Antithamnion amphigeneum A.Millar

Costanzo, Luca Giuseppe, Marletta, Giuliana & Alongi, Giuseppina, 2021, Non-indigenous macroalgal species in coralligenous habitats of the Marine Protected Area Isole Ciclopi (Sicily, Italy), Italian Botanist 11, pp. 31-44 : 31

Antithamnion amphigeneum A.Millar

Description.

The collected specimens match with the descriptions of Verlaque and Seridi (1991), Cormaci et al. (2004), Rodríguez-Prieto et al. (2013) and Verlaque et al. (2015). The thalli are pink-reddish, filamentous and uniseriate, consisting of creeping and erect axes, bearing distichous opposite whorl branches. The whorl branches have an isodiametric basal cell and bear opposite distichous simple or branched branchlets with only abaxial branchlets near the distal portion. As reported by Secilla et al. (1997), we noticed in our samples that the apical cells are blunt and sometimes provided with a single hyaline hair (Fig. 2A ). The lateral indeterminate branches arise replacing a branchlet and with the suppression of the opposite branchlet (Fig. 2B ). Moreover, in the collected specimens there were abundant gland cells located on the adaxial side of both normal and special branchlets, touching 2-3 cells. We found only sterile specimens.

Chorology.

Indo-Pacific.

Presumed introduction vector.

Fouling.

Remarks.

Hitherto in the Mediterranean, this species has only been reported in the western basin ( Verlaque et al. 2015) and in the Adriatic Sea ( Mačić and Ballesteros 2016). Therefore, the present report represents the first record of A. amphigeneum in the eastern Mediterranean.

Figures

Figure 2. Antithamnion amphigeneum a apical portion of an indefinite axes: the arrowhead shows a terminal hyaline hair b detail of lateral indeterminate branches, which arise by replacing a branchlet and with the suppression of the opposite branchlet (arrow).