Tissue specific ionomotive enzyme activity and K+ reabsorption reveal the rectum as an important ionoregulatory organ in larval<i>Chironomous riparius</i>exposed to varying salinity

Jonusaite, Sima; Kelly, Scott P.; Donini, Andrew

doi:10.1242/jeb.089219

Cited by 16 publications

(43 citation statements)

References 70 publications

(82 reference statements)

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“…The rectum of larval C. riparius is a site of K + absorption (see Jonusaite et al, 2013). The mean baseline K + flux (absorption, lumen to bath) measured at the recta in this study was 104.3±13.7 pmol cm −2 s −1 (n=38).…”

Section: The Journal Of Experimental Biologymentioning

confidence: 59%

“…Therefore, salinity and AST7 have similar effects on rectal NKA and VA activities. The actions of AST7 occur rapidly and hence cannot be mediated by changes in NKA and VA expression; however, it was suggested that larvae reared in brackish water may have lower expression of rectal NKA and VA than those reared in freshwater (Jonusaite et al, 2013). In an effort to determine whether the mechanisms of AST7-and salinity-induced changes in NKA and VA rectal activities are similar or different, NKA and VA protein expression studies on freshwaterand brackish-water-reared larvae were carried out.…”

Section: The Journal Of Experimental Biologymentioning

confidence: 99%

“…6). NKA and VA protein expression in recta of freshwater-and brackish-water-reared larvae A previous study demonstrated that recta of brackish-water-reared larvae have lower activities of NKA and VA compared with recta of freshwater-reared larvae (Jonusaite et al, 2013). Therefore, salinity and AST7 have similar effects on rectal NKA and VA activities.…”

mentioning

confidence: 92%

“…4). Application of 1 μmol l −1 Dippu-AST7 did not abolish contractions but inhibited the contractions by ~95%.Effects of Dippu-AST7 on K + absorption by the rectum, and NKA and VA activities in the rectumThe rectum of larval C. riparius is a site of K + absorption (see Jonusaite et al, 2013). The mean baseline K + flux (absorption, lumen to bath) measured at the recta in this study was 104.3±13.7 pmol cm −2 s −1 (n=38).…”

mentioning

confidence: 99%

“…Abrupt transfer to brackish water is accompanied by a sharp reduction in whole-body VA activity and a less pronounced decrease in whole-body NKA activity (Jonusaite et al, 2011). The greatest amount of NKA and VA activity can be attributed to the rectum, and the recta of larvae reared in brackish water have greatly reduced NKA and VA activities, which coincide with reduced ion reabsorption (Jonusaite et al, 2013).Although the larval response to abrupt and long-term (rearing) exposure to brackish water is the same, the mechanisms with which this is achieved are likely to be different. Abrupt exposure to elevated salinity would require a rapid response that could be…”

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confidence: 99%

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Allatostatin A-like immunoreactivity in the nervous system and gut of the larval midge, Chironomus riparius (Meigen): Modulation of hindgut motility, rectal K+ transport and implications for exposure to salinity

Robertson

Chasiotis

Galperin

et al. 2014

Journal of Experimental Biology

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Evidence for the presence of allatostatin (AST) A-like neuropeptides in the larval midge Chironomus riparius is reported. Immunohistochemical studies on the nervous system and gut revealed the presence of AST A-like immunoreactive (AST-IR) cells and processes. The nerve cord contained AST-IR processes that originated from cells in the brain and travelled the length of nerve cord to the terminal ganglion. Within each ganglion, these processes gave rise to varicosities, suggesting that they formed synapses with neurons in the ganglia. Endocrine cells containing AST-IR were present in three regions of the midgut: near the attachment of the Malpighian tubules, between the anterior and posterior midgut, and in the vicinity of the gastric caecae. The terminal ganglion also contained four AST-IR cells that gave rise to axons that projected onto the hindgut and posterior midgut. Application of a cockroach AST to the semi-isolated hindgut of larval C. riparius led to dosedependent inhibition of muscle contractions with an EC 50 of 10 nmol l −1 and a decrease in rectal K + reabsorption resulting from reduced rectal Na + /K + -ATPase and vacuolar type H + -ATPase activities. The results suggest the presence of endogenous AST-like neuropeptides in larval C. riparius, where these factors play a role in the function of the gut. Furthermore, regulation of ion reabsorption by ASTs at the rectum could serve as an ideal mechanism of ion regulation in the face of abrupt and acute elevated salt levels. KEY WORDS: Na INTRODUCTIONJuvenile hormones are synthesized by the corpora allata and control the juvenile characteristics of insects during growth and development. In adult insect females, juvenile hormones can also regulate reproductive activities such as the maturation of oocytes. Synthesis of juvenile hormones is inhibited by allatostatins (ASTs), members of a large and diverse family of peptides that are structurally characterized into three distinct groups (Gäde and Goldsworthy, 2003).The C-type allatostatins with an N-terminal pGlu residue and a free C terminus have been discovered in the moth Manduca sexta, the fly Drosophila melanogaster and the mosquito Aedes aegypti (Kramer et al., 1991;Williamson et al., 2001;Li et al., 2006). The B-type allatostatins all have a common Trp-(X6)-Trp-amide C terminus and were first discovered in the cricket (Wang et al., 2004). The A-type allatostatins (ASTs) were the first to be discovered in the cockroach and share a Phe-Gly-Leu-amide C terminus (Donly et al., 1993;Siju et al., 2014). RESEARCH ARTICLEDepartmentAll allatostatins inhibit juvenile hormone synthesis in at least one group or species of insect; however, many do not in other insects, and instead have known inhibitory activity on contractile properties of muscle (Gäde and Goldsworthy, 2003). In particular, the ASTs have been shown to inhibit contractions of visceral muscle including the foregut and hindgut (Lange et al., 1993;Sarkar et al., 2003;Predel et al., 2001;Matthews et al., 2008), and have been localized to end...

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Section: The Journal Of Experimental Biologymentioning

confidence: 59%

Section: The Journal Of Experimental Biologymentioning

confidence: 99%

mentioning

confidence: 92%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Allatostatin A-like immunoreactivity in the nervous system and gut of the larval midge, Chironomus riparius (Meigen): Modulation of hindgut motility, rectal K+ transport and implications for exposure to salinity

Robertson

Chasiotis

Galperin

et al. 2014

Journal of Experimental Biology

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FLUID AND ION SECRETION BY MALPIGHIAN TUBULES OF LARVAL CHIRONOMIDS, Chironomus riparius: EFFECTS OF REARING SALINITY, TRANSPORT INHIBITORS, AND SEROTONIN

Zadeh-Tahmasebi

Bui

Donini

2016

Arch Insect Biochem Physiol

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Larvae of Chironomus riparius respond to ion-poor and brackish water (IPW, BW) conditions by activating ion uptake mechanisms in the anal papillae and reducing ion absorption at the rectum, respectively. The role that the Malpighian tubules play in ion and osmoregulation under these conditions is not known in this species. This study examines rates of fluid secretion and major cation composition of secreted fluid from tubules of C. riparius reared in IPW, freshwater (FW) and BW. Fluid secretion of tubules from FW and BW larvae was similar but tubules from IPW larvae secrete fluid at higher rates, are more sensitive to serotonin stimulation, and the secreted fluid contains less Na(+) . Therefore in IPW, tubules work in concert with anal papillae to eliminate excess water while conserving Na(+) in the hemolymph. Tubules do not appear to play a significant role in ion/osmoregulation under BW. Serotonin immunoreactivity in the nervous system and gastrointestinal tract of larval C. riparius was similar to that seen in mosquito larvae with the exception that the hindgut was devoid of staining. Hemolymph serotonin titer was similar in FW and IPW; hence, serotonin is not responsible for the observed high rates of fluid secretion in IPW. Instead, it is suggested that serotonin may work in a synergistic manner with an unidentified hormonal factor in IPW. Ion transport mechanisms in the tubules of C. riparius are pharmacologically similar to those of other insects.

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The response of claudin-like transmembrane septate junction proteins to altered environmental ion levels in the larval mosquito Aedes aegypti

2016

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Septate junctions (SJs) occlude the paracellular pathway and function as paracellular diffusion barriers within invertebrate epithelia. However, integral components of SJs and their contribution to barrier properties have received considerably less attention than those of vertebrate occluding junctions. In arthropods, SJ proteins have only been identified in Drosophila and among these are three integral claudin-like proteins, Megatrachea (Mega), Sinuous (Sinu) and Kune-kune (Kune), as well as a receptor-like transmembrane SJ protein known as Neurexin IV (Nrx IV). In this study, mega, sinu, kune and nrx IV are identified and characterized in aquatic larvae of the mosquito Aedes aegypti and a role for these proteins in ionoregulatory homeostasis is considered. Transcripts encoding Mega, Sinu, Kune and Nrx IV were found in iono/osmoregulatory tissues such as the midgut, Malpighian tubules, hindgut and anal papillae, but abundance was greater in the hindgut and anal papillae. Using immunohistochemical and western blot analysis it was found that Kune localized to the regions of intercellular contact between epithelial cells of the rectum and posterior midgut and in the apical membrane domain of the syncytial epithelium of anal papillae. To investigate a potential role for integral SJ proteins in larval A. aegypti iono/osmoregulation, abundance was examined in animals reared in freshwater or brackish water (30 % seawater). In iono/osmoregulatory epithelia, larvae exhibited tissue-specific alterations in mega mRNA and Kune protein abundance, but not sinu or nrx IV mRNA. These studies provide a first look at the potential contribution of integral SJ components to iono/osmoregulatory homeostasis in an aquatic invertebrate.

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Tissue specific ionomotive enzyme activity and K+ reabsorption reveal the rectum as an important ionoregulatory organ in larvalChironomous ripariusexposed to varying salinity

Cited by 16 publications

References 70 publications

Allatostatin A-like immunoreactivity in the nervous system and gut of the larval midge, Chironomus riparius (Meigen): Modulation of hindgut motility, rectal K+ transport and implications for exposure to salinity

Allatostatin A-like immunoreactivity in the nervous system and gut of the larval midge, Chironomus riparius (Meigen): Modulation of hindgut motility, rectal K+ transport and implications for exposure to salinity

FLUID AND ION SECRETION BY MALPIGHIAN TUBULES OF LARVAL CHIRONOMIDS, Chironomus riparius: EFFECTS OF REARING SALINITY, TRANSPORT INHIBITORS, AND SEROTONIN

The response of claudin-like transmembrane septate junction proteins to altered environmental ion levels in the larval mosquito Aedes aegypti

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