Osmundea caspica (Zinova & Zaberzhinskaya) Maggs & L.M.McIvor comb. nov.

Fig. 5; Table 2

Basionym

Laurencia caspica Zinova & Zaberzhinskaya, Novosti Sistematiki Nizshikh Rastenii 1968: 30 –32 (Zinova & Zaberzhinskaja 1968).

Type material

AZERBAIJAN: Jun. 1962, K.M. Petrov, V.L. Komarov Botanical Institute (LE), Saint-Petersburg.

Type locality

Svinoy, Sangi-Mugan Island, Baku Archipelago, Caspian Sea, Azerbaijan.

Other material examined

AZERBAIJAN: Sangachal Bay, Sep. 2003, ERT Caspian Contractors BM001062596 (BM).

Distribution

Recorded from the Black Sea (Bulgaria and Romania) and Caspian Sea (Guiry & Guiry 2016), both of which are low salinity bodies of water.

Description

The description of L. caspica is published in Russian in a book that is not widely available, so here we provide the following description.

Thalli were 5–11 cm high, growing from a solid discoid basal holdfast; erect axes terete, about 1 mm in diameter, irregularly branched to three orders, with blunt apices, similar in general habit to Laurencia obtusa with the exception of the holdfast (Fig. 5A). In surface view of the cortex of live thalli, there were no ‘corps en cerise’; in surface view of preserved and stained cortical preparations, secondary pit connections were absent (Fig. 5B). In transverse section of axes, pericentral cells were not distinguishable, and the cortical cells were comparatively large and slightly radially elongated (Fig. 5C). Lenticular thickenings were absent in medullary cells.

Mature non-reproductive thalli, tetrasporophytes and males were collected but females are unknown. Tetrasporangia 80–110 µm in diameter occurred in bands below the apices of lateral branches. They were produced adaxially from random epidermal cells, cut off laterally from the mother cells. Spermatangial receptacles were terminal and open cup-shaped. Spermatangial structures were of the flament type (Nam et al. 2000); spermatangial flaments were unbranched, bearing numerous elongate spermatangia, and terminating in single large round to ovoid cells up to 40 µm in diameter (Fig. 5D–E).