The life cycle strategy of the ice-associated copepod, Paralabidocera antarctica (Calanoida, Copepoda), at Syowa Station, Antarctica

The vertical distribution, abundance, population structure and life cycle of the ice-associated copepod, Paralabidocera antarctica was studied in the fast ice near Syowa Station (69°00'S, 39°35'E) in the eastern part of Lützow-Holm Bay in 1970, 1975 and 1982. The results indicated that P. antarctica inhabited the ice-seawater interface throughout the year with a one year life cycle and was actually present in the sea ice for most of the year except the summer. P. antarctica overwintered as naupliar stages (NIV-NV) with slow development in sea ice during winter. P. antarctica population then developed rapidly and attained adulthood in the water just beneath the sea ice during spring-summer. P. antarctica depended entirely on ice algae for food throughout its whole life-span, suggesting that the ice-seawater interface provides favourable food conditions for P. antarctica. The slow development in naupliar stages in sea ice and short copepodite life span in the water suggest that P. antarctica may adapt its growth strategy to suit the varying fast ice/water interface environment.

Vertical distribution of Paralabidocera antarctica (Copepoda : Calanoida) in Ace Lake, Antarctica, in summer

In an ice-covered (thickness 1.68 m) meromictic lake, in early January 1982, a vertical profile of the population density of P. antarctica showed two peaks: from 7 to 130 cm beneath the ice, and just above the anoxylimnion at 10.0-10.5 m. Copepodite stages 111 and IV were dominant in the first (shallow) peak and stage CV was dominant in the second (deep) peak. Significantly more adult males than females were present within an entire vertical column of oxylimnion, but more adult females than males were present in a stratum 30 cm thick immediately beneath the ice.

The Occurence of Paralabidocera antarctica (I. C. Thomson) (Copepoda : Calanoida : Acartiidae) in an Antarctic Saline Lake

The systematic position and phylogenetic derivation of Paralabidocera is discussed. The female urosome and most of the appendages of a lacustrine form of P. antarctica are figured, as are the female urosome and male fifth legs of the paratypes of a synonym (P. hodgsoni Wolfenden). The significance of the tolerance of a broad range of salinities by P. antarctica for concepts of evolution of euryhalinity within the Acartiidae is pointed out.