14 August 2011 - 1 Sea Pen Video

A couple of days ago, I wrote about sea pens. Today, youtube suggested the following video which shows sea pens contracting to bury themselves under the sand over a four hour period. It's a clip taken from the BBC's Ocean series, so I hope it's visible outside the UK.

11th August 2011 - 1 First Pencils, Now Pens - Pen Urchins

Back in April, I wrote about the beautiful pencil urchins. Today, I came across this lovely collection of photographs of sea pens, so I thought I'd carry on with the stationary theme.

Name

The sea pens are types of soft coral of the order Pennatulacea, sub order Subselliflorae. The name 'sea pen' arises from their feather-like appearance which resembles a quill pen.

Photo by fiveinchpixie

The visible part of the sea pen can be up to 2 m in some species, such as the tall sea pen which can be found off the west coast of Scotland.

Life Cycle

A sea pen is a colonial animal, which means it is made up of individual polyps which together function as a whole animal. It begins life as a larva which roots itself and then develops into a stalk. This stalk is called a rachis. It has a root-like structure at its base which anchors it to the sea floor. Both this and this stalk are strengthened by calcium carbonate. The feather-like protrusions are made up of two new types of polyps formed through asexual reproduction. These polyps are responsible for feeding (gastrozoids) and respiration (siphonozoids). The gastrozoids capture food while the siphonozoids move water around to allow for gas exchange.

Some species reproduce by releasing eggs and sperm into the water, whereas in others the female retains the eggs and fertilisation is internal. The developing embryos are brooded until they have reached an advanced larval stage when they are released into the water, where they root to form new pens.

Habitat

Sea pens prefer deeper water, from 10 m to 2 km deep, where they are less likely to be uprooted. They tend to stay in one place but can re-establish themselves if necessary. They position themselves so currents ensure a steady flow of plankton, their main source of food.

Threats and Defences

Unfortunately, sea pens are often destroyed by prawn trawlers and dredgers as well as being prey for sea stars and nudibranchs. In defence, a sea pen may luminesce or deflate and retreat completely underground.

Sources

1. http://en.wikipedia.org/wiki/Sea_pen
2. http://www.bbc.co.uk/nature/blueplanet/factfiles/jellies/seapen_bg.shtml
3. http://www.naturalengland.org.uk/ourwork/marine/protectandmanage/mpa/mcz/features/habitats/seapen.aspx
4. http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3353#
5. http://www.advancedaquarist.com/2003/10/inverts
6. http://www.ehow.com/about_6418563_sea-pens.html

2nd August 2011 - 1 Placenta absorbed to protect brain in mice foetuses

Source: Naturenews: Placenta to the rescue - Zoë Corbyn

When a pregnant mouse is starved, the placenta breaks itself down to provide a steady supply of food to the foetus. The stage of development studied was crucial for hypothalamus development, and this uninterrupted supply of food protects it from damage. This part of the brain controls primal instincts, including maternal instincts. 

Is this result paralleled in humans? It is unknown and it would be unethical to carry out similar research on people but it is possible that some information may be obtained by studying the placenta after birth.

5th May 2011 Sparrow

Yesterday this cute little fellow was sitting on the fence in our garden waiting to be fed by its parent.

24th April 2011 Cockroaches

This brought back some memories for me of an amazing lady called Alice Gray (1914-1994) who was an entomologist at the American Museum of Natural History in New York. She kept pet cockroaches in her office there including some rather large Madagascar hissing cockroaches. I spent 4 1/2 months with her, learning about insects and origami. One very important lesson I learnt from her generosity was that to accept a gift is to allow the person the joy of giving, and to refuse is to deny them that.

18th April 2011 Pencil Urchin

Today  Pharyngula posted a picture on his blog which he didn't identify. In the comments, it was suggested that it is a pencil urchin so I thought I'd take a closer look at these strange creatures.

There are three different types of slate pencil urchin

• Eucidaris tribuloides found in the Atlantic Ocean, close to the shore,
• Heterocentrotus mammillatus found in the tropical waters of the Indo-Pacific region, but mainly Hawaii,
• Heterocentrotus trigonarius also found in the tropical waters of the Indo-Pacific region. 

Eucidaris tribuloides
Photo: Nick Hobgood (Wikimedia Commons)

Heterocentrotus trigonarius
Photo: David Burdick (NOAA)

Heterocentrotus mammillatus
Photo: Dr. Dwayne Meadows, NOAA/NMFS/OPR

Their spines are made from aragonite, which is a form of calcium carbonate.

Eucidaris tribuloides

These pencil urchins are brown to reddy brown. They range from about 2-5 inches in size. Their long spines are arranged in 10 rows with smalled spines between. Broken spines can be replaced.  The colour of their spines depends upon which algae covers them.

Their habitat is  a shallow coastal one up to depth about 50 m.  They are often found in seagrass beds, under rocks or in coral crevices. Their main diet is algae.

Heterocentrotus mammillatus

These slate pencil urchins are bright red. They have three types of spines. The longest are triangular which keep predators at bay. Underneath, they have shorter, flatter spines to clamp onto the reef. Finally, the whole body is encased in flat, armour-like spines.

Heterocentrotus trigonarius

These have longer spines than  Heterocentrotus mammillatus, although I can't find any precise details on either species which would enable this to be used to distinguish them.

Carbon Dioxide Levels in the Sea

In tests on various sea creatures, some built more shells when dissolved carbon dioxide levels, and thus acidity, were raised. When the level was raised to seven times the current level, the following was observed.

 This led to the dissolving of aragonite—the form of calcium carbonate produced by corals and some other marine calcifiers. Under such exposure, hard and soft clams, conchs, periwinkles, whelks and tropical urchins began to lose their shells. “If this dissolution process continued for sufficient time, then these organisms could lose their shell completely,” Ries said, “rendering them defenseless to predators.” [WHOI: News Release : In CO2-rich Environment, Some Ocean Dwellers Increase Shell Production]

The pencil urchins used in these experiments were Eucidaris tribuloides.

Summary of Sources

Pharyngula: Mary's Monday Metazoan
Tropical Fish Magazine: Eucidaris Tribuloides
WoRMS taxon details: Eucidaris tribuloides
WoRMS taxon details: Heterocentrotus mamillatus
WoRMS taxon details: Heterocentrotus trigonarius
Hawaiin Isles Hump Back Whale: Heterocentrotus mammillatus
WHOI: News Release : In CO2-rich Environment, Some Ocean Dwellers Increase Shell Production
Wikipedia: Eucidaris tribuloides  
Wikipedia: Heterocentrotus mammillatus
Wikipedia: Heterocentrotus trigonarius
Species-identification.org: Eucidaris tribuloides
Wikipedia: Aragonite

14th April 2011 Crystal Eyes

Some species of chiton, which is a mollusk, have eyes make of rock crystal. Their shells are also make of this. With these eyes, which are located in their shells, they can distinguish between a possible threat and a the natural dimming of light.  Their vision is probably around a thousand times coarser than human vision.

For them, protein eyes like we have would quickly be worn away.

http://news.nationalgeographic.com/news/2011/04/110414-eyes-rock-crystal-mineral-chiton-mollusk-vision-animals-science/

http://blogs.discovermagazine.com/notrocketscience/2011/04/14/chitons-see-with-eyes-made-of-rock/

14th April 2011 Ants go Home

Ants use a combination of vector addition and root mean square to find their way home.

When they move they estimate the direction (from the sun) and their distance travelled (how many steps). They add these vectors to always have a "home that way" vector.  Unfortunately small errors in either the distance or direction could lead to the ant not being home when she thinks she is.  What happens then?

An ant learns the appearance of the environment around the home.  Her eyesight is low resolution so she can not easily recognise home in the same way as we can by high resolution appearance, plus her environment is mostly trees and more trees.What she does is processes each new image in comparison to these images she has of home.  She does the equivalent of a root mean square of the difference between the pixels in the new image compared with one of her stock images. She moves, and recalculates. If the value is tending towards zero, she continues in that direction. If not, she tries a different route. When the value is zero, she is home.

http://plus.maths.org/content/finding-way-home

13th April 2011 Duck Reproduction

Duck sperm has antibacterial properties. The ability of the sperm to kill E. coli is higher in ducks with brighter beaks. In humans, E. coli harms sperm. [Source:   Discoblog]

A drake's penis is spiral. It is inverted inside the duck but it takes just 1/3 second to evert it. Instead of blood, lymph fluid is used to extend it. [Source: Duck Penises]

A duck's vagina is also spiral but it twists the other way! It also has pockets.  This may be so that the duck can control which drake fertilises the eggs.

Concerning spiral penises, pigs  have a penis with a corkscrew on the end. The sow's cervix also is formed as  a corkscrew. Unlike the ducks, both have the same orientation (left handed).  In order for the boar to be simulated to ejaculate, the penis has to lock into the cervix. This locking prevents backflow of semen.

7th April 2011 Blind Cavefish

Three separate populations of cave fish have evolved to be

• blind,
• pale,
• sleep 2-4 hours. 

 When interbred, these separate populations produced young that could see, showing that the genes causing the degenerate blindness were different in the different populations.

http://blogs.discovermagazine.com/notrocketscience/2011/04/07/sleepless-in-mexico-–-three-cavefish-groups-independently-evolved-to-lose-sleep/

6th April 2011 Contagious Yawning

There are five mammals, humans, chimpanzees, stumptail macaques, gelada baboons, and domesticated dogs,  in which contagious yawning has been observed.

In some experiments done with chimps, the chimps yawned more when members of their social group yawned than they did when members of another group yawned, maybe indicating empathy.

6th April 2011 Ants flow like Liquid

In a group, ants flow over each other in a similar way to a liquid and in water, spread out like a dye.

[25 April 2011: Changed video link to one without adverts. More information can be found at Not Rocket Science: Fire ants assemble into living waterproofrafts.]

5th April 2011 Aspirin kills Cats

Why is aspirin toxic to cats?

Aspirin is toxic to all cats from house cats to lions.

Aspirin is broken down in the liver using a protein called UGT1A6 by a gene with the same name. Cats hardly produce any of this protein because the cat genome has a broken, pseudogene version of this gene.

The northern elephant seal and brown hyena also have broken versions of UGT1A6.

Because cats eat mostly meat, the gene to help against plant poisons is dispensable so the broken gene has been free to spread through the population in a 'use it or lose it' way.

Cats also have low levels of amylase in their saliva, and they don't have a sweet tooth because TAS1R2, a gene involved in taste, is also a pseudogene.

Other mainly meat eaters, hypercarnivores have working copies of UGT1A6 and it is thought that cats went through a low population stage so any faulty versions of the gene were passed on.  The northern elephant seal has also gone through similar constraints.

5th April 2011 Keeping Warm

Apart from icefish using proteins to prevent themselves from freezing, the following creatures have mechanisms to cope with the cold too.

• Snow Fleas - glycine-rich antifreeze proteins
• Wood Frogs - draw their limbs into their bodies to prevent them from dying out, and use glucose. They hibernate at temperatures of -1 to -6C when up to 65% of their body fluid gradually crystallises into ice.
• Painted Turtle Hatchlings - hibernate 10 cm underground in their nests.
• Honey Bees  - huddle together.

3rd April 2011 - Piglet Squid

The piglet squid swims upside down compared with other squids so that its tentacles look like a mop of hair.

The ammonium ions in its body fluid help keep it buoyant. A large light producing organ (photophore) is located beneath each of its eyes.

Seawayblog - Several Photos

Cabrillo Marine Aquarium press release

31st March 2011 Cool Fish

Antarctic icefish (Channichthyidae) don't have haemoglobin so in order to transport oxygen around the body, they have a bigger heart and more blood. They have more capillaries for oxygen exchange.

They also have a protein which acts as antifreeze.  Synthetic versions of these have been created to try to stop transplant organs from being damaged by freezing.

Icefish lack hemoglobin