Leptocephalus larvae

Some of the most beautiful and conspicuous animals we encounter in the plankton images are leptocephalus larvae. Eels, bonefish, ladyfish, and tarpon form a diverse superorder of fishes (Elopomorpha) that all begin their planktonic lives as leptocephalus larvae, which are characterized by long and laterally compressed bodies that are almost completely transparent. This type of larva is known by scientists to be relatively primitive, meaning that leptocephalus larval forms have been utilized by fishes for millions of years – probably since the Cretaceous period.

In this image, the you can see the backbone and the myomeres along the body. On the left side, the mouth of this larva is open.

Tarpon and bonefish larvae are slightly modified from the classic leptocephalus form. Unlike the eel leptocephali, tarpon and bonefish larvae are thinner vertically and have a well-developed caudal fin, which they use to swim.

Partial image of the tail region of a tarpon, bonefish, or ladyfish.

Most leptocephalus larvae (sometimes referred to as “leptos”) have a large set of teeth that protrude outward. For a long time, the diet of leptos was a complete mystery because their guts appeared to be empty. We now know that they rely on particulate matter, also known as “marine snow”, as their primary food source (Miller et al. 2013). Our in situ imaging work has revealed that leptos are quite abundant, particularly in the northern Gulf of Mexico, and have a variety of complex behaviors that may help them survive in a realm of intense predation pressure. We recently published a paper presenting evidence that the morphology of these leptos indicates that they likely serve as Batesian mimics of cestid ctenophores, which are strikingly similar in appearance (Greer et al. 2016). By resembling an animal with low nutritional value that predators avoid (the cestid ctenophore), the leptos gain protection from predators. The only perceivable morphological difference is that leptos have a head and a dark backbone with myomeres (muscle strands) that are visible when viewed through a shadowgraph imager, while cestid ctenophores lack these features. For a fish predator relying on vision in a complex ocean light environment, it may not be able to tell the difference, which could explain why predation rates on leptos are much lower than expected (Miller et al. 2015).

Cestid ctenophore

Leptocephalus larva – note the similarity in morphology to the cestid ctenophore above.

Leptos display complex behaviors that can make them difficult to identify in the images (and likely has a similar effect on predators). This one is curled up. The main cues that this is indeed a lepto are the visible myomeres, and the head and tail are meeting on the left and right sides of the body, respectively.

Leptocephalus larvae are fascinating, and we are just beginning to unlock some of the secrets of their biology and ecology through imaging. By combining the data produced from imaging them in their natural environment with other techniques to assess diets and predation pressure, we hope to learn more about these animals and what processes impact their survival during their time in the plankton. After all, some of these leptos eventually grow up to do this:

Source: tampayacht.com

References

Greer AT, Woodson CB, Guigand CM, Cowen RK (2016) Larval fishes utilize Batesian mimicry as a survival strategy in the plankton. Mar Ecol Prog Ser 551:1-12

Miller MJ, Chikaraishi Y, Ogawa NO, Yamada Y, Tsukamoto K, Ohkouchi N (2013) A low trophic position of Japanese eel larvae indicates feeding on marine snow. Biol Lett 9:20120826

Miller MJ, Dubosc J, Vourey E, Tsukamoto K, Allain V (2015) Low occurrence rates of ubiquitously present leptocephalus larvae in the stomach contents of predatory fish. ICES J Mar Sci 72:1359-1369

Introducing Kelsey Swieca!

As a new member of the Plankton Portal Science Team, I would like to introduce myself. I am Kelsey Swieca, a Doctoral Student at Oregon State University under Drs. Su Sponaugle and Robert Cowen. Originally from Chicago, I moved to Oregon to attend the University of Oregon where I received my B.S. in Marine Biology. At Oregon State University I will use our first set of ISIIS images off the Oregon Coast to try and answer a few questions about larval fish interactions with prey, predators, and competitors.

Plankton distributions are typically patchy in nature forming aggregations of prey with their predators following suit. Although these prey aggregations enhance larval fish feeding, they may also promote predation and competition by decreasing spatial distances between larval fish and their predators and competitors who have all come to feed on the prey. My work aims to understand how different oceanographic conditions impact these spatial distributions and thus larval fish interactions in the highly productive and oceanographically dynamic Northern California Current.

I’m really excited to be a member of this team and look forward to classifying with you!

Kelsey_Shimada.png

Kelsey Swieca on a research cruise aboard the NOAA FSV Bell M. Shimada off the Oregon Coast in June, 2016.

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Dr. Robert Cowen and Kelsey Swieca in the dry lab of the NOAA FSV Bell M. Shimada, monitoring an ISIIS transect off the Oregon Coast. June, 2016.

What’s it like in a thin layer?

During the CONCORDE summer field sampling campaign, we had the good fortune of towing the ISIIS through a unique oceanographic feature called a “thin layer.” Thin layers are dense aggregations of phytoplankton or zooplankton that have a vertical dimension of less than 3 meters and have concentrations of at least 2-3 times the water column average abundance. They can span hundreds of meters to several kilometers in the horizontal dimension. This series of images shows how the plankton concentrations dramatically change from just underneath to above the thin layer. The hairlike objects are phytoplankton called diatoms, but there are also lots of zooplankton in the vicinity of the layer. Here you can see the barrel shaped doliolids, which are grazers of phytoplankton, as well as copepods and chaetognaths.

Image taken just below the thin layer

Image taken just below the thin layer

Within the thin layer

Just above the thin layer

Just above the thin layer you can see lots of marine snow particles and a chaetognath.

Further above the thin layer, the plankton concentrations are not as intense.

Further above the thin layer, the plankton concentrations are not as intense.

Keep in mind that all of these images were taken within a few meters of each other. It is amazing to see firsthand how dramatically the ocean environment can change, and how these organisms respond this variability. Is this something they normally experience? The next steps are to use the image data to quantify the changes in abundances and look at the different mechanisms that may have caused this thin layer to form.

PlanktonPlanet

innovative citizen sailing oceanography

Just discovered this, after reading the Tara Expedition news periodical while visiting Tara in Miami! This is a very interesting Citizen Science project inspired from the Tara Expeditions. The idea is to “recruit” the help of volunteer sailors across the world and have them collect plankton using a very simple method of sample preservation. The sample is then sent to a lab for DNA barcoding to look at the different species present in the sample. A very elegant way to do oceanography.

 

Fig-F-EN

go visit:  www.planktonplanet.org

Happy anniversary Plankton Portal 2.0!

Blog post by Jean-Olivier Irisson

A year ago, we announced Plankton Portal 2.0, which featured a more streamlined design, a simpler tagging interface, and most importantly, a whole new dataset. Since then, this new data from the Mediterranean Sea has spurred a lot of interest and plenty of new questions. Participants on the site were surprised by the difference in size of everyone’s favourite jellies, the Solmarisidae (Solmaris rhodoloma in California, Solmissus albescens in the Med), which are much larger! Siphonophores also seem more abundant there. And the Mediterraean data came with brand new categories of organisms to mark: nice and cute medusa ephyrae (i.e. baby jellies), elegant Pteropods and the elusive fish larvae.
In total, as of last Sunday, 368,361 organisms were marked, on 50,519 distinct images. Through time, the classifications were marked by two peaks in activity: a huge one when the new version was announced through a mailing to the Zooniverse community (thanks everyone!) and another one when we pushed for 1,000,000 classifications in total, to celebrate Jessica’s PhD defense. When we zoom in, we see activity fluctuating around 1000 and now 500 classifications per day. This is still great (but coming back to 1000 would be even better! 😉 ).
time_series
time_series_zoomed

 

The top 11 contributors, all authors of over 5000 classifications each, are displayed below. If you made this top 11, we owe you special thanks (and probably a beer too). We hope you will stay interested and involved in this project. If you did not, you should really not be disappointed because all other volunteers still collectively account for 60% of the classifications; so you matter very much! Hopefully all of you will be happy to see some of the outcome of your work below.
who

 

Time for a bit of science! The most common classification was… nothing, empty, zero, zlich, zip… Well, you get the idea. Indeed, when we film the sea, we most often see nothing (nothing living at least). Even though we pre-selected potentially interesting frames for Plankton Portal (the ones having some kind of large object in them), about a third of your classifications did not contain any organism we were interested in. In real life, the proportion of dead detritus vs. living organisms is more around 95% vs. 5%, so our pre-filtering still avoided you a lot of blank frames! In terms of organisms, the 10 most abundant are shown in the figure below.

what

 

Doliolids, Copepods, and Radiolarian colonies dominate the rest. We immediately noticed, when we shot the images, that Doliolids were particularly abundant. Those organisms are very effective filtering machines and they may therefore have an impact on the density of smaller organisms, in particular unicellular algae. The relative abundance of Copepods and Radiolarian colonies is to be interpreted carefully: Radiolarian colonies can be large and span several frames (therefore increasing the total count) and Copepods are likely under-estimated because we mostly see the larger ones with ISIIS, and they are not the dominant ones in the Mediterranean. Still, it echoes nicely a recent Nature paper by Tristan Biard (a contributor to PlanktonPortal’s talk, under the username Collodaria), which showed that Rhizaria (a large taxonomic group to which Radiolarians belong) can be equivalent in biomass to Copepods, who were previously thought to largely dominate the plankton. These findings were also based on in situ images, because these fragile Rhizaria cannot be collected with nets.

 

Finally, the images in the Mediterranean were collected along transects (i.e. straight lines) perpendicular to the shore. We were interested in how organisms were distributed along a gradient between coastal and open ocean conditions. In the plots below, the coast is on the left, the open ocean on the right and the vertical direction is depth (top: surface; bottom: 100 m depth). So you basically see a “slice” of water along which ISIIS undulated. The size of the dots is proportional to the number of classifications recorded. You can immediately notice that Doliolids (first plot) are concentrated near the surface, and fish larvae (second plot) even more so! This is a surprising finding for fish larvae, which sometimes ended up in concentrations of over 10  individuals per cubic meter, a number much higher than what was previously observed elsewhere, with conventional plankton nets.
distrib_doliolid_w_icondistrib_fish_w_icon
Radiolarian colonies, on the opposite, tend to be concentrated in mid water (see figure below). Within this messy picture, some structure seems to emerge. Indeed, the white lines on top of the plot are contours of the concentration of Chlorophyll A in the water (i.e. of the amount of unicellular algae). If you look carefully, you will see that those lines are moving up, towards the surface, as we travel offshore (from left to right on the plot). This is actually well known in this region. What is interesting is that the radiolarians seem so follow the same pattern, and that higher concentrations of colonies sit on top of this high Chlorophyll region. Something is definitely going on between these two!
distrib_radiolarian_colonies_w_icon
That’s it for now — thanks again to everyone for this wonderful year of activity! We apologise for not being as active as we would like to be on Talk. To that end, we thank the active moderators who take over this important responsibility. And finally, we thank Zooniverse for the great opportunity and community they created. Now, on to next year!

Stomatopods: amazing eyes

The more I learn about stomatopods (also known as “mantis shrimps”), the more fascinated I become with these true marvels of evolution. From the image data we have processed so far from the CONCORDE fall and spring field campaigns, it is pretty clear that stomatopod larvae were quite abundant in the nearshore waters of the northern Gulf of Mexico. As you can see from the images below, they are really cool looking animals – even Hollywood took notice, as stomatopods served as the inspiration behind the alien queen in the movie “Alien.”

Stomatopod larvae imaged in the northern Gulf of Mexico on October 30, 2015

Stomatopod larvae imaged in the northern Gulf of Mexico on October 30, 2015

The first thing you notice when you see the images of the larvae are those giant stalked eyes protruding from their heads. The eyes, which appear to be well developed in the larvae, are one of the most remarkable adaptations of the adult stomatopod. Unlike mammals and cephalopods, which have a camera like eye (single lens projecting an image onto a retina), stomatopods have a highly specialized compound eye, and each eye often moves independently from the other. They also have 12 visual pigments, giving them a huge range of detectable wavelengths, from infra-red to ultraviolet – much more than other invertebrates (Land & Nilsson 2012). In comaprison, humans only have three visual pigments (red, green, and blue), and the stomatopods can even detect different types of polarized light. Have you ever heard of circular polarized light? Well, they can see that too! The males have certain parts of the body can reflect circular polarized light in both right and left hand directions. The band across each eye has 4 rows of ommatidia that can see in color, and two rows (one on each end) detect polarized light (Chiou et al. 2008).

Image source: http://www.abc.net.au/catalyst/stories/3280489.htm

Image source: http://www.abc.net.au/catalyst/stories/3280489.htm Also, check out the interview with Dr. Justin Marshall who has been studying mantis shrimps for almost 20 years

Another impressive thing about stomatopods is their method of capturing prey. Different species of stomatopods use one of two different attack methods: smashing and spearing. You can tell what method it uses based on the morphology of the stomatopod appendages. The smashers have clubbed appendages that they flick outwards to smash their prey, and the spearers have pointy appendages that they can use to puncture their prey. The force created by these attacks is extremely powerful for their size. In fact, the movement of the appendages is so quick that it generates a large cavitation bubble. The phenomenon of cavitation happens when something in the water moves so fast that an empty space is created that the water cannot fill quickly enough. When a boat propeller rotates at a fast rate, it generates tiny cavitation bubbles. It is quite rare for an animal as small as the stomatopod to generate enough force to cause cavitation.

References:

Chiou T-H, Kleinlogel S, Cronin T, Caldwell R, Loeffler B, Siddiqi A, Goldizen A, Marshall J (2008) Circular polarization vision in a stomatopod crustacean. Current Biology 18:429-434

Land MF and Nilsson D-E (2012) Animal Eyes (2nd ed.) Oxford University Press

Fantastic Find Fridays: Feb 2016

Hey plankton hunters!  We are bringing you another round of Fantastic Finds from the Plankton Portal.  Citizen scientists continue to reel in new captures of some truly awesome plankton.  Here are just a few neat finds, ID’s, and novel taxa:

Pteropod mollusk

pteropod

Did you ever learn about marine butterflies in grade-school?  Well good, because there is no such thing as a marine butterfly.  This elegant-looking critter is a pteropod, a type of gastropod mollusk—in other words, a slug!  These mollusks are highly adapted for life in the water-column, as you can see from the butterfly-like wings, (or “parapodia” to a malacologist).  The pteropod wings are actually a highly-modified molluskan foot, i.e. the muscular and slime-secreting mass that slugs glide on.  Evolution really did these slugs a favor, as I do not think anyone could say “ewww!” to such a beautiful animal.

Calycophoran Siphonophore

caly_sipho

Now this is a fantastic image.  A close-up, finely-detailed capture of the head (nectosome) portion of a calycophoran siphonophore—so aptly referred to as a “rocket-ship sipho” here on the Plankton Portal.  The two siphon-like features propelling this colonial critter are very apparent in this image.  Maybe, in truth, siphon-ophore is a pretty apt name for this plankter as well.

Ctenophore: Thalassocalyce inconstans

thalass

Thalassocalyce inconstans is a predatory species of ctenophore, captured feeding in this frame.  The body of the ctenophore is contracted and engorged about the anteroposterior (vertical) axis, giving it the appearance of an inflated, heart-shaped balloon.  Within the fragile and transparent body, you can see the 8 condensed comb rows captured as an array of ragged segments crowning the aboral end.  Fine mesenterial canals also appear as contoured markings that line the engorged body. Ctenophores are tactile predators, meaning all predatory behavior is triggered by physical, non-visual stimulus.  Something in the water column bumped into this Thalasso and got it all riled up, providing ISIIS a great opportunity for this detailed capture of foraging behavior.  If we had a hydrophone for this deployment, I am fairly certain a satisfied lip-smacking would be recorded in a few seconds.

Copepods: Families Eucalanidae and Metridinidae. 

copepods

Copepods are abundant in these ISIIS data, and it is easy to forget what a broad diversity of these important crustaceans are classified on the site.  Here we have two broadly identifiable PP copepods for sample.  The image on the left shows a copepod belonging to the family Eucalinidae: it has a narrow, torpedo-shaped body and the anterior end of the head forms a pointed-triangle.  We think this critter might be a Rhincalanus spp.—if you look close you might be able to make out a small rostrum-like appendage extending forward and tucked down from the head, as well as what may be lateral spination at the end of each mid-body segment (prosome).  This guy’s cruising, antennas spread out and scanning the surroundings.  On the right, we have a copepod belonging to the family Metridinidae, perfectly poised for the ISIIS cam.  How do we guess this ID?  At the end of this copepods lengthy tail (urosome), look closely at the paired fin-like feature (ferka).   Along the outer edge, right before the separation of the individual ferka, can you make out a small, skirt-like protrusion?  If so, just tell your buddies: “hmm, check out that lengthy urosome and ferka segmentation; it must be a Metrinidae species,” and blamo—you are a crustacean taxonomist!

Anthomedusae: Leukartia spp.

anthomed

At first glance, you might be thinking “is this medusae sticking its tongue out at me?” Or maybe it is sporting a ten-gallon hat?  While I couldn’t blame you for such outlandish assertions (I mean, who would write such silly things?), this odd anthomedusae is readily identified to genus by the conical appendage extending from the bell (“apical process”) and causing much confusion on the Plankton Portal.  In this image we get a great view of many internal and external features of this Leukartia sp., including a crenulated (ragged) bell margin, a tall mouth (“manubrium”) in the center of the bell, and many long tentacles projected both downwards and in front of the bell.

Larvacean and mucous house

larvacean

We find a good deal of larvaceans on the site, but this capture is a real beauty.  Larvaceans are gelatinous plankton that filter-feed on detritus in the water column.  You see the critter poking its head out, like the cap on a rolled-up toothpaste tube?  That’s the larvacean, curled up in preparation to pump surrounding detritus through its elaborate mesh-like mucous house.  For a critter that takes up residency in its own secretion, this guy is pretty adorable!

Physonect Siphonophore

sipho_forage

Now this is quite the fantastic find!  Here we are looking at a large siphonophore projecting numerous tentacles across the frame.  It is all-hands-on-deck for this colonial jelly, as it is putting on a mighty foraging display for us.  The big guy is hungry—watch out, ISIIS.

There have been way too many great images to fit in this small serving of photogenic plankton.  We look forward to serving up more fantastic finds in the future.  Keep exploring, plankton hunters!

Harmful Algal Bloom in the Gulf of Mexico

For many of us living on the southern (Gulf) coast of the USA, it has become common to see numerous dead fishes floating in the bays and scattered across our beaches. Why is this happening? You may have heard on the news that there is a large harmful algal bloom (HAB) that began off the western coast of Florida and has slowly spread throughout the Gulf over the past few months. While the HABs occur somewhat regularly in Florida, it is quite rare for them to extend as far north as they have this year. The last major HAB of this particular dinoflagellate species (Karenia brevis) occurred ten years ago. The Mississippi Department of Marine Resources has been monitoring the bloom recently, and they have seen some of the negative effects of the ecosystem.

The lumpy greenish-translucent blob is Karenia brevis. These images were captured with the FlowCam, which is an instrument that images algal sized particles in a water sample.

The lumpy greenish-transparent blob (near the center of the photo) is Karenia brevis. These images were captured with the FlowCam, which is an instrument that images algal sized particles in a water sample.

thousdands of deadGulf Menhaden accumulate at a front off the coast of Mississippi. Fronts concentrate floating objects by providing a convergent flow.

Thousands of dead Gulf Menhaden accumulate at a front off the coast of Mississippi. Fronts concentrate floating objects (dead fish and other debris) by providing a convergent flow (photo by Adam Greer taken on Dec. 15, 2015).

So how do these tiny plankton kill the fish that we see washing up onshore? After all, the individual phytoplankton within the HAB are only about 20 microns in size (that is 0.02 mm). Karenia brevis (a.k.a. “the red tide” derived from its brownish-red color at high concentrations) naturally produces a compound known as brevetoxin – a potent neurotoxin that inhibits sodium channels required for many neurological processes. Some of the most abundant fish species in the Gulf of Mexico are filter feeders such as Gulf Menhaden. These are commercially important fish that feed by opening their mouths and swimming to capture as much phytoplankton as they can. Karenia brevis is often present off the Florida coast, but in low abundances. Under these circumstances, Karenia brevis does not harm the fish that consume it. Only when the concentrations reach extreme levels do the fish experience the negative effects of the brevetoxin. Filter feeders like the menhaden are most directly impacted by the phytoplankton-produced toxin; however, the organisms that consume these fish are also susceptible to the harmful neurological effects. Large black drum have also been washing up onshore, presumably killed by eating too many menhaden and other fish species that had built up high levels of toxin in their tissues. Even dolphins and birds can become very sick from eating these suddenly toxic fish.

Adam Boyette runs the FlowCam to characterize the phytoplankton community and monitor the HAB

University of Southern Mississippi scientist Adam Boyette runs the FlowCam to characterize the phytoplankton community and monitor the HAB.

Why is this bloom so severe this year? While there are probably a variety of factors at play, most agree that an unusually strong El Nino is likely the primary culprit. Along the Gulf coast recently, it has been unseasonably hot and dry. The winds have also been calm. This provides ideal conditions for Karenia brevis to proliferate and form dense aggregations. With cooling temperatures, the growth rates of these phytoplankton should decrease. The increasing amounts of rain and wind recently should cause these HAB patches to break up, diluting the extreme concentrations, which will hopefully mitigate the harmful effects on Gulf of Mexico ecosystem.

1 million classifications!

Last week, Jean-Olivier and Zuzana organized a push to one million (1,000,000) classifications here at Plankton Portal in honor of my defending my PhD on Friday, October 30, 2015.

Jessica_Luo_defense_titleslide

Title slide for Jessica’s defense seminar

The PhD defense at the University of Miami essentially consists of a 1-hour public seminar on my dissertation research, which I had conducted over the last five+ years, and then a multi-hour private question-and-answer session with my  committee. In my case, my committee consisted of my advisor, Dr. Robert K. Cowen, and four other professors, Drs. Su Sponaugle, Gary Hitchcock, Rob Condon, and Jean-Olivier Irission. At the end of the private session, if the work and the answers to the questions were deemed satisfactory, then the student passes and essentially is this granted a doctorate.

So I have two happy news: 1) My PhD defense was successful – all went well! and 2) We did it! Plankton Portal reached one million classifications by the time I defended!

PP_1million

The above photo shows Professor Cowen, me (Jessica), and Cedric Guigand with ISIIS (the instrument that collects all the cool images in Plankton Portal!) on board the R/V Walton Smith on a cruise in the Florida Keys this past summer. We had taken it in anticipation of a Plankton Portal classification milestone; little did I know that it would be in conjunction with my PhD milestone!

In my PhD, I looked at gelatinous zooplankton (jellies) in marine ecosystems from three contexts: in aggregations at fronts (that’s the California current dataset on Plankton Portal!), as predators of other plankton in driving vertical migrations, and as contributors to the global carbon cycle. For the first two parts (“chapters”), I focused on small jellies, and studied them using ISIIS, and for the last chapter, I conducted a modeling study on all jellies (medusas, comb jellies, and salps/pelagic tunicates) over the global oceans. It’s been a really educational process for me, learning about jellies, imaging systems, modeling, and overall, how to do science. I’ve been able to publish one of my dissertation chapters already, and look forward to publishing the rest over the next six months. Grad school has also been a really fun opportunity for me to get out in the field (on five research cruises), go to conferences all around the world (Japan, Spain, Hawaii), help run citizen science projects like Plankton Portal, and just overall meet some incredible people who do fascinating work. It’s been a total privilege, one that I haven’t taken lightly. And I look forward with anticipation to the journey to come. Onwards and upwards!

Images from the first leg

Things are going well onboard the R/V Point Sur as we finish up the first leg of the CONCORDE fall research expedition (www.con-corde.org). Although the water column has been well mixed from the recent windy conditions, we are seeing a lot of structure with regards to the biology. As we move along the transects, we see distinct changes in the plankton community. Here are just a few examples of the types of organisms we are seeing.

Plankton_20151029132211.638.avi_13_254_252_85_234jpg

This looks like something out of an alien movie, but it actually a stomatopod larva. Stomatopods are also known as mantis shrimps and, like many ocean animals, have egg and larval stages in the plankton. Adult stomatopods can give one of the most powerful strikes of any animal for its size. They use their club-like appendages seen in the image to bash their prey, stunning or killing it before consumption. Stomatopods, with their large compound eyes, also have some of the best visual acuity for any invertebrate.

Plankton_20151102112036.823.avi_176_296_267_874_1557jpg

Today we also found this larval squid (~1 cm in size). It was imaged right next to two similarly sized squid larvae, so we can only assume that they were spawned from the same parents or spawning event (i.e., they are members of the same cohort). Many larval animals may aggregate in this fashion to protect themselves from predators. Even though aggregating together may not reduce each individual’s chance of encountering a predator, the schooling behavior probably has a benefit because predators may become confused by the many potential targets in close proximity.

Plankton_20151029103645.818.avi_69_1069_1093_955_885jpg

This last image is one that is truly exceptional. It shows a large scyphomedusa (jellyfish) that covers almost the entire image. The field of view on the ISIIS is about 13 cm, and we can estimate that this individual is at least twice that size. It is likely a moon jelly (Aurelia spp.), but the most remarkable thing are the fish larvae aggregating underneath it. We can see four larvae that appear to be jacks or butterfish that seem to be using the moon jelly for shelter or protection. Jellyfish are often thought of as predators of fish larvae, but images like this one show that that interpretation may be a bit simplistic. A few types of fish larvae are known to use jellyfish for protection because some larval fish predators avoid eating jellyfish due to their stinging nematocysts and low nutritional value. It is extremely rare to document this kind of behavior, especially the large number of larvae aggregating under one moon jelly.