Biology of the king crab Paralomis birsteini on the continental slope off the western Antarctic Peninsula

Abstract

Predatory king crabs (Lithodidae) structure benthic communities in their native habitats and cause shifts in the composition of benthic assemblages when introduced to new environments. Cold temperatures have apparently excluded skeleton-breaking predators from the continental shelf around Antarctica for millions of years, but recent increases in sea temperatures off the western Antarctic Peninsula (WAP) may be allowing lithodids to return. Imaging surveys have revealed dense populations of the lithodid Paralomis birsteini (Macpherson 1988) living on the continental slope off the WAP, but the biology of these populations remains poorly understood. We collected 51 adult P. birsteini in a trapping study on the slope off Marguerite Bay, WAP from depths of 1200-1400 m. Of the 51 crabs, 42 were males and 9 were females. Four females were ovigerous, carrying eggs at various stages of development. Rates of parasitism and limb regeneration were comparable to populations of lithodids elsewhere in the world, although the proportion of limb loss was relatively high. Externa of the parasite Briarosaccus callosus was obvious in both males and females, with one individual bearing hyperparasites (probably Liriopsis pygmaea). Gill necrosis was also observed in several dissected males. The success of contemporary lithodid populations on the Antarctic slope suggests they have the potential to expand upward to the continental shelf.

Characterization of the exoskeleton of the Antarctic king crab Paralomis birsteini

“…The waters over the continental slope and rise (~500–2,000 m) are already undersaturated with respect to the specific Mg calcite mineralogy of many species that secrete high‐Mg calcite (Lebrato et al., ). Predatory king crabs (Lithodidae) currently inhabiting the Antarctic slope (Aronson et al., ; Smith, Aronson, Steffel et al., ; Smith, Aronson, Thatje et al., ) may be negatively impacted by the limited availability of CaCO 3 resources and the cold seawater temperatures, and as a result, their exoskeletons may be weakly constructed compared with temperate and tropical crustaceans from shallow, nearshore waters. Predation pressures on lithodids in Antarctica are thought to be low, however (Amsler et al., ; Aronson et al., ; Bansode, Eastman, & Aronson, ; Eastman et al., ), and consequently, they may allocate their limited resources to building their predatory chelae rather than their protective carapaces.…”

Population expansion of an Antarctic king crab?

“…Crabs were trapped at 1200-1400 m depth in a 100 × 100 km area off Marguerite Bay centered at 66°42'S, 72°12'W during an oceanographic cruise in 2015 (Smith et al 2017). Leg muscles were preserved in >70% ethanol and stored at or below -20°C.…”

“…King crabs (Lithodidae), which inhabit the slightly warmer waters of the upper continental slope, could be the vanguard of an invasion of shell-crushing predators in Antarctic shelf habitats (Aronson et al 2015(Aronson et al , 2017. Whether they can be considered invasive on the slope or whether they have been present there for millions of years remains an open question (Griffiths et al 2013).…”

Climate change and the threat of novel marine predators in Antarctica

“…, Smith et al. ). There appear to be no environmental barriers, thermal or otherwise, to prevent them from expanding upward onto the outer shelf (Thatje et al.…”

“…Sea temperatures over the slope and shelf off the western Antarctic Peninsula (WAP) have risen by as much as 1.5°C over the past 50 yr (Schmidtko et al 2014). Recently, lithodids have been recorded on the continental slope off Antarctica (Arana andRetamal 1999, Garc ıa Raso et al 2005), where they occur commonly in at least some areas (Aronson et al 2015b, Smith et al 2017. There appear to be no environmental barriers, thermal or otherwise, to prevent them from expanding upward onto the outer shelf (Thatje et al 2005, Smith et al 2012, Aronson et al 2015b, Smith et al 2017.…”