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Water Flea: A Resurrected Egg and its Features
There are various types of water flea and recently a type belonging to Daphnia Species was hatched from a 700-year old dormant egg. According to Business Insider, Scientists hatched tiny aquatic animal from dormant eggs that had been dwelling on the bottom of a lake for about 700 years. The hatched eggs was that of water flea known as Daphnia Pulicaria and might be the oldest animal eggs to ever come to life.
Daphnia Pulicaria resembles other Daphnia species and sometimes mixed up with Daphnia Pulex. However, it is characterized by its rounded carapace, large second antennae, remarkable rostrum and long tail spine. In addition, it lacks pronounced helmet and possesses an ocellus. Adult head is short, rounded and curving near the rostrum.
The tail spine tends to be longer than that of Daphnia Pulex. Though both have a pattern of 6 to 8 rows of elongated polygons between rostrum and the ocellus, the length of the polygon in D. Pulicaria is much longer than its width while that of D. Pulex are equal in length and width.
Reproduction and Habitat
Water flea like D. Pulicaria can be found in deeper waters of lakes with greater number occurring in the spring season. It can distribute widely in lakes depending on the presence of predators; and quality and availability of food resources. Some adult flea has been observed migrating to shallow water at night in order to avoid predation.
Some lakes are colonized every spring by Daphnia Pulicaria by hatching from diapausing eggs and reproducing by means of non-diapausing. These take place during favorable conditions. Adult males swim horizontally in a unique way while females swim at a slower speed vertically. This movement patterns increases the contact between male and female Daphnia Pulicaria. It is through chemical cues that recognition occurs once contact is made. Males avoid asexual reproducing females and only mate with receptive females.
Water flea is one of the aquatic animals that may remain dormant in their egg stage. This is actually necessary to survive certain environmental conditions such as freezing that can become a detriment to the active animal . Though entering dormancy appear to preserve the animal, it however, limits reproduction and food intake. In certain lake populations, only a small percent of female Daphnia Pulicaria switched to producing dormant eggs through the year whereas in others the majority of eggs produced in the late spring were dormant. Even though there were variations, populations that experienced low abundances in the active form showed higher incidence of dormancy than populations that thrived in high abundance throughout the year.