Winston Ponder retires

Winston Ponder has ‘retired’ – from meetings and admin in the Australian Museum, Sydney - to devote his energies to malacology. We wish him many happy years of fruitful, unfettered research and inspiring teaching.

Cannibalism in giant squid

Zoologists in Tasmania using PCR-based DNA detection among the prey remains in the gut of a male giant squid (Architeuthis dux) identified prey as blue grenadier, a fish that occurs from 450 to 800 m. There were also squid beaks, and DNA from an ingested tentacle fragment indicates the giant squid was a cannibal. 

Source: Deagle, B.E. et al. 2005. J. Hered. 96(4), 417-423.

Bipedal octopuses

Two species of octopus, O. marginatus from Indonesia and O. aculeatus from Australia have been filmed walking backwards on the distal parts of their two most ventral arms. The distal parts of each arm in turn rolls along the suckered edge, like a tank track. The speed of this method of locomotion is faster than their normal polypedal crawl. O. marginatus wraps its other arms around its body and resembles a rolling coconut, while O. aculeatus raises its other tentacles and resembles a clump of algae.

Source: Huffard CL et al. (2005). Science, 307, 1927.

Octopus arms mimic vertebrate limbs

On the other other hand, when an octopus uses an arm to move an object, such as moving a food item to its mouth, Sumbre and colleagues in Jerusalem show that it uses a vertebrate-like strategy. The arm is temporarily reconfigured into an articulated limb with stiff ‘upper arm’, ‘lower arm’ and ‘hand’, with the upper and lower arm segments of almost equal length. However, if the object is grasped some distance from the arm tip, the arm is divided anew into three shorter segments.

Source: Sumbre G. et al. (2005) Nature, 433, 595-6.

Jet flow in squid

A strobe-lit particle imaging study of squid swimming steadily in a moving water plume shows squid produce prolonged jets rather than individual vortex rings which the water plume prevents. Squid are more efficient at higher swimming speeds, but can employ a greater range of strategies (varying the frequency, period, angle and velocity of the jet) at intermediate swimming speeds. Source: Anderson E.J. & Grosenbaugh M.A. 2005. J. Exp. Biol. 208, 1125-46.

Costs of parasitism and of defense in freshwater mussels

Suzanne Mills and colleagues have investigated the remarkable symbiotic relationship between freshwater mussels and the European bitterling, a small fish of the carp family, in a tributary of the River Cam in East Anglia.

The female bitterling first inspects the quality of mussels within a male’s territory before laying eggs through its long ovipositor in the mussel’s gills.  In their latest work, they have found that mussels parasitised by bitterling embryos have significantly reduced ventilation rates, which probably reduces their food intake and survival.  Mussels might then be expected to defend themselves by ejecting the embryos. The evolutionary equilibrium hypothesis suggests that the host’s defense might be constrained if the costs of defence (such as the loss of the mussel’s glochidia) outweighed the costs of parasitism. Brooding female mussels might then be expected to retain more fish larvae than males, but in fact the reserve was found, leaving no support for the evolutionary equilibrium hypothesis. There may, however, be other costs and benefits, and differences in anatomy and ventilation rates may explain the greater ability of Unio to reject eggs compared to Anodonta. The alternative evolutionary lag hypothesis might seem to be supported since bitterling have only been introduced into Britain in the last 100 y, but low egg rejection also occurs in the Czech Republic, where mussels and bitterling have long occurred together.

Source: Mills, S.C. et al. 2005. Anim. Behav. 70, 31-37.

Shell composition doesn’t bias evolutionary record

Molluscan shells composed of calcite are usually better preserved as fossils than those composed of aragonite. This is worrying because it could introduce bias into records of large-scale evolutionary patterns. Susan Kidwell shows that genus duration in bivalves appears to be unrelated to shell composition, or, where apparent, is contrary to the expected bias.

Source: Kidwell, S. 2005. Science, 307, 914-917.

High-speed ballistic tooth release in cone snails

The peptide toxins in the venom of cone snails have been extensively studied, but the biomechanics of propelling the harpoon like tooth into the prey are not fully determined. Joseph Schulz and colleagues now show that the fish-hunting Conus catus first primes the tooth release mechanism before propelling the tooth at a velocity above 3 m s^-1, rather than directly pushing it with the proboscis muscles.

Source: Schulz J.R. et al. 2004. Biol. Bull. 207, 77-79.

Young pond snails learn slower and differently to adults

Juvenile Lymnaea are less capable than adults at learning and remembering not to surface to breath. The three neuron circuit driving aerial ventilation operates differently in juveniles and adults, even when the juveniles were motivated by a period of hypoxia or among a small set of juveniles which were surfacing as regularly as adults.

Source: McComb, S et al. 2005. J. Exp. Biol. 208, 1459-1467.

Scallop sculpture

A 4.1 m stainless steel sculpture by Maggi Hambling on Aldeburgh beach, Suffolk, unveiled in 2003, as a monument to the musician and composer Benjamin Britten.

Snails in Folklore

“The gypsies believe that the Earth-fairies are the foes of every kind of worm and creeping insect with the exception of the snail, which they therefore call the … earthy-horse. English gypsies, and the English peasantry, as well as gypsies, call snails ‘cattle, because they have horns.’ Snails are a type of voluptuousness, because they are hermaphrodite, and exceedingly giving to sexual indulgence, so that as many as half a dozen may be found mutually giving and taking pleasure. ... A snail’s shell forms a powerful fetish for a true believer. A girl can win (illicit) love from a man by inducing him to carry a snail shell which she has had for some time about her person. To present a snail shell is to make a very direct but not very delicate declaration of love to any one.”

Charles Godfrey Leland, 1891, ‘Gypsy Sorcery and Fortune-telling’, cited in ‘The Faber Book of Exploration’ 2002 (B. Allen, ed.).