The effect of food intake on the function of the reversible pulse distribution system in hydroids – an idiosyncratic approach • NN Marfenin, VS Dementiev • Journal of General Biology • Issue 2 • Volume 83, 2022

Using the example of colonial hydroids, it has been found that in decentralized systems, functional integration of the elements occurs even when there is no obvious need – there is no food to be transported from catchment areas to parts of the development. Metaphorically, “the engine continues to idle even if the car is stationary.” Food intake triggers system integration, e.g. “The engine starts to work harder and the car moves away.” And the most unusual thing about a car analogy is that for non-assembled systems “when the fuel is supplied from different parts, the engine performance varies”.

Some colonial hydroids are used in scientific research as models of decentralized organisms – without controls and without specialized organs (brain, heart, kidneys, etc.) that determine the differentiation of functions into a holistic formation. Unmanaged relationships of equal participants in nature and society are common. These are the interactions in ecosystems, populations and human relationships in many temporary collectivities. Even in highly developed organisms, decentralized relationships between cells form the basis of their function and growth. The interest in colonial hydroids is due to the fact that they have relationships between multicellular atoms that are easier to study compared to relationships between cells, as well as compared to relationships between mobile individuals. Colonial hydroids are particularly suitable for such studies, as their bodies are composed of only two layers of cells and all animals are clearly distinguishable and their connections can be more easily observed than in multilayered organisms of other groups.

Colonial hydroids are like many hydrates that are connected to each other by a tubular body (common sarcoma). It is essentially a multifaceted branching organism. The common body among the animals – the common flesh – is subdivided into fleas that crawl along the substrate and shoots that extend from them. The growth zones of the fleets and shoots are limited to their peaks. The form of the colonial organism is constantly changing, why. stolons and shoots grow, new shoots appear and lateral branches appear on them. An individual body cavity is filled with hydroplasm similar in composition to seawater. The animals capture the prey, digest it in part, after which the semi-digested mass enters the common cavity of the body and is delivered to other parts of the colony, especially to the growth zones at the tops of the fleets and shoots.

The method of transporting food particles to the hydroplasm is very unusual, because. The distribution system in hydroids (an analogue of the circulatory system) instead of a pulse (heart) includes many low-power pulses – animals and parts of the commons – tubes along the fleets and shoots. The power of a pulse is not enough to move the food particles to the opposite end of the bellows to the growth zone. The pulses of all animals are not coordinated, so the hydroplasm in the barn moves either in one direction or in the opposite direction. Inside the fleet, in its various parts, are small currents, which are often directed in opposite directions. This gives the impression of chaos.

However, food in such a colonial organism is rapidly transported by streams of hydroplasm from the animals that received it to distant growth zones. The transfer sequence is similar to a relay race, when food particles are transferred from one hydroplasmic microwave to another.

In this article, the researchers’ attention is focused on the issue of the influence of places where food enters the colony on the efficiency of the distribution system, i.e. the speed and distance of transport of particles suspended in the hydroplasm.

Researchers have developed hydroids Dynamena pumila (L., 1758) in the laboratory on glass plates. In the experiments, the food was obtained in a targeted and dosed manner either from the largest shoot (“mother”) from which the colony grew, or from the younger and shorter shoots closest to the top of the fleet, or from the shoots between them. larger and the top of the fleet.

Only 5 colonies were used, including: five shoots each and an unbranched fleet (Fig. 1). The researchers considered it inappropriate to increase the sample by dividing it into three groups, in which it is possible to average the results compared to conventional statistical methods. This decision is due to the great variability in the structure of the colonial organisms, in contrast to the solitary (single) organisms familiar to us. Instead of increasing the samples, the researchers applied the principles “Idiosyncratic approach” used more in sociology, i.e. comparing individual results. This approach is more informative in cases where the objects of study are very variable – individual.

Two methods were used to determine the direction and extent of hydroplasma flow (HPT): 1) time-lapse (frame-by-frame) micro-video recording of colonies and 2) every minute optical scan under the colony’s binoculars along its length. along the entire length. The first method allows you to accurately determine the regularity of HPTs, their length and duration, the volume of transported hydroplasm, and the amplitude and regularity of the transverse pulses of the tubular body (cenosark) at the site of micro-video capture. Thanks to the second method, it is possible to present an image of the movement of the hydroplasm throughout the column, to determine the length of the GST, a term from a series of local flows (Fig. 2).

It has been found that HPT in the barn is always rhythmic, both after feeding and after fasting during the day. In all colonies, after dose feeding, the length and duration of HPT, the maximum rate of HPT, the volume of transported hydroplasm increase, while the duration of the resting phases decreases.

The results obtained indicate an increase in the intensity of hydroplasmic movement after ingestion of a limited amount of food, as well as the possibility of continuous unidirectional transport of food particles from one end of the colony to the opposite. It has been found that the movement of food particles over considerable distances in the fleet is ensured not only by the pulses of the fed shoots, but also by all the other shoots. The described mechanism of action of HPT also operates in the absence of food, although the volumes of hydroplasma transported are much smaller in this case.

Differences in results were found for a number of parameters depending on where food was received in the colony.
When you only feed on large stem shoots, HPTs are higher, but their percentage is lower than with other feeding options.
• When feeding the distant shoot group, the mean velocity at the stolon at the base of the mother shoot proved to be higher than when feeding the mother shoot itself and the duration and volume of the transported hydroplasma were shorter.
The highest HPT rate and volume of transported hydroplasma at the base of the parent shoot was during the feeding of the middle shoots located between the mother and the top of the flotilla.
• Probably, the feeding site and the number of fed shoots significantly affect the formation of extensive feed movement along the fleet due to the different degree of consistency of the pulsating activity of the intermediate shoots in the chain of their interaction.
• Maternal escape under all feeding options plays a leading role in the operation of the distribution system.

Therefore, using the example of colonial hydroids, it has been found that in decentralized systems, the degree of integration and coordination of the elements depends on where the input signals reach, despite the fact that all the elements are of the same type and nature or between them. interaction remains essentially the same. This can be explained by the independent importance of the articulation architecture of the elements in a single whole.

Therefore, using the example of colonial hydroids, it was found that in decentralized systems, functional integration of elements occurs even when there is no obvious need – there is nothing to transfer from food capture to development. Metaphorically, “the engine continues to idle even if the car is stationary.” Food intake triggers system integration, e.g. “The engine starts to work harder and the car moves away.” And the most unusual thing about the car ratio is that for non-assembled systems “when fuel is supplied from different parts, engine performance varies”.

Read in the popular summaries of other research results on colonial hydroid function:
Effect of water temperature on aquatic vital points Dynamena pumila
The operation of the hydroid in conditions of running and stagnant water
Hydraulics and No Nerves: Lessons of Self-Organization from Colonial Hydroids

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