All organisms including insects are products of what they eat. Thus, a potential limitation to the development and growth of insects in the ocean is the acquisition of proper nutrition. Insects gain their nutritional requiements either directly through their diet or by building essential fatty acids through metabolic pathways. They use fatty acids for energy storage, as components in cell membranes, and to function in cellular signaling. Plant-feeding insects acquire certain long chain fatty acids (18 carbon chains) from their diets and they create longer chain fatty acids (20 carbon chains). Predatory insects acquire all of their fatty acids from their diets. Limitations to fattty acids reduce reproduction, increase developmental times and cause deformaties in adult insects. Therefor, insects may not be able to survive on the ocean because they cannot obtain essential fatty acids.
Does the potential dietary lipids for ocean insects differ from those available in freshwater? The answer is yes. Marine plankton contain high levels of 20 carbon unsaturated fatty acids and very little 18 carbon chain fatty acids. Analysis of the pelagic Halobates reveal that their fatty acids are like the plankton, high in 20-carbon fatty acids and low in 18-carbon fatty acids. This pattern is unique among insects and is not seen in closely-related water striders that live in estuaries. Presumably the species that live in the intertidal zone rely on terrestrial insects for their dietary fatty acids while the pelagic species are opportunistic and feed on plankton as a primary source of their diet.
Limitation of 18-carbon fatty acids causes wing malformations in other insects. Perhaps the difference in Halobates diet partly explains the absence of wings in adult forms. Though alternatively, many species of insects have lost their wings when they are no longer needed. For example, fleas and lice are wingless as adults and many island or high mountain-dwelling species do not have wings. Perhaps Halobates can disperse on the surface of the ocean and thus lacks the need for wings. And, the fact that Halobates manages to exist on the open ocean despite potentail dietary limitation of fatty acids suggests that other insects could live there as well unless some other factor is limiting.
Does the potential dietary lipids for ocean insects differ from those available in freshwater? The answer is yes. Marine plankton contain high levels of 20 carbon unsaturated fatty acids and very little 18 carbon chain fatty acids. Analysis of the pelagic Halobates reveal that their fatty acids are like the plankton, high in 20-carbon fatty acids and low in 18-carbon fatty acids. This pattern is unique among insects and is not seen in closely-related water striders that live in estuaries. Presumably the species that live in the intertidal zone rely on terrestrial insects for their dietary fatty acids while the pelagic species are opportunistic and feed on plankton as a primary source of their diet.
Limitation of 18-carbon fatty acids causes wing malformations in other insects. Perhaps the difference in Halobates diet partly explains the absence of wings in adult forms. Though alternatively, many species of insects have lost their wings when they are no longer needed. For example, fleas and lice are wingless as adults and many island or high mountain-dwelling species do not have wings. Perhaps Halobates can disperse on the surface of the ocean and thus lacks the need for wings. And, the fact that Halobates manages to exist on the open ocean despite potentail dietary limitation of fatty acids suggests that other insects could live there as well unless some other factor is limiting.