Nest guarding

While we're on the subject, I'll share this short video.  Many sunfish (in the Family Centrarchidae) also build and guard nests.  Often, it's the little males that pull guard duty.  That's the case in the longear sunfish, Lepomis megalotis.  While sampling a local stream, we watched this little guy and his buddies working hard guarding eggs from marauding bluegills.

A couple of stickleback stories...

The three-spined stickleback, Gasterosteus aculeatus, has been a heavy hitter in ichthyological research for decades.  Niko Tinbergen, who would share a Nobel Prize in 1973 with Karl von Frisch and Konrad Lorenz, helped create the field of ethology with his pioneering observations of stickleback courtship behavior.  I encountered sticklebacks during my time in Oregon and Alaska, but not since.  They're widespread across the Northern Hemisphere, but being coldwater guys they aren't typically found south of North Carolina on the Atlantic Coast.  That's too bad - they're great little fish for number of reasons.  They show a wealth of morphological diversity, making them ideal for the study of adaptation.  Although they're anadramous, typically spawning in fresh water but maturing in the sea, they can live out their lives in fresh or salt, and show a remarkable ability to deal with a wide range of salinities.  It's in their behavior, most notably their spawning behavior, that's been most heavily examined.  Males invest a lot of time and energy in buiding nests, to which they entice females and then guard ferociously until the eggs hatch.

Stickleback nest

Well, it appears that European sticklebacks have had a tough spring.  Rivers there are swollen from heavy rainfalls, and currents are higher than normal.  This means that male sticklebacks there are having to put in extra duty to make sure their nests don't get lost in the flood.  The nests are constructed of materials that the fish can find in the river, sand and pieces of plant material.  The building materials, though, are cemented together with "spiggin", a glycoprotein glue produced by the male stickleback.  Spiggin is produced during the breeding by hormonally-influenced epithelial cells in the kidneys.  According to results published in Avian Biology Research, this high-flow year is forcing the fish to produce more spiggin than normal - a task that could potentially draw energy away from other important processes.  Thus far, the fish seem to be holding their own - another indication of a fish that seems to be a master of adaptation. 

Shoaling sticklebacks (photo by
Steve Thomas)

While we're talking about sticklebacks...  Another of their interesting behaviors is the tendency of non-Researchers at the Konrad Lorenz Institute of Ethology offered individual sticklebacks the opportunity to join two schools of fish, one made up of siblings and one made up of unrelated individuals.  The sibling group was in some cases made up of familiar fish, and in other cases made up of relatives with which the test fish was unfamiliar.  The test fish chose to join the sibling group whether they were familiar with the members or not.  The researchers then extended the experiment, giving the sticklebacks a choice between groups of familiar and unfamiliar relatives.  Surprisingly, the test fish showed no preference.  In this case, the kin preference is driven by something other than familiarity.
breeding fish to gather in groups or shoals.  In the formation of these shoals, sticklebacks  prefer the company of relatives.  The basis for that preference has been uncertain - is it innate based on some sort of olfactory cue that identifies related individuals, or is it developed by interactions during the fish's life history.  

New Caribbean blenny

Haptoclinus dropi

From Zookeys, this report of a new haptoclinid blenny.  Haptoclinus dropi is tiny, about an inch long, and has the unusual four-sectioned dorsal fin of the other members of the genus.  It was discovered in the southern Caribbean at depths of about 160 meters as part of the Smithonian's Deep Reef Observation Project using the manned submersible Curasub.  The Curasub, which operates out of Substation Curacao, normally operates carrying tourists to depths of over 300 meters.

News

Time to catch up on a few items on the fish front.

Sharks may be worth more alive
than dead

A shark in the bush (so to speak) may be significantly more valuable than a shark in the hand.  A study published recently in Oryx - The International Journal of Conservation and using data from 70 sites in 45 countries estimates that shark-related ecotourism brings in over $300 million dollars annually, and that the value of the industry may more than double over the next two decades.  Contrast that to $630 million, the estimated value of global shark fisheries - and throw in the fact that value of those fisheries steadily declining. The takehome - leave those sharks alone.  Shark-related tourism in the Caribbean alone leads to over 5,000 jobs and produces over $100 million in revenue.

The lookdown, Selene vomer

In the new Proceedings of the National Academy of Sciences, we hear about new ideas related to fish camouflage in the open ocean.  Traditionally, it has been believed that a fish's best strategy in open water has been to make itself less visible by using a mirror effect, reflecting sunlight to allow the prospective predator or prey to blend into the background.  New research suggests that this strategy, while effective in some circumstances, does not work well in others.  This is particularly true when light penetrating the surface is polarized.  Turns out that many fish species are sensitive to polarization, and the the nature of polarized light is constantly changing.  This means that a mirror strategy won't always be the most effective camouflage.

The authors of the PNAS paper observed lookdowns (Selene vomer), and found that the fish were able to change the way in which light reflected from their bodies in a manner that approached the optimum with regard to camouflaging themselves.  In some light situations, that meant acting like a simple manner.  At other times, the reflected light was altered so as to make the fish less visible in a polarized environment.  It's unclear if the process is passive, with the skin of the fish responding to the available light, or if the fish or somehow activity changing the way light is reflected.

In the Prehistoric Fish o'the Day category, a paper appearing in Geodiversitas describes a new species of acanthodian which lived during the Devonian some 408 mya.  The fossils, discovered in Eastern Spain, are mainly from juveniles with none from fish larger than a meter in length.

Acanthodian

The acanthodians, sometimes referred to as "spiny sharks", were among the first of the jawed vertebrates.  They were characterized by a series of stout spines in front of all the fins.  Many of the early acanthodians had two rows of paired ventral fins.  This makes them particulary interesting to students of vertebrate evolution, as the rows of fins have been suggested (through the fin-fold theory) to have paved the way for the evolution of paired fins and, ultimately, limbs.

There are lots of different things that we call "fish", and they belong to lots of different taxonomic groups.  I mean, hagFISH aren't even considered vertebrates any longer.  Still, all of the 28,000 or so species that we refer to as fish all have some basic similarities, likely due to the unforgiving nature of the aquatic realm.  You can't be evolutionarily sloppy and function well in the water.  However, within the basic fish template, there's still room for a lot of diversity.  This week in Fish Biology, we'll be discussing body forms, the many ways that the basic fish design has been molded to better function in a specific role. Regardless, here's a teaser. Scientific binomials, so as not to give anything away in the common names.

What drives the...

...odd mouth of Nemichthys scolopaceus,

....the spectacular dorsal fin of Istiophorus platypterus,

...or the misshapen fins of Histrio histrio?

Is there adaptive value in the magnificent rostrum of Pristis pectinata,

...or of Polyodon spathula?















What about the greatly elongated pectoral fins of Cheilopogon melanurus,

...or pretty much anything about Ogcocephalus darwini?

Why does Chaenocephalus have yellow blood?












And, finally, what in blue blazes is going on with Macropinna microstoma?

Fish - eries

There's been a lot written in recent years about the plight of the world's fisheries.  Many of them are in real trouble as the result of overfishing.  One result has been a shift toward reliance on invertebrates like prawns, lobsters, and mollusks.  New research from the Environment Department at York suggests that these new, shellfish-dependent fisheries, may be subject to collapse with increasing stress from climate change.  The authors, in a paper appearing in Fish and Fisheries, suggest that it's imperative that we continue to work toward restoring the health of finfish based fisheries, and stress the need to marine protected areas to allow the restoration of diversity and productivity.

River monsters

A big-river specialist

OK, that was just to catch my students' eyes.  They're addicted, and we do hope to do some big fish work on the Tombigbee this summer.  What I want to talk about here though is not the size of the fish, but the size of the rivers.  A new study published in Frontiers in Ecology and the Environment looks at the prospects for saving big-river specialist fish, those guys that are dependent on big waters like the Mississippi.  The authors looked at distribution patterns of big-river specialists in the Mississippi basin, and found that moderately sized tributaries, those with 166 cubic meters per second, support 80% or more of the basin's 68 big water lovers.

This could be significant for conservation efforts.  There's little that can be done to restore natural conditions to the nation's major rivers.  Perhaps we would be better served to aim some conservation dollars toward these all-important tributaries.

FYI, that 166 cubic meter per second threshold is slightly in excess of 5,000 cubic feet per second (unfortunately, those are the default units on NOAA's hydrologic data reports, like those here).  If I've done the math right, the Tombigbee at Dempolis has a flow rate, at the moment, in the area of 8,000 cfs - that's about 225 cubic meters per second.

A new semester...

...starts tomorrow, and with it we'll try once again to be a bit more active here.  This semester brings Biology of Fish, as well as an online Evolution class - a couple of topics that should lend themselves well to blogging.  Even if it means not collapsing on the couch at the end of the day.

We'll start with this an interesting study examining the evolution of disease.  That's a topic that my evolution students will look at in depth later in the semester.  This one's in birds, house finches to be specific.

Pathogenic organisms can find themselves in a bit of a quandary.  They're dependent on their host organisms for survival, reproduction, and dispersal.  But they run the risk of overdoing it.  As they reproduce, the host may become sick.  If the numbers are too exorbitant, the host may even die.  If a pathogen reproduces in such numbers that it kills or disables its host prior to spreading to new ones, it'll soon be out of the parasite business.  However, coevolution of parasite and host can result in just the right balance of "sickness".

Virginia Tech's Dana Hawley and her coauthors, in a paper published in PLOS Biology, explore the evolution of house finch eye disease, a form of conjunctivitis in the invasive house finch caused by the Mycoplasma gallisepticum.  The researchers expected to see the disease become milder with passing time, all the better to expedite its spread.  They were surprised to see it actually become more virulent. In two different locations.

The house finch, Haemorhous mexicanus,
carrier of house finch eye disease 

What is particularly interesting in this case involves the two regions that were examined.  The study focused on birds from two different areas, California and the Eastern Seaboard.  Samples taken from sick birds in each area from 1994 through 2010 showed increasing virulence.  However, the bacterial strain the spread from east to west across the continent was less virulent.

Apparently, to spread, the bacteria needed healthier birds.  Birds that could fly a little further and live a little longer.  Once established in a location, though, more virulent strains could evolve - sicker birds may not disperse as well, but they produce lots of bacteria.

This relates to a number of other studies that have revealed some truisms about human disease.  For example, a pathogen that can be transmitted through the air or by an insect vector can afford to be more virulent than one that requires the host to be actively eating or drinking.  More to come on that.

Even more remarkable...

...also from New Scientist, this video from the Cetacean Research Institute in South Korea. It shows a group of long-beaked common dolphins (Delphinus capensis) apparently attempting to save an injured dolphin by using their bodies to keep their companion afloat. This went on for over a half hour, until the injured animal died and was allowed to sink.

Great video...

...from the New Scientist web site.

Elephant seals are known to dive to depths of over a mile, remaining submerged for more than an hour, in search of food.  We haven't been able to watch the process, at least at the depths, until this.  A teenager watching a live video feed for a camera at a depth of almost 900 meters in the North Pacific saw this elephant seal making a snack of a lamprey.

Back to work

Seems like it might be time to crank up the old starfish.  I'll be teaching evolution and vertebrate zoology this semester, along with an online offering in biogeography.  This makes for a nice way to share some ideas outside the classroom.  The main problem is overcoming inertia, which gets harder and harder with passing time.  If the posts seem a little forced, especially early on, bear with me.  We'll get there. 

As always, I'll focus here on the things I teach, and the things that fascinate interest my students and me.  That's fish, all things evolutionary, and assorted other items.  Sometimes we get distracted.



Mary Lee being tagged.

As a motivation to get going, I'll share this item on Ocearch.  It was brought to my attention by my daughter, currently residing in Jacksonville, FL.  Ocearch describe themselves as a "non-profit organization with a global reach for unprecedented research on the ocean's giants."  One of their preoccupations happens to be great white sharks, which they tag and track across the world.  One of their tagged great whites is Mary Lee, pictured at right.  Mary Lee, 16 feet long weighing almost 3500 pounds, was tagged last September off Cape Cod.  She spent the fall moving down the Atlantic Coast.  What caught my daughter's eye was the fact that, as of midnight on January 8th, Mary Lee was swimming in the surf zone off Jacksonville Beach.  She's moved a bit offshore over the last couple of days.  You can see where she is now if you follow the links on the Ocearch page, as well as follow a number of other tagged fish.  Pretty amazing stuff.