The first known case of eggs plus live birth from one pregnancy in a tiny lizard


Melanie Laird, University of Otago and Camilla Whittington, University of Sydney

For most animals, reproduction is straightforward: some species lay eggs, while others give birth to live babies.

But our recent research uncovered a fascinating mix between the two modes of reproduction. In an Australian skink, we observed the first example of both egg-laying and live-bearing within a single litter for any backboned animal.

This suggests some lizards can “hedge their bets” reproductively, taking a punt on both eggs and live-born babies to improve overall survival chances for offspring.




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Making reproductive leaps

Most vertebrate species (animals with a backbone) fall neatly into one of two distinctly different reproductive categories.

Oviparous species are egg-layers. These eggs may undergo external fertilisation – such as in spawning fish – or are fertilised and shelled internally, like those of reptiles and birds. Oviparous embryos rely on egg yolk as a source of nutrition to continue development until hatching.

In contrast, viviparous species are live bearers that carry their young to term. Some live-bearing species, including humans, support embryonic development internally via a placenta. Egg-laying is ancestral, meaning that modern live-bearers have descended from egg-laying ancestors.

Physiologically, the evolution of live birth from egg-laying is no mean feat. This transition requires a whole suite of changes, sometimes including the evolution of a placenta – an entirely new specialist organ – as well as loss of the hard outer eggshell, and keeping the embryo inside the body for a longer time.

The placenta is a highly complex organ. One of its jobs is to transfer nutrition to the developing baby.
from www.shutterstock.com

Despite these complex steps, reptiles, particularly snakes and lizards, appear to be unusually predisposed to making the leap to live birth. This capacity has evolved in at least 115 groups of reptiles independently.




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Having it both ways

It’s easy to see why reptiles, as a group, are fascinating models for studying how live birth evolves from egg-laying.

Of particular interest are two Australian skinks that have both live-bearing and egg-laying individuals (known as being bimodally reproductive). These lizards are incredibly valuable to evolutionary biologists as they offer a snapshot into evolutionary processes in action.

The three-toed skink Saiphos equalis is one such species. Reproduction in S. equalis varies geographically: populations around Sydney lay eggs, while those further north give birth to live young.

Whether individuals are live-bearing or egg-laying seems to be genetically determined: when researchers swap their environmental conditions (by moving them from one site to another), the females retain their original reproductive strategy.




Read more:
Lizards help us find out which came first: the baby or the egg?


Mothers know best

Our latest research shows this lizard is intriguing in another completely unexpected way.

We observed a live-bearing female that laid three eggs, and then gave birth to a living baby from the same litter weeks later. We incubated two of the eggs, one of which hatched to produce a healthy baby.

A live-bearing female S. equalis in our laboratory colony laid three eggs, one of which hatched to produce a healthy baby.
Camilla Whittington

This finding is remarkable for two reasons. First, as far as we are aware, this is the first example of both egg-laying and live birth within a single litter for any vertebrate.

Second, in some cases, individuals may be capable of “switching” between reproductive modes. In other words, as laying eggs and giving birth each come with their own advantages and disadvantages, individuals may be able to “choose” which option best suits the current situation.

Closer look at eggshells

To better understand this reproductive phenomenon, we investigated the structure of the egg coverings of these unusual embryos in minute detail (using an advanced technology called scanning electron microscopy).

We found that in this litter, the egg-coverings were thinner than those of normal egg-laying skinks and had structural characteristics that overlapped with those of both egg-layers and live-bearers (which have thinner coverings that are greatly reduced).

Egg coverings of S. equalis consist of an outer crust (C) and an inner shell membrane (SM). We compared the structure and thicknesses of these layers of both egg-laying (A) and live-bearing (B) S. equalis to identify similarities with our ‘unusual’ embryos (C).
Melanie Laird

How evolution works

We still don’t know the trigger that caused this female to lay eggs and give birth to a live baby from the same pregnancy.

However, our findings suggest that species “in transition” between egg-laying and live bearing may hedge their bets reproductively before a true transition to live birth evolves.

Being able to switch between reproductive modes may be advantageous, particularly in changing or uncertain environments.

The three-toed skink lives in eastern Australia.
Doug Beckers / flickr, CC BY

For example, extreme cold, drought or the presence of predators can be risky for vulnerable eggs exposed to the environment, meaning that mothers that can carry offspring to term may have the upper hand.

In contrast, lengthy pregnancies can be taxing on the mother, so depositing offspring earlier as an egg may be beneficial in some situations.

We suggest that other species in which live birth has evolved from egg-laying relatively recently may also use flexible reproductive tactics.

Further research into this small Australian lizard, which seems to occupy the grey area between live birth and egg-laying, will help us determine how and why species make major reproductive leaps.




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The Conversation


Melanie Laird, Postdoctoral Fellow, University of Otago and Camilla Whittington, Senior lecturer, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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How to grow crops on Mars if we are to live on the red planet



File 20180726 106502 1nt78ux.jpg?ixlib=rb 1.1
We can create the right kind of food plants to survive on Mars.
Shutterstock/SergeyDV

Briardo Llorente, Macquarie University

Preparations are already underway for missions that will land humans on Mars in a decade or so. But what would people eat if these missions eventually lead to the permanent colonisation of the red planet?

Once (if) humans do make it to Mars, a major challenge for any colony will be to generate a stable supply of food. The enormous costs of launching and resupplying resources from Earth will make that impractical.

Humans on Mars will need to move away from complete reliance on shipped cargo, and achieve a high level of self-sufficient and sustainable agriculture.




Read more:
Discovered: a huge liquid water lake beneath the southern pole of Mars


The recent discovery of liquid water on Mars – which adds new information to the question of whether we will find life on the planet – does raise the possibility of using such supplies to help grow food.

But water is only one of many things we will need if we’re to grow enough food on Mars.

What sort of food?

Previous work has suggested the use of microbes as a source of food on Mars. The use of hydroponic greenhouses and controlled environmental systems, similar to one being tested onboard the International Space Station to grow crops, is another option.

This month, in the journal Genes, we provide a new perspective based on the use of advanced synthetic biology to improve the potential performance of plant life on Mars.

Synthetic biology is a fast-growing field. It combines principles from engineering, DNA science, and computer science (among many other disciplines) to impart new and improved functions to living organisms.

Not only can we read DNA, but we can also design biological systems, test them, and even engineer whole organisms. Yeast is just one example of an industrial workhorse microbe whose whole genome is currently being re-engineered by an international consortium.

The technology has progressed so far that precision genetic engineering and automation can now be merged into automated robotic facilities, known as biofoundries.

These biofoundries can test millions of DNA designs in parallel to find the organisms with the qualities that we are looking for.

Mars: Earth-like but not Earth

Although Mars is the most Earth-like of our neighbouring planets, Mars and Earth differ in many ways.




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The gravity on Mars is around a third of that on Earth. Mars receives about half of the sunlight we get on Earth, but much higher levels of harmful ultraviolet (UV) and cosmic rays. The surface temperature of Mars is about -60℃ and it has a thin atmosphere primarily made of carbon dioxide.

Unlike Earth’s soil, which is humid and rich in nutrients and microorganisms that support plant growth, Mars is covered with regolith. This is an arid material that contains perchlorate chemicals that are toxic to humans.

Also – despite the latest sub-surface lake find – water on Mars mostly exists in the form of ice, and the low atmospheric pressure of the planet makes liquid water boil at around 5℃.

Plants on Earth have evolved for hundreds of millions of years and are adapted to terrestrial conditions, but they will not grow well on Mars.

This means that substantial resources that would be scarce and priceless for humans on Mars, like liquid water and energy, would need to be allocated to achieve efficient farming by artificially creating optimal plant growth conditions.

Adapting plants to Mars

A more rational alternative is to use synthetic biology to develop crops specifically for Mars. This formidable challenge can be tackled and fast-tracked by building a plant-focused Mars biofoundry.

Such an automated facility would be capable of expediting the engineering of biological designs and testing of their performance under simulated Martian conditions.

With adequate funding and active international collaboration, such an advanced facility could improve many of the traits required for making crops thrive on Mars within a decade.

This includes improving photosynthesis and photoprotection (to help protect plants from sunlight and UV rays), as well as drought and cold tolerance in plants, and engineering high-yield functional crops. We also need to modify microbes to detoxify and improve the Martian soil quality.

These are all challenges that are within the capability of modern synthetic biology.

Benefits for Earth

Developing the next generation of crops required for sustaining humans on Mars would also have great benefits for people on Earth.




Read more:
Before we colonise Mars, let’s look to our problems on Earth


The growing global population is increasing the demand for food. To meet this demand we must increase agricultural productivity, but we have to do so without negatively impacting our environment.

The best way to achieve these goals would be to improve the crops that are already widely used. Setting up facilities such as the proposed Mars Biofoundry would bring immense benefit to the turnaround time of plant research with implications for food security and environmental protection.

The ConversationSo ultimately, the main beneficiary of efforts to develop crops for Mars would be Earth.

Briardo Llorente, CSIRO Synthetic Biology Future Science Fellow, Macquarie University

This article was originally published on The Conversation. Read the original article.

Newly Discovered Fanged-Frog Gives Birth to Live Tadpoles


TIME

Scientists have discovered a rare frog in Indonesia that gives birth to live tadpoles, researchers report in a journal article published this week.

Herpatologist Jim McGuire found proof this summer that the frog, one of a group of roughly 25 species in Indonesia that have two fangs used for fighting, lays not eggs or even live froglets but live tadpoles. It’s the only frog species in the world to do so.

McGuire found the frogs on the Indonesian island of Sulawesi. He named to the species Limnonectes larvaepartus.

Two tadpoles, each about 10 millimeters long, shortly after birth.Jim McGuire—UC Berkeley

[Eureka]

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Earth Day (April 22): Picnic for the Planet


April 22 is Earth Day and to celebrate Earth Day, The Nature Conservancy is asking people to have a Picnic for the Planet. The idea is to raise awareness by going on a picnic to some outdoor location with a group of friends and to celebrate the planet we live on – or to give thanks for it.

For more visit:
http://earthday.nature.org/

Earth Day: April 22


Earth Day is about the earth and the people who live on it. The Earth Day Network believes that all people, no matter who they are, have a right to a healthy and sustainable environment. Those who support Earth Day are a veritable who’s who of environmentalism. The network not only educates and increases awareness of environmental issues, it also actively seeks to bring about change in order to achieve a healthy and sustainable environment.

Earth Day is celebrated on the 22nd April each year, with supporters getting involved in all manner of environmentally responsible activities.

Find out more about Earth Day and the Earth Day Network at:

http://www.earthday.org/

Next Trip: Back to Trekking


With the road trip now done and the car returned to Budget (rental), my thoughts have turned to my next holiday. I have a few road trip style adventures in the works, but my next holiday is likely to be a trekking adventure.

In the past I have twice walked across the Barrington Tops, completing the ‘Tops to Myall Heritage walk’ section as far as the township of Craven. I now plan to do the second section of the walk, from Craven to Hawks Nest – not far from where I now live. This has been something I have wanted to do for some time and now I intend to actually complete it.

There is no intended date at this stage, though I would hope to do it well before the end of this year. I would think it likely to be towards the early part of the second half of the year – if that makes sense.

Prior to setting out on this trek, I will be looking to update some of my gear (most of which has vanished in recent moves). I will be looking at a new tent and a sleeping bag for starters, as well as a new back pack. I’m sure there will be a few other things I will need to acquire before I set off as well.

Planning for this trip can all be followed on this Blog… stay tuned for further developments.