richard R.; Dunn, Casey W. (2019-10-29). "Morphology and development of the Portuguese man of war, Physalia physalis". Scientific Reports. 9 (1): 15522. Bibcode:2019NatSR...915522M. doi:10.1038/s41598-019-51842-1. ISSN 2045-2322. PMC 6820529. PMID 31664071.