Dynamene tubicauda Holdich, 1968

Vieira, Pedro E., Queiroga, Henrique, Costa, Filipe O. & Holdich, David M., 2016, Distribution and species identification in the crustacean isopod genus Dynamene Leach, 1814 along the North East Atlantic-Black Sea axis, ZooKeys 635, pp. 1-29 : 12-13

Dynamene tubicauda Holdich, 1968

Restricted synonymy.

Dynamene tubicauda Holdich (1968).

Dynamene tubicauda : Holdich (1968a, 1970); Lombardo (1984); Borg et al. (2006).

Material examined.

Specimens were examined from six Italian locations in the Bay of Naples and off the island of Elba, and one location off Malta - see the Suppl. materials 1 and 2. A number of literature records from Sicily have been included as the diagrams clearly indicate this species ( Lombardo 1984).

Key morphological characters.

The morphology of this species is unique amongst the known Dynamene species - in stage 8 males the pereon length and width are similar; the epimera and front of the head form a shelf; the antennular peduncle is expanded; there are two widely separated, peg-like pleotelsonic bosses; and the pleotelsonic foramen is at the end of a ventrally-closed tube (Fig. 2I). In stage 7 females the body is also flattened with the epimera forming a shelf round the body; the pleotelsonic foramen is at the end of a well-developed tube (Figs 3 J–K). See keys to stage 8 males and stage 7 females.

Size.

Adult males (stage 8) typically 3.0 × 2.0 mm, pre-ovigerous females (stage 7) typically 2.5 × 2.0 mm.

Life-history.

Nothing is known of the life-history of this species, other than the fact that sexual dimorphism occurs with males developing the bidentate process characteristic of the genus. Holdich (1968) only recorded males, but both sexes have been recorded in the present study. Lombardo (1984) was the first to describe the adult female.

Habitat.

This species has been found between 2-30 m amongst algae in muddy/sandy and coralline habitats, rock scrapings, freely swimming at 30 m, and also in sea grass meadows ( Lombardo 1984, Borg et al. 2006).

Colour.

Pale yellow. No polychromatism was observed.

Geographical distribution.

The distribution of this species shown in Holdich (1970) has been extended by the present study. However, it appears to be restricted to the eastern Mediterranean, having only been recorded off the west coast of Italy (Holdich 1968), Sicily ( Lombardo 1984) and Malta ( Borg et al. 2006) (Fig. 5F). The most northerly record is for the island of Elba and the most southerly is off Malta.

Remarks.

The distribution of this species is the most restricted of all the Dynamene species along the NE Atlantic-Black Sea axis. Considering the large number of samples examined during this study this restricted distribution is most likely real. Its unusual flattened shape and the position of the pleotelsonic foramen at the end of a tube, even in adult males, may be an adaptation to inhabiting sediments.