Eur. J. Entomol. 105 (5): 829-838, 2008 | DOI: 10.14411/eje.2008.110

Why does the Namib Desert tenebrionid Onymacris unguicularis (Coleoptera: Tenebrionidae) fog-bask?

Strinivasan G. NAIDU
Department of Physiology, Nelson R. Mandela School of Medicine, University of KwaZulu-Natal, 719 Umbilo Road, Durban 4041,

Dehydration of Onymacris unguicularis (Haag) for 10 days at 27C resulted in a weight loss of 14.9%, and a 37% decrease in haemolymph volume. Although there was an overall decrease in the lipid content during this period, metabolic water production was insufficient to maintain total body water (TBW). Rehydration resulted in increases in body weight (6.2% of initial weight), TBW (to normality), and haemolymph volume (sub-normal at the end of rehydration). Despite an increase of 44.0 mg in the wet weight of O. unguicularis after drinking for 1h, there was little change in the water content at this time, although the total lipid content increased significantly. Increases in haemolymph osmolality, sodium, potassium, chloride, amino acid and total sugar concentrations during dehydration were subject to osmoregulatory control. No evidence of an active amino acid-soluble protein interchange was noted during dehydration or rehydration. Haemolymph trehalose levels were significantly increased at the end of rehydration (relative to immediate pre-rehydration values), indicating de novo sugar synthesis at this time. Osmotic and ionic regulation was evident during rehydration, but control of OP during haemolymph-dilution is poor and accomplished largely by the addition to the haemolymph of free amino acids and solute(s) not measured in this study. There was little mobilization of sodium and chloride ions from storage sites at this time. The lesser osmoregulatory ability of Onymacris unguicularis and perhaps earlier susceptibility to osmotic stress, a significantly high normal blood glycerol level (relative to other diurnal adesmiine tenebrionids), and a water storage mechanism associated with synthesis of fat, probably all contribute to the development of fog-basking behaviour in this species. Water gain in O. unguicularis during periods of relative drought is probably largely accomplished by a greater food consumption.

Keywords: Water balance, osmoregulation, lipid, glycerol, Tenebrionidae, Onymacris unguicularis, Namib Desert

Received: May 20, 2008; Accepted: September 8, 2008; Published: December 30, 2008

Download citation

References

  1. ASAHINA E. 1966: Freezing and frost resistance in insects. In Merryman H.T. (ed.): Cryobiology. Academic Press, New York, pp. 451-484
  2. BAUST J.G. & MILLER L.K. 1970: Variations in glycerol content and its influence on cold-hardiness in the Alaskan carabid beetle, Pterostichus brevicornis. J. Insect Physiol. 16: 979-990 Go to original source...
  3. BROZA M., BORUT A. & PENER M.P. 1976: Osmoregulation in the desert tenebrionid beetle Trachyderma philistina Reiche during dehydration and subsequent rehydration. Israel J. Med. Sci. 12: 868-871
  4. CHINO H. 1957: Conversion of glycogen to sorbitol and glycerol in the diapause egg of the Bombyx silkworm. Nature 180: 606-607 Go to original source...
  5. COCHRAN D.G. 1985: Nitrogenous excretion. In Kerkut G.A. & Gilbert L.I. (eds): Comprehensive Insect Physiology Biochemistry and Pharmacology. Vol. 4. Pergamon Press, Oxford, New York, Toronto, Sydney, Paris, Frankfurt, pp. 467-506
  6. COHEN A.C., MARCH R.B. & PINTO J.D. 1986: Effects of water stress and rehydration on hemolymph volume and amino acid content in the blister beetle, Cysteodemus armatus. Comp. Biochem. Physiol. (A) 85: 743-746 Go to original source...
  7. COOPER P.D. 1982: Water balance and osmoregulation in a freeranging tenebrionid beetle, Onymacris unguicularis, of the Namib Desert. J. Insect Physiol. 28: 737-742 Go to original source...
  8. COUTCHIE P.A. & CROWE J.H. 1979a: Transport of water vapor by tenebrionid beetles. I. Kinetics. Physiol. Zool. 52: 67-87 Go to original source...
  9. COUTCHIE P.A. & CROWE J.H. 1979b: Transport of water vapor by tenebrionid beetles. II. Regulation of the osmolarity and composition of the haemolymph. Physiol. Zool. 52: 88-100 Go to original source...
  10. DJAJAKUSUMAH T. & MILES P.W. 1966: Changes in the relative amounts of soluble protein and amino acid in the haemolymph of the locust, Chortoicetes terminifera Walker, in relation to dehydration and subsequent hydration. Aust. J. Biol. Sci. 19: 1081-1094 Go to original source...
  11. DOEBBLER G.F. 1966: . Cryoprotective compounds: Review and discussion of structure and function. In Merryman H.T. (ed.): Cryobiology. Academic Press, New York, pp. 2-11
  12. EDNEY E.B. 1957: The Water Relations of Terrestrial Arthropods. Monographs in Experimental Biology 5, Cambridge University Press, Cambridge, 109 pp
  13. EDNEY E.B. 1977: Water Balance in Land Arthropods. Springer, Berlin, Heidelberg, New York, 282 pp
  14. HAMILTON W.J. 1975: Coloration and its thermal consequences for diurnal desert insects. In Hadley N.F. (ed.): Environmental Physiology of Desert Organisms. Dowden, Hutchinson and Ross, Stroudsburg, Pennsylvania, pp. 67-89
  15. HAMILTON W.J & SEELY M.K. 1976: Fog basking by the Namib Desert beetle, Onymacris unguicularis. Nature 262: 284-285 Go to original source...
  16. HATTINGH J., GANHAO M.F. & NAIDU S.G. 1984: Haemolymph composition in Namib Desert tenebrionid beetles. Comp. Biochem. Physiol. (A) 78: 541-545 Go to original source...
  17. HOLM E. & EDNEY E.B. 1973: Daily activity of Namib Desert beetles in relation to climate. Ecology 54: 45-56 Go to original source...
  18. HOLM E. & SCHOLTZ C.H. 1980: Structure and pattern of the Namib Desert dune ecosystem at Gobabeb. Madoqua 12(1): 3-39
  19. LEVENBOOK L. 1958: Intracellular water of larval tissues of the Southern Armyworm as determined by the use of 14Ccarboxyl inulin. J. Cell. Comp. Physiol. 52: 329-339 Go to original source...
  20. LOUW G.N., NICOLSON S.W. & SEELY M.K. 1986: Respiration beneath desert sand: carbon dioxide diffusion and respiratory patterns in a tenebrionid beetle. J. Exp. Biol. 120: 443-447
  21. LOWRY O.H., ROSENBROUGH N.J., FARR A.L. & RANDALL R.J. 1951: Protein measurement with the Folin phenol reagent. J. Biol Chem. 193: 265-275
  22. MACHIN J. 1975: Water balance in Tenebrio molitor L. larvae: The effect of atmospheric water absorption. J. Comp. Physiol. 101: 121-132 Go to original source...
  23. NAIDU S.G. 1998: Haemolymph amino acid, sugar and glycerol levels in the Namib Desert tenebrionid Stips stali during dehydration and rehydration. Comp. Biochem. Physiol. 119: 477-484 Go to original source...
  24. NAIDU S.G. 2001: Water balance and osmoregulation in Stenocara gracilipes, a wax-blooming tenebrionid beetle from the Namib Desert. J. Insect Physiol. 47: 1429-1440 Go to original source...
  25. NEWSHOLME E.A. & TAYLOR K. 1969: Glycerol kinase activities in muscles from vertebrates and invertebrates. Biochem. J. 112: 465-474 Go to original source...
  26. NICOLSON S.W. 1980: Water balance and osmoregulation in Onymacris plana, a tenebrionid beetle from the Namib Desert. J. Insect Physiol. 26: 315-320 Go to original source...
  27. RICHARDSON C.H., BURDETTE R.C. & EAGLESON C.W. 1931: The determination of the blood volume of insect larvae. Ann. Entomol. Soc. Am. 24: 503-507 Go to original source...
  28. RIDDLE W.A. 1986: Hemolymph osmoregulation in three species of beetles. Comp. Biochem. Physiol. 83: 619-626 Go to original source...
  29. RIDDLE W.A., CRAWFORD C.S. & ZEITONE A.H. 1976: Patterns of hemolymph osmoregulation in three desert arthropods. J. Comp. Physiol. 112: 295-305 Go to original source...
  30. ROBINSON M.D. & SEELY M.K. 1980: Physical and biotic environments of the southern Namib dune ecosystem. J. Arid Env. 3: 183-203
  31. SALT R.W. 1959: Role of glycerol in the cold-hardening of Bracon cephi (Gahan). Can. J. Zool. 37: 59-69 Go to original source...
  32. SCHEURER R. & LEUTHOLD R. 1969: Haemolymph proteins and water uptake in female Leucophaea maderae during the sexual cycle. J. Insect Physiol. 15: 1067-1077 Go to original source...
  33. SEELY M.K. 1979: Irregular fog as a water source for desert dune beetles. Oecologia (Berl.). 42: 213-227 Go to original source...
  34. SEELY M.K. 1983: Effective use of the desert dune environment as illustrated by the Namib tenebrionids. In Lebrun P., Andre H.M., De Medts A., Gregoire-Wibo C. & Wauthy G. (eds): Proceedings of the VIII International Colloquium of Soil Zoology. Dieu-Brichart, Ottignies-Louvain-la-Neuve, pp. 357-368
  35. SEELY M.K., LEWIS C.J., O'BRIEN K.A. & SUTTLE A.E. 1983: Fog response of tenebrionid beetles in the Namib Desert. J. Arid Env. 6: 135-144
  36. SEELY M.K., ROBERTS C.S. & MITCHELL D. 1988: High body temperatures of Namib dune tenebrionids - why? J. Arid Env. 14: 135-143
  37. SMITH A.U. 1961: Biological Effects of Freezing and Supercooling. Williams and Wilkins, Baltimore, 462 pp
  38. SOMME L. 1964: Effects of glycerol on cold-hardiness in insects. Can. J. Zool. 42: 87-101 Go to original source...
  39. SOMME L. 1965: Further observations on glycerol and coldhardiness in insects. Can. J. Zool. 43: 765-770 Go to original source...
  40. STOREY K.B. & STOREY J.M. 2005: Freeze tolerance. In Gerday C. & Glansdorff N. (eds): Extremophiles. Eolss Publishers, Oxford, UK, pp. 1-24
  41. TUCKER L.E. 1977a: Effect of dehydration and rehydration on the water content and Na+ and K+ balance in adult male Periplaneta americana. J. Exp. Biol. 71: 49-66
  42. TUCKER L.E. 1977b: The influence of age, diet and lipid content on survival, water balance and Na+ and K+ regulation in dehydrating cockroaches. J. Exp. Biol. 71: 81-93
  43. VAN HANDEL E. 1965: The obese mosquito. J. Physiol. 181: 478-486 Go to original source...
  44. VERRET J.M. & MILLS R.R. 1973: Water balance during vitellogenesis by the American cockroach: translocation of water during the cycle. J. Insect Physiol. 19: 1889-1901 Go to original source...
  45. VERRET J.M. & MILLS R.R. 1975a: Water balance during vitellogenesis by the American cockroach: hydration of the oocytes. J. Insect Physiol. 21: 1061-1064 Go to original source...
  46. VERRET J.M. & MILLS R.R. 1975b: Water balance during vitellogenesis by the American cockroach: distribution of water during the six day cycle. J. Insect Physiol. 21: 1841-1845 Go to original source...
  47. WALL B.J. 1970: Effects of dehydration and rehydration on Periplaneta americana. J. Insect Physiol. 16: 1027-1042 Go to original source...
  48. WHARTON R.A. 1983: Dispersal, diel periodicity, and longevity of Stips stali (Haag) (Coleoptera: Tenebrionidae). Coleopt. Bull. 37: 27-33
  49. WIGGLESWORTH V.B. 1972: The Principles of Insect Physiology. Chapman and Hall, London and New York, 827 pp