Studies On Larval Respiratory Systems And Respiratory Behaviors Of Two Aquatic Fireflies

Firefly(Coleoptera:Lampyridae),which had recorded 2,000 species,was distributing extensively in the world,but aquatic firefly was very rare,only had it named 7 species.A new aquatic species,Luciola leii(Coleoptera:Lampyridae),which is mainly living at the bottom in the natural water environment,belongs to one kind of benthic aquatic insects.However,Luciola substriata(Coleoptera:Lampyridae) mostly float on the surface in the natural water environment and move by back swimming,it belong to one kind of planktonic aquatic insects.The two aquatic fireflies were living in the lake, stream and paddyfield,which were characterized of clean,slow current and shallow.And these larvae,which eat of miniature aquatic snail,were the biologic nature enemy. Meanwhile,larvae need upper request for water quality,so the larvae may be deemed to one kind of water quality of monitoring insect.Due to the quicken process of urbanization, and destroy of human to nature environment.So the areas of habitat were gradually reduced.This dissertation was to study the dissimilarity of the respiratory system and respiratory behavior in Luciola leii and Luciola substriata.Study the optimal water environment parameter for larval breeding of Luciola leii,in order to provide scientific data for indoors large-scale rearing,and to study the larval feedback to different water quality,in order to provide scientific data for water quality of monitoring,according the characteristic of respiratory behavior.The structure of respiratory system during the 1^st - 2^nd instar and the 3^rd - 6^th instar of Luciola substriata larva was observed using micro-dissection,transmission electron microscope(TEM) and scanning electron microscope(SEM).The 1^st - 2^nd instar larva had trachea without air sacs,while the 3^rd - 6^th instar larva had trachea and air sacs in the respiratory system.The structure of the posterior spiracles of the 1^st - 2^nd instar larva was the same as that of the 3^rd - 6^th instar larva.Observations by TEM believed that the hairs on the culticle were tracheal gills.In this paper,we studied the structure of respiratory system and respiratory behaviors of Luciola leii larvae.The results showed that there had only tracheas without air sacs in the whole respiratory system of L.leii larvae.The spiracles were located on the prothorax, mesothorax and metathorax where had no tracheal gills distributed,the spiracles and tracheal gills were located on the 1^st - 8^th segments of abdomen,tracheal gills connected with the basement of the atrium which formed the shape of "√",and the tracheas in the tracheal gills connected with the spiracular trachea.The aim of exposed spiracles to air of L.leii and L.substriata are relative to respire through laboratory experiments and observations.L.leii larvae had three kinds of respiratory behaviors:using thoracic spiracles,abdominal spiracles and tracheal gills to breathe respectively.However,the abdominal spiracles were primarily used among them, which are mainly divided five ways in which the longest respiratory time is 8 h - 12 h.In the process of back swim of L.substriata,some abdominal segments with spiracles could expose to the air by swimming inertia,namely swim behavior and respiratory behavior occurred simultaneously.1^st - 2^nd instar larvae had tracheal gills,which primary respiratory organ.At the same time,they exposed their eighth abdominal segment to air when at rest,which usually occurred when 1^st - 2^nd instar larvae staying under the aquatic plant leaves(e.g.,Lemna minor(Arecidae:Lemnaceae)).In general,larvae did not crawl to the top of leaves and exposed its whole body to air.3^rd - 6^th instar larvae had only abdominal spiracles that had no hydrofuge hairs and without tracheal gills.During back swim of 3^rd - 6^th instar larvae,larval abdominal segments were periodically exposed to the air by inertia of seven swim steps.Besides,3^rd - 6^th instar larvae could crawl to the top of leaves to expose their whole body to air.We reported the influences of water temperature,depth and rearing density on respiratory behavior of 1^st - 6^th stages of L.leii larva.The results showed that respiratory duration was 8.83±1.34 h,the highest respiratory frequency(FR) was 2.3 times / h,the shortest subsurface interval(SI) duration was 0.53±0.27 h,and the optimal water temperature was approximately 23℃.Water depths of 5 cm - 70 cm didn't lead to the death and didn't influence respiratory behavior of 1^st - 6^th stages of L.leii larva.Different rearing density had more influences on L.leii larva,and the optimal rearing density was 1 - 3 individuality/64.8 cm³.The effects of four different kinds of water quality in urban waters of Wuhan on the larval respiratory behavior of L.leii(Coleoptera:Lampyridae) were evaluated by laboratory experiments.The feasibility was discussed to monitor multi - polluted and mixed wastewater by indexes of respiratory behavior.The results showed that the larval respiratory behavior of L.leii in lighted and dark conditions(simulation daylight and night - time) was influenced by typeâ…¢(Donghu Lake),typeâ…£(Tangxun Lake),typeâ…¤(Yezhi Lake) and type inferiorâ…¤(Nanhu Lake) water qualities,compared with tap water(CK).These larvae had distinctly different responses when they were put into typeâ…¢,typeâ…£,typeâ…¤and type inferiorâ…¤water qualities.Type inferiorâ…¤has the most significant influence on larval respiratory behavior among them(P＜0.05).Under experimental conditions,the respiratory frequency(FR) in type inferiorâ…¤water quality was 14±4.2 times / h,subsurface interval duration(SI) was 0.53±0.3,and the time of respiration was 6.88±1.6 h.The time of respiration and respiratory frequency(FR) were higher under typeâ…¢,typeâ…£and typeâ…¤water qualities,subsurface interval durations (SI) were shorter with typeâ…¢,typeâ…£and typeâ…¤water qualities.This results showed that the respiratory behavior of L.leii.In day and night,specifically the time of respiration,FR and SI could be used as a method of monitoring water quality for multipolluted and mixed wastewater.