Cordylophora caspia ( Pallas, 1771 )

Calder, Dale R., 2010, Some anthoathecate hydroids and limnopolyps (Cnidaria, Hydrozoa) from the Hawaiian archipelago 2590, Zootaxa 2590 (1), pp. 1-91 : 18-19

Cordylophora caspia ( Pallas, 1771)

Fig. 7

Tubularia caspia Pallas, 1771: 479 .

Cordylophora caspia .— Cooke, 1977: 81, fig. 9.

Type locality. “In Mari Caspio…” ( Pallas 1771).

Material examined. None.

Description. (From Cooke 1977: 81–82): “This rather large hydroid is characterized by irregular loosely branched stems up to 15 mm tall and 0.2 to 0.25 mm in diameter with polyps given off semialternately and terminally… The polyps are 1 mm to 2 mm in total length with 10 to 20 scattered filiform tentacles and are dull red distally. The perisarc of the stem ends well beneath the body of the polyp. Many gonophores are present on the colony, two to four (no more) on the stem, usually 1 mm or so below the terminal polyps (not as low on the side polyps). The orange gonophores are covered by the perisarc and are elongate-oval in shape, 1 mm long (including pedicel) by 0.3 mm maximum diameter.”

Remarks. An overview of Cordylophora caspia ( Pallas, 1771) and its biology has recently been given by Schuchert (2004). He provided a synonymy list, taxonomic comments, information on ecology and distribution, and an overview of morphological variation in the species. This hydroid is believed to have originated in the Ponto-Caspian region ( Folino-Rorem et al. 2009), and is currently the focus of numerous studies as an invasive species (see Zoological Record).

Cordylophora caspia in the recent past has generally been regarded as conspecific with C. lacustris Allman, 1843 ( Cairns et al. 2002). However, molecular studies now provide evidence of the existence of multiple cryptic species in C. caspia ( Schable et al. 2008) . Folino-Rorem et al. (2009) identified several lineages of these hydroids, each having different salinity tolerances. Some lineages had wide geographic ranges, yet different lineages were also frequently sympatric. Dispersal is thought to have occurred by shipping. No hydroids from Hawaii were included in the analyses of Folino-Rorem et al. (2009), and genetic affinity of the local population is unknown.

Hydroids assigned to the genus Cordylophora Allman, 1843 are circumglobal in brackish waters ( Schuchert 2004), and they penetrate into limnic biotopes, even those with soft water and low alkalinity ( Smith et al. 2002). Specimens have been widely utilized in experimental work on cnidarians ( Vervoort 1995), and are readily cultured ( Kinne 1977: 656). Optimum conditions for colony development under laboratory conditions ( Kinne 1956) are reportedly in waters of low salinity (2–18‰) and moderate temperature (11–18° C). In nature, colonies are frequently found at salinities of 7‰ or lower ( Vervoort 1946; Calder 1976). Hydroids become dormant during winter in regions with colder climates ( Smith 2001). Sexual reproduction occurs by fixed gonophores. According to Bouillon (1985), larvae may develop within the gonophores to an advanced stage, occasionally even to the young polyp stage.

This species was discovered on algae growing in anchialine waters (Halua Pond) on Cape Kinau, Maui, during the summers of 1974 and 1975 ( Cooke 1977; Carlton & Eldredge 2009). No material of C. caspia was found in collections at the Bishop Museum.

Reported distribution. Hawaii. Maui: Cape Kinau, in an anchialine pond on the chlorophyte Caulerpa serrulata ( Cooke 1977) .

Worldwide. Circumglobal in temperate and tropical brackish to fresh waters; 0–85 m ( Fraser 1944, as Cordylophora lacustris ; Vervoort 1946; Naumov 1960; Smith 2001; Smith et al. 2002; Schuchert 1996, 2004).