Part 1. History of the Discovery of Anomaly P

Part 2. Rediscovery of Anomaly P in Russia

Part 3. Research on the effects of Strigea robusta on amphibians


History of the Discovery of Anomaly P

The anomaly P was first documented by A. Silantiev (Silantiev, 1898) in water frogs captured in the Khrenovskiy Bor of Voronezh Province. Two specimens exhibiting polydactyly were noted in this finding. N.A. Kholodkovskiy (Kholodkovskiy, 1897), Silantiev's teacher, provided a detailed description of this discovery and received these specimens for study. The polydactyly observed in the water frog from the Khrenovskiy Bor was characterized by its symmetry, affecting not only the hind limbs but also the forelimbs. The hind limbs exhibited eight digits, while the forelimbs had five. This particular variant of anomalies (concomitant polydactyly in both fore and hind limbs) is considered by J. Rostand and A. Dubois (Rostand, 1971; Dubois, 1984) to be closely related to anomaly P.

Fig. 1. Nikolay A. Kholodkovskiy and his illustrations of the first record of anomalies in Russia (Kholodkovskiy, 1896).
These polydactyly cases, perhaps, belong to the anomaly P sydrome.

Another first record, registered in France, was reported in 1937 (Bonnet, Rey 1937). The authors described individuals with schizodactyly (a variant of polydactyly) collected between 1929 and 1931, as well as from 1935 to 1936, in the Villars-les-Dombes. Approximately 600 specimens were examined annually, totaling around 3,000 individuals over the study period. Polydactyly was noted on both fore and hind limbs of water frogs, which may characterize it as the anomaly P. The number of digits on the hind limbs ranged from six to seven, with a bifurcated inner digit, while one instance of schizodactyly was recorded on the forelimbs. The authors noted that due to the observed symmetry of this anomaly, it could not be attributed to traumatic limb loss, suggesting instead a hereditary nature (Bonnet, Rey, 1937).

Fig. 2. The appearance of schizodactyly on the hind and forelimbs of water frogs from Villars-les-Dombes (Bonnet, Rey 1937).

In the years following World War II, the scientist and renowned French writer Jean Rostand (1894–1977) initiated research on gynogenesis and the genetics of amphibians (Rostand, 1949). Rostand modified the methodology for obtaining gynogenetic offspring in the common toad (Bufo bufo) by exposing the eggs to cold temperatures, which, according to J. Rostand, led to diploidization and reduced the high mortality rates of tadpoles (Rostand, 1971). He investigated the gynogenetic offspring of the common toad and noted the manifestation of polydactyly during gynogenesis (Rostand, 1947). Crossbreeding common toads with polydactyly in their hind limbs resulted in offspring exhibiting this type of anomaly, indicating a recessive mode of inheritance for this mutation (Rostand 1949).

Fig. 3. Jean Rostand.

Rostand further explored this mutation in frogs of the genus Rana, which previously included water frogs, now classified within the genus Pelophylax. This led him to discover a prevalence of polydactyly among adult specimens of the edible frog, Rana esculenta, in the vicinity of the village of Trévignon. Of the 49 individuals collected by Helen Mugard from a water body near Trévignon, nine specimens (18%) exhibited polydactyly in their hind limbs. Some individuals also displayed polydactyly in their forelimbs. However, unlike with toads, studies on the heritability of this anomaly did not yield abnormal offspring, prompting Rostand to hypothesize a polygenic mode of inheritance, cytoplasmic inheritance, or that the anomaly was influenced by some environmental factor (Rostand, 1951).

To study the development of the anomaly, Rostand received a sample of late-stage tadpoles from Trévignon in 1952, some of which exhibited a new type of limb deformities. These included, in addition to polydactyly, significantly altered hind limbs: brachymelia, inversion of hind limbs, bony outgrowths, edema and tumors on hind limbs, and the formation of an additional small limb in the thigh region (Rostand, 1952). This anomaly was designated as "anomaly P". The author posited, and subsequent findings supported, that polydactyly represented a milder form of anomaly P, as there was a discernible continuum between all observed variants of anomalies. Each individual, despite similarities in manifestation, exhibited unique characteristics.

In his quest for the underlying cause, Rostand (see review: Rostand 1971; Dubois 1979; 2017) conducted various experiments: incubating eggs and larvae in brackish water or water from ponds where anomalies were present; exposing specimens to different chemical substances; prolonged exposure to high or low temperatures; dehydration; and over-ripening eggs before fertilization. Under ultraviolet radiation, Rostand induced polydactyly, polymelia, and brachymelia; however, these deformities differed from those observed in nature (Dubois, 2017). Experiments involving limb amputation demonstrated that abnormal individuals exhibited regeneration of a normal hind limb instead of the amputated anomalous limb at the bud stage (n = 7), at which point the anomaly could already be diagnosed (Rostand 1952). The regenerated limb was smaller and, in one out of seven cases, contained four digits instead of five, which Rostand (Rostand, 1952) associated with hyporegeneration. Prolonged study allowed for partial elucidation of the distribution of this rare phenomenon. Significantly deformed variants of anomaly P have been found in only seven localities throughout its history of study.

In addition to the two water bodies in the vicinity of the town of Concarneau (Trévignon and Penloché), an instance of the anomaly was recorded in one of the canals of Amsterdam in 1957 (Hillenius, 1959). Initially, these anomalies were attributed to the effects of radioactive waste; however, Rostand later classified them as anomaly P, which was determined not to be caused by radiation exposure. Another locality was identified for P. saharicus in Morocco (near Kenitra) by R. Lautié. Negative results from experiments involving the rearing of eggs and tadpoles in African "monster ponds" prevented Lautié from publishing data on this equally remarkable record (Rostand, 1971). M. Jacquot informed Rostand about the existence of a ‘Pond with Monsters’ in Lingé, located in the Indre province of France. The anomaly was also discovered by Jean-Pierre Vuagniaux in the Bombes ponds near Lyon. Finally, P. Darré found the anomaly in Saint-Philbert-de-Grandlieu, which is a locality where the most recent findings were reported.

Less affected individuals exhibiting polydactyly similar to that observed in the ‘Ponds with Monsters’ were also found in other localities across France:
1) Champdieu in Loire;
2) three ponds in Landes: Soustons,
3) Léon, and
4) Aureilhan; and
5) Bordeaux.

In addition to the two water bodies near the town of Concarneau (Trévignon and Penloché), four habitats exhibiting polydactyly were later identified by A. Dubois (Dubois, 1984):
6) Luxeuil-les-Bains in the Haute-Saône department;
7) Faverois in the Territoire de Belfort;
8) Fénetrange in Moselle; and
9) Tassenières in Jura.

In 1967, Rostand conducted a series of field experiments involving the rearing of tadpoles in specialized water cages (with small mesh sizes that prevented tadpoles from escaping; exact diameter not specified) in the water of a pond where the anomaly was discovered (Lingé, Indre) and did not observe any anomalous individuals (Rostand et al., 1967). However, in 1968, tadpoles were kept in such water cages alongside two species of fish — tench (Tinca tinca Linnaeus, 1758) and eel (Anguilla anguilla Linnaeus, 1758) — captured from the pond at Saint-Philbert-de-Grandlieu, where the anomaly was observed. The cages were placed in the same pond. A total of 410 tadpoles were involved in the experiment, of which 101 (24.6%) exhibited anomalies; among these, 39 (9.5%) showed severe forms of anomaly P. None of the control tadpoles, which were kept without fish, displayed any anomalies (Rostand, Darré, 1967).

Fig. 4. J. Rostand and P. Darré with experimental cells in a pond Saint-Philbert-de-Grandlieu.

Further investigations using chromatography and fish gastrointestinal contents from the yielded no positive results and were deemed futile, as the anomaly had completely disappeared from the natural population (Dubois, 1979). Histological examination and electron microscopy did not reveal any specific indicators pointing to an infectious agent associated with the anomaly (Rostand, 1971). Microbiological cultures of bacteria from mucus and subsequent rearing of tadpoles with bacteria grown on nutrient media also failed to produce desired outcomes (Surleve-Bazille, Cambar 1969). The same study described an experiment involving the rearing of approximately 20,000 water frog tadpoles with fish mucus, which did not yield positive results (Surleve-Bazille, Cambar, 1969). However, rearing tadpoles of the grass frog resulted in minor deformities, albeit different from those observed in water frogs (Surleve-Bazille et al., 1969).

The culmination of research on anomaly P was marked by Jean Rostand's book ‘Les étangs de monstres’ published in 1971 (Rostand, 1971). In this work, the author summarized previous findings and expressed hope for further investigation into this phenomenon due to its disappearance from the Grand-Lieu pond. Following M. Caullery's idea, Rostand proposed a hypothesis regarding the influence of a teratogenic virus on early developmental stages of the anomaly, suggesting that fish or some component of their diet might serve as vectors for this infectious agent.

References

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