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Accueil du site → Doctorat → Chine → 2013 → Biology of the Desert Beetle Oodescelis Chinensis and Functions of its Antifreeze Proteins

Xinjiang University (2013)

Biology of the Desert Beetle Oodescelis Chinensis and Functions of its Antifreeze Proteins

Wang Yan

Titre : Biology of the Desert Beetle Oodescelis Chinensis and Functions of its Antifreeze Proteins

Auteur : Wang Yan

Grade : Doctoral Dissertation 2013

Université : Xinjiang University

Résumé partiel
Oodescelis chinensis Kaszab (Coleoptera : Tenebrionidae) is a Chinese endemic species,which is only distributed in desert and semidesert regions of Xinjiang, China. Oodescelischinensis possesses significant ecological and economic values, and is suitable to be used as amodel creature because of its obviously sexual dimorphism and the habit of not killing eachother. O. chinensis lives through winter on the surface of soil, and the insect can surviveafter supercooling point test experiment. It is a suitable creature for studying antifreezeproteins. But its biology and antifreeze proteins remain largely unknown. Also, its laboratoryrearing and its sexual dimorphism are yet to be determined. In this study, the laboratoryrearing methods, the biological characteristics and the sexing methods of O. chinensis wereexamined. Furthermore, eleven antifreeze protein genes were isolated from overwinter adults,and the structures and functions of three antifreeze proteins were studied. This study laidfoundation for further research of the desert insect.The Glass Petri dishes added with humid cotton were used to cultivate the insect eggs,prepupae, pupae and teneral adults. The larvae were reared in insect rearing tubes with moistdesert sand. The water content of desert sand decreased from bottom to upper part because ofcapillarity, and the surface of the desert soil was dry. The wheat bran was added to raise larvaeof O. chinensis. It can finish its life cycle under the rearing condition. The survival rates ofeggs, first instar larvae, larvae after second instar, prepupae, pupae, and teneral adults were86.39±4.43%,92.85±1.22,55.22±5.65%,82.35±4.37,85.13±3.41%and86.00±7.37%,respectively. Oodescelis chinensis can successfully finish its life cycle, and the insect can passto the next generation normally in laboratory.O. chinensis adopts nocturnality to survive desert environment. It had one-year life cycleand overlapping generation, in Urumqi. The female/male ratio of adult insect was1:1. Theweight and elytrum length of female was obviously greater than that of male in adult. Therewere15instars during larvae stage. The coloration of each developmental stage gradually changed from creamy white to light brownish, brunneus or black. The egg laying period offemale adult lasts4months. On average, each female produced1032eggs. The adults andpupae have abviously sexual dimorphism apparences.The adult of Oodescelis chinensis has three externally visible gender-specificcharacteristics, and an inner characteristic on the8thsternite for sex determination. First, thereare broad claw pads in tarsus of the male adult fore legs and middle legs. These claw padswere consisted of slim flat bands which can be seen with scanning electron microscope. Theforeparts of the slim flat bands are slightly sharp and the tips are bent back. The back of thestructure has bamboo-shaped screw threads. Second, the hind legs of male adult are coveredwith bristle layers. Third, the first, second and fifth abdominal segments of male adult eachhas one bristle pad. The fourth, there is a trilateral indentation on the8thabdominal sternite inmale. However, these characteristics in male are absent in female adult. The fouthcharacteristic is very common in tenebrionidae beetles, such as Microdera punctipennis,Colposcelis microderoides microderoides, Anatolica polita borealis, Adesmia anomaladejeani, Sternoplax souvorowiana and Anatolica pseudiduma. A new method based on thedifference of the8thsternite was developed to determinate the sexes of desert beelte adults.This method could be widely used in sexing desert beeltes with100%accuracy and withoutdemage. The pupaes of O. chinensis also has three sexual characteristics. First, similar to maleadults, the tarsus of the male pupal fore legs and middle legs are obviously wider than that offemale, which will be developed to claw pads. Second, there are no obviously genitalopenings on the8thabdominal sternite in male pupae. Third, the8thabdominal sternite of malepupae is narrower than that of female. There are two closed prominencies at the end of the8thabdominal sternite in male pupae, but the two prominencies of female pupae are separated andlooked like nipples. The second and the third characteristic of pupae are universal inTenebrionidae beetle pupae, so it can be used in pupal sex determination of tenebrionidi beetlewithout damage. The claw pads in tarsus and indentation on the8thabdominal sternite of Oodescelis chinensis male adults are helpful during coupling and mating.Eleven antifreeze genes were isolated from antifreeze tolerant desert beetle O. chinensisin this research. The primary structure of these protein comprised of tandem repeats of12-aasequence [TCT(I)xSxxCxxAx] with regularly spaced Cys at intervals of6-aa residues, andthere are23-aa signal peptides in the N-terminal part of these antifreeze proteins. The genesof these antifreeze proteins can be divided into two types.

Mots clés : Chinese endemic species freeze-tolerant insect rearing method biology sexidentification antifreeze proteins expression and purification function analysis

Présentation (Dissertation topics)

Page publiée le 2 avril 2014, mise à jour le 10 janvier 2018