Jetting in jellyfish, scallops, squids leads on to: . Lecture 9 Bio 325. Jetting propulsion in Arthropoda, Odonata: whichfunctions also with gas exchange. Jetting propulsion in colonial Hydrozoa involves nectophores. Jetting propulsion by salps: tunicates in chains.
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Jetting in jellyfish, scallops, squids leads on to:
Lecture 9 Bio 325
Jetting propulsion in Arthropoda, Odonata: whichfunctions also with gas exchange.
Jetting propulsion in colonial Hydrozoa involves nectophores.
Jetting propulsion by salps: tunicates in chains.
Notochord as muscular hydrostat
Freshwater insects that use jetting to escape and to breathe.
Some dragonfly immatures (Order Odonata) jet water out of their rectum, the posterior chamber of their gut which is also a respiratory chamber; they use nozzle-shaped (tapered) terminal sclerites to increase momentum (mass X velocity) and to aim flow just like a squid siphon; telescoping in and out of abdominal segments + haemocoel pressure powers water intake and outflow; filaments filled with tracheae project into rectum lumen for gas exchange.
Mill P.J., Pickard R.S. 1975. Jet-propulsion in anisopteran dragonfly larvae. J. comp. Physiol. 97(4): 329-338.
Wilson, E.O. 1975. Sociobiology. Harvard, Cambridge Mass.
from Meglitsch P.A. Invertebrate Zoology
gastrozooid, gonozooid, dactylozooid, pneumatophore, etc.
Physalia: Portuguese Man ‘o War
They use stinging cells nematocysts
to capture fish prey.
Zooids: nectophores: squirt out jets of seawater to propel the colony.
gastrozooids are sac-like, specialized for ingestion and distribution of nutrients to rest of colony dactylozooids with batteries of nematocysts etc.
Nectophore zooids in a hydrozoan Cnidarian
A colony of zooids: at one end specialized as swimming individuals called nectophores, also called swimming bells. They jet seawater out of their subumbrellar openings, moving the colony, trailing behind on a fishing stem (stem transports nourishment by a shared coelenteron) about in the water column, presumably in a co-ordinated fashion.
“A propulsive jet for locomotion is created by rhythmic compression of muscle bands encircling the barrel-shaped body. Fluid enters the anterior oral siphon to fill the mostly hollow body of the salp. ...oral lips close and circular muscle bands contract, decreasing the volume of the jet chamber so that fluid is accelerated out of the posterior atrial siphon.” [antagonists?] “...unique in possessing incurrent and excurrent siphons on opposite ends of the body allowing for unidirectional flow and reverse swimming during escape”.
Peter J. Bryant
Salp chains: individuals (zooids) strung together in colonies
Sutherland K.R., Madin L.P. 2010. Comparative jet wake structure and swimming performance of salps. J. exp. Biol. 213: 2967-2975.
Are there fish
evolved to jet?
***contrast with annelids: ventral solid nerve cord; anterior blood flow in dorsal vessel
myotome block separations
evident here just below dorsal ‘fin’
Barrington E.J.W. 1965. The Biology of the Hemichordata and Protochordata.
Oliver & Boyd, Edinburgh & London.
Assigned reading: Long, J.H. Jr. et al. 2002. The notochord of hagfish Myxine glutinosa: visco-elastic properties and mechanical functions during steady swimming. J. exp. Biol. 205: 3819-3831.
Notochord is another example of a hydrostat, and given that it involves muscle,
perhaps it is reasonable to think of it as a muscular hydrostat.
Summarizing the working and functions of the notochord: it is not just a simple fluid-filled chamber surrounded by connective tissue acting to translocate muscle forces
Inland fishes of NY, Cornell
Many bony fishes have a single median gas bag in their body used to change their density, giving neutral buoyancy at different levels in the water column. This bladder, situated just below the backbone and just above the viscera, contains oxygen at a high concentration; the oxygen is actively secreted from the blood.
Ancestors of bony fishes, living in fresh water, evolved lungs to supplement their gills in times of drought. When some of these ancestors reinvaded the seas these lungs evolved into swim bladders.
Fisheries & Oceans Canada