Fig 1.
Map of study region. Black dots represent bottom trawl stations (RV POLARSTERN cruise PS79) in the vicinity of the South Shetland Islands in March-April 2012.
Sampling depths and biological parameters of octopods collected are summarized in Table 1.
Table 1.
Octopod species examined including biological parameters (Sex, DML = dorsal mantle length, BM = body mass, N = specimen numbers, Depth = sampling depth ranges, and Beaks read = number of beaks that were read to quantify growth increments).
Fig 2.
The two halves of a sectioned upper beak from a female of Pareledone aequipapillae.
Scale bar = 1 mm; The arrow indicates the counting axis.
Fig 3.
Growth increments in the inner surface of the upper beak lateral wall from a juvenile female stage II of P. charcoti (DML 43, BM 24 g).
Left, posterior region close to the border; Center, medial region of the beak; Right, anterior region close to the rostrum where the first increments were formed, showing check marks in the shoulder region (magnification 50x).
Fig 4.
Size distribution at different maturity stages of the most numerous species. Grey circles are outliers.
Table 2.
Results of Mann–Whitney–Wilcoxon test for differences of size or weight between sexes.
Fig 5.
Length-weight relationship of the seven most numerous octopod species. Scale of axes differs between species due to size differences.
Fig 6.
Upper (left) and lower (right) beaks of the five most abundant species of Antarctic octopods analyzed in this study. A—Muusoctopus rigbyae; B—Adelieledone polymorpha; C—Pareledone aequipapillae; D—Pareledone charcoti; E–Megaleledone setebos. Scale bars represent 1 mm.
Fig 7.
Increment width in different regions of the lateral walls of the octopus beaks analyzed.
The anterior region indicates the oldest portion close to the rostrum while the posterior region bear recent formed increments near to the edge of the crest.
Table 3.
Summary of reproductive attributes examined from females and males at advanced maturity of different species.
DML—dorsal mantle length (mm); BM—body mass (g); GSI—gonadosomatic index; Oocyte N.g-1—number of oocytes per gram of BM; Sperm. length—spermatophores length in mm; Sperm. (N)—number of spermatophores per individual; N—specimens examined. Mean values given in parentheses.
Fig 8.
Number of growth increments (mean from two counts) at different maturity stages for the four main species analyzed.
Vertical bars indicate presence of only 1 specimen. The largest specimen of Megaleledone setebos is not included.
Fig 9.
Length frequency distribution of oocytes at different maturity stages for Muusoctopus rigbyae, Pareledone aequipapillae, Pareledone charcoti and Pareledone felix.
Fig 10.
Growth curves showing the relationship between growth increments number (N) and body mass (g) of four species analyzed in this study.
Clockwise species order: M. rigbyae, P. charcoti, P. aequipapillae and M. setebos.
Table 4.
Instantaneous growth rates (G) for four Antarctic octopod species.
Avr BM–Average body mass (g) for the age class. Dash indicates data unavailability.