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In the only known instance of a mammal
acquiring a lethal toxin from a plant for defence, researchers
have discovered that the African crested rat gets its
poison from the Acokanthera tree, the same source used by East
African hunters for their poison arrows.
The rodent applies the poisonous plant toxin
to sponge-like hair on its flanks. It is a fascinating example
of how a species can evolve a unique set of defences in response
to pressure from predation.
Scientists have long suspected that the
African crested rat is poisonous, primarily due to the animal’s
specialized behaviour, such as exposing a black-and-white
colouration on its flanks when threatened by predators, and
accounts of dogs becoming ill or dying after encounters with the
rat. The rat gnaws and masticates the bark of the tree,
(avoiding the leaves and fruit) and applies the ‘slaver’ to
special hairs on its flanks, which have a unique structure. When
examined under the electron microscope they were found to have a
perforated cylindrical structure that facilitated the rapid
absorption of the poisonous saliva. Interestingly, this poison,
ouabain, has also been used by doctors for centuries as a
clinical treatment against congestive heart failure.
 A
dolphin that lives around the east coast of South America called
the Guiana Dolphin (Sotalia
guianensis)
resembles the much more common Bottlenose Dolphin and like all
of the toothed cetaceans it hunts and locates food using sound,
but researchers have discovered that at close range, it can also
sense
electrical signals. They are not as sensitive
as sharks and rays, but can detect signals of the same size as
those produced in water when fish move their muscles.
Electroreception is well known in fish and
amphibians, but until now the only mammal example was the
platypus. The researchers first found that structures on the
animals head were probably sensory organs, then found that it
could detect electric fields in water.
The Guiana Dolphin feeds a lot on the bottom
of the sea, and it lives in water where there can be a lot of
silt and mud suspended, so electrolocation would be a great
benefit in these conditions.
A 78-million-year-old, 15•4 ft long fossil of an
adult plesiosaur,
Polycotylus
latippinus, one
of the
giant, carnivorous, four-flippered reptiles
that lived in the Mesozoic Era was found to be pregnant with the
fossilized remains of the embryo inside.
The embryonic skeleton contained within,
shows much of the developing body, including ribs, 20 vertebrae,
shoulders, hips, and paddle bones. The research establishes that
these dual fossils are the first evidence that plesiosaurs gave
birth to live young, rather than hatching their offspring from
eggs on land.
Although live birth (or viviparity) has been
documented in several other groups of Mesozoic aquatic reptiles,
no previous evidence of it has been found it the important order
of plesiosaurs.
The First Basking Shark of the year turned up off
Roskilly on March 20th,
seen by BDMLR divers at a depth of 8 metres. There were 4 more
sightings in April, these were 3 singles and a pod of three
young ones and a further 4 reports during May, which were 3
singles and a pair which makes 12 sharks in total up to the end
of May. During the same period last year there were 46 reported
sightings with well over 100 sharks seen. I wonder if the sharks
are still here but the plankton is remaining deeper and the
sharks
feeding deeper, like the first one seen in March, and so the
sharks are not being seen. Only 11 were reported in June, 12 in
July and 11 in August, so only 80 have been reported up to the
end of August.
Bottlenose
Dolphins were reported 5 times and Common Dolphins 17 times, 5
other reports of small pods of unidentified dolphins were
probably Bottlenose and one report of a pod of over 50 off St
Agnes were probably Common Dolphins.
Twentyfive
reports of Harbour Porpoises were all between Porthgwarra and
Pendeen, largest pod was of 18 off Gwennap Head. 6 reports of
Minke Whales were of 4 singles and 2 pairs.
There were 13
reported sightings of Ocean Sunfish 11 were single fish and
there was a pair off Gwennap Head on the 14th and 4 there on the
2nd of August. 25 reports of Grey Seals were all from the
Gwennap Head area and there was a reported sighting of 3 Blue
Sharks from a boat off The Lizard on the 28th of the month.
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