Heligmosomoides polygyrus

January 27, 2012 § 2 Comments

Heligmosomoides polygyrus

Preliminary sketch for drawing to measure 1.5m x 1.5m.

Heligmosomoides polygyrus is a common nematode found in the duodenum and small intestine of woodmice and other rodents. It is often used to model human helminth infection in laboratory mice.

These worms are 5–20mm in length and bright red due to the pigmentation of their tissues. They are usually heavily coiled, with the female having 12–15 coils and the male 8–12. The male can be distinguished from the female by a prominent copulatory bursa and two long, thin spicules at the posterior end.

They have a direct life cycle. The eggs pass out with the faeces of the host into the environment. After 2 days they hatch as larvae which are about 300μm in length. The larvae moult 3 days later but retain the shed cuticle for protection. It is at this point they become infective. The larvae shed the outer protective sheath after they are eaten by a suitable host. The larvae then penetrate the submucosa of the duodenum where they undergo 2 further moults. About 7 days later the male and female adult worms emerge into the lumen of the duodenum where they attach to the epithelial layer and begin to feed off the contents of the gut. The adult worms mate and eggs are shed in the faeces. The complete life cycle from egg to egg takes a minimum of 15 days, and the female worms will live inside their host for 8 months.

These worms often form cysts in the wall of the intestine. These cysts often become infected with bacteria, but it is not yet known if these are harmful to the host.

This nematode has been previously called Nematospiroides dubius.

Methuselah

January 11, 2012 § Leave a comment

Methuselah

Sketch for life-sized drawing of bowhead whale (Balaeana mysticetus) – to measure 10m x 6m.

The bowhead whale (Balaena mysticetus) is a baleen whale of the right whale family Balaenidae. A stocky dark-colored whale without a dorsal fin, it can grow to 20 m (66 ft) in length. This thick-bodied species can weigh 75 tonnes (74 long tons; 83 short tons) to 100 tonnes (98 long tons; 110 short tons), second only in mass to the blue whale, although the bowhead’s maximum length is less than that of several other great whales. It lives entirely in the nutrient rich Arctic and sub-Arctic waters; unlike other whales that migrate to feed or reproduce in low latitude waters. It is also known as Greenland right whale or Arctic whale. American whalemen called it the Steeple-top, Polar whale, or Russia or Russian whale. The bowhead has the largest mouth of any animal and is perhaps the longest-living mammal.

Bowheads were once thought to live 60 to 70 years, similar to other whales, however, discoveries of 19th century ivory, slate and jade spear points in freshly killed whales in 1993, 1995, 1999, and 2007 triggered research based on structures in the whale’s eye, suggesting that at least some individuals reached 150–200 years old. The amino acid racemization process has provided the scientific basis for these claims, although this process is controversial and has failed to correlate well with other dating methods.

In May 2007, a 50 tonnes (49 long tons; 55 short tons) specimen caught off the Alaskan coast was discovered with the head of an explosive harpoon embedded deep beneath its neck blubber. The 3.5 inches (89 mm) arrow-shaped projectile was manufactured around 1890 in New Bedford, Massachusetts, a major whaling center, suggesting the animal may have survived a similar hunt more than a century ago.

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