How sea snakes avoid predators


This 2015 video says about itself:

Many people don’t realize that there are snakes that live in the ocean. And believe it or not, they’re actually considerably more venomous than land snakes! Jonathan travels to Australia and the Philippines to find these marine reptiles, and learns why they are almost completely harmless to divers.

From the University of Adelaide in Australia:

‘Seeing’ tails help sea snakes avoid predators

February 15, 2019

New research has revealed the fascinating adaptation of some Australian sea snakes that helps protect their vulnerable paddle-shaped tails from predators.

An international study led by the University of Adelaide shows that several species of Australian sea snakes can sense light on their tail skin, prompting them to withdraw their tails under shelter. The study has also produced new insights into the evolution and genetics of this rare light sense.

The researchers found that olive sea snakes (Aipysurus laevis) and other Aipysurus species move their tail away from light. They believe this is an adaptation to keep the tail hidden from sharks and other predators.

“Sea snakes live their entire lives at sea, swimming with paddle-shaped tails and resting at times during the day under coral or rocky overhangs,” says study lead author Jenna Crowe-Riddell, PhD candidate in the University of Adelaide’s School of Biological Sciences. “Because sea snakes have long bodies, the tail-paddle is a large distance from the head, so benefits from having a light-sense ability of its own.

“The olive sea snake was the only reptile, out of more than 10,000 reptile species, that was known to respond to light on the skin in this way.”

The researchers tested for light-sensitive tails in eight species of sea snakes, but found that only three species had the light-sense ability. They concluded the unique ability probably evolved in the ancestor of just six closely related Australian species.

“There are more than 60 species of sea snake so that’s less than 10% of all sea snakes,” says Ms Crowe-Riddell. “We don’t know why this rare sense has evolved in just a few Aipysurus species.”

The researchers used RNA sequencing to see what genes are active in the skin of sea snakes. They discovered a gene for a light-sensitive protein called melanopsin, and several genes that are involved in converting light into information in the nervous system.

“Melanopsin is used in a range of genetic pathways that are linked to sensing overall light levels around us. It is even used by some animals, including humans, for regulating sleep cycles and in frogs to change their skin colour as a camouflage,” says Ms Crowe-Riddell.

Lead scientist Dr Kate Sanders, ARC Future Fellow at the University of Adelaide, says: “We’ve confirmed the ability of olive sea snakes to sense light in their tails and found the same ability in two other species. We’ve identified a shortlist of genes that are likely to be involved in detecting light. But further study will be needed to target these genes before we can really understand the genetic pathways involved in this fascinating behaviour.”

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Sea snakes don’t drink seawater


This 2014 video says about itself:

In this exciting adventure, Jonathan travels to Manuk, a tiny, uninhabited volcanic island several hundred miles from the nearest populated island in Indonesia, on a mission to discover why the waters of this remote place are teeming with thousands of venomous sea snakes!

And if you love sea snakes, check out our adventure with sea snakes in Australia:

From the University of Florida in the USA:

Sea snakes that can’t drink seawater

Zoology researchers solve mystery of how sea snakes quench their thirst

February 8, 2019

Summary: New research shows that pelagic sea snakes quench their thirst by drinking freshwater that collects on the surface of the ocean after heavy rainfall.

Surrounded by salty water, sea snakes sometimes live a thirsty existence. Previously, scientists thought that they were able to drink seawater, but recent research has shown that they need to access freshwater. A new study published in PLOS ONE on Feb. 7 and led by Harvey Lillywhite, professor of biology of the University of Florida, shows that sea snakes living where there is drought relieve their dehydration as soon as the wet season hits, and do so by obtaining freshwater from “lenses” that form on the surface of the ocean during heavy rain — events in which the salinity at the surface decreases enough for the water to be drinkable.

The yellow-bellied sea snake (Hydrophis platurus) is the only reptile in the order Squamata that lives on the open sea. It has one of the largest geographic ranges of any vertebrate species. Given its broad range and seafaring existence, during the dry season (6-7 months at the study site in Costa Rica) it has no access to freshwater. How they survive in regions of drought seems to hinge upon access to freshwater lenses, but little is known about how marine vertebrates react to or consume rainfall. “This study contributes to a fuller understanding of how pelagic sea snakes, and possibly other marine animals, avoid desiccation following seasonal drought at sea,” said Lillywhite.

The researchers captured 99 sea snakes off the coast of Costa Rica (interestingly, the snakes have never been observed in estuaries) and offered them freshwater in a laboratory environment. The team happened to be there just as six months of drought broke and the rainy season began. They found that only 13 percent of snakes captured after the rainfall began accepted the offer, compared to 80 percent of those captured before. The rainfall must have quenched their thirst.

The study continues many years of work by Lillywhite. The present paper was coauthored by Mark Sandfoss, Lillywhite’s current PhD student, Coleman Sheehy, his former student who is now the Collections Manager in Herpetology at the Florida Museum of Natural History, and then-Fulbright visiting scholar Jenna Crowe-Riddell.

“How these animals locate and harvest precipitation is important in view of the recent declines and extinctions of some species of sea snakes,” said Lillywhite. The question remains: How will climate change and its effects on precipitation impact the sea snakes?

How snakes lost their limbs


This February 2018 video says about itself:

90 million years ago, an ancient snake known as Najash had…legs. It is by no means the only snake to have limbs either. But what’s even stranger: we’re not at all sure where it came from.

From the Fundação de Amparo à Pesquisa do Estado de São Paulo in Brazil:

Research explains how snakes lost their limbs

The study is part of an effort to understand how changes in the genome lead to changes in phenotypes

February 6, 2019

Snakes and lizards are reptiles that belong to the order Squamata. They share several traits but differ in one obvious respect: snakes do not have limbs. The two suborders diverged more than 100 million years ago.

Identification of the genetic factors involved in this loss of limbs is a focus of the article “Phenotype loss is associated with widespread divergence of the gene regulatory landscape in evolution” published by Juliana Gusson Roscito and collaborators in Nature Communications.

Another equally interesting focus of the article is eye degeneration in certain subterranean mammals.

“We investigated these two cases in order to understand a much more general process, which is how genome changes during evolution lead to phenotype changes,” Roscito told.

Currently working as a researcher at the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, Roscito has been a postdoctoral fellow in Brazil and a research intern abroad with São Paulo Research Foundation — FAPESP’s support. Her postdoctoral scholarship was linked to the Thematic Project “Comparative phylogeography, phylogeny, paleoclimate modeling and taxonomy of neotropical reptiles and amphibians,” for which Miguel Trefaut Urbano Rodrigues is the principal investigator under the aegis of the FAPESP Research Program on Biodiversity Characterization, Conservation, Restoration and Sustainable Use (BIOTA-FAPESP).

Rodrigues is a Full Professor at the University of São Paulo’s Bioscience Institute (IB-USP) in Brazil and supervised Roscito’s postdoctoral research. He is also a coauthor of the recently published article.

“The research consisted of an investigation of the genomes of several species of vertebrates, including the identification of genomic regions that changed only in snakes or subterranean mammals, while remaining unchanged in other species that have not lost their limbs or have normal eyes,” Roscito said.

“In mammals with degenerated visual systems, we know several genes have been lost, such as those associated with the eye’s crystalline lens and with the retina’s photoreceptor cells. These genes underwent mutations during the evolutionary process. Eventually, they completely lost their functionality, meaning the capacity to encode proteins. But that’s not what happened to snakes, which haven’t lost the genes associated with limb formation. To be more precise, the study that sequenced the genome of a snake did detect the loss of one gene, but only one. Therefore, the approach we chose in our research consisted of investigating not the genes but the elements that regulate gene expression.”

Gene expression depends on regulatory elements for the information the gene contains to be transcribed into RNA (ribonucleic acid) and later translated into protein. This process is regulated by cis-regulatory elements (CREs), which are sequences of nucleotides in DNA (deoxyribonucleic acid) located near the genes they regulate. CREs control the spatiotemporal and quantitative patterns of gene expression.

“A regulatory element can activate or inhibit the expression of a gene in a certain part of the organism, such as the limbs, for example, while a different regulatory element can activate or inhibit the expression of the same gene in a different part, such as the head. If the gene is lost, it ceases to be expressed in both places and can often have a negative effect on the organism’s formation.

However, if only one of the regulatory elements is lost, expression may disappear in one part while being conserved in the other,” Roscito explained.

Tegu lizard

From a computational standpoint, CREs are not as easy to identify as genes. Genes have a characteristic syntax, with base pairs that show where the genes begin and end. This is not the case for CREs, so they have to be identified indirectly. This identification is normally based on the conservation of DNA sequences among many different species.

“To detect the divergence of specific sequences in snakes, it’s necessary to compare the genomes of snakes with the genomes of various reptiles and other vertebrates that have fully developed limbs. Genome sequences for reptiles with well-developed limbs are scarce, so we sequenced and assembled the genome of the fully limbed tegu lizard, Salvator merianae. This is the first species of the teiid lineage ever sequenced,” the authors said.

“Using the tegu genome as a reference, we created an alignment of the genomes of several species, including two snakes (boa and python), three other limbed reptiles (green anole lizard, dragon lizard and gecko), three birds, an alligator, three turtles, 14 mammals, a frog, and a coelacanth. This alignment of 29 genomes was used as the basis for all further analyses.”

The researchers identified more than 5,000 DNA regions that are considered candidate regulatory elements in several species. They then searched the large database using ingenious technical procedures that are described in detail in the article and obtained a set of CREs the mutation of which may have led to the disappearance of limbs in the ancestors of snakes.

“There are several studies concerning a well-known regulatory element that regulates a gene that, when modified, causes various defects in limbs. Snakes have mutations in this CRE. In a study published in 2016, the mouse CRE was replaced with the snake version, resulting in practically limbless descendants. This was a functional demonstration of a mechanism that may have led to limb loss in snakes. However, this CRE is only one of the regulatory elements for one of several genes that control limb formation,” Roscito said.

“Our study extended the set of CREs. We showed that several other regulatory elements responsible for regulating many genes have mutated in snakes. The signature is far more comprehensive. An entire signaling cascade is affected.”

New snake species discovery in other snake’s stomach


This 26 December 2018 French language video is about a new snake species, Cenaspis aenigma, discovered in another snake’s stomach.

From the University of Texas at Arlington in the USA:

New species of snake found in stomach of predator snake

January 19, 2019

Herpetologists at The University of Texas at Arlington have described a previously unknown species of snake that was discovered inside the stomach of another snake more than four decades ago.

The new snake has been named Cenaspis aenigma, which translates from Latin as “mysterious dinner snake”. It is described in a recent paper in the Journal of Herpetology titled “Caudals and Calyces: The Curious Case of a Consumed Chiapan Colubroid.” The paper was co-authored by Jonathan Campbell, UTA professor of biology; Eric Smith, UTA associate professor of biology; and Alexander Hall, who earned a UTA doctorate in quantitative biology in 2016.

The researchers’ work identifies Cenaspis as not only a new species but also an entirely new genus.

The specimen was found in the stomach of a Central American coral snake — a species that has been known to eat smaller snakes — by palm harvesters in the southern Mexico state of Chiapas in 1976. The 10-inch long specimen was preserved in a museum collection. Amazingly, a live specimen has never been found in the ensuing 42 years.

“This small snake was obtained now over 40 years ago, and the report of its discovery has been a long time in coming”, the co-authors wrote in the Journal of Herpetology paper. “We were optimistic that additional specimens might be secured, but after at least a dozen more trips into the region spanning several decades, we have been unrewarded.”

Cenaspis has several unique features that defy placing it in any known genus and clearly distinguishes it from all known genera. These include undivided subcaudal scales, or enlarged plates on the underside of its tail; a lack of spines and presence of cup-like structures called calyces on its hemipenes, or paired male reproductive organs found in snakes and lizards; and the shape of its skull.

The first two of those features are not found in any other known snake in the family Colubridae in the Western Hemisphere. Colubridae is the largest snake family and includes just over 51 percent of all known living snake species.

Utilizing the vast resources of UTA’s Amphibian and Reptile Diversity Research Center for comparative purposes, the researchers made CT scans of dozens of specimens of snakes. The biologists believe that due to some of the specimen’s physical features, Cenaspis is likely a burrowing snake that feeds on insects and spiders. Campbell believes that Cenaspis is not extinct but has eluded capture due to its burrowing lifestyle and other elusive habits.

“This provides evidence of just how secretive some snakes can be”, Campbell told National Geographic, which ran a story about the discovery in its Dec, 19, 2018, edition. “Combine their elusive habits with restricted ranges and some snakes do not turn up often.”

He noted said that because of the snake’s unique nature, the Chiapas highlands area of southern Mexico where it was found all those years ago should be considered for protected status, so that more unknown species can be discovered and not face possible extinction.

Most dangerous marine animals, video


This 12 January 2019 video says about itself:

In this Blue World Academy, Jonathan talks about the most dangerous animals in the sea–and sharks are not even on the list! Animals like the flower urchin, blue-ringed octopus, cone shell, box jellyfish, stonefish and sea snake are extremely dangerous sea creatures!

Timber rattlesnakes threatened by mountaintop removal mining


This 2014 video is called Facts about the basic biology and ecology of timber rattlesnakes.

From the Ecological Society of America in the USA:

Does mountaintop removal also remove rattlesnakes?

Mining operations in Appalachia permanently alter habitat availability for rattlesnakes

January 3, 2019

Summary: Timber rattlesnakes, according to the study’s author, are among the most docile creatures in Appalachia. They choose places to hibernate that are more likely to be surface mined due to their ridgetop locations. Mining thus put this species at a disadvantage and reduces the biodiversity of the area.

On the Cumberland Plateau in eastern Kentucky, surface coal mining is destroying ridgelines and mountaintops, and along with them, the habitat of a surprisingly gentle reptile species — the timber rattlesnake.

“Timber rattlesnakes may be the most docile, calm animals of their size in eastern US forests,” Thomas Maigret, a researcher from the University of Kentucky, said. “On several occasions, I’ve witnessed spiders using a rattlesnake as an anchor for a web. Females, especially, move very infrequently, and pose almost no threat to a careful human.”

Unfortunately for the timber rattlesnake (Crotalus horridus) and other species in this region — both plant and animal — surface coal mining requires complete removal of mature forest cover and the upper soil layers. This means that soil is scraped away, rocks disturbed and dug out, plants and trees removed, or the ridgetop landscape flattened and made more uniform to reach the coal buried in the earth. This alteration eliminates many diverse, unique places for animals to live and hibernate. The central Appalachia region spans eastern Kentucky, northeastern Tennessee, southwest Virginia, and southern West Virginia and is one of the most diverse non-tropical ecosystems in the world with thousands of plant and animal species, many that are only found there.

Maigret and his colleagues tracked timber rattlesnakes in a study published today in the Ecological Society of America’s journal Frontiers in Ecology and the Environment. The researchers implanted radio transmitters in snakes of the Cumberland Plateau and tracked their movements until they retreated to hibernation sites in the fall. The data gathered provided a roadmap for identifying other potential hibernating sites, or “hibernacula”, across the study area.

“Snakes of the eastern U.S. vary in their hibernacula selection behavior, and for many species not much is known about hibernacula preferences,” Maigret explained. “For example, many aquatic snakes prefer damp hibernacula near the streams where they reside during the summer. But for other species, any warm, protected crevice they can fit into seems to suffice.”

By analyzing remote-sensing and satellite imagery, mining maps, and permit data from the USGS and other sources, the researchers were then able to determine how mining might affect a wide range of hibernation sites.

They found that because timber rattlesnakes tend to hibernate in the same places that make ideal mines, surface mining disproportionately alters or eliminates their preferred habitat. “Other species with habitat preferences similar to timber rattlesnakes — including some snakes — may also be affected disproportionately by mining. On the other hand,” Maigret said, “species associated with middle or lower slopes will not be affected by mining to the same extent.”

In other words, the mining operations here are selecting against timber rattlesnake habitat, effectively cutting into the region’s biodiversity.

The Surface Mining Control and Reclamation Act of 1977 does not require mining companies to reforest the area to the original mountaintop landscape after mining has wrapped up. The law does dictate that the “approximate original contours” of a site be re-established, in an attempt to not leave the area uninhabitable by the species that once lived there. However, it is rare for forests and biodiversity to fully recover from mining-related disturbances, to the detriment of many animals and their habitats.

Is the damage done to mountain-tops irreversible? While researchers are actively improving the ability to restore habitats on reclaimed mine lands, surface mining acts as an eraser of unique ecosystems, creating a uniform landscape where there once were diverse habitat options. In the Cumberland Plateau, mining leaves conservation and management efforts very little to work with even after an operation restores the approximate original mountaintop landscape.

Still, Maigret is optimistic about the future of restoring mined areas for the docile rattlesnakes. “Coal mining in central Appalachia has serious economic headwinds,” he stated, “and may never return to the rates of surface mining of the late 20th century. Timber rattlesnakes are resilient, and their ability to adapt to previous landscape changes — including massive deforestation in the 19th and early 20th century — should not be underestimated.”