I came across this interesting article. It shows that chimps can plan forward and that they have the ability to foresee particular mental states. This also implies that they are self aware. This is one of the last areas that the religious have clung on to in a vain attempt to claim that humans are somehow special and outwith the rest of nature.
Showing posts with label Zoology. Show all posts
Showing posts with label Zoology. Show all posts
Tuesday, 10 March 2009
Sunday, 8 February 2009
Maiacetus Inuus: A New Transitional fossil Of The Whale Lineage
Whale evolution is something that I have blogged on before. This paper describes the discovery of yet another transitional fossil between artiodactyls and whales. The new species is called Maiacetus inuus, which means mother whale of inuus ( Inuus being the Roman god of fertility). It is so called, because one specimen was pregnant (the foetus is the blue shaded object below). What is interesting is that it is in a head down position; modern whales give birth tail first. This suggests that birth still took place on land. Not surprisingly, it is found in the right part of the world to be an intermediate form (Pakistan) and its morphology dates to the correct era too; 47.5 million years old. This makes it older than the more whale like Basilosaurids, and younger than the more primitive Ambulocetus, Indohyus and Pakicetids.
Sunday, 1 February 2009
Pesky Pistol Shrimps
I have a pistol shrimp in my reef aquarium. They are supposed to be safe with other inhabitants, but I found one of the cleaner shrimp dead and a couple of sexy shrimp have gone missing (I presume they are so called because they "dance" while they walk). I did a bit of research and apparently not all species are safe and found the video below of one stunning a cleaner shrimp. This is quite fascinating - when the little bastards are not eating their tank mates.
They have a specialised claw that sends out a violent jet of water and a sound wave that whacks its prey. This video goes into the mechanics of the sound production.
This hunting/defense adaptation is also a problem for deluded Young Earth Creationists who believe god made all animals vegetarian. How did they get this adaptation without evolution? No doubt they will pull some bollocks out their collective chuffs like god intended them to eat coconuts and the snap breaks the shell.
A final interesting thing about these shrimp is that they often enter a symbiotic relationship with certain species of goby. The goby provides the lookout and bits of food and the shrimp provides a protective burrow and firepower. This an example of being co-operative yet selfish. It is such a creationist lie that natural selection means kill everything.
Anyway, I wonder who would win in a square go between a pistol shrimp and a mantis shrimp (which can deliver a blow equivalent to being hit by a .22 bullet). Following Bruce Lee's advice of using your longest weapon, I would bet on the pistol shrimp. All we need now is Harry hill to proclaim Fiiiiight!
Tuesday, 4 November 2008
Shrimp On A Treadmill
This video shows a shrimp on a treadmill. The study was aimed at comparing the difference between healthy and sick shrimps in travelling to get food. Not surprisingly healthy ones were faster and ran for longer than sick ones. What is surprising however, is the fact that the healthy ones can run up to 66 feet a minute and keep it up for 3 hours. Beat that Paula Radcliffe - and it doesn't have to stop to piss in public either.
Monday, 11 August 2008
Sexually Deviant Monosexual Fish
Lee asked for some more details on that sexually deviant little fish the Amazon molly (Poecililia formosa). It not only violates leviticus 18:23 , but also laughs at god's hybridisation laws (Lev 19:19) so I’m happy to oblige.
To remind you, they are an all female species that require males of closely related species to reproduce – hence their naming after the tribe of Greek mythology. They are native to the area between the Rio Grande and Tuxpan in Northeast Mexico. It is thought they arose around 100 000 years ago (about 120 000 generations) through the hybridisation of two closely related species; a female Poecilia mexicana and a male Poecilia latipinna. This is the same genus the popular Guppy (P. reticulata) belongs to. This group are unusual in that fertilisation is internal. The male has a modified anal fin called a gonopodium, that acts as a penetrative organ (techno speak for love pump). This can be a significant proportion of the male’s body length, particularly in the genera Priapichthys and Phallichthys (below). No prizes for guessing what the names mean.
Normally, eggs and sperm contain half the number of chromosomes of normal body cells. Upon fertilisation, the normal number is made up – half from the egg and half from the sperm. P. formosa females however, produce eggs that have a full complement of chromosomes, but require sperm from a closely related species (such as the two ancestral species or P. latipunctata and more rarely P. sphenops) to start off the developmental process, but the overwhelming number of offspring receive no genetic input from the male. They are effectively clones of the female. Not much is known about the mechanism, but penetrating the egg can be enough to trigger division. It has been known for a long time that physically piercing the eggs of some species is enough to trigger the first few cellular divisions of embryo formation.
There are some interesting costs and benefits to this system of reproduction. The benefits include the fact that all members of the species can produce offspring; all off which are identical to the parent. There is also an added bonus that beneficial mutations are more likely to survive. It therefore may be possible for unisexual species to take over a habitat. However, one of the drawbacks is that this species absolutely needs males of competing species. Another is that there is no genetic exchange between clones. This would be bad should a new parasite evolve. Another problem is that deleterious mutations can’t be replaced through sex with non affected individuals. In fact, it is estimated that this species would only survive for 70 000 years before accumulated mutations made it go extinct. This principle is called Muller’s Ratchet.
These is some evidence that in very rare occasions, the males can contribute to the genome of the offspring as individuals are occasionally with three or even four sets of chromosomes (four sets could potentially allow the species to one day become sexual again as chromosomes have to have an identical partner to form normal eggs and sperm). Another rare mechanism is that small sub genomic amounts of DNA may come from the sperm. This could form minchromosomes. This allows parts of these chromosomes to replace mutated genes to be repaired by cutting them out and replacing them. There is at least one report that only the somatic (body) cells receive these minichromosomes – and only a small proportion at that. So in this case at least, the minichromosomes can not be transferred to the offspring. There still seems to be a mystery about how this species still exists. Another simpler explanation might be that the species is constantly being re-created through new hybridisations.
There is also a perceived cost to the parasitized males – they waste sperm and resources mating with the wrong species – a mating that will decrease their reproductive fitness. However, it turns out showing interest in another species actually makes hisown females more interested in him. Apparently this works with women too – show interest in the friend of the one you are interested in and that will make the one you are interested in more competitive..
Finally, some species of shark can do without males altogether – at least in the short term.
To remind you, they are an all female species that require males of closely related species to reproduce – hence their naming after the tribe of Greek mythology. They are native to the area between the Rio Grande and Tuxpan in Northeast Mexico. It is thought they arose around 100 000 years ago (about 120 000 generations) through the hybridisation of two closely related species; a female Poecilia mexicana and a male Poecilia latipinna. This is the same genus the popular Guppy (P. reticulata) belongs to. This group are unusual in that fertilisation is internal. The male has a modified anal fin called a gonopodium, that acts as a penetrative organ (techno speak for love pump). This can be a significant proportion of the male’s body length, particularly in the genera Priapichthys and Phallichthys (below). No prizes for guessing what the names mean.
Normally, eggs and sperm contain half the number of chromosomes of normal body cells. Upon fertilisation, the normal number is made up – half from the egg and half from the sperm. P. formosa females however, produce eggs that have a full complement of chromosomes, but require sperm from a closely related species (such as the two ancestral species or P. latipunctata and more rarely P. sphenops) to start off the developmental process, but the overwhelming number of offspring receive no genetic input from the male. They are effectively clones of the female. Not much is known about the mechanism, but penetrating the egg can be enough to trigger division. It has been known for a long time that physically piercing the eggs of some species is enough to trigger the first few cellular divisions of embryo formation.
There are some interesting costs and benefits to this system of reproduction. The benefits include the fact that all members of the species can produce offspring; all off which are identical to the parent. There is also an added bonus that beneficial mutations are more likely to survive. It therefore may be possible for unisexual species to take over a habitat. However, one of the drawbacks is that this species absolutely needs males of competing species. Another is that there is no genetic exchange between clones. This would be bad should a new parasite evolve. Another problem is that deleterious mutations can’t be replaced through sex with non affected individuals. In fact, it is estimated that this species would only survive for 70 000 years before accumulated mutations made it go extinct. This principle is called Muller’s Ratchet.
These is some evidence that in very rare occasions, the males can contribute to the genome of the offspring as individuals are occasionally with three or even four sets of chromosomes (four sets could potentially allow the species to one day become sexual again as chromosomes have to have an identical partner to form normal eggs and sperm). Another rare mechanism is that small sub genomic amounts of DNA may come from the sperm. This could form minchromosomes. This allows parts of these chromosomes to replace mutated genes to be repaired by cutting them out and replacing them. There is at least one report that only the somatic (body) cells receive these minichromosomes – and only a small proportion at that. So in this case at least, the minichromosomes can not be transferred to the offspring. There still seems to be a mystery about how this species still exists. Another simpler explanation might be that the species is constantly being re-created through new hybridisations.
There is also a perceived cost to the parasitized males – they waste sperm and resources mating with the wrong species – a mating that will decrease their reproductive fitness. However, it turns out showing interest in another species actually makes hisown females more interested in him. Apparently this works with women too – show interest in the friend of the one you are interested in and that will make the one you are interested in more competitive..
Finally, some species of shark can do without males altogether – at least in the short term.
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