Effects of serotonergic agents on survival and hemolymph composition of the larval mosquitoAedes aegypti(Diptera: Culicidae, L.)in vivo: does serotonin regulate hemolymph acid–base homeostasis?

Abstract

SUMMARYThe role of serotonin in the regulation of larval Aedes aegypti hemolymph composition was investigated in vivo using two reuptake inhibitors (SSRIs), alaproclate HCl and 6-nitroquipazine maleate, and the receptor antagonist methiothepin mesylate. Larvae were placed in media differing in pH and salinity in the presence and absence of serotonergic agents. The toxicity of each agent was strongly influenced by ambient pH. For each agent, toxicity was negligible in acidic media, intermediate in neutral media and greatest in alkaline media. By contrast, toxicity of all agents was independent of salinity. No effects on mass-specific body water or hemolymph volume were observed whereas hemolymph osmotic pressure, Na + concentrations and pH differed significantly among treatments. 6-nitroquipazine caused a decrease in Na + from 115±1.7 to 103±0.9mmoll , respectively) whereas these agents did not influence acid excretion rates in pH 7 or pH 11 media. The hypothesis that serotonin is involved in hemolymph acid-base balance is discussed.

Mechanisms of pH control in the midgut ofLutzomyia longipalpis: roles for ingested molecules and hormones

“…This process stimulates water absorption by the midgut and urine formation by the Malpighian tubules (Te Brugge et al, 2009). Indirect evidence suggests that serotonin release also occurs in mosquitoes during the hematophagic process (Novak and Rowley, 1994;Novak et al, 1995;Clark et al, 2009). Even among the non-hematophagous larvae of mosquitoes, studies have shown that serotonin acts on the midgut to increase the transepithelial voltage and, consequently, the rate of alkalization (Onken et al, 2008;Onken and Moffet, 2009).…”

The plasticity of extracellular fluid homeostasis in insects

“…Active transport mechanisms in the anal papillae may absorb 159 nosmol of electrolytes with 0.10 µl water, to bring the ECF to the new set point at 0.95 µl volume and an osmotic pressure of 329 mOsm (Fig. 5B, e→f ); namely, the values measured in freshwater mosquitoes by Clark et al (2009).…”

“…Accordingly, excreted urine has an osmotic concentration of 20 mOsm, which is within the diluting capability of the rectum (Clark et al, 2009;Ramsay, 1950). Furthermore, the balance of inputs and outputs yields 733 mOsm as the osmotic concentration of the fluid absorbed in the rectum (Fig.…”

The neurotransmitters serotonin and glutamate accelerate the heart rate of the mosquito Anopheles gambiae

“…In mosquitoes, serotonin (also known as 5-hydroxytryptamine or 5-HT) is involved in feeding behavior, salivation, the transport of ions across the midgut and the Malpighian tubules, and the regulation of hemolymph composition (Clark and Bradley, 1997;Clark et al, 1999;Clark et al, 2009;Kinney et al, 2014;Novak et al, 1995;Novak and Rowley, 1994). Less is known about the function of glutamate in mosquitoes, but a significant body of work performed in other insects has shown that glutamate is released by motor neurons at the neuromuscular junction, which initiates the depolarization of the sarcolemma and leads to the contraction of muscle (Harrison et al, 2012).…”