Description Of Early Invertebrate Developmental Stages

Introduction

Animals can be classified into two main group which are invertebrates andvertebrates. Vertebrates animal is the animal that have a backbone while invertebratesdoes not have back bone such as fly and flatworm. Vertebrates are well-developedbrain which have advanced nervous system and the cellular skin are protected by outer covering. However, invertebrate is supported by hard outer skeleton withattachment of muscles as body protection. Invertebrate usually small insects withsimple nervous system but still important in food chain in life. The animals also havetheir own life cycle with different period of time. Usually the life cycle ofinvertebrates animals such as insects are shorter compare to the vertebrates.

In this experiment, we study the life cycle which from the first stage to last stage anddevelopmental stage of invertebrate by using the blow flies. This insect belongs to theorder Diptera or two- winged flies and the family is known as Calliphoridae and itshas very large group containing a number of families and many species so closelyresemble the house fly that to the untrained eye they cannot be distinguished. Next, the genus of the house fly used is known as Lucilia and the specific name of thisinsect is Lucilia sericata. This flies are usually found with association with activitiesof human and well- known pest of both home and farm. There are four stages in thisinsect life cycle which are egg stage, larvae stage, pupae stage and adult stage. Thisinsect suited for study and experimentation in the body segment or pattern formationplus life cycle is short which are 2 weeks. L. sericata also importance in veterinary, medical and especially in forensic science which help to investigate insectcolonization because it relates to the time of death, aiding enforcement ininvestigations. The immature flies also used for the estimation of minimum portion ofpost-mortem interval (PMI). Besides, in medical and veterinary field, L. sericata isusually used species in wound of human injuries treatment which conventionaltreatment fail to heal. This treatment known as maggot therapy treatment. The larvaewere place on the wound to feed the necrotic tissue and bacteria that infected woundplus the larvae also secrete the antimicrobial enzymes and promotes healthy tissuegrowth.

Procedure

1. A flytrap has been setted up and placed at garbage region.
2. Eggs are obtained using a pair of forceps from the captured female fly on theflytrap.
3. Eggs are placed in a clean petri dish and are supplied with basic necessities (air, ideal environment, food, water).
4. The developmental stages of the housefly are observed throughout the period of 2 weeks by using a microscope.
5. Chloroform is used to make the adult common green bottle fly (Lucilia sericata)remain unconscious during observation under microscope.
6. The results are recorded and analysed.

Discussion

Distributed all over temperate and tropical regions but mainly southernhemisphere (Africa & Australia), Lucilia Sericata which common name is greenbottle fly, usually roams around carrion, excreta and garbage areas. These greenbottle flies known to complete life cycle of 2-3 weeks and within those approximatedays, undergo whole metamorphosis with distinct egg, larval or maggot, pupal andadult stages. Warmer temperature which is usually preferred, hatching takes up 9hours and meanwhile, in cooler conditions, hatching occurs within 3 days. Tropicaland warmer regions are in favour of their settlements and natality. Female green bottleflies might able to lay 2000 to 3000 eggs in 9 to 10 batches within only 3 weeks. The first stage of fly life cycle is where the female adult lays the fertilized eggs.

Before the female blowfly can mating, it is needed to consume some proteinmeanwhile the male blow fly need to be sexually mature when it is beingborn. Depending on the species, these flies lay eggs in different locations, sizes andshapes. The ideal site of egg is material that the larvae will eat when they hatch fromthe eggs. The female adults usually choose to deposit her eggs on the dung, organicmanure, sewage, accumulated plant materials and in our case, the blow fly laid eggson the meat or carrion. The garbage which includes waste associated with the foodpreparation, cooking and serving at home and public places and with the storage, handling and sale of food which including fruits and vegetables in markets, functioned as the main medium for breeding for the eggs.

The eggs which are shiny white in colour and resemble a small grains of rice, layseparately but piled in small clusters at room temperatures, 25˚C to 30˚C. The lengthof the egg is about 1 mm, slightly curved and elliptical in shape with one end issomewhat broader than the another end. Each is dorsally marked by two and curved, rib-like longitudinal thickenings or ridges. These eggs need to be in warm, moistcondition for them to hatch into larvae. The stage of eggs only lasts about 24 to 48hours before proceeds to the next stage of their life cycle. The second stage for the development of housefly is the larva stage or also knownas maggot stage. This is the main feeding stage. This larvae emerges after the eggshatch within 24 hours or can even take longer time depends on their surroundingtemperature. The larvae appearance is like a pale-worms, typically creamy whitish incolour, conical-shaped with a complete peritreme on their posterior spiracles. Flylarvae have both anterior and posterior spiracles which is important for theirrespiration. Between their tails and head is a muscular, segmented body, a simpleintestine and a pair of very large salivary glands. They wriggle easily through a corpse, secreting digestive enzyme and spreading putrefying bacteria which help create theirsoupy environment. It takes 8 – 20 hours for a legless larva to be emerged from theegg, and considerably under warm weather.

Fly larvae or maggots are known as a remarkable eating engine. Mouth hooks isarmed at their front end for them to profligate in rotting flesh, shredded from thecorpse. A chamber, where their anus and posterior spiracles are located, is at the rearends of the maggots. Maggots can breath-feeding 24 hours a day because ofpossession of the spiracle in a posterior location. Basically, the phase of larval or maggots formation consist of 3 stages. The firstlarval stage is where it initially feeds on fluid exuded from the body and migrates intobody. It usually takes about 1 day from the hatching to the first moult. The secondlarval stage is where it moves around in the larval mass. The process to develop fromfirst moult to second moult also takes about approximately 1 day.

Last but not least, the third stage is where the larva increase greatly in size and they still moves in mass. It usually takes about 2 days for the second moult to fully develop into pre-pupa. The sole purpose of larva is to eat and store energy for the upcoming stage wherethey begin feeding immediately and develop in the material at where the egg was laid. Larval development requires optimal temperature of 35 to 38oC for them to survive tothe next stage. However, the larval survival is greatest at 17 to 32oC. With optimaltemperature, larva will complete their development in 4 to 13 days approximately.

Then, after the maggot stages, it will enter the pupa stage where the appearancewill change in color as it will darken and harden. The color will vary in color fromreddish brown, light brown lastly black as the pupa ages increase. It also about9-10mm long with a width around 3-4 mm, as the shape willslightly different from previous stages which it being bluntly rounded at the end as wecan see in the result. Theoretically, the pre-pupa will find a suitable pupation sitewhich usually in soil, dry and dark place before it transforms into the pupa. Duringthis stage, metamorphosis will take place form the larva to the adult fly. The co-acetate type of exarate pupa is one of the three types will take place during this stageto develop a hard barrel-shaped puparium.

After that, a hard and strong outer shell also will be developed to protects the pupafrom the predator while it changes it into the adult fly. Inside the pupa protective shell, the larva will fully develop the appendages and the body segments of an adulthousefly for it to undergo the change of its shape and to have it own function. In termsof the process, the total time taken spent for this pupa stage is about 6- 14 days at 32to 37 Celcius for its temperature. However, if the temperature is too low, the pupamight have to stay in the soil until the temperature back to normal and suitable beforeit emerge to adult fly. In this state, it will not eat, motionless and does not protectthemselves as it is in the soil.

The size of the pupa also tell an important information and it will describe thecharacteristics regarding its gender as for a small pupa are usually males while thelarge in size compared to the other mostly is female. Also in this stage, we able toobserve the formation of the inflated bump on the fly’s head that used for theemerging fly to escape out from the pupa shell. The bloating and it shrinking sacs, orwe called as ptilinum on the front of its head will be used as the substitute for thepneumatic hammer since the housefly does not have teeth to bite out from its pupacase. But once the housefly fully emerged, the bump will depress back into a houseflyhead. The last stage of housefly life cycle is the adult stage where the fly hatched fromthe pupa after around 4 to 6 days. Based on the results, this last stage morphologically differences from the pupa and larvae. The fly has compound eyes, arista, antenna, mouth parts, mesothorax, forelegs, middle legs, hind legs, femur, tibia, tarsus, abdominal segment, balancer, thoracic stigma and wings. The head part hascompound eyes are reddish color and the mouthparts are sponging. The flies usually ametallic green or have copper green color. The flies able to live around 15 to 25 days which depends on the environmental conditions. Plus, the adult female has larger sizecompared to male, which around 8 to 10 mm overall diameter. After a few dayhatched, this fly is capable of reproduction. The adult female can lay the eggs rarelymore than five times which more 120 to 130 eggs were lays on each occasion. Flieslays many eggs to ensure the higher survival rate. The adult fly usually feed on allkinds of human food, the excreta and garbage, and animal excrement. The food mustbe in liquid state because of the mouthparts structure where the liquid foods aresucked up while the solid food wetted with saliva to dissolve, and then to ingest.

Ecologically, flies found the resting places such as floors, ceilings or interiorsurfaces as outdoors on the ground during non-actively feeding. But at night, whichthis period the flies normally inactive, the flies commonly find resting places thatsuitable areas for feeding, breeding and sheltered away from wind.

Conclusion

A common green bottle fly, Lucilia sericata, in an invertebrates groups of animalwhere they do not have spinal column or backbone. They usually supplementary withanimal faeces, but now they has familiarized well to feed on trash and even foods, soit is plentiful almost anywhere people live. The complete metamorphosis of ahousefly will take approximately 2 weeks which includes stages of eggs, maggots, pupal and finally adult fly and their life cycle is affected by their surroundingtemperature & condition which varies in each of the stage. High temperature decreases the duration of the development whereas low temperature will increase the developmental period. Dissimilarity in temperature and humidity influence growthand the estimation time since death will indirectly being influenced too. An adultfemale green bottle fly can lays about 200 eggs in a day and usually can layapproximately 2000 to 3000 eggs in her lifetime. It is observed that the maggots obviously change in the length and size from first larval stage to the third larval stagebefore they turns into pupa and lastly developed into adult fly that can eventuallyproduce more flies population in the future. Hence, from the experiment we can conclude that the development of flies consist of four main stages which are EggStage, Larval Stage, Pupal Stage and lastly Adult Stage. Besides, from the research, we found out that the duration for the development of flies differ from one anotherdepending on their surrounding condition.