Monday, 25 August 2014

Species of the Week: Sexton Beetles

Sexton Beetles (Nicrophorus), also known as Burying Beetles, are fascinating little insects with an amazing life-cycle. They are one of the only insects in which both the male and the female look after their young. These beetles have a level of parental care comparable to birds!

A Common Sexton beetle, Nicrophorus vespilloides

Because they rear their young on the carcass of a small animal, such as a rodent or small bird, it is important that they can detect a dead body. They have sensory organs called chemoreceptors on their club-shaped antennae. These organs can detect the scent of a carcass drifting on the breeze from up to a mile away.
Naturally, a single carcass will attract several Sexton Beetles. The individuals will fight on the dead body, ramming into each other like miniature stags. The males fight other males, and the females fight other females - but the opposite sexes will not fight each other. Eventually, most beetles are driven off, leaving only a single pair left on the carcass.
Straight away, they begin to dig away at the soil underneath the body, creating a hollow for the carcass to fit into. All feathers or fur will be removed from the body, and used to line the hollow. The carcass will be coated in antibacterial and antifungal secretions from the Sexton Beetle's mouth and anus. Finally, the body will be formed into a ball and pushed into the hollow, then covered in soil. This whole process usually takes about 8 hours.
At this point the female usually mates with the male and lays her eggs in the soil around the carcass. However, the female does not always have to mate, as she can fertilise her eggs using sperm collected and stored from a previous copulation with a different male.
The larvae will hatch out and immediately begin to gorge themselves on the carcass. Though they can feed themselves, the parents sometimes help them along a little. They bite chunks off the carcass, then digest it, then regurgitate it for the larvae's consumption. Ready-digested chunks of rotting meat - yum!

Sexton Beetle larva gorging themselves on the rotting, ball-shaped carcass.

It's pretty gross, but you have to admire the parent Sextons, they do a great job of making sure that their offspring have the best start in life. It's not exactly one big happy family, though. If too many eggs hatch, and there's not enough rotting meat to feed them all, the adults will kill some of their own larvae!
Eventually, the larvae will burrow into the surrounding soil and pupate.

An amazing, but pretty gross, life-cycle! I hope that you've enjoyed this week's species. If anybody has any ideas for my next Species of the Week, then let me know by commenting on this post.

Until next time, keep on the wild side!

Monday, 18 August 2014

Species of the Week: Lysibia Wasps

You may have heard of the parasitic wasps that lay their eggs in an unfortunate host, but have ymaybe_ard of hyperparasitoid wasps? A hyperparasite is a parasite that parasitizes another parasite. That's exactlly what a Lysibia wasp does - they parasitize other parasitic wasps. Lysibia sp. have a curious relationship with brassicas, Small White butterflies, and Cotesia glomerata, a parasitic wasp.
It all starts with a Small White caterpillar feeding upon a brassica. In response to being eaten, the plant releases a chemical into the air, signalling its distress. When a female Cotesia glomerata wasp detects this chemical, it will come down and inject its eggs into the caterpillars. The wasp larvae emerge from the eggs and worm their way out from underneath the caterpillar's skin, killing it. What a horrible way to die!

A Small White (Pieris rapae) caterpillar

At this point the wasp larva will pupate, but they may not even get that far. The Lysibia sp. can also detect the chemical given off by the brassica, and so knows exactly where to go to find its host. The female will come and inject her eggs into the Cotesia larva or pupa, and thus the parasite becomes the parasitized.

A Lysibia female injects her eggs into Cotesia larva
Things can't get any more complicated, right? Wrong - because even the hyperparasitoid can become parisitized! Other Lysibia individuals will sometimes parasitize the larva of the same species, making it a hyperparasitoid and hyper-hyperparasitoid!
 A Lysibia sp. adult
This post turned out to be not so much about Lysibia itself, but the entire food chain.
I'm not sure if a hyper-hyper-hyperparasitoid exists, but I'm keeping an eye out for one!
Until next time, keep on the wild side!

Wednesday, 6 August 2014

Species of the Week: Limpet

This is my first 'Species of the Week' post. Every week I'll look at a different species, so if anyone has any animals that they particularly want me to talk about, then just let me know in a comment.

This week's species is the humble limpet. Actually, limpets are a group, Patellogastropoda, not a species. The most common species in the UK is, surprise surprise, the Common Limpet (Patella vulgata).
 All limpets, vulgata or not, share a similar body plan. If you managed to pull a limpet off a rock and looked at its fleshy underside, you would see a oval-shaped mouth and 2 main tentacles called cephalic tentacles, at the base of which are a pair of primitive eyes. Most of its underside consists of its single foot, surrounded by the mantle, a soft outer body wall. Around the edges of the mantle, there is a ring of tiny, feathery tentacles called pallial tentacles.

 A limpet's underside

If you are walking along the shoreline, you may notice that some rocks have ring-shaped indentations in them. They are created by limpets, and are known as home-scars. A limpet will make one by rubbing its shell against the rock until its shell can fit snugly into the indentation. Each individual has its own home-scar, and will stay there while the tide is out. By clamping down into the home-scar, they create pockets of sea water inside their shells, allowing their gills to still function.

 Common Limpets and some home-scars

When the tide comes in, the limpets leave their home-scars and go foraging for algae. They have a tongue covered in teeth-like serrations, which it uses to scrape the algae from the rock. Each individual has its own grazing territory, and if another limpet enters it, a fight will probably ensue. The limpets will ram their shells together, and attempt to knock the opponent off the rock.
Everywhere a limpet goes, it leaves a slime trail, which it follows back to its home scar as soon as the tide begins to go out. It is thought that the slime also acts as a fertilizer, helping the algae to grow back. This way, the limpet hardly ever runs out of algae in its grazing grounds.
Several species of predatory starfish readily attack limpets, but these intertidal molluscs are more vicious than you might think. The smaller limpets will simply hunker down onto the rock, but the larger ones fight back. They will wait until the starfish has the tip of one of its arms under the limpet's shell, then it'll slam the shell down. This creates painful, deep cuts and sometimes even severs the tip of the limb. After several slams, the starfish usually leaves the limpet in peace.
I'm still researching the life cycle. There seems to be various interesting things about it, including a gender change. However, the information is a bit sketchy, and several texts contradict each other. When I've got more information, I'll update this post.

It's plain to see that the humble limpet, mundane and boring at first glance, is in fact a fascinating creature.

Until next time, keep on the wild side!

Tuesday, 5 August 2014

Forest and Sea Spectacular

First of all, I would like to apologise for the lack of posts recently.
On August 1st, my Mum and I went on a Yorkshire Coast Nature event called 'Forest and Sea Spectacular'. It was taken by Richard Baines, the lead tour guide at Yorkshire Coast Nature. Richard is a lovely man, always really friendly and willing to answer any questions. We went to the breathtaking Langdale Forest in the morning, and I was blown away by the number of bird species that we spotted. We saw some fantastic birds of prey, including a Goshawk (Accipiter gentilis), 2 Sparrowhawks (Accipiter nisus), 4 Buzzards (Buteo buteo), a Kestrel (Falco tinnunculus), and a Hobby (Falco subbuteo)! Both the Goshawk and the Hobby were firsts for me.

An image of the Northern Goshawk that I found on the Internet
Eurasian Hobby, again this picture was found on the Internet
I also spotted a Scorpion Fly (Panorpa communis), which are lovely insects that I am quite fond of. This insect can easily be identified by its tail, which it raises like a scorpion, hence the name. Despite its dangerous namesake, the tail has no stinger of any sort and is instead used primarily for courtship.
The bizarre Scorpion Fly
 We also saw 3 Common Crossbills (Loxia curvirostra), which was very exciting because I had never seen them before. They are so named because the bill overlaps at the tips. The males are red, but the females are brown-green. Their unique bill allows them to get to pine seeds inside pinecones.

A male Common Crossbill

In the afternoon, we went to Staithes, a small fishing village near Whitby. From there we went out on a boat with a large amount of chum (very smelly leftover bits of fish). Bit by bit, we through the chum overboard to attract seabirds. We saw several Fulmars (Fulmaris glacialis), Herring Gulls (Larus argentatus), and a few Gannets (Morus bassanus).

A Fulmar, note its strange 'tube nose'

My favourite seabird that we saw was the Great Skua (Stercorarius skua), an impressive, large bird with dark plumage. They are the pirates of the seabird world, forcing other birds to give up their meals. They will take on birds as large as Gannets, even attacking and killing smaller sea birds such as Puffins (Fratercula arctica)!

 A Great Skua

The skipper was very kind and allowed me to have a go at actually sailing the boat! We also checked 2 lobster pots, and I had the opportunity to hold a lobster.
I had a really good time, and I would highly recommend going on a Yorkshire Coast Nature tour.

Until next time, keep on the wild side!