19 November 2005

Papers read this week

Musical accompaniment: Philip Glass: Etudes for Piano, vol. I.

Villalobos et al. 1995. Life cycle and field abundance of the snail Succinea costaricana (Stylommatophora: Succineidae), a tropical agricultural pest. Rev. Biol. Trop. 43:181-188.
Besides detailed information on the reproduction, development and lifespan of this land snail, the paper also offers some tidbits of interesting facts. For example, the authors report that these snails can reproduce without mating. (Other species of succineids had previously been reported to do so.) This presumably involves selfing, which means that a snail uses its own sperm to fertilize its own eggs (remember, they are hermaphrodites). They also note that one captive snail that had lost its entire shell was able to regenerate another one. Moreover, the authors measured the crawling speed of their snails. Mean speed of 8 juveniles "over horizontal moist filter paper" was 16.2 mm/min. If the snails could maintain that speed for 1 hour, they would travel only about 97 cm, barely a meter. They are slow, aren't they?

Ramos, et al. 2004. Overcoming an evolutionary conflict: Removal of a reproductive organ greatly increases locomotor performance. PNAS 101:4883-4887. Free Full Text
Male spiders in the genus Tidarren are much more smaller than females (see photo below from the original paper). However, the males' pair of pedipalps (appendages in front of the head), used for sperm transfer, are disproportionately large. Males remove one of these large pedipalps before maturing. To test the hypothesis that such large pedipalps might interfere with locomotion and that their removal facilities locomotion, the authors compared maximum speed and endurance of male spiders before and after pedipalp removal. Their results show that pedipalp removal increases both maximum speed and endurance. This is an example of an evolutionary conflict: a structure evolved for one function, in this case, pedipalps for reproduction, impairing other vital activities, in this case, locomotion. And this appears to have led, as the authors note, to the evolution of a novel behavior: removal of one pedipalp.


This guy certainly needs penis, or rather pedipalp enlargement.

Blackstone, et al. 2005. H2S Induces a Suspended Animation-Like State in Mice. Science 308:518.
When mice breathe small amounts of hydrogen sulfide (80 ppm), their metabolism is reversibly inhibited and their body temperature lowered. For example, after 6 hours, their metabolic rate dropped by ~90%. The authors speculate that hydrogen sulfide-induced suspended animation might be useful for various medical conditions (in humans, not mice), such as trauma and during surgery.

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