Peculiarities of adaptation of Stichorchis

subtriquetrus (Trematoda, Cladorchiidae) in

beaver populations

B.V. Romashov, N.B. Romashova

Voronezh biosphere reserve, Voronezh, Russia

8 th International Beaver Symposium

Denmark, 18-20 September 2018

Thirty-three helminth species have been registered in two species of beaver.

The basis of helminthofauna of beavers is monospecific species of helminths.

The manifestation of monospecificity in helminths is the result of the joint

evolution of the beaver-parasite system.

The formation of a parasitic system was primarily affected by:

First, the features of the biology of the beaver.

Secondly, the habitat of the beaver is the ecological conditions of the biotopes.

Among the helminths, the most

common is the trematode Stichorchis

subtriquetrus.

For S. subtriquetrus, high rates of

infection have been identified - the

extent of infection and the abundance

index (the abundance index) of

helminths.

This trematode affects the population

dynamics of beavers.

Life cycle of Stichorchis subtriquetrus: а - Bithyniidae mollusks; b – cercaria S. subriquetrus; c – metacercaria S. subriquetrus.

The life cycle is dixental, includes the intermediate host - freshwater mollusks, free-living stages - cercariae and

metacercaria. Metacercaria is an inflectional larva, attached to aquatic plants. Maritas of S. subriquetrus

parasitize the large intestine of beavers.

a

b

c

The ecology of beavers of different

ages influences the abundance

dynamics (abundance index) of

hemipopulations of Stichorchis

subtriquetrus.

The age of beavers, the features of

feeding and behavior of beavers

affect the dynamics of abundance

(an abundance index) of

hemipopulations of S. subtriquetrus.

In the beaver yearlings (4-11 mounts), the maximum abundance of S. subtriquetrus was revealed and the

highest rate of growth in the number of S. subtriquetrus hemipopulations was recorded.

The index of abundance of S. subtriquetrus increases six-fold in beavers at the age of 7-10 months in

relation to the first period of infection (3-4 months).

The data obtained show that S. subtriquetrus can affect the number of beavers' yearlings.

0

53,7

148,8

366,3

0

50

100

150

200

250

300

350

400

1-2months

3-4months

5-6months

7-10months

abu

nd

ance

ind

ex

Age of the beaver, season

Dynamics of the abundance index of

S. subtriquetrus in beavers

Beaver at the age from one to two years registered a tendency to decrease the index of abundance of

maritas S. subtriquetrus by 30% in comparison with juveniles.

During the year, a seasonal variation in the infection of year-old beavers was detected, the maximum of

S. subtriquetrus marked in summer and autumn.

0

53,7

148,8

366,3

173,3

317,5

0

50

100

150

200

250

300

350

400

1-2months

3-4months

5-6months

7-10months

1 year,Spring

1,5 years,Autumn

abu

nd

ance

ind

ex

Age of the beaver, season

Dynamics of the abundance index of

S. subtriquetrus in beavers

In adult beavers, a significant decrease in the abundance index of S. subtriquetrus is registered.

The results obtained indicate the stabilization and stable functioning of the parasite-host system - S.

subtriquetrus + C. fiber in adult beavers.

0

53,7

148,8

366,3

173,3

317,5

151,3

286,3

151,5

0

50

100

150

200

250

300

350

400

1-2months

3-4months

5-6months

7-10months

1 year,Spring

1,5 years,Autumn

2 years,Spring

2,5 years,Autumn

adults

abu

nd

ance

ind

ex

Age of the beaver, season

Dynamics of the abundance index of

S. subtriquetrus in beavers

The most active phase of infection of S. subtriquetrus beavers was detected in summer and autumn.

Maximum number of maritas of S. subtriquetrus in beaver population was registered in the autumn, the

minimum - in the spring.

111,1

206,3

486,1

167,5

0

100

200

300

400

500

600

spring summer autumn winter

Seasonal dynamics of the abundance index of S. subtriquetrus in the Voronesh population of beavers

Life expectancy of maritas of S. subtriquetrus is 30 months (2.5 years) and includes three periods: pre-

reproductive (2 months), reproductive (28 months) and post-productive (less than 1 month).

The greatest productivity in maritas of S. subtriquetrus is noted at the age of two to six months, maximum

at the age of three months.

7,3

18,1

37,3

7,4 6,2

2,8 3,2 3,6 2,4 2,2 1,6 1,1 1,1 1,5 1,5 1,5 0,7 0,5

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

%

reproductive period, months

Life expectancy and reproductive period marit S. subtriquvertus

Dynamics of the number of different age groups of S. subtriquetrus in

the Voronezh population of beavers. The highest numbers are

registered among maritas in size groups from 5 to 13 mm.

2,8

12,5

21,6

38,2 38,6

28,8

8,3

1,1 0,3 0

5

10

15

20

25

30

35

40

45

1-2,9 3-4,9 5-6,9 7-8,9 9-10,9 11-12,9 13-14,9 15-16,9 17-18,9

abu

nd

ance

ind

ex

marite sizes, mm

The daily productivity of the adult marita S. subtriquetrus

averages 60 eggs.

By the number of eggs of S. subtriquetrus, as a result of

studies of feces, it is possible to determine the intensity of

infection of the beaver - the number of maritas in the

infected animal.

Thank you for attention!