Fróðskaparrit - 01.01.2004, Síða 301

FESKVATNS SVAMPAR (PORIFERA: SPONGILLIDAE) í FØROYUM
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I
Postglacial material was put at disposal by
O. Bennike.
Results
Order HAPLOSCLERIDA
Family Spongillidae
Genus Racekiela Volkmer-Ribeiro, 1998
Racekiela ryderi (Potts, 1882)
Good general descriptions: Penney & Racek (1968: 117,
pl. 10), Poirrier (1977: 63, Figs. 1-4) and Økland and
Økland (1989:180, Figs. 3-6), Pronzato and Manconi
(2001:32, Figs. 23-24.
Previous records: Southern end of Sørvágsvatn,
Vágar, on a plant stem and a small stone (A. Dampf and
K. vonRosen, 02.09.1912).
New records: AboutlO gemmules from a core taken
at 62°09.4’N, 6°45.8’W in Skálafjørður, Eysturoy. The
gemmules were extracted from a lacustrine layer 93 cm
below the present sea bottom. The layer is dated to about
8560 years B.P.
Material deposilion: Museum fíir Naturkunde der
Humboldt Universitat, Berlin, and Zoological Museum.
University of Copenhagen.
Description of the material (Fig. I): The single recent
sample is a small crust 1 cm thick, and measuring 2

Fig. 1. Spicules of
Racekiela ryderi
(After Anidt, 1928).
x 2 crn. It is of loose consistency and very soft. The
colour in preserved condition is greyish brown. Dermal
membrane and oscules are not visible, the outer layer
probably missing. The skeleton is a network of thin
fibers witli little spongin. Megascleres are spiny, slightly
curved oxea, 272-338 pm long, on average 315 pm, and
9-15 pm thick. Gemmule spicules are amphidiscs of two
size categories. The larger are 40-50 pm long with the
endplates about 20 pm in diameter and divided into 4-8
teeth. The shaft is 6-6.5 pm thick and provided with up
to 10 strong spines. The smaller amphidisc category is
20-30 pm long with the endplates 19-23 pm in diameter
and divided into 15-25 teeth. The shaft is 3-5 pm thick
and smooth or provided with I -2 spines.
The gemmules from the core are in a bad state
compared to recent gemmules, but after some search the
two categories of amphidiscs were found in the wall and
both appearence and size fit R. ryderi. Large amphidiscs
are 42 pm long, with disc about 18 pm in diamter; small
amphidiscs are 26-30 pm long, with disc about 20 pm in
diameter.
Geographical distribution: R. ryderi is a highly
variable amphiatlantic species with main distribution
in eastern North America, from Nova Scotia to Texas,
with a single record from Belize, and from the Atlantic
coast inland into the Mississippi basin. The distribution
in western Europe is, on the other hand, restricted to
scattered records from coastal areas and islands: Sherkin
Island south of Ireland (Tendal, unpubl.), Clare Island
west of Ireland (Stephens, 1912), parts of the coasts of
Ireland (Hanitsch, 1895; Stephens, 1920), the Island
of Mull west of Scotland (Annandale, 1908), the outer
Hebrides (Forrest, 1936; Waterston, 1981), the Faroe
Islands (Arndt, 1928) and western Norway (Økland and
Økland, 1989; 1991).
Remarks: Reinvestigation of Arndts material con-
ftrmed the details of his description (1928) of which
Spárck’s (1934) account seems to have been a mere
reiteration.
The gemmules from the core were deposited in a lake
after the deglaciation about 10,000 years ago. Around
8000 years B.P. what is now the treshhold of the fjord
was overtlown by the sea and Skálafjørður came into
existence (Bennike et al.. 1998).