On Three Northern Species of Hydractinia

Abstract

Three species of Hydractinia, H. allmani Bonnevie, H. carica Bergh and H. monocarpa Allman from the Arctic are redescribed from numerous colonies. The great differences noted between colonies of the same species are shown to depend on the stage of reproductive exhaustion reached when the colonies were taken. What is known of their biology and distribution is summarized. ON THREE NORTHERN SPECIES OF HYDRACTINIA This paper is confined to observations on three northern species, Hydractinia cdlmani Bonne vie, Hydractinia carica Bergh and Hydractinia monocarpa Allman, and is based on the rich arctic and subarctic collections of the Naturhistoriska Riksmuseum,Stockholm. Some of the material has been briefly described by Elof Jaderholm, but all the locality records of colonies in the Riksmuseum have been reported by him in various papers.

Reconciling genealogical and morphological species in a worldwide study of the Family Hydractiniidae (Cnidaria, Hydrozoa)

“…This species does not extend the shell of its hermit crab hosts, and is also found in Iceland (Figs 2B and 3). This species has eumedusoids (Rees 1956; Schuchert 2001) with four radial canals, as does the unusual H. antonii (Miglietta 2006), which is also found in the Bering Sea. H. antonii has a calcified skeleton that is very different from the calcified skeleton in the distantly related hydractiniid Janaria ( see discussion below).…”

The European athecate hydroids and their medusae (Hydrozoa, Cnidaria): Filifera Part 3

“…Distribution: An arctic species, occurring in deep waters off northern Norway, eastern Greenland, Spitsbergen, Iceland, Arctic seas north of Russia, Sea of Okhotsk, Kuriles (Rees, 1956a;Naumov, 1969). Along the European coasts, it occurs as far Biology: Epizooic on gastropod shells inhabited by molluscs, preferably of the genus Colus (syn.…”

“…Along the European coasts, it occurs as far Biology: Epizooic on gastropod shells inhabited by molluscs, preferably of the genus Colus (syn. Sipho) (Family Buccinidae), in depths of 3-1500 m, mainly between 40 and 250 m. Water temperatures -1.2 to 2.7 °C (Rees, 1956a).…”

“…Remarks: A distinct and unproblematic species, the synonymy and history of which has been outlined by Rees (1956aRees ( , 1956b. The morphology is rather variable, the gonozooids are very prone to reproductive exhaustion.…”

“…The morphology is rather variable, the gonozooids are very prone to reproductive exhaustion. Male and female medusoids can occur in the same colony (Rees, 1956a).…”