giant Antarctic isopod Glyptonotus antarcticus

Glyptonotus antarcticus is found throughout Antarctica and the Antarctic Peninsula, South Shetland Islands, South Orkney Islands, South Sandwich Islands, and South Georgia Island from intertidal to 790 meters depth [6,7]. G. antarcticus is up to twenty centimeters in length and seventy grams in weight [8]. The color of G. antarcticus varies but generally is olive-brown, with its appendages less dark and yellowish; keels, segment margins, and coxal plate margins are lighter with a red-brown tint [6].

Glyptonotus antarcticus is an omnivore and eats what it finds, including brittle seastars, gastropod molluscs, isopods (including small ones of its own species -- cannibalism), sea urchins, pelecypods, carrion, krill, and polychaete worms (including Flabelligera mundata); food availability is more important than food type [3,6,7,9]. Its large, powerful mouth parts enable it to dine on hard animals like brittle seastars and sea urchins [3]. As a large benthic predator and scavenger, its ecological role is analogous to that of crabs and lobsters in temperate waters. G. antarcticus is nocturnal with a diurnal activity pattern; during the day, it seeks shelter under stones and algae and, at night, it hunts for food [6]. G. antarcticus must be fed at least twice a week to stay healthy [6].

Here Glyptonotus antarcticus is poking around in the newly formed anchor ice in shallow water under the McMurdo sea ice with the seastar Odontaster validus alongside. The body cuticle of G. antarcticus has microstructures discouraging settlement by foraminifera and larval stages of sessile organisms [1]. The armored spiny body of G. antarcticus protects it well when it's fully grown; small ones are prey items though. Its predators are notothenid fish (Notothenia neglecta [2] and Trematomus bernacchii [3]) and the octopus Pareledone sp. [4]. G. antarcticus lives five to eight years and the interval between moults is 100 - 730 days [6].

You can see a newly-released juvenile just below the parent's antenna.

Glyptonotus antarcticus has a non-seasonal breeding cycle and young are released throughout the year [6].

Glyptonotus antarcticus incubates and raises its young in a brood pouch (marsupium) as an adaptation to slow development in such cold and adverse conditions [5,6]. Here are pre-emergent young taken from the brood pouch, with their yolk still attached. The developing young ingest non-viable eggs (adelphophagy) and maternal secretions [5].


Here's a closer view of a newly-released juvenile Glyptonotus antarcticus on the tubular sponge Sphaerotylus antarcticus.

Female G. antarcticus usually die after releasing their brood but a few may moult and breed again [6].



The piscicolid leech eggs Glyptonotobdella antarctica is known to move between the giant Antarctic isopod Glyptonotus antarcticus, Sterechinus sea urchins, and some species of the octopus Pareledone [10].

As shown here, egg cocoons of this leech can be found on the ventral (under) side of the giant Antarctic isopod Glyptonotus antarcticus [10].



A closer view of a leech egg cocoon on Glyptonotus antarcticus.

Most likely the leech Glyptonotobdella antarctica moves between different hosts and their potential prey [10].

1: Zoomorphologie, 94(2):209-216, 1980; 2: Antarctic Science  2(3):207-213, 1990; 3: Royal Society of New Zealand, Transactions, Zoology, 8(15):163-168, 1967; 4: Polar Biology 13(5):347-354, 1993; 5: Polar Biology 13(3):145-149, 1993; 6: Antarctic Isopoda Valvifera. JW Wagele. Koenigstein ; Champaign, Ill. : Koeltz Scientific Books, 1991; 7: Antarctic Valviferans (Crustacea, Isopoda, Valvifera) : New Genera, New Species, and Redescriptions. A Brandt. Leiden ; New York : EJ Brill, 1990; 8: Ninth European Marine Biology Symposium. H Barnes, ed. Aberdeen : Aberdeen University Press, 1975. pp 707-724; 9: Peter Brueggeman, personal communication (observed G. antarcticus attacking and eating Flabelligera mundata on time-lapsed video), 1999; 10: Polar Biology 13(5):347-354, 1993

Text ©Peter Brueggeman. Photographs ©Peter Brueggeman, Paul Cziko & Norbert Wu. Photographs may not be used in any form without the express written permission of Peter Brueggeman, Paul Cziko & Norbert Wu. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?