Name: Noctuidae Insect Preparation, Dissection, and Ovarian Tissue Analysis
Uploaded: 2023-07-14T14:30:00
Description: Watch this Scientific Journal Video about Noctuidae Insect Preparation, Dissection, and Ovarian Tissue Analysis at JoVE.com

noctuidae insect preparation, dissection, and ovarian tissue analysis

Dissection for Identifying Migratory Insects via Ovarian Reproductive Analysis

Migration of insects plays a vital role in population dynamics of global insect distribution for insects like Helicoverpa armigera - the cotton bollworm, Mythimna separate - the oriental armyworm, Spodoptera litura - the taro caterpillar, Spodoptera exigua - the beet armyworm, that have been reported as serious pests in China1,2,3,4. The long travel distances, seasonal movements, high fecundity of migratory pests, and ecological factors have brought great difficulties in the prediction, forecast, and control of these pests5. Pest migration monitoring is required to reveal the adaptability and behavioral changes that facilitate migratory pests according to climate changes or cycles6. To sustain their growth, reproduction, and survival, insects have acquired sequential adaptability during evolution; this series of adaptive life has generated many changes in the reproductive system, such as migratory strategy leading to control of ovarian development in the long migratory process.
Ovarian development is common in migratory pests, which affects the growth of their population7. Therefore, ovarian development has been a hot topic of migratory pest research for a long time. A series of studies have led to several ovarian development indicators and classification strategies. Until now, several methods have been used to analyze ovary development, e.g., Loxostege sticticalis - the meadow moth- ovary development which includes the initial feathering stage, the early spawning period, the spawning period, and the end of oviposition8. Some researchers divide ovarian levels on the bases of yolk color development in migratory Lepidopteran pests, such as S. exigua - the beet armyworm, Pseudaletia unipuncta - the true armyworm, and Cnaphalocrocis medinalis- the rice leaf-folder, etc.9,10,11,12. In previous studies, the ovarian development levels for pests, such as cotton bollworm and rice leaf roller, were divided into five stages: yolk deposition stage, egg grain maturity stage, mature waiting for birth, peak ovogenesis period, and end spawning stage13,14. The ovarian development of the European corn borer was divided into six developmental stages: yolk deposition stage, egg maturation, pre-eggs dispositioning, peak spawning stage, and end-spawning stage15.
Moreover, insects of the same genus have different stages of development, such as ovarian development levels of Spodoptera frugiperda - the fall armyworm - falls into four levels: yolk deposition stage, mature waiting for delivery, peak ovi-positivity, and end spawning stage16. On the other hand, ovarian development in Spodoptera exigua - the beet moth - has five levels: transparent, vitellogenesis, maturation of eggs, egg release, and late egg-laying levels17.
Former studies can only classify development from single to multiple ovarian development levels using color maturity of yolk, oviposition, and egg developments, but classification cannot be done based on anatomy of the reproductive system. The development of an ovary based on the morphogenesis anatomy is a less studied area. Here, the dissection method was designed to predict migratory females in the population using two ovarian tissue types, to elaborate their reproductive dynamics based on the anatomical morphogenesis of -ovarian development stage and mating sac- providing direct evidence to distinguish migratory wild-type females.
Some studies have found that, migratory Noctuidae insect species were frequently captured by searchlights18. The ovary of most migratory Noctuidae insect species is in the early stages of development during the initial stage of migration and the ovarian level increases with the migratory progress. In this study, the dissection method for ovarian development grades is described, to study the two reproductive tissues of different female population pests, captured by search light. This method not only advances the research to understand the migratory dynamics, but also facilities in insect classification, insect physiology study, pest prediction, and forecasting of female pest species.

Author Spotlight: Analysis of Ovarian Anatomy in Migratory Insects to Overcome Experimental Challenges 

Dissection and Grading of Ovarian Development in Wild-Type Female Insects

We aim to apply easy and this newest method for migratory pest, in describing the ovarian anatomy of migratory females. This information will be useful to analyze similar individual species. To predict migratory female insects is pretty challenging.Therefore, visualization of ovarian anatomy is quite easy and very useful.

Watch this Scientific Journal Video about Noctuidae Insect Preparation, Dissection, and Ovarian Tissue Analysis at JoVE.com

Noctuidae Insect Preparation, Dissection, and Ovarian Tissue Analysis  

Noctuidae Insect Preparation, Dissection, and Ovarian Tissue Analysis

Begin by transferring all the collected Noctuidae insects from the net bag to a net cage. Next, provide a Petri dish containing a sterilized 10%honey water solution. Set the cage in a stable environment.Choose wild type female insects that have ventured inside the cage that same day. Carefully transfer these insects into individual vial tubes, ensuring each tube is sealed with a cotton lid. For insect dissection, first place a freshly paralyzed female insect into a dissecting Petri dish containing absolute ethanol.To ensure a clean dissection, infiltrate the insect with absolute alcohol and rinse it in clean water. Next, using forceps, separate the dorsal wings at the junction of the chest and abdomen. Transfer the abdomen into a new disposable dish filled with two to five millimeters of water.Using dissecting forceps, gently peel the abdominal exoskeleton, starting from the pointed mouth dorsoventrally to the tail. Replicate these steps on the other side and place it in clean water to disperse the intact tissues. Now delicately peel off the epidermis fat tissues using forceps and gently pull and release the ovaries.With a pair of dissecting forceps, gently remove fat particles and any surrounding organs from the ovaries. Gradually peel off the mating sac from the middle and eliminate fat particles attached to the ovarian tubes. Gently hold onto the ovary and mating sac from the vertical posterior end, then slowly unfold it downwards.To prevent damage, transfer the ovary into a new or clean Petri dish filled with water. Hold the ovarian tip and unfold the ovary inwardly. Assess the egg maturity for the insect using color and size indicators.Then judge the ovarian grade according to the egg development. After dissection, make sure to separate the female mating sac tissues from the intact ovaries. Examine the morphology as mating sac anatomical features differ from species to species.Next, analyze the ovarian anatomy by dividing the ovarian tissues into five distinct grades. Lastly, capture images of the ovary using a digital camera as per the requirements of the experiment. Four different stages of ovarian development were observed, including the milky white transparent stage with underdeveloped ovaries, the yolk deposition stage with large slightly immature eggs, the ripening stage with bright yellow bead-shaped eggs and the end spawning stage with few or no egg grains.The mating sac of a wild type insect Helicoverpa armigera had a columnar right helix with an inner lumen. Mythimna separata had a G-shaped mating sac with dark brown bands. The mating sac of Agrotis ipsilon was linear with large coils outer back cysts.Spaelotis valida had a slightly brownish thin J-shaped mating sac, while Spodoptera exigua showed a white translucent dumbbell-shaped sac with a bubble cyst in the middle. The mating sac of Spodoptera litura was red with an upper milky white transparent mouth and a faintly visible internal cystic cavity. Pseudoptera lepigone mating sac was small and coiled with closed outer cysts.Mamestra brassicae had olive colored double coiled sacs with outer cysts. Old worm ovarian grading showed transparent and elastic ovarian ducts with grade one visible oocytes. At grade two, the ovarian duct became transparent with tender yellow eggs.At grade three, large fat bodies were absent with the duct being thickest at the ovipositor. Grades four and five showed clusters and fewer eggs in the ovaries with pale yellow and greenish color. All five ovarian grades were also observed in the armyworm, in the tarot caterpillar, and in the bollworm.

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