Which preservation method is commonly used for aquatic specimens during collection?

The common preservation method for aquatic specimens during collection is the use of formalin or ethanol preservation. This technique is widely employed because these chemicals effectively inhibit microbial growth and decomposition, allowing the delicate tissues of aquatic organisms to be preserved in their natural state for longer periods.

Formalin, which is a solution of formaldehyde in water, is particularly effective in cross-linking proteins and stabilizing cellular structures, thus maintaining the morphology of the specimens. Ethanol serves a similar purpose by dehydrating the tissues and preventing decay. Both methods are suitable for a wide variety of aquatic organisms, including fish, amphibians, and invertebrates, making them versatile choices for researchers needing to study specimens later.

In contrast, freezing specimens may lead to cellular damage due to ice crystal formation, which can compromise the integrity of the specimen. Drying specimens in sunlight can also cause too rapid a dehydration which may alter or destroy the physical characteristics of the samples. Storing specimens in freshwater, although it may seem logical for aquatic organisms, is not effective for preservation due to the potential for decomposition and growth of microorganisms.

Thus, formalin or ethanol preservation remains the standard due to its ability to effectively preserve the essential features of aquatic organisms over time.