Walking sharks discovery off Australia


This 20 January 2020 video is called New species of walking shark found in Indonesia.

From the University of Queensland in Australia:

Walking sharks discovered in the tropics

January 21, 2020

Four new species of tropical sharks that use their fins to walk are causing a stir in waters off northern Australia and New Guinea.

While that might strike fear into the hearts of some people, University of Queensland researchers say the only creatures with cause to worry are small fish and invertebrates.

The walking sharks were discovered during a 12-year study with Conservation International, the CSIRO, Florida Museum of Natural History, the Indonesian Institute of Sciences and Indonesian Ministry of Marine Affairs and Fisheries.

UQ’s Dr Christine Dudgeon said the ornately patterned sharks were the top predator on reefs during low tides when they used their fins to walk in very shallow water.

“At less than a metre long on average, walking sharks present no threat to people but their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and molluscs,” Dr Dudgeon said.

“These unique features are not shared with their closest relatives the bamboo sharks or more distant relatives in the carpet shark order including wobbegongs and whale sharks.

The four new species almost doubled the total number of known walking sharks to nine.

Dr Dudgeon said they live in coastal waters around northern Australia and the island of New Guinea, and occupy their own separate region.

“We estimated the connection between the species based on comparisons between their mitochondrial DNA which is passed down through the maternal lineage. This DNA codes for the mitochondria which are the parts of cells that transform oxygen and nutrients from food into energy for cells,” Dr Dudgeon said.

“Data suggests the new species evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species,” she said.

“They may have moved by swimming or walking on their fins, but it’s also possible they ‘hitched’ a ride on reefs moving westward across the top of New Guinea, about two million years ago.

“We believe there are more walking shark species still waiting to be discovered.”

Dr Dudgeon said future research would help researchers to better understand why the region was home to some of the greatest marine biodiversity on the planet.

Fangtooth fish, deep-sea video


This 17 January 2020 video says about itself:

The fangtooth, or ogrefish, has extra-long, sharp teeth and a face only a mother could love. This fierce-looking fish actually gets no bigger than the average adult human hand. The fangtooth is found in meso- and bathy-pelagic waters worldwide. Dark skin and scales provide camouflage in these dim ocean depths, assisting them with catching prey (fish, shrimp, and squid) and avoiding hungry predators (tuna and marlin). Their prominent lateral line system detects water movement and compensates for poor eyesight and low light conditions. The fangtooth has been spotted just eight times in the past 30 years of MBARI ROV expeditions.

How remora fishes hitchhike with sharks, whales


This June 2016 video says about itself:

Everything You Need to Know About Those Fish That Attach to Sharks

It’s called a remora, and you’ve probably seen it before. It attaches to fish and marine mammals all the time. But get this: It doesn’t attach with its mouth. It’s got a suction cup it wears as a hat.

From the New Jersey Institute of Technology in the USA:

Discovery reveals how remora fishes know when to hitch a ride aboard their hosts

January 15, 2020

Summary: Researchers have detailed the discovery of a tactile-sensory system stowed within the suction disc of remora, believed to enable the fish to acutely sense contact pressure with host surfaces and gauge ocean forces in order to determine when to initiate their attachment, as well as adjust their hold on hosts while traversing long distances.

Remoras are among the most successful marine hitchhikers, thanks to powerful suction discs that allow them to stay tightly fastened to the bodies of sharks, whales and other hosts despite incredible drag forces while traveling through the ocean. But how do these suckerfish sense the exact moment when they must “stick their landing” and board their speedy hosts in the first place?

A team of biologists at New Jersey Institute of Technology (NJIT), Friday Harbor Labs at University of Washington (FHL-UW) and The George Washington University (GWU) now offers an answer.

In findings published in the Journal of the Royal Society Open Science, researchers have detailed the discovery of a tactile-sensory system stowed within the suction disc of remora, believed to enable the fish to acutely sense contact pressure with host surfaces and gauge ocean forces in order to determine when to initiate their attachment, as well as adjust their hold on hosts while traversing long distances.

Specifically, the study describes the discovery of groupings of push-rod-like touch receptors, or mechanoreceptor complexes, embedded in the outer lip of the remora adhesive disc, which have been known to aid other organisms in responding to touch and shear forces.

Researchers say the finding marks the first time such touch-sensory complexes have been described in fishes, as the structure was previously only known in extant monotremes — platypus and echidnas.

“One of the wildest things about this work was not only finding a mechanoreceptor complex not previously known to fishes, but that the only other organisms known to possess them are monotremes,” said Brooke Flammang, NJIT professor of biological sciences and lead author of the study. “This is exciting because it shows how much we as integrative comparative biologists still have to learn about the sensory world of organisms.”

“When I was in graduate school, conventional wisdom was that fishes did not have such mechanoreceptors,” said Patricia Hernandez, one of the study’s authors at The George Washington University. “The discovery that these fishes share convergent receptors with echidnas is really exciting and points us in the right direction for discovering similar convergence in other fishes.”

While conducting various imaging studies to examine the head and disc of Echeneis naucrates, a common sharksucker remora, the team successfully identified the complexes: dome-like protrusions along the surface of the soft tissue lip surrounding the remora’s adhesive disc. Each dome packs below it a column of cells with three vesicle chains containing sensory nerves that stretch from the disc’s epidermal layer down to its dermal layer. In addition to sensing contact, these complexes are thought to respond to shear stress, which would provide feedback information to the remora if it was losing its grip and sliding backward on its host.

“When we first noticed these structures we were a little thrown off,” said Karly Cohen, a Ph.D. biology student at FHL-UW and an author on the study. “We knew they had to be sensory because of the plethora of nerves, but they didn’t look like lateral line structures, which are one of the main ways fishes sense their environment. We dove into the literature to try and find structures that fit the morphology of those we saw in the remora histology. Finally landing on the push-rod receptors known in echidnas was so exciting. … It was validation of the morphology we were seeing and it took us into a realm of mechnosensation that we were not necessarily considering when thinking about how the remora stick.”

Notably, in further examining seven other remora species, the team found that those species known to frequently piggyback on larger and faster hosts, like pelagic billfish, are equipped with nearly double the mechanoreceptor complexes of remora species that typically hitchhike on slower swimmers, such as reef fishes.

“On animals swimming very fast where the remora may be under increased drag conditions, the need to recognize loss of contact and make an instant correction is more crucial than on slower swimming hosts,” noted Flammang.

Flammang and colleagues say that the touch-signaling complexes found in remoras suggest not only that fishes may be able to sense their environment in ways not previously realized, but that specialized mechanoreceptors may also be a much more common feature among basal vertebrates than was previously thought as well.

“The interesting aspect here is that push-rods are only otherwise known in platypus and echidnas,” said Flammang. “Obviously, there is no close phylogenetic relationship between remoras and monotremes, so this likely means that there are a lot of mechanoreceptors in vertebrates that just haven’t been found in a wide breadth of organisms. We hope this paper brings this structure to the attention of other researchers for comparative study on how their organisms sense the environment.”

Saving Cayman Islands coral reef fish


This 2016 video says about itself:

Join researchers from the Reef Environmental Education Foundation and the Cayman Islands Department of Environment as they study one of the last great reproductive populations of Nassau Grouper. Normally a solitary species, during the winter full moons Nassau Grouper travel, sometimes over great distances, to “group” together and spawn. While most of the known spawning sites in the Caribbean have been fished out over the years, the west end of Little Cayman in the Cayman Islands is home to largest known reproductive spawning aggregation of this endangered species.

From the University of California – San Diego in the USA:

Collaborative conservation approach for endangered reef fish yields dramatic results

January 6, 2020

A new study from researchers at the Scripps Institution of Oceanography at the University of California San Diego has documented a successful recovery effort among Nassau Grouper populations in the Cayman Islands thanks to an approach involving government agencies, academic researchers, and nonprofit organizations.

The study, published January 6, 2020 in Proceedings of the National Academy of Sciences, used a two-pronged approach including tagging and video census data for monitoring and counting Nassau Grouper populations in an effort to more accurately estimate annual numbers of fish in the population and thus provide insight into the effects of ongoing conservation efforts. While many governments have enacted regional or seasonal fishing closures in an attempt to allow recovery of overfished stocks of aggregating reef fishes, this is one of the first studies to provide evidence that these measures can be successful.

“Normally, Nassau Grouper are relatively solitary, and tend to be hard to catch,” said Lynn Waterhouse, a former PhD student in the Semmens Lab at Scripps Oceanography and research biologist at the John G. Shedd Aquarium in Chicago. “But at spawning, they come together en masse to form annual spawning aggregations, where historically tens of thousands of fish come together to reproduce, so they’re very easy for fishermen to catch.”

Due to overfishing during spawning, the species has suffered region-wide stock collapse. By the 1980s large aggregations had all but disappeared from the Caribbean region. Of the remaining aggregations, few contained more than 1,000 individuals and the species is currently listed as critically endangered by the International Union for Conservation of Nature.

In 2001, an aggregation of around 7,000 Nassau Grouper was discovered near Little Cayman, the smallest of the three islands located south of Cuba in the Caribbean Sea. In 2003, the subsequent rapid overfishing of the aggregation drove the Cayman Islands Government to enact aggressive management policies by banning fishing at aggregation sites during the spawning season. Through the Grouper Moon Project, the Cayman Islands Department of Environment (CI-DOE) partnered with a citizen conservation group called Reef Environmental Education Foundation (REEF) and scientists from Scripps Oceanography and Oregon State University to develop a monitoring strategy for the remaining Cayman Island aggregations.

“We developed a unique approach for monitoring these populations over the course of nearly two decades,” said senior author Brice Semmens, an associate professor and ecologist at Scripps Oceanography. “This included a combination of using mark and recapture tagging techniques to track the proportion of tagged fish and video transects to count fish across the aggregation.”

The researchers faced a number of obstacles, including funding challenges and particularly difficult monitoring conditions — the Nassau Grouper has the unfortunate habit of aggregating at inconvenient and often dangerous locations along the reef shelf edge, making it difficult for divers to easily observe and tag the aggregation. But with the support of the CI-DOE, the team has been able to maintain their monitoring efforts for over 15 years.

Importantly, the researchers did not just track the number of fish in the aggregation — they worked together with the CI-DOE and local communities to share results and discuss next steps. After reviewing the data being collected by the Grouper Moon Project, in 2016 the government initiated an even more progressive fishing policy, banning all fishing of Nassau Grouper during the winter spawning season along with limits on the number and size of fish that can be kept.

As a result, the team was astonished at how quickly the Nassau Grouper population recovered — over the last 10 years the aggregation on Little Cayman had nearly tripled in size, going from around 1,200 fish in 2009 to over 7,000 in 2018. This growth was due, at least in part, to a rapid increase in the addition of new, younger fish to the aggregation.

“This really demonstrates the power of this collaborative approach to conservation,” said co-author Christy Pattengill-Semmens, REEF’s director of science. “We were able to monitor the population and provide information to support management as the data came in, allowing the Cayman government to respond rapidly with policy changes.

“These efforts have been successful because of the strength of the partnerships among the government, academic research groups, and nonprofits,” she added. “CI-DOE also has a long history of working with fishing communities in the islands.”

The team also emphasized that these results show that patience is key.

“Due to the way these fish breed and the timing and location of spawning events, it can take several generations before the right ocean conditions ultimately facilitate young grouper joining an aggregation,” said Pattengill-Semmens. “This means that communities and governments may need to implement protection strategies over the course of years or even decades to meet their management targets.”

“This is an ideal approach for conservation,” said Semmens. “Just doing the science isn’t enough. You need to partner with groups and governments capable of turning science into conservation decisions that support the local community.”

Florida, USA invasive fish, wrong name corrected


This 2014 aquarium video says about itself:

A pair of my ‘next generation’ Cichlasoma dimerus are guarding a huge number of fry . . . all from a female about 3″ SL.

From the Florida Museum of Natural History in the USA:

Fish switch: Identity of mystery invader in Florida waters corrected after 20 years

January 8, 2020

Sometimes scientists make mistakes. Case in point is the chanchita, a South American freshwater fish that has been swimming in Florida’s waters for at least two decades, all the while identified by experts as another invader, the black acara.

Although the two species look strikingly similar, the black acara is tropical, a native of equatorial South America, while the subtropical chanchita isn’t typically found north of Southern Brazil. Because the chanchita is more cold-tolerant, researchers say it could have a more widespread impact in Florida than the black acara and could threaten native species in North Central Florida ecosystems.

“Even the professionals get it wrong,” said Robert Robins, Florida Museum of Natural History ichthyology collection manager. “The chanchita has been right here, right under our noses. It’s spread into seven different counties and five different river drainages in Florida, well beyond the Tampa Bay drainage where it appears to have been first introduced.”

Introduced by the pet trade, the black acara has been a well-known invader in the Miami area since the 1950s and is now common in South Florida. When a similar cichlid appeared in the waters draining into North Tampa Bay around 2000, scientists assumed the black acara was simply expanding its range or had been introduced a second time.

The misidentification was finally spotted by sharp-eyed amateur fish collectors as well as Mary Brown, a biologist who studies non-native fishes. Brown questioned Robins’ assertion that a specimen he brought home from holiday collecting near Tampa in 2017 was a black acara, Cichlasoma bimaculatum. Although the fish had the same general appearance, something wasn’t adding up.

“The body color and the pattern on the scales on its head just looked a little different,” said Brown, a scientist at the U.S. Geological Survey Wetland and Aquatic Research Center. “It wasn’t the same as the black acara I’ve come across while conducting non-native fish surveys in South Florida.”

Meanwhile Ryan Crutchfield, founder of the fish identification database FishMap.org, was getting feedback from amateur collectors that he’d misidentified a fish as a black acara for an article on the history of the species in Florida. Crutchfield, Robins and Brown took a closer look at the specimens in question, eventually identifying them as the chanchita, Cichlasoma dimerus.

“I don’t think anyone except for the amateurs who have an interest in fishes of Florida thought twice about whether or not these fish were black acara,” Robins said. “They’re out there collecting stuff while quite honestly a lot of us are stuck behind our computers typing emails.”

Because of their hardiness and bright colors, cichlids are often coveted by aquarists. But with about 1,900 species — 20 of which are invasive in Florida — and constant revision to the family’s classification, cichlid identification becomes tricky, Robins said.

Robins said that life color, or how a fish appears in its environment, was likely an essential indicator to amateur collectors the chanchita had found its way to Central Florida. Cichlids can change color according to their surroundings, temperament and time of day. But the colorful variations between species disappear in a laboratory setting, where they’re often preserved in alcohol and lose nearly all coloration.

“When we started going out into the field and collecting them and actually finding them in breeding condition or as dominant males, they’re stunningly beautiful,” Robins said. “I think that’s what the amateur community was keying in on. They’re the ones detecting life color, and that was really instructive in determining this was a different species.”

Once the researchers determined the Tampa invader wasn’t a black acara, it came down to microscopic differences in physiology to identify the species as the chanchita. They relied on CT scanning to zoom in on the number of teeth in the specimen’s outer lower jaw and tiny fingerlike structures along the fish’s fourth gill arch.

The Florida Museum’s ichthyology collection was instrumental in providing insight into the chanchita’s invasion timeline, with specimens dating back 20 years. These specimens had been incorrectly cataloged as black acara, but were key indicators of when the chanchita colonized Central Florida, where the species formed reproducing populations as early as 2000.

Brown said non-native fish species like the chanchita have the potential to impact Florida’s aquatic ecosystems by outcompeting native fishes for habitat and food resources.

“Locating and identifying non-native fishes requires an interdisciplinary approach and coordination with partners from across the state,” she said. “This finding is leading us to look at other non-native fish species — it’s possible that there may be other fish out there that are misidentified, and properly identifying the species is critical for proper management.”

Florida is a welcoming arena for invaders to compete with native species and one another due to the state’s intersection of tropical and temperate climates. Constant invasions pose a challenge to conservationists and can often threaten already-endangered native species. Robins said Florida waters could be the chanchita’s first chance at meeting the black acara — and what happens afterward is anyone’s guess.

“Will they hybridize? Would it matter other than just making things more confusing? Are there other species of acara that have been let loose and established populations? What’s actually happening in the environment?” Robins said. “Florida’s aquatic ecosystems are, in a nutshell, one big experiment.”

Ancient fish fins before evolution to amphibians


This 2016 video says about itself:

The evolution of fish began about 530 million years ago during the Cambrian explosion. Early fish from the fossil record are represented by a group of small, jawless, armoured fish known as ostracoderms. Jawless fish lineages are mostly extinct. An extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placoderm fossils. The diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors. The evolution of fish is not studied as a single event. since fish do not represent a monophyletic group but a paraphyletic one (by exclusion of the tetrapods).

From the University of Chicago Medical Center in the USA:

How fish fins evolved just before the transition to land

December 31, 2019

Research on fossilized fish from the late Devonian period, roughly 375 million years ago, details the evolution of fins as they began to transition into limbs fit for walking on land.

The new study by paleontologists from the University of Chicago, published this week in the Proceedings of the National Academy of Sciences, uses CT scanning to examine the shape and structure of fin rays while still encased in surrounding rock. The imaging tools allowed the researchers to construct digital 3D models of the entire fin of the fishapod Tiktaalik roseae and its relatives in the fossil record for the first time. They could then use these models to infer how the fins worked and changed as they evolved into limbs.

Much of the research on fins during this key transitional stage focuses on the large, distinct bones and pieces of cartilage that correspond to those of our upper arm, forearm, wrist, and digits. Known as the “endoskeleton”, researchers trace how these bones changed to become recognizable arms, legs and fingers in tetrapods, or four-legged creatures.

The delicate rays and spines of a fish’s fins form a second, no less important “dermal” skeleton, which was also undergoing evolutionary changes in this period. These pieces are often overlooked because they can fall apart when the animals are fossilized or because they are removed intentionally by fossil preparators to reveal the larger bones of the endoskeleton. Dermal rays form most of the surface area of many fish fins but were completely lost in the earliest creatures with limbs.

“We’re trying to understand the general trends and evolution of the dermal skeleton before all those other changes happened and fully-fledged limbs evolved,” said Thomas Stewart, PhD, a postdoctoral researcher who led the new study. “If you want to understand how animals were evolving to use their fins in this part of history, this is an important data set.”

Seeing ancient fins in 3D

Stewart and his colleagues worked with three late Devonian fishes with primitive features of tetrapods: Sauripterus taylori, Eusthenopteron foordi and Tiktaalik roseae, which was discovered in 2006 by a team led by UChicago paleontologist Neil Shubin, PhD, the senior author of the new study. Sauripterus and Eusthenopteron were believed to have been fully aquatic and used their pectoral fins for swimming, although they may have been able to prop themselves up on the bottom of lakes and streams. Tiktaalik may have been able to support most of its weight with its fins and perhaps even used them to venture out of the water for short trips across shallows and mudflats.

“By seeing the entire fin of Tiktaalik we gain a clearer picture of how it propped itself up and moved about. The fin had a kind of palm that could lie flush against the muddy bottoms of rivers and streams,” Shubin said.

Stewart and Shubin worked with undergraduate student Ihna Yoo and Justin Lemberg, PhD, another researcher in Shubin’s lab, to scan specimens of these fossils while they were still encased in rock. Using imaging software, they then reconstructed 3D models that allowed them to move, rotate and visualize the dermal skeleton as if it were completely extracted from the surrounding material.

The models showed that the fin rays of these animals were simplified, and the overall size of the fin web was smaller than that of their fishier predecessors. Surprisingly, they also saw that the top and bottom of the fins were becoming asymmetric. Fin rays are actually formed by pairs of bones. In Eusthenopteron, for example, the dorsal, or top, fin ray was slightly larger and longer than the ventral, or bottom one. Tiktaalik’s dorsal rays were several times larger than its ventral rays, suggesting that it had muscles that extended on the underside of its fins, like the fleshy base of the palm, to help support its weight.

“This provides further information that allows us to understand how an animal like Tiktaalik was using its fins in this transition,” Stewart said. “Animals went from swimming freely and using their fins to control the flow of water around them, to becoming adapted to pushing off against the surface at the bottom of the water.”

Stewart and his colleagues also compared the dermal skeletons of living fish like sturgeon and lungfish to understand the patterns they were seeing in the fossils. They saw some of the same asymmetrical differences between the top and bottom of the fins, suggesting that those changes played a larger role in the evolution of fishes.

“That gives us more confidence and another data set to say these patterns are real, widespread and important for fishes, not just in the fossil record as it relates to the fin-to-limb transition, but the function of fins broadly.”