Insights to the genetic structure of <i>Calanus helgolandicus</i> (Calanoida: Copepoda) from deep-sea specimens in the Balearic Sea

Abstract

Calanus helgolandicus is widely distributed across the northeast Atlantic and Mediterranean, and also found in the Black Sea where it is referred to as Calanus euxinus. Previous genetic studies do not include deep-water specimens despite high abundances at bathypelagic and mesopelagic depths. Our objective is to compare the genetic structure of C. heloglandicus from the deep Balearic Sea to that of coastal populations in the Northeastern Atlantic Ocean, the Adriatic Sea, and the Black Sea defined from previous research. We use a portion of the mitochondrial gene cytochrome oxidase I from 41 individuals of C. helgolandicus collected at 2170 m depth in the Balearic Sea to estimate genetic differentiation between geographic regions and elucidate phylogeographic patterns. Results show that populations do not follow an isolation by distance model. Instead, the lowest genetic differentiation is between two distant basins, the deep Balearic Sea and the Black Sea. The results can be explained by the presence of two types of C. helgolandicus, a coastal, shallow water, type and an oceanic, deep water, type that diapauses at great depths. Genetic differentiation between coastal populations is maintained by oceanographic barriers, while differentiation in oceanic populations is lower due to dispersal by deep ocean currents.

First finding of live specimens of non-native copepod Calanus finmarchicus (Gunnerus, 1770) in the Sea of Marmara

“…The Black Sea population of C. helgolandicus was allocated a separate species, C. euxinus, based on the difference in the distribution of supernumerary pores on the second and third urosome segments of adult females (Fleminger & Hulsemann 1987;Hulsemann 1991). Many authors have also used this naming in publications, however, further morphological (Isinibilir et al 2009) and genetic analysis (Ünal et al 2006;Yebra et al 2011;Figueroa et al 2019) has indicated that the supernumerary pores are not sufficient indicators for species differentiation hence the name C. helgolandicus should be used. The female Calanus finmarchicus collected on 3 April 2018 (Figure 2a) had a total body length of L tot =3.60 mm, prosome length l pr =2.84 mm, and prosome width d pr =0.85 mm.…”

“…Only two species of copepods of the genus Calanus have been found in this part of the Mediterranean Sea: C. helgolandicus and C. tenuicornis (Brodskii 1950;Weikert et al 2001), and only one of them, C. helgolandicus, permanently lives in the Sea of Marmara and the Black Sea (Svetlichny et al 2006;2010). In the Black Sea, the population of this species is also referred to as Calanus euxinus (Hulsemann 1991), however, according to the results of a morphological (Isinibilir et al 2009) and genetic analysis (Ünal et al 2006;Yebra et al 2011;Figueroa et al 2019), C. euxinus does not have differences in species rank from C. helgolandicus living in the Mediterranean basin (e.g. the Black Sea, the Sea of Marmara, the Aegean Sea, the Adriatic Sea) and in the North Atlantic.…”

Microplastic Consumption and Its Effect on Respiration Rate and Motility of Calanus helgolandicus From the Marmara Sea

“…In addition, it should be taken into account that the difference in the number of urosomal supernumerary pores in Black Sea females may be due to the fundamentally lower salinity of this sea. Finally, by a series of molecular studies, it was shown that level of genetic differentiation between Calanus helgolandicus and Calanus euxinus is typical for conspecific calanoid copepod populations (Papadopoulos et al, 2005;Unal et al, 2006;Yebra et al, 2011;Figueroa et al, 2019) within European waters, despite very distinct geographic barriers/conditions prevail for the Black Sea. Therefore, the species of Calanus in the present study is referred to as Calanus helgolandicus, which has been referred to as C. euxinus or C. ponticus in different studies from the Marmara Sea or the Black Sea.…”