Daphnia (Ctenodaphnia) mediterranea Alonso 1985

Daphnia (Ctenodaphnia) mediterranea Alonso, 1985 (Figs. 2A–H) Type locality. Gosque lagoon, Sevilla, Spain. Short diagnosis of population from Kalmykia. Parthenogenetic female. Transparent and ovoid body, height/length approx. 0.6, short caudal spine (Fig. 2A). Head relatively small, lacking a helmet and keel, compound eye in a low ocular dome, small ocellus. Rostrum short, widely rounded (Fig. 2D–E). Carapace subovoid, a shallow depression between carapace and head. Head shield with rounded fornices (Fig. 2F–G). Well developed anterior projection of the carapace (Fig. 2F: arrow, G), lacking denticles in the Kalmyk population unlike the Spanish one (Alonso, 1996), reaching the most anterior portion of the head but not forming a cephalic plate, as in D. atkinsoni. Dorsal margin of the valves with a continuous row of minute, densely spaced teeth. Posterior portion of valve ventral margin with a row of small setules, a group of setae on the middle of the ventral margin. Postanal angle of postabdomen smooth, preanal and postanal margins straight, ventral margin almost straight. Anal and postanal portion with numerous small anal teeth. Postabdominal claw relatively short. Antenna I (Fig. 2D–E) as a relatively large cylindrical body projecting behind the rostrum (note that in Spanish populations its tip only reaches tip of rostrum, see Alonso (1985, 1996); nine terminal aesthetascs approximately as long as the antennular body, antennular sensory seta short, located at the base of the body of antenna I. Antenna II formula: setae 1–1–3/0–0–1–3. Limbs as typical of the subgenus. Limb V exopodite with two distal setae (arrows), the proximal most distal seta somewhat shorter than the most distal seta (Fig. 2H: arrows). Juvenile female. (Fig. 2B) Body elongated, dorsal margin almost straight, height /length approx. 0.5. Caudal spine relatively longer as compared to adults. Juvenile male. Body elongated, head with rounded rostrum and antenna I separated from the head by a joint, height /length approx. 0.55 (Fig. 2C). Limb I bearing a copulatory hook on the IDL and a very long additional seta on the ODL. No adult males were found. Size. In our material: female length 1–2.1 mm (without caudal spine), height 0.5–1.24 mm; juvenile male approx. 1.15 mm, height approx. 0.6 mm. Differential diagnosis. Here we represent the differential diagnosis mainly based on parthenogenetic females, as ephippial females and males were absent in Kalmyk population. D. (C.) mediterranea could be differentiated from most Eurasian D. (Ctenodaphnia) species by its relatively large antenna I wich reaches the tip of the rostrum or even projects behind it. Such a relatively large antenna I is also characteristic of some daphniids of the Major Clade 2, namely the D. (C.) atkinsoni group and D. (C.) triquetra, but they have a head plate which is completely absent in D. (C.) mediterranea. On the contrary, antenna I is very short or even almost completely reduced in many ctenodaphniids (D. hispanica, D. lumholtzi, D. tibetana, D. chevreuxi, D. fusca, D. similis group), and is relatively large in D. magna, but does not reach the tip of rostrum. In D. (C.) mediterranea, the exopodite of thoracic limb V has two well-developed distal setae unlike the D. similis s.l. species group (D. similis, D. sinensis, D. inopinata and D. arabica). In D. (C.) mediterranea, the most proximal distal seta of the exopodite of limb V is shorter than the most distal seta, as in most ctenodaphnids and unlike D. fusca and D. chevreuxi. According to Alonso (1985: P. 221) the most obvious features of the gamogenetic specimens of D. mediterranea are the following: “3. The ephippium is elliptic, its only attached to the dorsal keel along the posterior two thirds. 4 The basal appendage of the antenna I of the male exceeds the head length”. Distribution, biology. Previously D. (C.) mediterranea was found in several countries of Mediterranean Europe: South and Central Spain, continental Italy and Sicily (Alonso, 1985, 1996; Margaritora, 1985; Benzie, 2005; Marrone et al., 2005) and few countries of Africa including Alger (Ghaouaci et al., 2018). Most probably, the species is more widely distributed in the region as most previous records of “ D. dolichocephala Sars, 1895 ” (e.g. Negrea, 1983 from Romania; Bromley, 1993 from Israel) could also belong to D. mediterranea (Alonso, 1985). We believe that some earlier records of D. ulomski Behning, 1941 (Güher, 2014) also represented misidentifications of D. (C.) mediterranea, and the latter is also present in Turkey. Note that D. (C.) mediterranea was already reported from the Black Sea drainage in Romania by Negrea (1983) as D. (C.) dolichocephala. Also it is recorded in a single locality of Iran belonging to the Caspian Sea drainage (Mohammadyari et al. 2017). Molecular phylogeny. The ML tree for Major Clade 2 of D. (Ctenodaphnia) is represented in Fig. 3. The Major Clade 2 is clearly subdivided into two subclades: a weakly supported Subclade 1 with the majority of species (not discussed here) and a highly supported Subclade 2 containing D. (C.) menucoensis, D. (C.) salina and D. (C.) mediterranea. The Kalmykian sequence apparently belongs to D. (C.) mediterranea, grouping with the PP472427 sequence from Cyprus; this pair then groups with the sequences from continental Spain (FJ427485, FJ427409), but the genetic distances are small within a 100% supported clade of D. (C.) mediterranea.