Bathyphysa
Genus of hydrozoans
From Wikipedia, the free encyclopedia
Bathyphysa is a genus of hydrozoan siphonophores within the family Rhizophysidae. It has 3 species.[2]
| Bathyphysa | |
|---|---|
| |
| Bathyphysa conifera | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hydrozoa |
| Order: | Siphonophorae |
| Family: | Rhizophysidae |
| Genus: | Bathyphysa Studer, 1878[1] |
| Species[2] | |
| |
| Synonyms[2] | |
Taxonomy
In 1878, marine biologist Théophile Rudolphe Studer first described the genus using samples of Bathyphysa conifera that had been wrapped around plumb lines.[4] This discovery was followed by that of the Bathyphysa sibogae in 1908, through specimens collected on trawls during the Siboga expedition.[5]
The Bathyphysa genus is included in the cystonect suborder, meaning organisms within it lack a nectosome and that zooids develop straight from the stem, as opposed to "pro-bud" development in calycophorae and physonectae.[6] Within the Rhizophysidae family, Bathyphysa mainly differ from their relatives, Rhyzophysa, in that their gastrozooids develop wing-like ptera to increase surface area and buoyancy.[7]
There is debate over whether the third species, Bathyphysa japonica, should be considered a valid group. Recent research suggests it has no distinct characteristics from other species in the genus.[8]
Morphology
Species belonging to the Bathyphysa genus are siphonophores composed of various zooids that serve to function together as a single organism. Similar to the members of the order Cystonectae, these colonies harbor a pneumatophore, a gas filled chamber that contributes to their buoyancy, which also bears different zooid types[9]. These zooids each have their own respective roles in a siphonophores biology, including feeding and reproduction. A defining feature of siphonophore colony organization illustrates the high degree of specialization among zooids in their lineage[10].
Research on siphonophore morphology has examined feeding structures within the genus. For most siphonophores, prey is captured with tentilla, used to immobilize prey through the complex arrangements of nematocysts[10]. However, studies on siphonophore tentilla evolution suggests that the Bathyphysa conifera lacks this specialized structure[11]. The lack of this trait has been interpreted as an evolutionary loss within certain cystonect lineages and has been used in broader studies investigating the evolution of feeding morphology in siphonophores[11].
Studies of development in siphonophore colonies provide further insight into the more structural organization of the genus. Asexual budding along the colony stem, where zooid types emerge as the colony grows are how zooids produce[6]. Feeding zooids (gastrozooids) and reproductive structures (gonodendra) arise through budding directly along the stem, contributing to the modular organization of the colony[6]. This strategy of development allows siphonophore colonies to maintain a division of labor among zooids, maintaing unity and coordination.
