Zoologists from St Petersburg University have identified a trend towards an increase in the number of protective carapace scutes of sea turtles on the island of Sri Lanka

The scientists from St Petersburg University have studied the carapace scute variability of olive ridley sea turtles living near the equator in the Indian Ocean near the island of Sri Lanka.

The findings of the research supported by St Petersburg University’s grants are published in Russian Journal of Herpetology.

An important element of the turtle’s structure is the presence of large horny scutes on the carapace — the so-called pholidosis. They are of taxonomic (species-specific) and phylogenetic (i.e. evolutionary) importance. The general plan of the scute arrangement is characterised by great evolutionary stability. It has not changed much in the more than 200 million years that turtles have been around. The scientists from St Petersburg University think that this stability is related to the conservatism of the genetic basis for the formation of the scute pattern. 

Despite this general stability, many turtles are characterised by individual variability of the scutes, and the range of these abnormal patterns is quite large.

Hundreds of anomalous individuals of turtles of different species have been described in the literature. They differ in the number and shape of the scutes, violating the stability of the general plan of their structure. It is believed that such instability of pholidosis is primarily related to the negative effects of external environmental factors.

Gennady Cherepanov, Professor in the Department of Vertebrate Zoology, St Petersburg University

"As experiments by many researchers have shown, temperature effects during critical periods of embryonic development can lead to 100% of abnormal pholidosis in hatchling turtles. However, in natural populations, the percentage of abnormal individuals is usually not high," said Gennady Cherepanov, Professor in the Department of Vertebrate Zoology at St Petersburg University. 

Olive ridley turtles (Lepidochelys olivacea) are characterised by a significant natural diversity of scute variations, and it was these turtles that the zoologists from St Petersburg University studied. The research was carried out without removing the animals from their natural environment.

The southern coast of Sri Lanka has several kilometres of coastline and is an active breeding ground for sea turtles. Additionally, there are many turtle hatcheries where staff and volunteers collect turtle eggs from natural clutches, incubate them in predator-proof enclosures, and release them into the wild after hatching and a short stay.

The scientists from St Petersburg University photographed the newborn turtles from the dorsal and ventral sides, then made a detailed description of the carapace and the arrangement of the horny scutes. The zoologists studied 655 hatchlings from nine clutches and identified 120 patterns of carapace scutes, differing in the number of horny elements. However, it was not possible to identify a single standard of carapace scute pattern, as is the case with other turtles. Additionally, comparison of the pholidosis variability in hatchlings from different clutches revealed the presence of specific scute anomalies. The scientists assumed that the clutch differences are more related to the genetic characteristics of the breeding turtles than to the influence of environmental factors.

"The olive ridley turtle is characterised by an unstable state of carapace pholidosis, but clearly shows an evolutionary trend towards an increase in the number of scutes — polymerisation. It is possible that the high variability in horny scutes may have evolutionary significance. The presumably symmetrical variations of the scute patterns may reflect intraspecific genetic variability. This significantly improves the ability of sea turtles to adapt and survive in a constantly changing environment," said Gennady Cherepanov.

The research has been extensive, studying not only turtles but also other tropical animals such as the Indian elephant and the megabat.

St Petersburg University, the oldest university in Russia, was founded on 28 January (8 February) 1724. This is the day when Peter the Great issued a decree establishing the University and the Russian Academy of Sciences. Today, St Petersburg University is an internationally recognised centre for education, research and culture. In 2024, St Petersburg University celebrates its 300th anniversary. 

The plan of events during the celebration of the anniversary of the University was approved at the meeting of the Organising Committee for the celebration of St Petersburg University’s 300th anniversary. The meeting was chaired by Dmitry Chernyshenko, Deputy Prime Minister of the Russian Federation. Among the events are: the naming of a minor planet in honour of St Petersburg University; the issuance of bank cards with a special design; and the branding of the aircraft of the Rossiya Airlines to name just a few. To mark the 300th anniversary of St Petersburg University, a postage stamp depicting the Twelve Collegia building and the monument to Count Sergey Uvarov was issued. 

By the decision of the Governor of St Petersburg Alexander Beglov, 2024 is a year of the 300th anniversary of St Petersburg University in St Petersburg. On the day of the University’s 300th anniversary torches were lit on the Rostral Columns on the Spit of Vasilyevsky Island. St Petersburg University flags were raised on the Palace Bridge. The city public transport was decorated with the University’s symbols. New tourist maps will feature the locations of the University buildings, with thematic and historical materials about the University placed nearby. During St Petersburg’s City Day celebrations in May 2024, St Petersburg University will be a participating venue. The traditional ‘Scarlet Sails Festival’ will also be dedicated to the anniversaries of St Petersburg University and the Russian Academy of Sciences. Additionally, the University has launched a website dedicated to the upcoming holiday. The website contains information about outstanding University staff, students, and alumni; scientific achievements; and details of events held as part of the celebration of the 300th anniversary of the University.