Neoturris pileata ( Forsskål, 1775 )

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 : 16-18

Neoturris pileata ( Forsskål, 1775)

Figs. 15, 16

Medusa pileata Forsskål, 1775: 110 [medusa stage].

Neoturris pileata .— Edwards, 1965: 461.— Rees & Rowe, 1969: 10.— Schuchert, 2007: 336.

FIGURE 15. Neoturris pileata : part of colony with two hydranths and a medusa bud, ROMIZ B3932. Scale equals 1.0 mm.

Type locality. Mediterranean Sea ( Forsskål 1775: 110).

Museum material. Kosterhavet, 58°49.446’N, 10°57.718’E, 45–48 m, 07.ix.2010, biological dredge, R / V Nereus , two colonies, on two specimens of Nucula sulcata , up to 1.5 mm high, without gonophores, ROMIZ B3895.–Kosterhavet, 58°56.608’N, 11°05.314’E, 70 m, 15.ix.2010, biological dredge, R / V Nereus , one colony, up to 2 mm high, on Nucula sulcata , with medusa buds, ROMIZ B3932.

Remarks. Edwards (1965) linked a hydroid found on bivalves of the genus Nucula in the Clyde Sea Area, Scotland, to the medusa Neoturris pileata ( Forsskål, 1775) . Descriptions and illustrations were given of this hydroid, and of various stages in the development of its medusa. Hydroids examined here corresponded with his account of N. pileata . Rees & Rowe (1969) also reported hydroids of N. pileata on Nucula sulcata off the Swedish west coast, and obtained young medusae from material collected at Väderöarna. The same specimens, collected late September and early October 1964, were examined and briefly discussed by Edwards (1965: 461). Medusae appear during winter and last until late summer in the North Sea, but may be found in the Skagerrak and Kattegat until October ( Edwards 1965).

The hydroid of N. pileata closely resembles that of Perigonimus abyssi G.O. Sars, 1874 (= Leuckartiara abyssi ) from western Norway, but Edwards (1965) maintained both as valid because of a lack of knowledge about the adult medusa of the latter. Schuchert (2007) kept them distinct for the same reason. Moreover, Schuchert showed that N. pileata has been found only on shells of the bivalve Nucula , and especially on N. sulcata , while L. abyssi has been found on the scaphopod Dentalium dentale as well as the bivalves Nucula and Nuculana . It had earlier been speculated that P. abyssi might be the hydroid stage of N. pileata or a species of Leuckartiara Hartlaub, 1913 ( Rees 1938: 22; Russell 1953: 188). While similar to Leuckartiara octona ( Fleming, 1823) , hydroids of N. pileata tend to be shorter and less branched, and their newly-liberated medusae have four unequally developed perradial tentacles instead of just two ( Edwards 1965; Schuchert 2007).

In contrast to the hydroid of L. octona , which occurs on a variety of substrates, N. pileata appears to be substrate-specific on species of Nucula , small bivalves inhabiting bottoms of fine mud. Colonies, adapted to life buried in mud, occur mainly on anterior and ventral surfaces of the shells ( Edwards 1965; Schuchert 2007).

The cnidome of Neoturris pileata includes desmonemes and heterotrichous microbasic euryteles ( Fig. 16 ).

Reported distribution. West coast of Sweden.—Kosterfjord ( Rees & Rowe 1969) to Gullmarfjord ( Schuchert 2007).

Elsewhere.—North Atlantic from Norway to western Sweden and Scotland ( Schuchert 2007). The medusa stage is known from Norway (to 64°N) and Iceland southwards to north Africa, including the Mediterranean Sea ( Edwards 1965), but not from North America ( Cairns et al. 2002). The westernmost report of the medusa is from the central North Atlantic (49°49’N, 30°22’W) over the Mid-Atlantic Ridge ( Kramp 1947: 62).

Figures

FIGURE 16. Neoturris pileata, nematocysts, ROMIZ B3932: a, desmoneme; b, two heterotrichous microbasic euryteles; c, two heterotrichous microbasic euryteles.