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Research Article | DOI: https://doi.org/
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Copyright: © Khaled Kh Al-Khafaji. This is an open-access article distributed under the terms of The Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Received: 30 November -0001 | Accepted: 27 December 2018 | Published: 04 January 2019
Keywords: behavior, temperature, color, Palaemon elegans, puddle shrimp
Animals can change color either rapidly in response to changes in their immediate environment or slow as the seasons change. Such plasticity can permit local adaptation but it can also be constrained by physiological and behavioral mechanisms. Palaemon elegans occurrence in high temperature ranges, but as it lowers (up to 10-5 °C) it begins to reduce its movements until it is completely still, almost in lethargy. To this change of behavior is bound a change in the coloration of the animal's body, which changes from being completely transparent with bright blue and yellow tones to being translucent, with much paler blues and yellows.
Many organisms change color in response to changing temperatures because different color intensities can affect thermal budgets (Angilletta, 2009). Yet, color patterns can vary with latitude (Lacey et al., 2010; Martin et al., 2010) and altitude (Karl et al., 2009; Parkash et al., 2009). The ability to change color and its potential variation across latitudes can be just as important as plastic responses to changes in local conditions. In a latitudinal and seasonal context we could expect greater plasticity where local thermal change is more variable.
The motor activity of any living being is a phenomenon that is always manifested with a regular variation and not as a continuous process (Randall et al., 1998). Therefore, when we study a behavior, of whatever nature, we must take into account that it may be due to an internal cause, which explains the behavior at the physiological level, or has an exogenous originie there is an external cause that Has triggered the individual's motor response (McFarland & Pickens, 1965; Carranza, 1994). Triggers can be light, humidity, temperature, salinity, etc. (McFarland and Pickens, 1965), and act on organisms through the nervous and endocrine systems (Alcock, 1978).
Temperature plays a very important role in the metabolism of animals (McFarland and Pickens, 1965; Dalla-Via, 1985; Schmidt-Nielsen, 1997). In the poikilothermal animals body temperature oscillates as a function of the ambient temperature, so that the low temperatures suppose a decrease of the speed of the chemical reactions and, therefore, a slowdown of the metabolism (Hill and Wyse, 2006). Therefore, they have developed various mechanisms to regulate body temperature, such as through the generation of heat by muscle contractions, circulatory changes (vasoconstriction and vasodilation) to decrease or increase the flow of heat to the skin or sweat to lose heat By evaporation (Vernberg, 1981). However, the response to changes in temperature is not always in the same direction and depends on the processes of adaptation. Thus, McFarland and Pickens (1965) observed that, although metabolic rates did not change markedly, when shrimp Palaemonetes vulgaris was exposed to warm temperatures, individuals adapted to these temperatures swam more rapidly per unit of oxygen consumed than those adapted to Average or cold temperatures. The inverse effect was observed for shrimp adapted to cold water.
The aim of this study is to evaluate the behavior of Palaemon elegans in the face of a sudden temperature change in the medium and its influence on a possible change in the coloration of the individual's body.
Palaemon elegans is a species very easy to find in the intertidal zone of the pond connected to Garmat Ali River and Shatt Al-Arab River. It is usually distributed in shallow waters, up to 15 meters, is omnivorous, nocturnal habits, and its body is transparent with horizontal lines of brownish color and blue and yellow stripes on the legs (Sanz, 1987). It tolerates high temperature and salinity ranges and can reach 6.5 cm, being the female larger than the male (Espino et al., 2006).
A total of 100 shrimps of (Palaemon elegans), approximately 3 cm long, were collected from pond in Garmat Ali University near Garmat Ali River. The specimens were transported to the laboratory where they were kept in 20 liter tanks for a period of 24 hours, without feeding. After this period, 10 specimens were selected which were separated and introduced into individual compartments, resulting from subdividing a 20-liter tank similar to that of acclimatization, at an initial temperature of 25 ° C. The animals were kept at this temperature for 30 minutes before gradually lowering the water temperature from 25 to 5 °C. This was decreased rapidly (10 ° C every 60 minutes) until reaching 15 ° C. From here it decreased more slowly until reaching the final 5 °C. The total process lasted four hours.
Throughout the process we observed the behavior of each individual, as well as body coloration. For assessing the number of movements made by each animal (swimming movements in the water column, swimming movements only on the bottom or without movements, on the bottom). Likewise, for the color an evaluation of vividness (translucent body color with bright blue and yellow tones in the tweezers or translucent body color with pale blue and yellow tones in the tweezers) was established.
Statistical analysis of the data was done using the Excel (Microsoft).
There was a significant change in the behavior of the individuals with respect to the decrease in temperature, mainly from 25 °C, this being a phase Important in the transition of a state of activity (with swimming movements in the water column) to reduce the movements to short displacements on the bottom and finally, at 5 °C, to a phase of immobility or lethargy.
On the other hand, the changes described in the behavior are linked to a loss of vividness in color, changing from bright colors in the body and tweezers to pale tones at temperatures below 15 °C. Thus, a significant relationship between the vivacity of body color and the amount and types of movements displayed by the animal was observed.
The drop in temperature abruptly results in a significant loss in the mobility of puddle shrimp as a consequence of the influence of this on muscle activity and the metabolic relationships that occur in them (Berglund and Bengtsson 1981; Dalla-Via , 1985a). at 20-15 ° C, these crustaceans experience a significant reduction in their swimming activity, to move to a phase of more limited movements, with some disorientation, of displacements on the bottom. At 15- 10 ° C enter a phase of inactivity and, at 5 ° C, even lethargy. It is possible that at lower temperatures these animals enter a phase of paralysis, possibly as a pre-death step (Vernberg, 1981; Pascual-Jiménez, 2011.)
These changes in the pattern of movements are accompanied by changes in body color, from transparency to bright, almost iridescent colors, to a somewhat less translucent color structure, with paler, lighter color bands. These changes in the vividness of the coloration are noted a little after the changes in swimming activity, at 15-10 ° C. Possibly, these changes in body color are related to the effect of temperature on the chromatophores and proteins that constitute the pigments, as well as on the muscular activity itself, losing the transparency to become the somewhat more opaque muscle (Bauer, 1981; Dalla-Via, 1985b).
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