Leuckartiara octona ( Fleming, 1823 )

Calder, Dale R., 2012, On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region 3171, Zootaxa 3171 (1), pp. 1-77 : 16

Leuckartiara octona ( Fleming, 1823)

Fig. 14

Geryonia octona Fleming, 1823: 298 [medusa stage].

Perigonimus repens .— Segerstedt, 1889: 9, 24.— Lönnberg, 1903: 60.— Jäderholm, 1909: 45, pl. 1, figs. 15, 16.— Jägerskiöld, 1971: 64.

Leuckartiara octona .— Rees & Rowe, 1969: 10.

Type locality. UK: Scotland, Aberdeen Bay ( Fleming 1823: 298) .

Museum material. Väderöarna, 58°34.931’N, 11°04.931’E, 121– 50 m, 13.ix.2010, biological dredge, R / V Nereus , on rugose squat lobster ( Munida rugosa ), six branched colony fragments, up to 6 mm high, with gonophores, ROMIZ B3931.

Remarks. An historical account and detailed description of the hydroid of Leuckartiara octona ( Fleming, 1823) , long known in part as Perigonimus repens ( Wright, 1858) , was given by Rees (1938). In a revision of the genus Perigonimus M. Sars, 1846 , Rees (1956a) included eight nominal species, and provisionally a ninth ( Perigonimus abyssi G.O. Sars, 1874 ), in the synonymy of L. octona . The identity and lengthy synonymy of the medusa stage of L. octona had been clarified earlier by Hartlaub (1913). Current knowledge on taxonomy, nomenclature, life cycle, and seasonality of this species has been summarized by Schuchert (2007). He followed Edwards (1965) in recognizing L. abyssi , similar to L. octona but even more like Neoturris pileata ( Forsskål, 1775) , as valid pending more information on its life cycle. The three, with similar hydroids, are sympatric in southwestern Scandinavia.

The hydroid of L. octona is epizoic on a variety of substrates, including crustaceans, molluscs (bivalves, gastropods, scaphopods, chitons), ascidians, other hydroids, the polychaete Aphrodite , and even a species of fish ( Agonus cataphractus ), as well as stones ( Stechow 1929; Leloup 1934; Kramp 1935b; Rees 1938; Russell 1953; Latham 1963; Rees & Rowe 1969; Christiansen 1972; Schuchert 2007). Colonies vary in morphology and size, and in occurrence of gonophores, depending upon factors including food, substrate, and even location on a given substrate such as upper and lower surfaces of gastropod shells ( Rees 1938; Millard 1975). Hydroids examined here, growing on the exoskeleton of Munida rugosa , were mostly erect and branched, with medusa buds arising from stems and pedicels.

Jägerskiöld (1971) reported hydroids of this boreal species at 95 stations along the west coast of Sweden, and it was also frequent in samples from the Oslofjord ( Christiansen 1972). In Denmark it is common off the west coast of Jutland, in the Skagerrak, and in the northeastern Kattegat, but rare in the southern Kattegat ( Kramp 1935b). Colonies with gonophores were observed from May to October in the Oslofjord ( Christiansen 1972). Young medusae appear during May or June in Danish waters, and the species is abundant there in autumn ( Kramp 1926). Medusae of L. octona are quite long-lived and can be carried considerable distances offshore ( Kramp 1926; Russell 1953).

Citations of Fleming’s (1823) original account of this species are often given in error, even in a number of major monographic works (e.g., Russell 1953; Kramp 1961). His paper was published in the Edinburgh Philosophical Journal (not the Edinburgh New Philosophical Journal), and the brief description appears on page 298, not 299.

Reported distribution. West coast of Sweden.—From near the border with Norway ( Jägerskiöld 1971) to the Öresund ( Segerstedt 1889).

Elsewhere.—North Atlantic from northern Norway to the Mediterranean Sea in the east, and from Labrador to Rhode Island in the west ( Schuchert 2007). It is generally thought to be circumglobal in temperate and tropical neritic waters.

Figures

FIGURE 14. Leuckartiara octona: part of colony with hydrocaulus, hydranths, and gonophores, ROMIZ B3931. Scale equals 1.0 mm.