Náttúrufræðingurinn - 1985, Blaðsíða 24

sem náttúruvalið verki á sambýlið í
heild sinni — en allir einstaklingar
sambýlis eru af sömu arfgerð (gena-
týpu), þar sem þeir eru myndaðir kyn-
laust af sama einstaklingi í upphafi (úr
blasta eða lirfu) — sé allur valþrýsting-
ur fljótur að segja til sín. Ef til vill gæti
F. sultana svarað slíkri samkeppni frá
P. repens á þennan hátt. Skýringarinn-
ar á því að báðar tegundirnar dafna
jafn vel og raun ber vitni sé því að leita
í árangursríkari framleiðslu lirfa F.
sultana, sem vegi upp að einhverju
leyti dreifingarhæfni og lirfufram-
leiðslu P. repens.
HEIMILDIR
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tions of Michigan ectoprocta, and dyna-
mics of natural populations of Plu-
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95-123.
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among the ectoprocta: Physical and
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vatnadýr á íslandi. - Náttúrufr. 43:
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Smaller Coelomate Groups. Vol. 5. —
McGraw-Hill Book Company, New
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laemata. — Zool. Verh. Leiden 93: 1—
159.
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macroinvertebrate fauna, with special
reference to Chironomidae (Diptera)
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SUMMARY
Aspects of the life-cycles of
Fredericella sultana and
Plumatella repens
(Bryozoa : Phylactolaemata)
in the lake Urriðakotsvatn
south-west Iceland
by
Sigmar Arnar Steingrímsson
Marine Research Institute
Skúlagata 4
121 Reykjavík
A brief account on the general biology
of Bryozoans is given and the life-cycles of
Fredericella sultana (Blumenbach) and
Plumatella repens (Linnaeus) in the lake
Urriðakotsvatn south-west Iceland is
described (Fig. 1). The study was made in
April to September 1981.
Germination of statoblasts of F. sultana
started soon after the ice had melted in
early April (temperature range 3 to 8°C.
70