Coelomic Pressure Research Articles

Effects of Water Temperature on Coelomic Pressure and Ventilation in the Respiratory Tree of Japanese Common Sea Cucumber, Apostichopus japonicus

Effects of Water Temperature on Coelomic Pressure and Ventilation in the Respiratory Tree of Japanese Common Sea Cucumber, Apostichopus japonicus

Relationship between Coelomic Pressure and Ventilation in the Respiratory Tree of the Japanese Common Sea Cucumber, Apostichopus japonicus

Relationship between Coelomic Pressure and Ventilation in the Respiratory Tree of the Japanese Common Sea Cucumber, Apostichopus japonicus

Biological response of earthworm, Eisenia foetida (Savigny) to an organophosphorous pesticide, profenofos

Acute toxicity, morphological alterations and histological effects of an organophosphorus insecticide, profenofos (PFF) to earthworm, Eisenia foetida were evaluated by direct contact through a filter paper. The 24 and 48 h LC 50 was 4.56 and 3.55 μg cm −2, respectively. Morphological and histological observations showed body ruptures, bloody lesions, and internal excessive formation of glandular cell mass and disintegration of circular and longitudinal muscles, which failed to regulate the internal coelomic pressure, leading to fragmentation in earthworms. Neurotoxic potentiality of PFF was assessed by measuring acetylcholinesterase (AChE). AChE basal K m and V max values were 0.26 mM and 0.15 μmol min −1 mg −1 protein, respectively. PFF alters the in vitro K m value, resulting in a competitive type of inhibition. The inhibitory constant K i was 2.52×10 −6 M. Morphological alterations and histological effects should be monitored in addition to AChE inhibition to assess OP pesticide contamination in soil ecosystems.

A mechanical model of growth in regular sea urchins: predictions of shape and a developmental morphospace

The shapes of several urchins are correctly predicted by a model that uses only measured height and diameter as fitted variables. The predicted shape is based on the engineering theory of thin shells, which is conventionally used to calculate the shapes of a fluid droplet on a horizontal plane, and of `buckle-free' engineered domes. The magnitudes of forces theoretically required to generate urchin shapes at realistic sizes are similar to forces typically exerted on the skeleton by self-weight, podia and coelomic pressure. An urchin's shape, despite complex details of plate growth, is thus determined by a force balance at each point in the skeleton. Despite the skeleton's apparent rigidity, over developmental time it must deform in a manner similar to a stretchy balloon. This membrane model of morphogenesis specifies two developmental shape parameters: (i) the apical curvature; and (ii) a ratio of the mimicked vertical gradient of pressure (podial forces, etc.) to the internal coelomic pressure. An ontogenetic series of urchins is represented as a curved line in a two-dimensional, developmental morphospace. This morphospace, which is useful for studying developmental constraints and macroevolutionary dynamics, explains observed patterns of allometry in height and diameter in urchins.

Causes and Consequences of Fluctuating Coelomic Pressure in Sea Urchins.

We measured coelomic pressure in sea urchins to determine whether it was high enough to support a pneu hypothesis of growth. In Strongylocentrotus purpuratus the pressure was found to fluctuate rhythmically about a mean of -8 Pa, and was negative for 70% of the time. This is at variance with the theoretically required positive pressures of the pneu hypothesis. Furthermore, there were no sustained significant differences between the pressure patterns of fed and starved urchins, presumed to be growing and not growing, respectively. The rhythmical fluctuations in pressure were caused by movements of the lantern which changed the curvature and tension of the peristomial membrane. We developed a mathematical and morphological model relating lantern movements, membrane tension, and pressure, that correctly predicts the magnitude of the fluctuations. Pressures predicted by the model depend also on coelomic volume changes. In Lytechinus variegatus simultaneous retraction of the podia, which causes expansion of the ampullae, resulted in an 8.8 Pa increase in coelomic pressure, relative to the pressure during simultaneous podial protraction.

INHALING WITHOUT RIBS: THE PROBLEM OF SUCTION IN SOFT-BODIED INVERTEBRATES

Most animals rely upon rigid skeletal structures to withstand the negative pressures required for inhalation. Some soft-bodied invertebrates (innkeeper worms, sea cucumbers) have pumping cloacae that are able to "inhale" without any hard supporting structures. Geometric analyses suggest that inhalation cannot be produced by relaxation of coelomic pressure and contraction of radial muscles connecting the body wall. Coelomic pressure must be maintained for body wall support and radial muscle antagonism. Mathematical models predict that maximum attainble suction in a hydrostatically supported sac-within-a-sac like the cloaca-body wall system will be proportional to coelomic pressure and exponentially related to the ratio of body wall diameter to cloacal diameter. A mechanical model gives results consistent with these predictions. "Cloacal" suctions are proportional to "coelomic" pressure, and maximum suction (20 x coelomic pressure) is produced when the cloaca is small relative to the body wall. In vivo recordings of pressure relationships during cloacal pumping in innkeeper worms (Urechis caupo) confirm that coelomic pressure is not relaxed to permit inhalation. No animals have been found which use a hydrostatically-supported system to produce extreme suction, with the possible exception of nematodes. Squids apparently utilize the potential of such a mechanism for producing large stroke volumes at low suctions with minimum structural complexity; the mantle is a sac-within-a-sac system which pumps large volumes for respiration and locomotion.

The burrowing of Nereis diversicolor O.F. Müller, together with some observations on Arenicola marina (L.) (Annelida: Polychaeta)

The mechanism of burrowing in Nereis diversicolor O.F. Müller is described. Proboscis eversion in order to make a hole in the substratum is accompanied by a coelomic pressure pulse of 1.2–7.5 kPa, compared with a value of ≈0.3 kPa during ambulatory activity. Forward movement of the tail in the later stages of burial is by longitudinal contraction, usually accompanied by a pulse of about 2 kPa. The septa appear to act as effective hydrostatic pressure barriers during burrowing. In the flange-proboscis sequences of Arenicola marina (L.) the coelomic pressure in the trunk during erection of the flanges is generally slightly higher than that in the head, while the reverse applies during the low-volume proboscis eversion. Major progression of the anterior usually occurs during the first flange-proboscis sequence of each cycle and that of the posterior early in the dilation sequence. External pressure recordings of irrigation-defaecation cycles are given. Nereis uses a similar method of burrowing to that of the free-moving Nephtys but the coelomic pulses of the former are lower, as in the rate of burial (about 0.02 cm s −1) which is similar to that of Arenicola. Closure of the septa of Nereis during burial suggests that its burrowing mechanism is not as versatile as that of Nephtys.

Pressure Difference in Adjacent Segments and Movement of Septa in Earthworm Locomotion

ABSTRACT The nature and timing of septal movements during gentle crawling have been examined in relation to the coelomic pressure (Pc) in and between adjacent segments. Between neighbouring anterior segments the phase lag was 0·05−0·1 s and the maximum Pc difference 3·3 cm water. The mean Po in a leading segment exceeded that in a trailing segment by 0·9 ± 0·06 cm water. In forward crawling, the septa bulged maximally backward and forward when segments were half elongated and half shortened respectively, and were flat when segments were longest and shortest: the area of a septum in an elongated segment was one quarter that in a shortened one and thus a septum is strongest (small and thick) when the Pc to be longitudinally confined is highest. Bulging of septa is closely related to the intersegmental Pc difference. Bulging forces acting on a septum range from o to about 1 g wt. The pressure drop along a worm is not linear and the ventral foramina may act as ‘septal valves’ to equalize coelomic volume and pressure when required. The influence of gut, septum and body wall movements on each other is discussed.

Respiratory mechanics in the bird

1. 1. Air sac and coelomic pressures were measured in chickens and geese. 2. 2. The coelomic pressure wave is composed of the air sac wave together with a wave originating from the stretching or bulging of internal septa during respiration. 3. 3. A model is presented which features the overall mechanical characteristics of the respiratory system, and which generates pressures that are related to each other in the manner of those in the normal bird.

Coelomic pressure and electromyogram in earthworm locomotion

1. 1. A method is described for recording electromyograms and coelomic pressure simultaneously from a segment of Lumbricus terrestris L. 2. 2. Contraction of the longitudinal muscles results in a “shortening peak” of coelomic pressure, and contraction of the circular muscles results in an “elongation peak”. 3. 3. Sequential muscular activation in successive segments is demonstrated, associated with a locomotory wave. 4. 4. Small, single potentials on the electromyogram may correspond with tonic muscular contractions.

Functional design and evolution of the polychaete Aphrodite aculeata

The body form of Aphrodite is attributed to its exploitation of the nereid creeping mechanism. It employs a fast stepping pattern, individual limb movements being extension and retraction of the neuropodium with coordinated chaetal movement. The downward and backward propulsive stroke raises the worm clear of a hard substratum. The notopodium is stabilized and its long chaetae raised and lowered in defence.The segments are short but wide. The body wall muscles, relieved of locomotory function, are a basketwork of longitudinal and diagonal muscles capable of maintaining constant body dimensions. Muscles of the appendages originate from stabilized points on the body wall. Trunk septa are reduced, in association with the constant body shape, but the first few septa form a membrane enclosing the proboscis. Complete and muscular septa occur in the rectal segments.During respiratory movements the elytra are depressed by intrinsic and extrinsic elytrophore muscles and elevated by coelomic pressure. Coelomic pressure drops immediately before elytral depression and is controlled by the body wall muscles, especially the diagonal muscles. Aphrodite differs from its near relative Hermione in the reduction of septa and simplification of body musculature.

The Mechanism of Proboscis Movement in Arenicola

ABSTRACT The mechanism of proboscis movement is analysed in detail in Arenicola marina L. and A. ecaudata Johnston, and discussed in relation to the properties of the hydrostatic skeleton. Proboscis activity is based on the following cycle of movements in both species. Stage I. The circular muscles of the body-wall and buccal mass contract; the head narrows and lengthens. Stage IIa. The circular muscles of the mouth and buccal mass relax; the gular membrane (or ‘first diaphragm’ of previous authors) contracts; the mouth opens and the buccal mass emerges. Stage IIb. The longitudinal muscles of the buccal mass and body-wall contract; the head shortens and widens and the pharynx emerges. Stage III. As Stage I. The two species differ anatomically and in their hydrostatic relationships. In ecaudata, the forward movement of body-fluid which extrudes and distends the proboscis is largely due to the contraction of the gular membrane and septal pouches. In marina, the essential mechanism is the relaxation of the oral region which allows the general coelomic pressure to extrude the proboscis. The gular membrane of marina contracts as that of ecaudata does, but its anatomy is different and it appears to be a degenerating structure as far as proboscis extrusion is concerned. Withdrawal of the proboscis may occur while the head is still shortening and widening in Stage 116, or while it is lengthening and narrowing in Stage III. The proboscis is used both in feeding and in burrowing; in the latter case nothing enters through the mouth; the difference is largely caused by variation in the timing of withdrawal relative to the 3-stage cycle.

Coelomic pressures in sipunculus nudus.

The relationship between coelomic pressures and body movements has been investigated in Phascolosoma gouldi and, mainly, Sipunculus nudus.During "defense movements, pressure in Phascolosoma is commonly 50 cm. of water, in Sipunculus 70 to 80 cm. During "defense immobility," the highest pressure recorded, in Phascolosoma, was 108 cm. There does not seem to be a relation between body size and maximum pressure.Six phases of burrowing movements have been distinguished in Sipunculus and related to coelomic pressure. An important pressure rise coincides with a bending movement of the central part the body. This "hump" and the high pressures associated with it have functions which are described. Very low coelomic fluid pressures suffice to cause evension of the proboscis. Pressure is a necessary and sufficient condition for proboscis eversion in free water, while in sand the proboscis muscles seem to play an essential role during proboscis eversion in relation to the thixotropic property of stirred sand.During most experiments, minimum pressures were very constant, while maximum pressures varied a great deal. During burrowing movements in free water, the highest pressure recorded in Phascolosoma was 25.0 cm., in Sipunculus 39.6 cm. of body fluid. During burrowing in sand, pressure of 96 cm. water was reached by Sipunculus.The frequency of pressure cycles seems to be independent of the absolute pressure.The coordination between the cycles of pressure and proboscis movements is variable. Therefore the retractor muscles and the muscles of the body wall are probably dependent on nervous centers which are not closely associated.Pressure variations during burrowing have an influence on circulation of coelomic fluid.