EFFECTS OF ARTIFICIAL PHOTOPERIOD ON THE BODY COLOURATION IN THE ORNAMENTAL FISH

In Orange balloon Molly, Poecilia sphenops, the development of chronic stress due to continuous exposure to artificial LED lighting irrespective to photoperiod causes deterioration in the body colour even in the presence of carotenoid rich green water and artificial feed with added additives in the experimental fish tank setup. In the present study, the effects of continuous exposure to lighting and its consecutive development of chronic stress causes the body colouration to fade off in the freshwater ornamental live bearer, Poecilia sphenops, though the fishes were provided with colour enhancing as well as stress relieving factors. Several trials showed that, whatever may be the colour enhancing agents provided, artificial lighting for long exposure irrelevant to the normal photoperiod remains as a strong anti-colouration as well as stress inducing factor and remains unaffected to any antagonistic factors. To conclude photoperiod is an essential factor to be concerned for colour enhancement in Poecilia sphenops.


INTRODUCTION
Ornamental fish trade is one of the quickly growing markets in the world. More than 125 countries around the globe are involved in this trade either as an importer or exporter. Most of the fishes that are sold by the aquarium are bought by hobbyists (Dey., 2016). Ornamental fishes are bought for their fascinating and attractive skin colour and pattern. The sexual selection acts on colour and patterns leading colourful displays and also more diverse colouration pattern (Endler., 1980). The prices of the fishes are fixed based on their brilliant skin colour and pattern. The body of fishes shows a wide range of skin colours ranging from yellow, orange, blue, purple, green, etc.(Animal colouration / Wikipedia.com). These colourations are due to colour pigments such as carotenoids (Biological pigments / Wikipedia.com). These pigments cannot be stored beneath the skin permanently. As fishes cannot synthesize their own colouring pigments de novo, the colouring agents which are synthesized by some plants, algae and microorganisms, need to be incorporated in their diet (Johnson et al., 1991). There are some factors like photoperiod, feeds with added pigments and green water which directly affects the colour pigmentation in the fishes. Some fish feeds with artificially synthesized colour pigments are commercially available in markets to enhance the body colour. Green water which is rich in micro alga, C. vulgaris has become a potent pigment source, which imparts yellow/blue hues. The biomass of this alga had already been proved to be useful in the diets of rainbow trout yielding both muscle and skin pigmentation effects (Gouveia et al., 1997). It has also been reported that it contains carotenoid pigments in concentrations of up to 0.4% (dry wt), of which, 80% were potential red hue inducing pigments (Gouveia et al., 1996). Other than green water, commercial feeds with added additives such as astaxanthin is also used to enhance colouration (Gupta et al., 2007). Apart from all those factors, photoperiod has an important effect since it is one of the stimuli that cue the internal biological clock about the seasonal changes in the environment. Light is a key environmental factor that synchronizes all stages of fish from embryo development to sexual maturation (Bairwa et al., 2013).
Photoperiod is most useful in predicting environmental conditions in the future or at distant localities; photoperiod provides a go/ no-go signal that initiates a usually irrevocable cascade of physiological and development processes that culminate in reproduction, dormancy and migration. Day length provides a highly reliable calendar that animals can use to anticipate and prepare for seasonal change (Sarkar et al., 2011). Photoperiod is an important physical factor that affects the growth, reproduction and many other functions of the fish. Light and dark cycle provides internal harmonization for the rhythmic synthesis and release of hormones (i.e. melatonin), whose signal affects rhythmic physiological function in fish (Bairwa et al., 2013). This study is carried out to prove that among all factors, photoperiod is a strong factor influencing the colour pigmentation adopting ornamental live bearer, Balloon Molly fish (Poecilia sphenops) as the animal model.

Apparatus setup-
female)  Age of the fish -Adult  Gestational history:

Gravida
Nil Parity Nil

Methods
To prove photoperiod has a strong influence over body colour, the comfortable method is to compare with other factors that are also engaged in enhancing body colouration in ornamental fishes. Experiments carried out with combination of these factors give us a good platform for comparing their effects. Along with control trial there are six experiments carried out in this study.

RESULTS
The results of the experiments given in this project are the observations made from the trials based on the following criteria. • Fading or enhancement in body colour. • Healthy and active swimming • Courtship behaviour

Control
In this control trial with normal environmental factors, the colour of the body remains bright with regular body patterns. The fishes were noticed with normal and active swimming all through the trial for complete 1 week. Courtship behaviour between the male and female was spotted several times. • Colour is bright. • Healthy swimming is observed. • Courtship behaviour is seen frequently. • Sign of copulation is seen.

Observations during the Experiments
Based on the observations (Table 1) made during the experimental trials with a combination of different factors, we can conclude the cumulative results with the gained outputs. With the observations made from the experiments it is easy to conclude whether the fishes are in stress during the trials and on correlating the factors and the observations we can conclude the primary factor that mostly influences the stress and also the body colour pigmentation.

Correlation between the factors and the observations
Correlation is an effective tool to find which factor influences the result the most by correlating the inputs (photoperiod, green water & pigmented feed) with the observations (colour, movement & courtship behaviour). The factors and the observations are first tabulated to test for correlation (Table. 2).

Correlation between Water condition and Observed colour
In this calculation, water condition is taken as an independent variable and the observed body colour is considered as a dependent variable since the colouration is either enhanced or deteriorated by the influence of the water condition either green water or clear water. Pearson's coefficient of correlation, r = -0.1667 (poor relation) Since the Pearson's coefficient, r = -0.1667 the relation between the independent factor (water condition) has a poor relation with the dependent factor (body colour).

Correlation between commercial feed and Observed colour
In this calculation, pigmented feed is taken as an independent variable and the observed body colour is considered as a dependent variable since the colouration is either enhanced or deteriorated by the influence of the pigmented feed or nonpigmented feed. Pearson's coefficient of correlation, r = 0.166 (poor relation) Since the Pearson's coefficient, r = 0.166 the relation between the independent factor commercial feed has a poor relation with the dependent factor body colour.

Correlation between photoperiod and Observed colour
In this calculation, photoperiod is taken as an independent variable and the observed body colour is considered as a dependent variable since the colouration is either enhanced or deteriorated by the influence of the natural photoperiod or induced photoperiod.

Fig. 3. Correlation between photoperiod and body colour
Pearson's coefficient of correlation, r = 1 (strong linear relation) Since the Pearson's coefficient, r = 1 the relation between the independent factor commercial feed has a strong linear relation with the dependent factor body colour.