Twilight’s home: A new cave-dwelling coral from the western Pacific

Leptoseris corals love the gloom. They grow in shaded nooks and crevices and on the sea floor at depths where many other corals do not thrive. They are particularly common in mesophotic reefs, where the light is muted and all but a few wavelengths are filtered out. Several species live at more than 100 m and one, Leptoseris hawaiiensis, has been recorded at 160 m at Johnston Atoll in the Pacific Ocean.

This low-light lifestyle makes it awkward for the endosymbiotic zooxanthellae that live within the coral’s tissue. Zooxanthellae are photosynthetic, requiring a hit of light to drive the chemical reactions that build carbohydrates. Down in the shadows and the perpetual twilight of the mesophotic zone there’s not a lot of illumination to go around. But they make do. Elements of the Leptoseris skeleton — especially the ledge-like menianes that fit in close with the polyp’s tissue — are thought to play a part in snaffling light and making it available to the endosymbiotic zooxanthellae. Survival is a team effort.

Until recently, all species were known to be zooxanthellate, but a newly described Leptoseris from the western Pacific breaks that pattern.

Living specimens of Leptoseris troglodyta sp. n. a) Philippines, Cebu Strait, W of Bohol, NW of Cabilao Island, 10–30 m depth (7 November 1999); b) Indonesia, NE Kalimantan, Berau Islands, S of Derawan Island, 7–10 m depth (4 October 2003). (Image from Hoeksema, 2012)

Leptoseris troglodyta Hoeksema, 2012, lives in marine caves in water between 5 and 35 m deep and has been recorded from sites in eastern Indonesia, the central Philippine Islands, Palau, Guam and the Louisiade Archipelago of Papua New Guinea.

Although this species lacks zooxanthellae, it still possesses the menianes that help to harvest light in other Leptoseris species. This combination raises the question of which came first in Leptoseris — zooxanthellae or no zooxanthellae?

It might be tempting to assume that L. troglodyta had zooxanthellate antecedents and has ditched the endosymbionts as part of its adaptation to cave-dwelling, leaving the menianes as evolutionary hangers on. But research on Dactylotrochus cervicornis, another azooxanthellate and menianes-possessing genus in the same family (Agariciidae) suggests that things might not necessarily have gone that way. So the question remains: Did the zooxanthellae precede the menianes or did the menianes precede the zooxanthellae? This, as Dr Hoeksema says, is ‘a “chicken or the egg” causality dilemma’. Further studies will shed light (ahem) on the conundrum.

 

References

Hoeksema, BW. (2012) Forever in the dark: the cave-dwelling azooxanthellate reef coral Leptoseris troglodyta sp. n. (Scleractinia,  Agariciidae). ZooKeys 228: 21–37, doi: 10.3897/zookeys.228.3798

Kitahara, MV., Stolarski, J., Miller, DJ., Benzoni, F., Stake, J. & Cairns, SD. (2012) The first modern solitary Agariciidae (Anthozoa, Scleractinia) revealed by molecular and microstructural analysis. Invertebrate Systematics 26: 303–315. doi: 10.1071/IS11053

A trick of the tail: how snails escape snail-eating snakes

There’s not much chance of a land snail outrunning a predator, so a slow-moving gastropod must rely on other measures to stay out of trouble. The shell is an effective defence, but it’s not perfect. Some predators can crush them. Others, such as the song thrush and pitta, smash them open on rocks. Carabid beetles and firefly larvae are small enough to breach the defences by slipping through the only gap in the armour — the shell aperture. Even the best protection has a weak spot.

Not only do snails in some parts of Asia have to survive these usual suspects — brute force crushers and smashers and those sneaky nibblers — but they also have to deal with specialist predators: snail-eating snakes. Iwasakii’s snail-eater, Pareas iwasakii, has asymmetrical jaws that are adapted to extract snails from their shells. (Click here to to watch a video of the snake in action.)

Researcher Masaki Hoso of the Naturalis Biodiversity Centre in the Netherlands has discovered that Satsuma caliginosa, a camaenid land snail from Japan, has evolved counter-measures to escape its serpentine hunter.

The range of Satsuma caliginosa partly overlaps that of Iwasaki’s snail-eater. Where the two are separate, the interior of the Satsuma shell aperture is smooth, but where predator and prey occur together, the shell aperture is lined with several low barriers that narrow the opening and prevent the snake grabbing hold of the snail and dragging it out. Unfortunately for Satsuma, these barriers only develop in adults.

Masaki Hoso found that Satsuma employs an equally effective but more drastic method of staying alive until the shell barriers develop. When snagged by a snake, the snail sheds its tail. (Really, the hind part of the foot.) Result: predator gets a bite-sized morsel of prey and prey gets to live another day.

(a–c) Foot regeneration of S. caliginosa in the wild. (a) S. caliginosa caliginosa with an intact, (b) a regenerating and (c) a regenerated foot. (d) Proportion of S. caliginosa with a regenerating or regenerated foot in the wild. (Image from Hoso, 2012)

But this process of autotomy is costly. Regrowing the shed tail requires a lot of energy and while that is taking place, resources are diverted from shell growth. For immature snails, this involves a trade off between defence mechanisms. Dropping the tail is a life-saver, but delays the development of apertural barriers. Still, dropping the tail means that the snail can survive long enough to grow those apertural barriers.

Reference

Hoso, M. (2012) Cost of autotomy drives ontogenetic switching in antipredator mechanisms under developmental constraints in a land snail. Proceedings of the Royal Society B. doi: 10.1098/rspb.2012.1943

 

 

 

From the Rare Book Room: Rumphius’ Herbarium Amboinense

Source: Botanicus

Source: Botanicus

While employed as a merchant for the Vereenigde Oost-Indische Compagnie, Georg Rumphius (Rumpf) compiled a comprehensive catalogue of the plants of the Spice Islands. His work, Herbarium Amboinense or Het Amboinsche Kruidboek, covered well over a thousand species and took more than 30 years to complete. It remains a text of great botanical and historical significance. It is also a testament to Rumphius’ dedication.

Rumphius began his study of the Spice Islands flora in 1657. He persevered with the work through a succession of personal tragedies. In 1670, he lost his sight to glaucoma. Four years later, his wife and a daughter died in an earthquake. Then, in 1687, when his manuscript was close to completion, a fire destroyed his books, collections and illustrations. Rumphius and his assistants started again, finishing the first six parts of the work in 1690.

But the originals were lost at sea on the way to the Netherlands. Fortunately, before the originals had been dispatched, the Governor had ordered that copies be made and retained in Batavia. Replacements, which included revisions by Rumphius, were sent in 1694. Further parts of Herbarium Amboinense arrived in Amsterdam over the next few years, with the last (Actuarium) sent from Batavia in May, 1702. Having completed his life’s work, Rumphius died a few weeks later on 15 June.

At first, the VOC refused to publish the manuscript because it contained information that the company considered economically and politically sensitive. Although they lifted the ban in 1704, almost 40 years passed before Herbarium Amboinense went to press. It was eventually published in 1741 with a Latin translation by Johannes Burman.

Few copies are available in libraries, but Herbarium Amboinense — and many other rare and historical texts — are accessible online at Botanicus, an initiative of the Missouri Botanical Garden Library.

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Vereenigde Oost-Indische Compagnie = Dutch East India Company

Spice Islands = Maluku Islands

Batavia = Jakarta

Presentations that don’t bore, bewilder or bamboozle

When a presentation program tempts you with all its bells and whistles, it is hard to resist. Bright colours? Yeah. Fancy fonts? Why not? Animations? Now you’re talking. Load ’em up. But forget your entertainment; it’s time to consider what your audience wants.

The range of options available in these programs can make or break a presentation. We’ve all been to at least one where the presenter did not choose them wisely. So how do you put together a visual presentation that complements your words?

Over the past couple of decades, I’ve given hundreds of presentations, most of them lectures to university students. I’ve also prepared lecture presentations to be given by other academics. I follow these guidelines to ensure I put together a presentation that sets off the message and doesn’t distract the audience.

Tailor your presentation to the audience. The audience is not there to gaze adoringly at you. (Although some might be, because you’re a fine human being). The audience has turned up to be informed, enlightened and inspired by your words. They want to understand what you’re telling them. ‘One size fits all’ presentations, which are suitable for a range of audiences, are rare. Rarer still are people who can adjust their talks as they go. I’m not one of those people and if you’re not one either, then make all the changes before you start. This requires some homework if you are unfamiliar with the demographics of your audience.

Keep the content simple. One statement or fact per slide is enough. Two if you must. Three is really iffy. People will start reading the slide as soon as it appears and will keep going to the end. While they are reading, they won’t be listening to you. So don’t let those sharply honed jokes and apposite turns of phrase become victims of your desire to pack in the information.

Don’t make the presentation look like a GeoCities site from the 1990s. Fussy backgrounds, clashing colours and fancy fonts (individually or in combination) will drive your audience crazy. Not only will your slides be distracting, but they might also be hard to read. Don’t make your audience work too hard: they get enough of that in their jobs. Keep it simple.

And as we’re on the subject, remember that your audience might include people who have less than perfect vision, so consider their requirements. Well-spaced text, clear fonts and high contrast between text and background are all helpful.

And while you’re cutting out the fiddly bits, keep graphics as undemanding as possible. Graphs and other illustrations are essential. Need to show the relationship between global temperatures and the number of pirates? You can’t go past a graph. But remember that it is hard to take in too much information at one time. Keep graphs as basic as possible.

Be judicious with animations. Resist the desire to liven up a presentation with typewriter sounds, dancing pink elephants or mice scuttling along the bottom of the page. Using animations is like streaking — it’s something that seems like a good idea at the time. Long after the message has faded, the memory of those animations will keep returning to your audience like some ghastly zombie. Think very hard about cute animations and then kill them with a sharpened shovel. (The same applies to over-worked metaphors.)

If it is important that your audience remember the details of your presentation, consider providing handouts. Note-taking is a skill. If your talk contains a lot of facts, quotes, references, addresses or other information, it can be helpful for the audience to have access to a summary. Hand these out ahead of the talk, so everyone has a chance to read them before you start.

Clear everything else but your presentation from the folder or flashdrive. Do you really want the file called Cyoot Kittehs opening unbidden while you set up your presentation? Because that is what will happen. Maybe only once, but that’s enough. If it does happen, the wrong file will be projected onto a huge screen and everyone will have the opportunity to judge your taste. Be known for your great talk, not for your pictures of cats with fruit on their heads.

Always plan for a worst case scenario. Things go wrong, so try to have a contingency plan if the projector fails or the laptop freezes. Could you keep going without illustrations? Are there any props you could use? Could you give the rest of the talk in interpretive dance? Okay, maybe not that one. But do whatever you can to keep going.

Above all, have fun. Remember that a presentation is not a punishment for you or the audience. Good luck!

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How to make your audience love you (and not throw things)

1. Match your talk to your audience
2. Make only 1 – 2 points per slide
3. Keep the layout simple
4. Use colours sparingly
5. Use graphics sparingly
6. Use animations sparingly
7. In fact, do everything sparingly
8. Rehearse
9. Consider handouts for the audience (notes, not bribes)
10. Clear everything except your presentation from the folder/flashdrive