Tetrameridae Travassos, 1914

Syrota, Ya. Yu., Greben, O. B., Poluda, A. M., Maleha, O. M., Lisitsyna, O. I. & Kornyushin, V. V., 2018, Helminths Of The Mallard, Anas Platyrhynchos (Aves, Anatidae) In Ukraine: Analysis Of The Diversity In Mixed Forest Zone And The Black Sea Region, Vestnik Zoologii 52 (4), pp. 267-278 : 272-277

Family Tetrameridae Travassos, 1914

Tetrameres fissispina (Diesing,1861) — proventriculus, esophagus. 5.2 %, 5(2–8). Volyn Region (Lutsk and Stara Vyzhivka Districts).

Tetrameres sp. — proventriculus. 6.2 %, 1(1). Chernihiv Region ( Ripky District ). This specimen was not identified to the species level because it was a female.

Of 33 species of helminths found in the sample from the mixed forest zone, there were 10 species of trematodes, 18 species of cestodes, four species of nematodes and one species of acanthocephalans. At the same time, in the samples from the steppe zone only 24 species of helminths were found: 13 species of trematodes, seven species of cestodes, three species of nematodes, and one species of acanthocephalans. Twelve species were common to both samples. SØrensen index is 0.421 for these samples. The prevalence of infection with 95 % confidence interval and the average intensity with range are given for each species found on separate territory ( figs. 2 , 3 ). The following species of helminths recorded in the steppe zone were not found in the mixed forest zone in this study: Amidostomoides acutum (Lundahl, 1848) , Cotylurus cornutus (Rudolphi, 1808) , Cryptocotyle concava (Creplin, 1825) , Echinoparyphium recurvatum (Linstow, 1873) , Himasthla elongata (Mehlis, 1831) , Paramonostomum pseudalveatum Price, 1931 , Polymorphus magnus Skrjabin, 1913 . Psilochasmus longicirratus Skrjabin, 1913 , Psilochasmus oxyurus (Creplin, 1825) , Prosthogonimus rarus (Braun, 1901) , Streptocara crassicauda (Creplin, 1829) .

Analysis of space-time distribution of Mallards ( fig. 4) on the territory of Ukraine in different periods of year shows rather weak relationships between birds from northern and southern regions. There are only few registered cases of direct movements of ringed Mallards between these parts of the country. The ducks of Polissia are known to spend winter in Western Europe, while the South-Ukrainian ducks stay in winter either in the same region or leave for Southern Europe. There could be together both “southern” and “northern” Mallards, but the number of these birds is small. Similar situation could be observed in places of massive ducks´ moulting (Northern Caspian, Kuban) ( Kotyukov, Rusanov, 1997). This makes it possible to consider the helminth faunas from the two regions as different that, and in turn, allows us to analyse them as independent samples.

The overall prevalence of infection in the sample from the mixed forest zone was 92 %, and in the sample from the steppe zone it was 100 %. Comparison of the prevalence by taxonomic groups of helminths revealed statistically significant difference only for nematodes (table 1). The infection with this group of helminths was significantly higher in the South of Ukraine. Comparison of the prevalence of helminth species common to both samples (table 2) did not show statistically significant differences for all species except for N. attenuatus .

*Comparison for acanthocephalan was not performed since one species was found in each region. Species Aploparaksis furcigera Apatemon gracilis Bilharziella polonica Diorchis acuminatus Diorchis stefanskii Echinostoma revolutum group Fimbriaria fasciolaris Hypoderaeum conoideum Microsomacanthus paracompressa Notocotylus attenuatus Sobolevicanthus gracilis Tetrameres fissispina p-value 1.000 0.416 0.486 1.000 0.139 0.332 0.036 0.018 1.000 0.000 0.668 0.240 p-value (with Holm correction) 1.000 1.000 1.000 1.000 1.000 1.000 0.360 0.198 1.000 0.000 1.000 1.000

Chao 1 estimator for the sample from the mixed forest zone was equal to observed species richness, whereas for samples from the steppe zone it added 2 more species. Other estimators provide from 4 to 9 unfound species for both territories (table 3). Considering features of the estimators, such result indicates that the size of the samples was enough for detecting the most widespread species of helminths, but it did not allow to detect all rare species.

Result of nMDS ( fig. 5 ) showed a high degree of similarity between Mallards from both samples. Tendency for aggregation of the samples from the steppe zone in the upper right part of the graph is noticeable. Mallards from each sample were present in every cluster except for two clusters which contained only one bird each. So, it can be concluded that the species composition of Mallards on the territory of the mixed forest zone differs from the species composition of Mallards on the territory of the steppe zone less than it would have been expected based on a simple comparison of the actual list of identified species.

Analysis of literature data shows that most species previously found in Mallard from the mixed forest zone of Ukraine were also registered in our study. Undetected species can be included in the number of species foreseen by estimators of species diversity. It is evident that in the mixed forest zone there are no species requiring salt-water intermediate hosts: C. concava , H. elongata , and P. pseudalveatum .

Looking at the differences between groups of helminths we can see that Mallards from the mixed forest zone are less infected with nematodes, especially with A. acutum . This species was not found in the sample from the mixed forest zone while in the sample from the steppe zone it is a rather common species. This nematode has a direct life cycle and is a common parasite of Anatidae ( Anderson, 2000) . Its absence could be the evidence of the low concentration of Mallards, although such assumption does not exclude the existence of local centres, undetected in the present study, with high level of prevalence.

The most common helminth species (the lower limit of confidence interval for prevalence is greater than 10 %) of Mallards in the mixed forest zone are A. furcigera , B. polonica , A. gracilis , E. revolutum group, F. fasciolaris , H. conoideum . And the most common helminths species of Mallards in the steppe zone are N. attenuatus , F. fasciolaris , C. concava , B. polonica . Thus, B. polonica and F. fasciolaris are the most common species in both samples. C. concava is absent in the mixed forest zone because its circulation is connected with saltwater. N. attenuatus is not included in the list of the most common species in the mixed forest zone while the prevalence of this species in another sample is very high. Taking into account that the final host acquire N. attenuatus by swallowing the adolescariae ( Filimonova, 1985), the high prevalence of infection can be another evidence, along with absence of A. acutum , of a relatively lower concentration of Mallards in the mixed forest zone.

Another four species considered as very common in the mixed forest zone sample, are also present in the sample from the steppe zone; however, they are not among the most common species. Because we did not find statistically significant differences in prevalence of these species between samples examined and the small size of analysed sample from the steppe zone, we can assume that these species could be among the most common species provided the larger sample from the steppe zone.

Since our samples contain birds gathered in different years, we see long-term tendencies based on the identified helminths. We can state that two samples collected in very different time and different places tend to be more similar. This is shown in the similar qualitative composition and the prevalence of infection with common helminth species. Given the tendency to isolation of those two territorial groups of Mallards, there is evidently no isolation of their helminth faunas over a long period of time. That is why, the helminth fauna of these two groups of Mallards appears to be the united faunal complex.

Microscopic studies were done with using the equipment of the Centre of Collective Use of Scientific Equipment “Animalia” (Schmalhausen Institute of Zoology, NAS of Ukraine). We are grateful to Dr. Igor Dzeverin for his comments that helped a lot to improve this work. We wish to express our gratitude to Yuliya Vakulenko for her help with translation.

Figures

Fig. 2. Prevalence (with lower and upper confidence intervals at significant level 95 %) and average intensity (with range; in case when one or two birds were infected by a certain type of helminth, then the actual intensity values are given) of Mallard´s infection with: A — cestodes from the mixed forest zone; B — cestodes from the steppe zone; C — nematodes and acanthocephalans from the mixed forest zone; D — nematodes and acanthocephalans from the steppe zone.* Logarithmic scale was used.

Fig. 3. Prevalence (with lower and upper confidence intervals at significant level 95 %) and mean intensity (with range; in case when only one or two birds were infected by a certain type of helminth, then the actual intensity values are given) of Mallard´s infection with: A — trematodes from the mixed forest zone; B — trematodes from the steppe zone. * Logarithmic scale was used

Fig. 5. Configuration of 2-dimensional MDS for specimens of Mallard from the mixed forest zone (P) and from the steppe zone (B) with overlapping clusters at similarity level of 15 %.