БИОЛОГИЯ КРЕВЕТКИ PALAEMON ELEGANS RATHKE, 1836 (DECAPODA: CARIDEA: PALAEMONIDAE) ЮГО-ВОСТОЧНОЙ БАЛТИКИ

Каменная креветка Palaemon elegans Rathke, 1836 – широко распространенный инвазивный вид, бентофаг-полифаг, значимый в питании рыб, в ряде стран – промысловый объект. После вселения в Балтийское море успешно акклиматизировалась, широко распространилась, вытеснив аборигенные виды креветок палемонов. Наблюдается недостаток знаний о биологии креветки из морских поселений у берегов Калининградской области. Получены новые данные о размерных, половых, весовых характеристиках и репродукции P. elegans Юго-Восточной Балтики. Соотношение полов чаще приближалось к равному, общая длина тела составила 9,8–50,0 мм при длине карапакса 4,0–11,6; максимальные размеры самок больше, чем самцов. Масса тела креветок достигала 1,37 г; весовой рост несколько опережал линейный. Первое спаривание у самок могло происходить при длине карапакса до 5 мм; при 4–9 мм они впервые созревали и нерестились, откладывая до 1500 яиц размерами 0,45–0,58 х 0,50–0,60 мм, эмбрионов вынашивали. За первую половину эмбриогенеза наблюдалось увеличение объема яиц в среднем в 1,4 раза; значимых потерь эмбрионов не обнаружено. За нерестовый сезон (май – начало сентября) самки могут размножаться минимум дважды. Оценка половых, размерных, репродукционных параметров у креветок трех морских поселений показала их достаточное единообразие. Сравнение полученных результатов с таковыми для креветок Калининградского залива позволило предположить, что поселения моря и залива – части одной популяции вида Palaemon elegans в водах Калининградской области.

TO STUDY THE BIOECOLOGY OF CASPIAN SHRIMPS

Only two species of shrimps live in the Caspian Sea: Palaemon elegans and P. adspersus (Crustacea, Decapoda: Palaemonidae), which were introduced to the Caspian Sea in 1931-1934 during the introduction of mullets. Data on the biology of these species of shrimps are reflected only in the works by E.N. Kudelina (1950) and M.P. Marochkina (1980). This determines the relevance of research on the current state of the Caspian shrimp population. The material was collected in various areas of the Middle Caspian Sea in the summer-autumn period. Both species live up to five meters deep. P. elegans prefer coastal underwater objects with dense thickets, P. adspersus - open shallow waters with sandy-muddy soil. To the north of Makhachkala, P. elegans predominates, to the south, the number of both species is the same, and to the east, P. adspersus dominates. The characteristics of breeding females are presented, and the dependence of fecundity on the length of egg-bearing females is revealed. The absolute fecundity increased with the increase in the size of the females. Regression equations reflecting the relationship between fecundity and length of egg-bearing females of P. elegans and P. adspersus are calculated, expressed by power equations, respectively: E = 0.044947 · L265356 and E = 2.323 · L17.4, where: E - fecundity, L-length. In October 2017, in May and October 2018, several specimens of the subtropical freshwater shrimp Macrobrachium nipponense were found downstream of the Terek River. Probably, in the near future, the species composition of the Caspian shrimp will be replenished with another species.

Seasonal dynamics of population and age composition of the trematode Gynaecotyla adunca larvae (Linton, 1905) Yamaguti, 1939 in the Black Sea

The purpose of the research is analyzing the seasonal dynamics for the number and the hemipopulation structure of the trematode Gynaecotyla adunca larvae in shrimps of the genus Palaemon Weber, 1795 and determining the dependence of their infection with the metacercariae G. adunca on the host size and the season of the year in the water area of Sevastopol.Materials and methods. Samples of aquatic organisms were collected monthly during 2012 in two different biotopes, the estuary of the Chernaya River and the Kazachya Bay. We examined a total of 2,445 specimens of the Hydrobia acuta mollusk, 200 specimens of the Palaemon elegans shrimp in the estuary of the Chernaya River, and 2,248 specimens of the H. acuta mollusks and 64 specimens of P. adsepsus in the water area of Kazachya Bay. Shrimps were caught with a 1 × 0.4 m seine with a 6–8 mm mesh. The mollusks were collected with a hand grab sampler with a sampling area of 0.04 m2. The mollusks and shrimps were classified in accordance with the World Register of Marine Species. All mollusk and shrimp tissues were examined by the compression method under an MBS-10 binocular microscope. Descriptive statistics was calculated using Statistica 6 for Windows.Results and discussion. We have found that the parthenita G. adunca is characterized by asynchronous emergence of secondary sporocyst that contain cercariae, while the metacercariae G. adunca hemipopulation is characterized by an overdispersed distribution, which indirectly indicates a low density of the host population and its constant migration. We analyzed seasonal dynamics of the found microfallid larvae population. The metacercariae G. adunca are characterized by one peak of infection with trematodes in summer.

Impacts of the Invasive Seaweed Asparagopsis armata Exudate on Energetic Metabolism of Rock Pool Invertebrates

The marine red algae Asparagopsis armata is an invasive species gaining competitive advantage by releasing large amounts of toxic compounds to the surrounding invaded area. The main objective of this study was to evaluate the effects of this invasive seaweed on marine invertebrates by exposing the common prawn Palaemon elegans and the marine snail Gibbula umbilicalis to the exudate of this seaweed. The seaweed was collected and placed in a tank for 12 h in the dark in a 1:10 ratio. Afterwards the seawater medium containing the released secondary metabolites was collected for further testing. Lethal and sublethal effects of A. armata were investigated. Biochemical biomarker responses associated with energy metabolism (lactate dehydrogenase, LDH; electron transport system activity, ETS; lipid, protein and carbohydrate content) were analysed. The biomarker responses showed physiological status impairment of invertebrates after exposure to low concentrations of this algal exudate. The highest concentrations of exudate significantly increased lipid content in both organisms. In the shrimp, protein content, ETS, and LDH were also significantly increased. By contrast, these parameters were significantly decreased in G. umbilicalis. A behavioural impairment was also observed in G. umbilicalis exposed to A. armata exudate, reducing feeding consumption. These results represent an important step in the research of natural toxic exudates released to the environment and prospective effects of this seaweed in invaded communities under increasing global change scenarios.

Impacts of The Invasive Seaweed Asparagopsis armata Exudate on Rockpool Invertebrates

The marine red algae Asparagopsis armata is an invasive species which competitive advantage arises from the production and release of large amounts of toxic compounds to the surrounding invaded area, reducing the abundance of native species. The main objective of this study was to evaluate the effects of this invasive seaweed on marine invertebrates by exposing the common prawn Palaemon elegans and the marine snail Gibbula umbilicalis to the exudate of this macroalgae. The seaweed was collected and placed in tanks, for 12 hours, in the dark in a 1:10 ratio. Afterwards the media containing its secondary metabolites was collected for further testing. Lethal and sublethal effects of A. armata were investigated. Biochemical biomarkers responses associated with energy metabolism (lactate dehydrogenase, LDH; electron transport system activity, ETS; content in lipids, proteins and carbohydrates) were analysed. The biomarker responses showed invertebrates’ physiological status impairment after exposure to low concentrations of this algae exudate. Highest concentrations of exudate significantly increased lipid content in both organisms. In the shrimp, protein content, ETS, and LDH were also significantly increased. On the contrary, these parameters were significantly decreased in G. umbilicalis. A behavioural impairment was also observed in G. umbilicalis exposed to A. armata exudate, with reduction in feeding consumption. These results represent an important step in the research of natural toxic exudates released to the environment and prospective effects of this seaweed in invaded communities under increasing global change scenarios.