In the waterbodies of central Russia, the Urals and western Siberia four species of Crustacea, related to the genus Mesocyclops, are widely distributed: M. (s.str.) leuckarti (Claus), M. (Thermocyclops) oithonoides Sars, [M.](Th.) crassus (Fisch.) and M. (Th.) dybowskii (Lande). Numbers and biomass of Mesocyclops oithonoides in the pelagic water of various water-bodies of the Urals are presented and observations on the above mentioned species are discussed

Ulomskii, S.N.

English

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Freshwater Biological Association 
FBA Translation (New Series) N. 66 
Title: On the ecology of species belonging to the genus Mesocyclops Sars 
(Crustacea, Copepoda) dwelling in the waterbodies of the Urals and 
Pri-Ural territory. 
Author(s) ULOMSKII S.N. 
Reference: Zool. Zh. 44, 1, 127-130 
Original language: Russian 
Date of publication of original; 1965 
Translator: I. Pettman 
Date of publication of translation: 1973 
Number of pages of translation: 7 
FBA Translations are to be considered as "provisional". As a rule 
they have not been prepared by expert translators, nor have they 
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They are available from The Librarian, 
Freshwater Biological Association, 
The Ferry House, 
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England, 
at the current rate for xerox copying. 
(1) 
ULOMSKII S.N. 
On the ecology of species belonging to the genus Mesocyclops Sars (Crustacea, 
Copepoda) dwelling in the waterbodies of the Urals and Pri - Ural territory. 
In the waterbodies of central Russia, the Urals and western Siberia four 
species of Crustacea, related to the genus Mesocyclops, are widely distributed: 
M. (s.str.) leuckarti (Claus), M. (Thermocyclops) oithonoides Sars, [M.](Th.) 
crassus (Fisch.) and M. (Th.) dybowskii (Lande). 
The first three species produce mass forms of plankton in lakes, ponds 
and reservoirs, where they usually breed in enormous quantities. They have 
positive (as a food basis for fish) and negative (intermediate host of a series 
of parasitic worms of animals and man) economic importance. Therefore a study of 
these organisms, besides being of theoretical interest, has a practical importance. 
The last species - M. dybowskii is encountered rarely, mainly in shallow water bodies 
with dense submerged macrophytes (ponds, the littoral lakes); they do not reach any 
significant numbers. 
M. leuckarti inhabits the majority of our water-bodies throughout the year. 
In the summer the Crustacea live in the pelagial but in winter - in the pelogin 
(Copepodits ). Here in temperatures ≥ 2° it is found in an active state. M. 
crassus, with a lowering of the water temperature in the autumn to 11 - 12°, on 
the other hand, completely disappears from the water-bodies, leaving quiescent 
eggs for reproduction of the next generation (as also M. dybowskii). The life 
cycle of M. oithonoides has not been completely described (Rylov, 1948; Ulomskii, 
1960). 
M. oithonoides, in comparison with the other mass forms of this genus (M. 
leuckarti, M. crassus), have a restricted range of growth depending on the 
character and degree of mineralisation of the water (Table 1.) 
[M.] Translators addition. 
2. 
Numbers and biomass of Mesocyclops oithonoides in the pelagic water of various 
water-bodies of the Urals (summer) (in thousands of specimens/m3 and mg/m3). 
Table 1. 
(3) 
In brackish-waters, in which according to V. I. Vernadskii (1934) the 
salinity fluctuated between the limits of 1-10°/oo, crustacea, as a rule, were 
absent. The greatest numbers of them were observed in fresh, neutral-alkaline, 
water-bodies with soft calcium-hydrocarbonate water, located in the taiga, 
wooded steppe and steppe zones. These species penetrate long distances along 
the river systems to the north and south, populating in mass, bodies of water of 
floodlands where they often dwell jointly with M. leuckarti and M. crassus. 
M. oithonoides, as well as M. leuckarti, during the course of the whole 
year inhabit both shallow and deep water-bodies of the Ural. In shallow water-
bodies it dwells in summer (July - August) in the pelagic waters but during the 
cold times (October/November to April) it migrates to the pelogin layers. In 
the spring-summer and the summer-autumn periods it inhabits both biotopes 
simultaneously. With a satisfactory gas regime in the lower layers of water 
and relatively high temperature of the pelogin in the winter (2-5°) crustacea 
manage an active form of life at the bottom of water-bodies. In lakes with 
unfavourable gas regimes in winter as well as in good ponds fed by springs, and 
reservoirs with low water temperatures in the periods of ice cover (0.1 - 0.3°) 
copepodit stages of M. oithonoides overwinter on the bottom in an anabiotic or 
close to an anabiosis state. 
In the deep lakes of the Ural mountain areas with good gas regimes 
M. oithonoides dwells in the pelagic waters throughout the year (Table 2). In 
the coldwater lakes Turgoyak and Uvil'dy (almost without flow) only this species 
of the mass forms of Cyclops of pelagic plankton appears. In the occasional 
very good years the productivity of the copepods reaches in summer in Lake Turgoyak 
14.5 thousand specimens /m3 (138.9 mg/m3) and in Lake Uvil'dy 14.0 thousand 
specimens /m3 (130.0 mg/m3). A significant quantitative growth of M. oithonoides 
is observed in summer also in other deep lakes of the Urals (Kirety; Bol'shie Kasli), 
particularly in their well warmed bays (Table 1). 
The vertical distribution of M. oithonoides in deep water bodies has been 
more fully observed in lakes Uvil'dy and Turgoyak (Table 2). In the warmest times 
of the year the maximum density of Crustacea lives in the warmest upper 10 metre 
layer of water. In September they were shown to inhabit the upper (0-10m) and 
middle (l0-20m) layers. In late autumn, after cooling of the whole mass of the 
body of water, the largest numbers of M. oithonoides were observed in the middle 
(l0-20m) and lower (20-30m) layers. During this time the adult specimens were 
not now found and the whole population of crustacea consisted of copepodits 
(II-V copepodit stages). After the freezing of the lake and establishment of 
the inverted temperature stratification the warmer lower and middle layers of 
water have the greatest density of M. oithonoides. In Lake Turgoyak which is 
warmer and has silt deposits, the numbers and biomass of M. oithonoides towards 
the end of the ice-covered period usually exceed by 8 to 9 times those in the 
pelagic waters of the colder Lake Uvil'dy (Table 2). In winter in these deep 
lakes the copepodits M. oithonoides do not sink into the pelogin where it is 
almost as cold as in the lower layers of water. 
(4) 
Table for the determination of species of the genus Mesocyclops 
by ecological indicators 1) 
1. (4) Inhabiting water-bodies in winter and summer 
(all the year) .. 2 
2. (3) At cold times of the year (November - April) 
completely absent from the pelagic waters and 
migrated into the pelogin, where at a temperature 
of 2 they manage an active life-form. 
Mesoeuryhaline M. (s. str.) leucarti (Claus.) 
3. (2) Inhabiting pelagic waters of deep lakes the 
whole year. In shallow water-bodies in winter 
migrating from the pelagic waters into the 
pelogin. Freshwater species M. (th.) oithonoides Sars. 
4. (1) Inhabiting water-bodies only at warm times of 
the year (May - September) 2) 5 
5. (6) Mass forms of pelagic plankton of lakes and 
reservoirs. Mesoeuryhaline (S upto 3°/oo)... M.(th.) crassus (Fisch.) 
6. (5) Characteristic for dense submerged macrophytes. 
Freshwater species M. (Th.) dybowskii (Lande) 
The ecological peculiarities of species of the genus Mesocyclops are such 
accurate indicators that they can serve as reliable indicators by themselves, 
characterising the species. This has not always been so, for a long time 
only morphological differences have been used not infrequently leading to 
erroneous diagnosis of species: during this M. oithonoides and M. crassus are 
not infrequently confused and the former indication of M. dybowskii in brackish 
water-bodies "requires verification" (Rylov, 1948). 
With the present level of knowledge it is not possible for the present 
table to be fully completed but in due course ecological indicators will have 
a significance for diagnostic aspects not smaller than morphological 
distinctions. 
2) 
Not taking into account quiescent eggs. 
Numbers (specimens/m3) and wet weight (mg/m3) of the population of M. oithonoides in 
the pelagic waters of lakes Uvil'dy and Turgoyak. 
Table 2. 5. 
(6) 
We have only once found M. oithonoides in brackish water-bodies - Lake 
Burukhtal (100 hectares). A lake - the remainder of the bed of a drying up 
river; it is situated amongst the saline steppe of the Adamovsk river in the 
Orenburgsk region. The salinization of the water-body, gradually increasing 
due to a decreasing amount and then cessation of flow, favoured the establishing 
of M. oithonoides in the new body of water owing to the adaptation of this form 
to gradually increasing saline water. At the present time the lake presents 
itself as a long (about 40 km.) and narrow (upto 60 m.) arm, one end of which 
almost joins Lake Chalkar (50°45' latitude and 61°00' longitude), and the other 
is lost in the steppe. The depth of the water-body in one place attains 7.2 m. 
On the mineral character of the lake, it is regarded as a water body with sodium 
chloride water (s =2.32°/00). On 16th June 1951 with a water temperature of 
- 19° (surface), pH = 8.38 and 0 2 - 10.5 mgO/litre, the numbers of M. oithonoides 
in Lake Burukhtal reached 7.9 thousand specimens /m3(75.8 mg/m3). 
Measurement of parts of the body of M. oithonoides from Lake Burukhtal 
showed that, according to morphological indications produced, this species was 
essentially not distinguishable from individuals out of other water-bodies of 
the Urals : Lake Turgoyak, Verkhne-Isetsk pond (Ulomskii 1959). By correlating 
parts of the body they approximated to Crustacea from the non-flowing Lake 
Turgoyak. Historically and firmly established colonies of M. oithonoides in the 
isolated and now saline Lake Burukhtal have a rare non-characteristic appearance 
by no means showing an inclination of Crustacea of this species to euryhalinety. 
Thus, considering types of independent examination of the forms, 
M. oithonoides, M. leuckarti, M. crassus, and M. dybowskii can be identified not 
only by morphological differences (Rylov 1948), but also accurately by ecological 
indications. Among these crustacea M. oithonoides of southern origin appears 
to be the greatest coldness form of genus, since in winter and in summer it inhabits 
the pelagial of the deep and cold Ural lakes. After that follows M. leuckarti, 
wintering in an active state in the pelogin (T° ≥ 2°) with a satisfactory gas 
regime. M. crassus and M. dybowskii are not observed in water bodies in winter, 
they occupy the last places in this biothermal series (thermophiles). 
When considering saline waters M. leuckarti and M. crassus appear to be 
mesoeuryhalyne forms; they inhabit fresh and saline water bodies. M. oithonoides 
and M. dybowskii, on the other hand, inhabit freshwater lakes and ponds; the 
rare case of these typical freshwater forms being observed in saline water-bodies 
appears non-characteristic. M. oithonoides, M. leuckarti and M. crassus are the 
mass forms of plankton of our water bodies. M. dybowskii is considered to live 
in the calm littoral, mildly overgrown submerged vegetation; its population 
never reaches significant numbers. 
VERNADSKII V. I. 1934 Ocherki geokhimii, M 
[Treatise of geochemistry, Moscow] 
RYLOVE V. M. 1948 Cyclopoida presnykl vod. 
Fauna S.S.S.R., Rakoobraznye, 3, (3). 
[Cyclopoida of freshwaters] 
ULOMSKII S. N. 1959 Vliyanie vneshnei sredy na formoobrazovaniya 
u nizshikh vakoobraznykh, Dokl. Soveshch. 
po obshch. vopr. biol. posvyashch. 
100 - letiyu darninizma. Izd. Tomsk, un-ta 
[the influence of the external surroundings 
on the form of lower Crustacea]. 
1960 O sezonnykh izmeneniyakh chislennosti i 
biomassy organizmov v vodoemakh Urala, 
Tr. Vses. gidrobiol. o-va, 10. 
[concerning the seasonal changes of numbers 
and biomass of organisms in the water-bodies 
of the Urals]. 
REFERENCES 
(7) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Notice 
 
 
Please note that these translations were produced to assist the scientific staff of the 
FBA (Freshwater Biological Association) in their research. These translations were 
done by scientific staff with relevant language skills and not by professional 
translators. 
 
 
 


On the ecology of species belonging to the genus Mesocyclops Sars (Crustacea, Copepoda) dwelling in the water-bodies of the Urals and Pri-Ural territory. [Translation from: Zoologicheskie Zhurnal 44(1) 127-130, 1965. ]

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On the ecology of species belonging to the genus Mesocyclops Sars (Crustacea, Copepoda) dwelling in the water-bodies of the Urals and Pri-Ural territory. [Translation from: Zoologicheskie Zhurnal 44(1) 127-130, 1965. ]

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