n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Die suurstofverbruikskoers van verskillende lewenstadia van die endoparasitiese nematode, (Nematoda: Tylenchida) tydens nie- en post-anhidrobiose : navorsings- en oorsigartikels

Volume 29, Issue 1
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173


Die suurstofverbruikskoers (VO) van die endoparasitiese nematode versamel vanaf mieliewortelkulture is gemeet met behulp van 'n Cartesiese duiker. Die metings met die duiker wat uit Perspex gemasjineer is, berus in beginsel op manometriese veranderinge van die duiker in 'n flottasiebuis van 'n manometeropstelling.

Die gemiddelde VO van 10 metings per lewenstadium, uitgedruk in nanoliters per uur per lewenstadium van nie-anhidrobiote (eiers: 7.96; jeugstadia: 6.13; volwassenes: 26.04) is vergelyk met dié van post-anhidrobiote, 12 uur na herstel uit anhidrobiose. Die gemiddelde VO van die post-anhidrobiote vir die drie lewenstadia (eiers: 19.34; jeugstadia: 14.17; volwassenes: 32.86) is statisties betekenisvol hoër in vergelyking met dié van nie-anhidrobiote. Die redes vir die verskil in VO waardes word bespreek. Die VO is ook uitgedruk in nanoliter per uur per mikrogram volwasse nematode na toepassing van 'n vergelyking verkry uit die literatuur. Dit is gevind dat die suurstofverbruik per een gram 503 keer meer is as die suurstofverbruik per een gram soogdier die grootte van 'n volwasse bees.

, widely distributed in tropical and subtropical regions, is an endoparasite in roots of maize and other crop plants. The nematode is attracted to plant roots by CO and root exudates and feeds primarily on cells of the root cortex, making channels and openings where the eggs are deposited, with the result that secondary infection occurs due to bacteria and fungi. Nothing is known about the respiration physiology of this nematode and how it manages to survive during dry seasons. To measure the oxygen consumption rate (VO ) of individual (less than half a millimeter long), a special measuring technique namely Cartesian diver micro-respirometry was applied. The Cartesian divers were machined from Perspex, and proved to be more accurate to measure VO compared with heavier glass divers used in similar experiments on free living nematodes. An accuracy of better than one nanoliter of oxygen consumed per hour was achieved with a single inside the diver. Cartesian diver micro-respirometry measurements are based in principle on the manometric changes that occur in a flotation tube in a manometer set-up when oxygen is consumed by and CO from the animal is chemically absorbed. VO was measured for eggs (length: ≤ 0.05 mm), larvae (length: 0.36 mm) and adults (length: 0.47 mm) before induction to anhydrobiosis. from infected maize roots were extracted and exposed aseptically to maize root cultures in a grow cabinet at 50 % to 60% relative humidity at 28 °C using eggs, larvae and adults. VO was also measured for post-anhydrobiotic eggs, larvae and adults by taking 50 individuals, eggs and larvae from the culture and placing them in Petri-dishes with 1% agar/water to dry out for 11 days at 28 °C and 50% relative humidity. The VO was measured after the anhydrobiotic eggs, larvae and adults were re-hydrated for 12 hours in a high humidity atmosphere. The average VO value found for ten consecutive measurements during a 50 minute period of one adult using the diver technique was 32.8 nanoliter per hour. The differences between the ten VO values were less than 3.5 %, an indication of the accuracy of the diver measurements. The average VO values from ten measurements per life stage, expressed in nanolitres per hour per life stage of the pre-anhydrobiotes (eggs: 7.96; larva: 6.13; adult: 26.04) were compared with those of post-anhydrobiotes 12 hours after anhydrobiosis. The average VO values of the post-anhydrobiotes for the three life stages (egg: 19.34; larva: 14.17; adult: 32.86) were statistically significantly higher in comparison with the pre-anhydrobiotes. The reasons for the difference are that high concentrations of metabolites, probably in the form of trehalose, accumulate during the anhydrobiosis stage to be utilized during the post-anhydrobiotic revival period. The oxygen consumption rate was also expressed in nanolitres per hour per microgram adult nematode after applying the following equation taken from the literature: M = a2 x b/16 x 1000 where M = mass (µg) of adult nematode; a = largest body width (µm); b = body length (µm). Using this equation it was found that one gram uses 503 times more oxygen compared with one gram mammal the size of a cow. This high specific oxygen consumption rate (MO ) is a direct indication of the large metabolic damage this endoparasitic nematode can have on the metabolic substrates provided by the roots of the various plant crops it parasitize.

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