Echinogammarus trichiatus ( Martynov, 1932 )

Rewicz, Tomasz, Konopacka, Alicja, Bącela-Spychalska, Karolina, Özbek, Murat & Grabowski, Michał, 2016, First records of two formerly overlooked Ponto-Caspian amphipods from Turkey: Echinogammarus trichiatus (Martynov, 1932) and Dikerogammarus villosus (Sovinsky, 1894), Turkish Journal of Zoology 40 (3), pp. 328-335 : 331-333

Echinogammarus trichiatus ( Martynov, 1932)

syn. Chaetogammarus trichiatus Martynov, 1932 , syn. Chaetogammarus tenellus major Carausu, 1943

Specimens examined: Turkey, Lake Durusu , near the village of Balaban N 41.3163, E 28.62055. 01.09.2007, 17 ind., leg M. Grabowski, K. Bącela-Spychalska .

Diagnosis: Medium large species, males 12–15.5 mm, females 10–13 mm. In males, antenna II and pereopod III densely covered with long, curled setae. Such setation is also typically present on rami of uropod III, yet they were absent in all the examined individuals from Lake Durusu ( Figure 3 ). In females the setation is less dense and predominantly straight. Urosome segments I and II with four groups of spines (two dorso-lateral and two lateral), usually with 3–4 spines in each group. On the third urosome segment only two lateral groups are present; dorsolateral groups are reduced to two dorsomedian spines only. The diagnostic features for the species are illustrated in Figure 4 . The species may be identified based on the following literature: Cărăușu (1943), Cărăușu et al. (1955), Mordukhaj-Boltovskoj et al. (1969), Eggers and Martens (2001), and Konopacka (2004).

Molecular identification: Due to the lack of dense and curly uropod setation in individuals from Lake Durusu, which is one of the key features for E. trichiatus , we used an mtDNA COI gene for their additional molecular

REWICZ et al. / Turk J Zool identification. The two obtained haplotypes (Etri-1 and Etri-2) clustered (with 100% bootstrap value) within one clade with GenBank obtained sequences of E. trichiatus from Ukraine, Romania, and Western Europe ( Table 1;

Figure 5 ). Additionally, the mean K2P distance between all the compared haplotypes of E. trichiatus was 0.008

0.02

(±0.003 S.E.), which is way below the 0.03 upper threshold for the intraspecific genetic distance defined by Costa et al. (2009) and Hebert et al. (2003). In conclusion, despite the lack of one important key feature, the individuals can be unambiguously identified as E. trichiatus . Thus, our finding extends the known morphological variability of the species.

Remarks: So far, eight species of the genus Echinogammarus have been reported from Turkish inland and estuarine waters ( Özbek and Ustaoğlu, 2005). Yet, after E. ischnus (Stebbing, 1899) , E. trichiatus is the only other Echinogammarus species belonging to the Ponto-Caspian complex (sensu Stock, 1974) reported from the Turkey. It is important to remark that often in the literature the species occurs under its synonymic names, Chaetogammarus trichiatus Martynov, 1932 or Chaetogammarus tenellus major Carausu, 1943 . This taxonomic confusion has been discussed in detail by Rachalewski et al. (2013a). Echinogammarus trichiatus is indigenous to the basins of the Black and Azov seas. It occurs in the lower course of the Danube River and its delta as well as in fresh and slightly brackish limans and coastal lakes along the northwestern Black Sea coast. The most eastern record of the species came from the river Khosta on the Caucasian Black Sea coast, which is the locus typicus for that species ( Martynov, 1932). The preferable habitat of E. trichiatus is hard substrate such as gravel and pebbles, but it was found also in reeds and among macrophytes (unpublished data). The species invaded inland waters of Western Europe via the southern invasion corridor (sensu Bij de Vaate et al., 2002). Surprisingly the first record of E. trichiatus outside its native range came from the upper Danube in Germany. Thus it may be expected that the species’ spread was due to human-mediated transport. Subsequently, the species was found in France, Belgium, Netherlands, and recently in Poland. The species’ invasion history and its present distribution in Europe are summarized by Boets et al. (2012) and Rachalewski et al. (2013a). Taking into account that this first record of the species in Turkey comes from the Ponto-Caspian region, we may conclude that, as in the case of D. villosus , Echinogammarus trichiatus is native to Lake Durusu and its presence there was previously overlooked.

Figures

Figure 3. SEM picture of atypical U3 in Echinogammarus trichiatus from Lake Durusu.

Figure 4. Morphological features of the Echinogammarus trichiatus. A1 - antenna I; A2 - antenna II; G1 - gnathopod I; P3 - pereiopod III; P7 - pereiopod VII; U3 - uropod III; UR - urosome (after Cărăușu, 1943, modified).

Figure 5. Neighbor-joining tree based on COI p-distances for haplotypes of Echinogammarus trichiatus and Echinogammarus ischnus. Gammarus fossarum was used as an outgroup. Only bootstrap supports above 50% were reported. Bold indicates haplotypes coming from Lake Durusu, obtained in this study.