Hole boring of crustacean prey by the octopus Eledone cirrhosa (Mollusca, Cephalopoda)

Abstract

Eledone cirrhosa has been found to make a borehole in the carapace of a high proportion of its crustacean prey. This is the first account of drilling in crustaceans by octopus. The frequency of incidence of the boring behaviour varied between prey species from 17 to 93% of those killed. The incidence of boreholes was higher in crabs killed by small octopuses. Using crabs mainly of the genera Cancer, Carcinus, Corystes and Macropipus, the distribution and orientation of the boreholes was recorded. The boreholes occurred in any part of the carapace but the great majority were found close to the mid‐line and in the posterior half. The long axis of the oval penetration was usually aligned with the anteroposterior axis of the crab. The Mediterranean species Eledone moschata was also found to bore crabs, and newly hatched juveniles of this species are capable of boring as early as their second killing of a live crab. No evidence was found that Octopus vulgaris normally bores the carapace of crabs.

An Overview of Predation Evidence Found on Fossil Decapod Crustaceans With New Examples of Drill Holes Attributed to Gastropods and Octopods

“…Position of Drill Holes.-The few drill holes in the propodi are on both the inner (2) and outer (1) sides of the propodus, whereas Wirtz (2005) noted that drill holes attributed to octopods were always located on the inner side of the propodus. The position of these drill holes on carapaces is mostly recorded from the dorsal side of the carapace for modern crabs (Boyle and Knobloch, 1981;Guerra and Nixon, 1987), which is in agreement with the single specimen reported here. Although the elbow crab Platylambrus sp.…”

“…3), with the outer drill-hole diameters usually being ,1 mm (Table 3), which is comparable to, and somewhat smaller than, those found in extant decapods (see Boyle and Knobloch, 1981;Nixon and Boyle, 1982;Guerra and Nixon, 1987;Mather and Nixon, 1995), and smaller than those observed in mollusks (e.g., Arnold and Arnold, 1969;Nixon and Maconnachie, 1988). The form and size of these drill holes conform with drill holes produced by octopods and reported from extant invertebrates including decapods, even though variation exists in the shape and form of these drill holes (e.g., Arnold and Arnold, 1969;Boyle and Knobloch, 1981;Nixon and Maconnachie, 1988). Bromley (1993) erected the ichnotaxon Oichnus ovalis for these oval drill holes attributed to octopods.…”

“…They also reported that the hermit crab Pagurus bernhardus was drilled on the dorsal carapace, and further mentioned (their table 1) that the lobsters Homarus vulgaris (5Homarus gammarus) and Nephrops norvegicus were drilled, although the location of the drill holes was not provided. Drilling is not restricted to adult octopods: Boyle and Knobloch (1981) also found that juveniles of Eledrone moschata drilled crab carapaces and chelipeds.…”

“…Surprisingly, Iribarne et al (1993) found that Octopus tehuelchus drilled the gastropod shell Tegula patagonica inhabited by the hermit crab Pagurus sp. In the most comprehensive study on octopods drilling decapods, Boyle and Knobloch (1981) found that Eledrone cirrhosa drilled a wide variety of crabs, mostly in the center of the dorsal carapace or slightly posterior to it. They also reported that the hermit crab Pagurus bernhardus was drilled on the dorsal carapace, and further mentioned (their table 1) that the lobsters Homarus vulgaris (5Homarus gammarus) and Nephrops norvegicus were drilled, although the location of the drill holes was not provided.…”

“…Predators of extant marine decapods are fairly well known and include a wide variety of bony and cartilaginous fish (e.g., Warner, 1977;Heck and Wilson, 1987;Phillips, 2006), decapods (e.g., Heck and Wilson, 1987) including conspecific decapods (5cannibalism) (e.g., Kurihara and Okamoto, 1987;Hines and Ruiz, 1995), birds such as the herring gull, curlew, and eider (Cadée, 1994(Cadée, , 1995(Cadée, , 2007, octopods (e.g., Boyle and Knobloch, 1981;Runham et al, 1997), gastropods (Huelsken, 2011), cuttlefish (e.g., Halm et al, 2000;Alves et al, 2006), the shelled cephalopod Nautilus (Ward and Wicksten, 1980), and mammals including man (Warner, 1977).…”