Genetic variability, biomass parameters, elemental composition and energy content of the non-indigenous hydromedusa Craspedacusta sowerbii in North America

Abstract

The freshwater hydrozoan Craspedacusta sowerbii was introduced to habitats around the world and they spread into the surrounding water bodies thereafter. Despite an increase in reported observations, little is known about its genetics, physiology and ecology. The present study examined the organic content, elemental composition and energy content of jellyfish collected in Canada and the USA and compared these metrics with their marine counterparts and other co-occurring zooplankton. Specimens from the sampled lakes were sexed and molecularly characterized. Molecular, stoichiometric and energetic information is critical in determining distribution pathways and trophic connections. Molecular analyses showed two closely related sequences in North America, one shared by the Canadian and Japanese specimens, while another one is widely present across the Americas. Organic and all elemental contents were higher compared to marine jellyfish species. Estimated energy content of C. sowerbii was 20–27 kJ g DW−1, which is 2-fold higher than for marine hydrozoans and compared well with cladocerans, copepods and rotifers. Estimated C/P values indicated that cladocerans and copepods are suitable prey for C. sowerbii and that jellyfish may compete with juvenile fish to fulfill similar nutrient demands. Freshwater jellyfish were stoichiometrically and energetically different from marine hydrozoans, indicating higher importance in freshwater food webs than previously thought.

Distribution and Genetic Lineages of the Craspedacusta sowerbii Species Complex (Cnidaria, Olindiidae) in Italy

“…A further clade, although still to be verified, could comprise a sequence of unknown origin (A.N., MZ569028). The unstable placement of the third clade with the two identical Swiss (Ringwiler Weier) and Japanese (Osaka) mtDNA COI sequences have already been highlighted [21,[23][24][25] and needs more comprehensive molecular sampling from these and other locations around the world to be clarified [25]. Our mtDNA COI analysis supports for uncorrected p-distances between clades "C1" and "C2" at 15.7%, in agreement with values found in other studies: 15% [19] and 14% [12].…”

“…The analysis of the available Craspedacusta mtDNA COI sequences agrees with previous studies [20,21,[23][24][25], and it supports the existence of at least three distinctive clades within Craspedacusta sowerbii s.l. : "clade C1", which comprises sequences from Morocco, Spain, Central-Northern Italy, Germany, India, and the Chinese province of Sichuan (Figure 3); "clade C2", which comprises sequencies from Chile, Canada, the USA, Sicily (Southern Italy), Northern Italy, Germany, Czech Republic, Greece, China, Singapore, and Japan, and six sequences of unknown origin; and "Clade C3", which comprises a sequence from Switzerland (MF000493 Ringwiler Weier), one from Japan (MZ326744 Osaka), and one of unknown origin.…”

“…In agreement with previous studies, molecular evidence based on mtDNA shows the presence in Italian inland waters of at least two distinct genetic lineages within Craspedacusta sowerbii s.l. (clade "C1" and clade "C2"), that presumably represent separate species [12,14,[19][20][21][23][24][25]. The nomenclatural solution of the new genetically distinct Craspedacusta species remains problematic and a taxonomic revision is needed [12,25].…”

“…(clade "C1" and clade "C2"), that presumably represent separate species [12,14,[19][20][21][23][24][25]. The nomenclatural solution of the new genetically distinct Craspedacusta species remains problematic and a taxonomic revision is needed [12,25]. Genetic analysis of the holotypes and paratypes of distinct species of Craspedacusta preserved in zoological collections of museums is mandatory to define which is the true Craspedacusta sowerbii [12].…”

“…Molecular studies suggest the existence of at least three distinctive Craspedacusta lineages of putative species rank: "sowerbii" Lankester, 1880; "kiatingi" Gaw & Kung, 1939; and "sinensis" Gaw & Kung, 1939 [13,[17][18][19][20][21]. At least two lineages of Craspedacusta sowerbii invaded Central Europe [12,14,22] and Italy [13,20], whereas worldwide, mtDNA COI analyses showed the presence of at least three main Craspedacusta lineages [21,[23][24][25]. In Italy, Craspedacusta was first recorded in 1946 in a tank at the University of Rome [26], and further sightings have been reported for various natural and artificial aquatic habitats [27].…”