Caucasirella: a new genus and three new species of groundwater amphipods from the Caucasus

Amphipods are small crustaceans. Some live in rivers and the sea, others in groundwater. The new paper deals with the latter: amphipods of the family Crangonyctidae that live in the foothills of the western Caucasus.

Until now these animals were placed in the genus Lyurella. Its type species, Lyurella hyrcana, is known from the southern Caspian coast, from Azerbaijan and Iran. Five species from the Black Sea coast had been placed in the same genus.

Morphological and genetic analysis showed that the western Caucasian species form a separate genus. The authors named it Caucasirella, after the Greater Caucasus range. They moved the five earlier species into the new genus and described three new ones. Caucasirella now holds eight species.

All three species were collected in 2024–2025 in the Black Sea foothills of Krasnodar Krai.

Caucasirella shapsuhica. From the upper reach of the Shapsuho River, Tuapse district, which also gives it its name. The largest male is 5.2 mm, the largest female 6.5 mm.

Caucasirella lazareviensis. From a small left tributary of the Psezuapse near the village of Maryino, in the Lazarevsky district of Sochi. The name comes from the district. Males reach 5 mm, females 5.5 mm.

Caucasirella mzymtiensis. From a small spring in the valley of the Chvizhepse River, a right tributary of the Mzymta, near Adler. The name comes from the Mzymta. Males reach 5 mm, females 5.5 mm.

The authors consider lazareviensis and mzymtiensis probably endemic, living only in these places.

Caucasirella species are 5–7 mm long. The body is pale whitish, yellowish or reddish and translucent. The eyes are black and clearly visible, and the head carries yellow spots that are probably sensitive to light.

They live in groundwater, but not in caves. Their habitat is the hyporheic zone, water that moves through the gravel and sand beneath a riverbed, and springs. C. fanagorica, for example, lives on the bottom of small rivers and springs, under stones and large pebbles. It avoids sunlight but does not burrow into the ground.

The paper also describes juveniles of the genus for the first time, using C. lazareviensis. Juveniles differ markedly from adults in the structure of their legs, tail parts and swimming legs. According to the authors, such changes during growth had not been described for any species of Crangonyctidae before.

Molecular analysis suggests that Caucasirella and Lyurella split about 10–7.5 million years ago, in the Miocene, while the Caucasus range was rising. Today Caucasirella lives in the western Caucasus and Lyurella in Hyrcania, on the southern Caspian coast.

Georgia lies between the two ranges. According to the paper, the easternmost species of the related genus Synurella are known from the coastal swamps of Poti and Kobuleti (Samegrelo-Zemo Svaneti, Adjara). In central Georgia there are no recent records of these genera. The authors suggest that the Caucasus range acts as a biogeographic barrier for them.

Another member of the same family, Diasynurella wachuschtii, is known from the Tskhratskaro pass near Bakuriani (Samtskhe-Javakheti). In the authors’ view, this shows that the region is biologically rich and that new discoveries in this group are likely.

Range. The new species are known from very few places so far, lazareviensis and mzymtiensis from a single site each. Their real ranges are unknown.

Georgia. The authors explain the gap in central Georgia by the Caucasus barrier, but also expect new discoveries. What lives in the springs and in the water beneath riverbeds of central Georgia is still unknown.

Georgian names. These species have no Georgian names.

More discoveries of small soil and water animals are in the news section.