The organization and structure of nerve and muscle in the jellyfish Cyanea capillata (coelenterata; scyphozoa)

Summary The traditional view of the cnidarian nervous system is of a diffuse nerve net that functions as both a conducting and an integrating system; this is considered an indicator of a primitive condition. Yet, in medusoid members, varying degrees of nerve net compression and neuronal condensation into ganglion-like structures represent more centralized integrating centers. In some jellyfish, this relegates nerve nets to motor distribution systems. The neuronal condensation follows a precept of neuronal organization of higher animals with a relatively close association with the development and elaboration of sensory structures. Nerve nets still represent an efficient system for diffuse, non-directional activation of broad, two-dimensional effector sheets, as required by the radial, non-cephalized body construction. However, in most jellyfish, an argument can be made for the presence of centralized nervous systems that interact with the more diffuse nerve nets.

Section: A Nerve Net Is a Nerve Net Is A Nerve Net?mentioning

confidence: 99%

Do jellyfish have central nervous systems?

Satterlie

2011

“…Scyphomedusae swim through sustained contractions of the subumbrellar musculature and the myofibril layer of this muscle tissue is heavily interdigitated with the mesogleal gel (Gladfelter, 1972;Anderson and Schwab, 1981). These myofibrils contain neither microtubles nor sarcoplasmic reticulum, and it has been proposed that the mesoglea must be directly responsible for supplying calcium to the myofibril cells (Anderson and Schwab, 1981).…”

Section: Intragel Oxygenmentioning

confidence: 99%

“…The internal gel milieu is a dynamic environment. It accommodates buoyancy changes due to salinity shifts (Mills, 1984;Wright and Purcell, 1997), and gel likely provides important ions to musculature (Anderson and Schwab, 1981). We now know that gel also plays a key role in supporting oxygen delivery to tissues.…”

Section: Role Of Gel In Jellyfish Biologymentioning

confidence: 99%

Intragel oxygen promotes hypoxia tolerance of scyphomedusae

Thuesen

Rutherford

Brommer

et al. 2005

SUMMARY Populations of jellyfish are known to thrive in many low oxygen environments, however, the physiological mechanisms that permit these organisms to live in hypoxia remain unknown. The oxyregulatory abilities of four species of scyphomedusae were investigated, and it was found that Aurelia labiata, Phacellophora camtschatica, Cyanea capillata and Chrysaora quinquecirrha maintain steady oxygen consumption to below 20 hPa oxygen (<10% air saturation). Oxygen content of the mesoglea of A. labiata was measured using a fibre optic oxygen optode, and oxygen profiles through the gel are characterised by a gradient that decreases from just below normoxia at the aboral subsurface to ∼85% air saturation near the subumbrellar musculature. This gradient sustains oxyregulation by scyphomedusae, and it is demonstrated that A. labiata must be using intragel oxygen to meet its metabolic needs. Gel can also be used as an oxygen reservoir when A. labiata moves into hypoxia. Gel oxygen is depleted after about 2 h in anoxia and recovers to 70% of normal after 2.5 h in normoxia. Behaviour experiments in the laboratory showed that Aurelia labiata behaves similarly in normoxia and hypoxia (30% and 18% air saturation). The acute threshold for provoking behavioural changes in A. labiata is somewhere near its critical partial pressure, and oxygen stratification stimulates swimming back and forth across the oxycline. Intragel oxygen dynamics are recognised as a fundamental component of medusan physiology.

“…The motor nerve net that transmits excitation from pacemaker neurons to the swim musculature and from one rhopalium to another (Anderson and Schwab, 1981;Anderson and Schwab, 1983) is a two-dimensional network of large neurons covering the subumbrella surface, and able to transmit activity in any direction. In Cyanea, communication between neurons depends upon bi-directional synapses with either side of the synaptic junction being able to release chemical transmitter (Anderson, 1985).…”

Section: Scyphomedusaementioning

confidence: 99%

“…Swimming consists of a wave of contraction originating from the rhopalia (Romanes, 1877) with the fastest pacemaker determining the overall swim frequency (Horridge, 1959;Passano, 1965). This slowly propagated contraction is in contrast to the almost synchronized contraction seen in hydrozoan jellyfish.The motor nerve net that transmits excitation from pacemaker neurons to the swim musculature and from one rhopalium to another (Anderson and Schwab, 1981;Anderson and Schwab, 1983) is a two-dimensional network of large neurons covering the subumbrella surface, and able to transmit activity in any direction. In Cyanea, communication between neurons depends upon bi-directional synapses with either side of the synaptic junction being able to release chemical transmitter (Anderson, 1985).…”

mentioning

confidence: 99%

Electrogenesis in the lower Metazoa and implications for neuronal integration

Meech

2015

Electrogenic communication appears to have evolved independently in a variety of animal and plant lineages. Considered here are metazoan cells as disparate as the loose three-dimensional parenchyma of glass sponges, the two-dimensional epithelial sheets of hydrozoan jellyfish and the egg cell membranes of the ctenophore Beroe ovata, all of which are capable of generating electrical impulses. Neuronal electrogenesis may have evolved independently in ctenophores and cnidarians but the dearth of electrophysiological data relating to ctenophore nerves means that our attention is focused on the Cnidaria, whose nervous systems have been the subject of extensive study. The aim here is to show how their active and passive neuronal properties interact to give integrated behaviour. Neuronal electrogenesis, goes beyond simply relaying 'states of excitement' and utilizes the equivalent of a set of basic electrical 'apps' to integrate incoming sensory information with internally generated pacemaker activity. A small number of membrane-based processes make up these analogue applications. Passive components include the decremental spread of current determined by cellular anatomy; active components include ion channels specified by their selectivity and voltage dependence. A recurring theme is the role of inactivating potassium channels in regulating performance. Although different aspects of cnidarian behaviour are controlled by separate neuronal systems, integrated responses and coordinated movements depend on interactions between them. Integrative interactions discussed here include those between feeding and swimming, between tentacle contraction and swimming and between slow and fast swimming in the hydrozoan jellyfish Aglantha digitale. KEY WORDS: Cnidaria, Ctenophores, Electrogenesis, Ion channel, Ionic currents, Sponges Introduction: electrogenesis in early MetazoaIt is evident that many of the ion channel variants involved in signal propagation in multicellular life forms have their origins in bacteria and other single-celled species. In fact, propagating impulses arise in a number of different evolutionary lineages. In each case, natural selection co-opted much the same set of ion channels but inserted them into a different cell matrix. Besides networks of neuronal-like cells, these matrices include the loose three-dimensional parenchyma of glass sponges such as Rhabdocalyptus (Leys and Mackie, 1997;Leys et al., 1999) and the two-dimensional epithelial sheets found in the Hydrozoa (Mackie, 1965;Mackie, 1976;Mackie and Passano, 1968). The following is a brief description of four classes of non-neuronal electrogenesis followed by a more detailed REVIEWSchool of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK.*Author for correspondence (r.meech@bristol.ac.uk) account of integrative aspects of neuronal electrogenesis as exhibited by the Cnidaria. For an account that includes aspects of electrogenesis in the Protozoa, see Meech and Mackie (Meech and Mackie, 2007), for a more general account,...