Author: Emina

Field | Žumberak Mountains 2020

Emina1 Comment

In a previous post about my time at the Žumberak Mountains I mainly focused on my time with the Crustacean group, but today I’d like to write a bit more about my general experience out there in the field. As I already mentioned, I was unable to attend for the whole week, and instead opted for four days only, but all of those four days were completely filled with exploring and socializing (which was, at the time, allowed in our country and county).

Žumberak Mountains, and its Nature Park, is only one hour drive away from Zagreb, however, due to the proximity to the Slovenian border, GPS can steer you in couple of wrong directions, so after collecting some extra things for the campsite, I called Petra, one of the camp leaders, to give me right directions. Everything went rather smoothly, until I almost hit a llama that was chilling in the middle of the road, just behind a steep curve. After my initial confusion cleared up, and the llama left the road, I cautiously continued to drive, wondering what all these llamas were doing in the middle of Europe anyway. As it turns out, there is a bio-park in close proximity, and I guess they escaped their enclosure.
Couple of kilometres down, the road suddenly turned into a macadam, as I basically entered the woods, followed by the sound of a strong stream that was following the road. Well, the road followed the stream, more or less. That evening wasn’t very eventful – I was mostly talking to colleagues and taking pictures; it was rather cold, so we lit up a big fire in the pit, the only one I experienced during my time in the camp.

  • Buphthalmum salicifolium – ox-eye
  • Araneus diadematus – cross spider

As for sleeping arrangements, we had a huge meadow where most of tents were already erected. However, despite bringing my own tent with me (and later borrowing it to my friend Iva), I actually decided to sleep in the car. For one, I was already too tired, and it was way too dark for me to set it up, and I also hypothesized that, since everyone was in a very good mood, people could be loud at night, returning to their sleeping places. Since my strict medication schedule requires interrupted sleep, I rolled down my passenger seat, changed into warmer clothes, and slipped into my sleeping bag. I remember falling asleep slowly, feeling as if I was in a horror movie, as branches were slowly snapping and the big drops of rain were hitting the car.

My next day was a big crayfish adventure, as was the day after it. Honestly, remembering it after all this time, both days somehow melted into one big experience of driving around, asking for directions, walking too much for my taste, and laughing in the car, courtesy of the Crustacean group, who are ones of the funniest people I’ve met.
What I would like to write in a greater detail than I did in my previous post, is the “night-hunt”, or night-time crayfish catching & release session. We started the walk when there was still light out, but it got dark even before we reached the stream; during this year, due to heavy COVID-19 restrictions I couldn’t go anywhere, and it seems that I also forgot how dark it can actually get in the woods. Literal pitch black.
That, however, didn’t stop the group from catching crayfish (they also visually inspected them for the signs of the crayfish plague). We all had lamps, of course, but like I already pointed out, crayfish are surprisingly fast – catching them with your bare hands definitely requires skill!

My last day at Žumberak was magical as well. It was actually a day off, so most of groups decided to just go see-sighting, including the Crustacean group. We drove for an hour or maybe an hour and a half to reach a road with many stunning waterfalls. We set our own pace, and set to investigate and take as many pictures as possible. I wasn’t able to enjoy it as much as I wanted because I had a really persistent abdominal pain (at one point, I couldn’t even walk properly anymore, and had to wait in the car), but despite that, I still managed to take some photos and videos. I hope you’ll enjoy them as much as I did!

With the year we have, with pandemic still raging, this expedition is the only one I was able to be a part of, but I surely hope 2021 will bring new expeditions, new adventures, and new opportunities 🙂

Asplenium scolopendrium – hart’s-tongue fern


Reading | Savage Harvest

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Today’s book I would like to share with you is Savage Harvest: A Tale of Cannibals, Colonialism, and Michael Rockefeller’s Tragic Quest for Primitive Art by Carl Hoffman. For my Twitter followers, me writing about this book is surely not a surprise – I mentioned it couple of times already, praising it both on- and offline.

As a huge true crime buff, I was intrigued by the disappearance of Michael Rockefeller and stumbled upon the book recommendation on a subreddit. I have a habit of immediately searching for the book, which led me to the Amazon store, with a discount for Kindle edition. I clicked as fast as I could on that “one-click” buy button and then… Life got in the way, as it usually is with me and books. I think almost a year has passed before I started reading it, and couple of months before I finally finished it – not because I found it boring, but because my studying, and at times, health issues, were taking up the most of my time.

Still, a true crime book and slow reading tempo don’t really equal a book review on a science blog, right? Well, that would be true, if the book was only about that. Savage Harvest is actually a blend between a biography, travelling diary, and anthropological research. I went into the book expecting to gain insight into Rockefeller’s life and death, but I learned so much about the indigenous culture in New Guinea; Hoffman also gives an astonishing historical overview of the political and cultural situation, the discovery, and tribal relations of the New Guinea.

When I was a child, I used to watch many documentaries, and the word “cannibalism” was often mentioned in rather hush tones, and as the only descriptor of certain tribes. No rituals, no gods, no traditions mentioned, just… cannibalism. By the time I started reading Savage Harvest, I was aware of the complexities that followed a culture, any culture, and especially one as complicated as the culture of New Guinea seemed to me. But reading this book, I learned so much more; the people of New Guinea weren’t some distant islanders on a spot on a map far away anymore, they became actual people, with their intricate system of believes, complicated language, and centuries-old traditions.
The book also touches on racism and culture clashes, and how, for centuries, indigenous cultures were merited through the western lenses, forced to adapt to our rules and religion; New Guinea was not an exception to this rule, as it was colonized by various European countries for years, mostly notably the Netherlands, which claimed the western part of the island.

As a non-native English speaker, I always rate a book by the flow and how easily I can understand it; this book is getting my highest praises. I also really liked how some chapters were written in the present (author’s) time, and some were purely in the past, but all of them worked perfectly in coherence. Furthermore, it’s obvious that Carl Hoffman tried to immerse himself as much as possible, in order to gain a relatively objective insight into the tribal culture he was investigating; he learned how to speak the Indonesian language and even lived with the tribe in the southwest of New Guinea, the same place which Rockefeller was visiting, collecting cultural artifacts, and ultimately disappeared from.

The whole book is, to me, a fascinating insight, and a fantastic mixture of genres that I didn’t expect to work that well together. I recommend this book to everyone who loves to read, even if they don’t have a big interest in topics this book deals with.

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If you read this book, I would very much like to hear your thoughts and opinions; did you like it as much as I did? Will this book find its way to your reading list? Let me know in the comments!

Field | Crayfish alert at Žumberak Mountains

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Hi everyone, and welcome back to my blog. I took a month+ long break, during which I focused on my health and final exams at my University. At the same time, BIUS – Biology Students Association was preparing for their annual field trip, that I really wanted to be a part of!
BIUS is an association that gathers many Biology students from our department and focuses mainly on field trips, excursions, and expert lectures, all in order to complement and expand our Biology-related knowledge about certain topics. BIUS is also a publisher behind In Vivo Magazine, for which I serve as editor-in-chief.

Firstly, however, I would like to write a bit about my love for scientific (and a little less scientific) field trips. My primary love is the lab, after all. However, I grew up in a tiny village, surrounded by a living world – woods, animals, endless fields of tall grass… I actually started to think about studying something science based, perhaps Biology even, way back in the primary school, after wanting to identify all the bugs and spiders I would find in my front yard.
During my first two years of Bachelor’s degree, the thought of going out to the field didn’t really cross my mind, but it all changed in the middle of my third year, when I realized that something was lacking in my life, and that something turned out to be raw nature.

Photo by Đina Nola

This year’s big field excursion lasted for eight days, but I was only able to attend for the last four. Usually, BIUS organizes this kind of excursions twice a year, in May and September, but due to the pandemic, it was completely moved to the end of September, when situation in Croatia improved. Every year, a new terrain is explored, usually switching between continental and marine area. For this year, the leadership chose the Žumberak Mountains which are located on a border with Slovenia, and are approximately one hour drive from Zagreb. Žumberak is a mountain range divided into two parts, the Samobor Hills and the Žumberak Hills, both comprising the protected nature park Žumberak – Samobor Hills. It is home to many plant, fungal, and animal species, some of which are endangered or sensitive.

At first, shortly after arriving I was planning to spend every day with a different group, but in the end, I spent all the days driving around with the Crustacean group. I wasn’t sure how much fun is that going to be, since I knew very little about freshwater crayfish, apart from researching crayfish plague for a little while as an undergrad during an elective lab course.
I was already familiar with two members, Lena and Ljudevit Luka, since we are the same generation and took multiple classes together, and I also knew Anita and Karla a little bit; the whole group was very determined to carry out their research but with the sprinkle of carefreeness. I didn’t feel excluded for one bit and they were extremely patient with me taking photographs and filming videos.

So, what did Crustacean group actually do? Anita kindly explained their goals:

  • monitoring of the species Austropotamobius torrentium, also known as stone crayfish (how many specimens, in which streams are they located, what gender…)
  • taking swabs of crayfish cuticles in order to check for crayfish plague pathogen; this is later investigated by using the PCR method
  • taking water samples using special filters in order to check for crayfish presence; this is later investigated by analyzing the eDNA (environmental DNA)

How does that actually look like out in the field?
The first thing we did every morning, was to check the map and the roads; sometimes, we drove for more than one hour to reach a destination. Then we walked up to a stream, which sometimes proved to be rather tricky, since some seemed to dry up overnight. The most important thing we did before and after walking in every stream, creek or puddle was to disinfect our rubber boots, in order not to accidentally transfer pathogens to different habitats.

The group was very active even before my arrival, so we checked some permanent streams where they already set up special crayfish traps, that were actually made of old plastic bottles, with some tasty hot dog sausages in them. (Don’t worry, those traps are reusable! They just have to be washed thoroughly.) After taking out crayfish, one by one, they are measured and gently rubbed with a toothbrush, in a special buffer, to collect possible crayfish plague pathogen. Every tube containing that buffer is then labeled and safely stored. Crayfish are carefully released back into the stream, at the same place where they were found.

However, sometimes we went to streams for the first time, which meant no traps. So how do you catch a crayfish then? With hands. Usually they were hiding under rocks, but what most people probably wouldn’t expect, is that they are freakishly fast. Still, even during night-time catching & release, every member of the group was highly skilled in catching them. They could also easily discern female from male specimens, and Ljudevit Luka readily explained how, and also sent additional images (the ones below). In short, the main difference is that male crayfish have gonopods, while females don’t. (Gonopods are modified legs that are substantial during mating.)

A female stone crayfish
Male stone crayfish, gonopods are visible
With permission from Ljudevit Luka & Lena

In four days that I spent with this wonderful group, I learned a lot and had a really amazing time. I wanted this post to focus mostly on crayfish, but I’m planning to post another one, where I will write a little bit more about travelling, our camping site, and wonderful nature I was able to document. I also took many videos, which I’m currently editing in one coherent, presentable, work, which I initially planned to release at the same time as this article, but life got a little bit in the way.
I sincerely hope you liked this write-up, and will read my next one as well!

Here you can find social media of some of the members of the Crustacean group, as well as the KarioAstacidae website, a student project led by Ljudevit Luka and Lena, which focuses on Astacidae populations in Zagreb.

KarioAstacidae
Anita’s Instagram
Ljudevit Luka’s Instagram

Short science posts | Hydrozoa

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Hydrozoa are the last cnidarian class I’m going to write about. They can exist in two distinct shapes, as hydromedusa and hydropolyp (same as Scyphozoa and Cubozoa). Despite perhaps expecting hydrozoans to be the most advanced in both nervous and sensory systems, they don’t actually have any rophalium. Furthermore, some hydromedusae don’t even have nerve nets. However, they have two nerve rings (outer and inner) on the margins of their bells which are regarded as ganglia by some scientists.

These rings consist of neural pathways which process different sensory inputs (such as light and gravity). Aglantha digitale, a hydrozoan species, has been reported to have as much as 14 distinct neural pathways. A. digitale is also distinct from the other species in the class by having two swimming “modes” – slow (which is a characteristic for all hydrozoan) and escape mode. Transmission through giant ring neurons is responsible for both modes, but the escape mode requires a stronger contraction. The slow swim mode is activated by the input from the pacemaker, which triggers slow calcium spikes. Direct mechanical nerve ring stimulation by tentacles triggers fast sodium spikes. In short, giant ring neurons are capable of generating two different kinds of action potentials.

bsh

Gap junctions are also present in (and only in) Hydrozoa, and they transfer electrical signals through the musculature. Furthermore, I would like to emphasize that despite some hydromedusae not having a nerve net, some in fact do, and so do hydropolyps. In polyps, however, some groupings of the neurons could be found around their mouth.

Literature & more information:
Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb
Do jellyfish have central nervous systems?
Jellyfish nervous systems

Short science posts | Cubozoa (most advanced cnidarian nerve system)

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Cubozoa, or box jellyfish, are another cnidarian class. Their name stems from their distinct cube-like shape. Cubozoa are also distinct from other cnidarian because their venom can be fatal to humans. As with all cnidarians, box jellyfish have two nerve nets and, like Scyphozoa, rophalia. However, box jellyfish also have a distinct nerve ring, as well as more developed eyes that consist of a lens, cornea, pupil, and a layer of retinal cells. Altogether, Cubozoa have 24 eyes, which makes them the most advanced cnidarian class in the sensory aspect.

Rophalia are mutually connected via the mentioned nerve ring. This ring is believed to be an integration center for the swimming, visual, and tentacle systems; it is comprised of oversized neurons, as well as some smaller neurites.
The communication between the nerve net and jellyfish muscles is regulated by chemical synapses.

Most of the information relating to Cubozoa, I already mentioned in the previous post about Scyphozoa, so I only wanted to relay the main differences between the two. These two classes are so similar that, until recently, they were actually considered one class.

Literature & more information:
Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb
The ring nerve of the box jellyfish Tripedalia cystophora
Do jellyfish have central nervous systems?
Jellyfish nervous systems


Biology in popular culture – movies&TV (part 1)

Emina1 Comment

I already wrote couple of posts on this topic, and today I’m focusing on several examples from movies and TV shows I’ve recently watched. The movies I’m going to write about are Lara Croft: Tomb Raider – The Cradle of Life, The Good Liar, Charlie’s Angels (2019 version), and Paranoid TV show. So, if you are planning to watch those, just a warning that there will probably be spoilers below!

Let’s start with the obvious and amusing misportrayal: in Lara Croft: Tomb Raider – The Cradle of Life (2003 movie), Lara is riding sharks in the opening sequence. I think no one would believe this is actually possible, but shark petting videos recently became very popular. However, many researches are strongly discouraging this type of behaviour.

Photo by Laura College on Unsplash

The Good Liar (2019 movie) is an interesting thriller with really good cast that I actually enjoyed. Without giving out too much of the plot, I’ll just mention one scene where Helen Mirren’s character gives the haircut to the character played by Ian McKellen. She uses cut hair for the DNA analysis, factually linking McKellen’s character for the past crimes.
Of course, we all know that without the root, there is no DNA to analyze, right? Not quite.
Most companies that do DNA analysis require hair with follicles in order to extract DNA for analysis; however, they mostly deal with paternities, so they need the nuclear DNA. Mitochondrial DNA, on the other hand, apparently can be extracted from the hair itself. For the movie’s purposes, I think nuclear DNA was needed, so this seems like a movie mistake. But, recently scientists did manage to successfully extract nuclear DNA from rootless hair, but that DNA is often fragmented and complicated to extract.
I would also just like to mention that I believe this movie explains trauma and coping surprisingly well for a Hollywoood movie.

In Charlie’s Angels (2019 movie), which I hoped would be more enjoyable than it was, a very interesting premise was introduced; in order to effortlessly communicate, members of the team get a certain tattoo (at least I think it’s a tattoo, but don’t 100% quote me on that) and they can hear thanks to it. So, my first thought was, wow, they really went sci-fi on this one, but it sounded too out there. And then I remembered bone conduction. Simply, bone conduction allows you to hear the transmission, without blocking the outside sounds. And yes, only you can hear it. There are headphones already in use for this type of thing, and they can be also used to help with some kinds of hearing impairments. These headphones are placed on the skull, and I haven’t seen it implemented in a tattoo yet, but it’s actually a neat idea.

Paranoid (2016 TV show) is, in my opinion, really bad, despite only tangential connection to Biology. This show feel anti-medication and anti-psychiatrists, portrays them in a very bad light, and chooses not to mention how much medications and psychotherapy are actually helping people. The premise is also built on one of the cliche “anti-big pharma” representations. I was honestly insulted, despite not working in any of these fields. There is a also a subplot concerning a female character who had provocative photos of her taken 15 years ago, and she is not longer in possession of said photos; she is blackmailed with the possibility of leaking those. Her love interest immediately accuses her of things I won’t write here, but you get the main idea. I mean, am I the only one who sees this as highly problematic
This TV show is doing some serious damage to the health care, it is insulting to physicians, it is insulting to patients, and I honestly can’t believe that no one during the whole production didn’t say anything.

Photo by analuisa gamboa on Unsplash

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I hope you like these kind of posts, because I already have enough material for another one (there are a lot of Biology & science mistakes on the big screen). What is your favourite movie mistake related to Biology?

Short science posts | Scyphozoa – more advanced nervous system

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Scyphozoa (true jellyfish) are much more interesting (in a neurobiological way) than previously described corals. One major difference is that Scyphozoa are pelagic animals, which means they are not fixed to the ground. They also have two diffuse nerve nets (subepidermal and subgastrodermal) that consist of bipolar and multipolar neurons – the impulse conduction has been measured at 0,15 m/s. Both nets coordinate the movements of an animal towards the food. Some scientists, however, differentiate one diffuse and one motor nerve net. The motor net is in charge of the activation of muscle contractions after receiving signals from the so-called pacemaker organs (which are in charge of the swimming rhythm). The diffuse net, in this case, is in charge of marginal tentacle contraction and it is also believed it communicates sensory information to jellyfish musculature. Neurons of the motor nerve net are connected by chemical synapses, while neurons of diffuse nerve net are connected by peptidergic synapses that were noted in Anthozoa as well.

Sycphozoa also have much more developed sensory organs than any of the animals previously mentioned. These sensory structures are called rhopalia and they are located on the edges of the jellyfish bell – there are usually four of them (or a number that’s a multiple of four). Rhopalia contain multiple sensory receptors – statocyst (balance receptor), ocelli (light sensitivity), a mechanoreceptor, a chemoreceptor, and aforementioned pacemaker neurons.

I would also like to note here that some authors (I’m referring here to the article “Do jellyfish have central nervous systems?” by R. A. Satterlie) believe this kind of nerve net explanation is rather simplified and that there exist some evidence suggesting that jellyfish have a centralized nervous system, mainly that rophalia are in fact rudimentary ganglia and could be regarded as integrative centers. However, any communications between rhopalia themselves exist only through the nerve nets.

Literature & more information:
Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb
Do jellyfish have central nervous systems?
Jellyfish nervous systems

Studying | My favourite online courses

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I don’t know about you, but I just love doing online courses, especially when they deal in subjects I don’t get to explore in my college courses. Over the years, I tried many different platforms, such as YouTube, Google Digital Garage, Khan Academy, Udemy, and, my favourite, Coursera. As a matter of fact, I discovered Coursera back when they started in 2012; most of the courses I took were on topics of Neuroscience and Molecular Biology. At first, courses and certificates were completely free, but with time, they started offering paid vs. free, as well as many specializations and even some college degree courses. However, many of the courses are still available to watch and do quizzes, just without the certification.

Disclaimer: this post is not sponsored by Coursera.

Synapses, Neurons and Brains – available here

This course, offered by Hebrew University of Jerusalem, is actually the very first course I took, and at the time was one of the rare Neuroscience courses. I have only good memories about this one – it is a good introductory course into the field and the professor explained the curriculum very well. Also, the course mentions real projects that deal with neural networks and brain reconstructions, such as Blue Brain Project. I didn’t mention this previously, but every course also comes with subtitles (in English at least) and transcripts, so you can follow along easier.

The Addicted Brain – available here

The Addicted Brain (by Emory University) is another course appropriate for beginners in this topic – I was initially interested not only because of the topic of addiction, but also because various mechanisms of how drugs interact with the brain were presented. The course also covers the topic of drugs in society, although this part mainly concerns United States of America. Also, I don’t know if this is something that’s important to you, but I followed professor’s narration easily – his voice is calming and he speaks very understandably.

Medical Neuroscience – available here

Medical Neuroscience (by Duke University) is not only the most advanced course of the ones mentioned here, but the most advanced course I ever took. Actually, I started it once or twice before, but dropped out because it required a lot of time and dedication that, at times, I just didn’t have due to my University obligations. This course is really extensive and requires some before-knowledge, but is also very satisfactory when you finish it. The only problem I had with this one is that sometimes I felt that questions in quizzes were asking for details that to me seemed almost overlooked in the videos. However, I felt like this course was quite important for my studies, since I have a strong interest in Neuroscience, but lacked the medicinal perspective.

All quizzes are multiple choice answers, with usually one correct answer (sometimes more correct answers). I vaguely remember some questions where you had to connect some phrases (like 1-d, 2-c, etc) as well, but haven’t came across those recently. Also, the quizzes I did were never timed and you can take one quiz 3 times every eight hours (they keep your highest score).

Coursera also offers financial aid – you can fill out an application where you explain why is the course you’re applying for important to you and why you can’t afford it. So far, I’ve heard of many positive experiences where they gave grants.

There are also two Neuroscience related courses I am planning to take – Human Neuroanatomy (to revise a bit) and Computational Neuroscience, which deals with using Python in Neuroscience research. I would very happily review those for you, in a greater detail, if this is something you’d like to read about!

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What is your opinion on online courses – do you think they’re useful or a waste of time? Did you perhaps take some of the ones I mentioned? If yes, I would love to hear from your!

Short science posts | Anthozoa & nerve cells

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Anthozoa (corals & anemones) are interesting animals that live exclusively in seas and oceans. Since they are regarded as sessile organisms, their nervous system is not very advanced. In a previous post, I mentioned that all cnidarians have two diffuse neural nets, and that is true for Anthozoans as well. Multipolar nerve net neurons are connected with synapses, and they also possess sensory cells that are particularly numerous around the mouth and on the tentacles.

One paper investigated traveling of electrical waves in a coral nerve network in coral colonies in genus Palythoa. It was experimentally observed that this electrical wave spreads at the constant speed from the site of simulation. Furthermore, peptidergic neurons (the ones using neuropeptides to communicate) were also noted in Anthozoa.

Did I draw this when I was 5 or 25? – A mystery.

Nematostella vectensis, also known as starlet sea anemone, is a species of Anthozoa that is known as a model organism – its genome and development have been carefully studied, including its nervous system. In this species, oral and pharyngeal nerve rings have been reported, as well as  longitudinal tracts of neurites (neurites are usually axons or dendrites). These findings would suggest that some groupings of neural cells exist in at least some Anthozoan species after all. Sensory neurons, interneurons, motorneurons, and neurosecretory‐like gland cells were also reported to exist in N. vectensis.

Note: in case I didn’t mention this before, cnidocytes are often considered neural cells because they display mechanosensory properties and calcium dependent neural‐like properties as well.

Literature & more information:
Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb
The rise of the starlet sea anemone Nematostella vectensis as a model system to investigate development and regeneration
Cnidarians and the evolutionary origin of the nervous system
Model of traveling waves in a coral nerve network

Short science posts | What is a nerve net?

Emina2 Comments

A nerve net is a type of nervous system that consists of many neurons but there is no brain or cephalization. Nerve nets are found in animals with radial symmetry (Cnidaria) and biradial symmetry (Ctenophora). Despite being called a net, there sometimes exist some groupings of neural cells in some Cnidaria classes, which I will write more about during the next couple of weeks.
Cnidaria are specific due to their specialized organelles, cnidocytes, which they utilize to hunt for food or use for securing itself to a surface. Some cnidocytes contain toxins that can paralyze their prey (the burning sensation you may have felt when touching a sea anemone 😉).
As a rule, Cnidaria have two diffuse nerve nets, one in the epidermal layer and a second one in the gastrodermal layer. In between these two layers is the mesoglea, a layer that functions as sort of a skeleton. The epidermal net consists of bipolar and multipolar nerve cells, while the gastrodermal net is made up of only multipolar cells.

Cerianthus membranaecus (known as cylinder anemone or coloured tube anemone)

Cnidarian nerve systems are fascinating but also quite unexplored. What is known is that nerve cells consist of two types of neurons, sensory neurons that respond to stimuli and motor neurons which ultimately trigger a response. Chemical synapses exist and provide the communication between the neurons. Hormones have also been reported in some cnidarians (steroids, neuropeptides) but it is still not known how exactly these signalling molecules work.

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In the next couple of weeks, I will write a post about every cnidarian class and also ctenophores, focusing on their nervous and sensory systems. If you have any questions or would like me to focus on something, please let me know!

Literature & more information:
Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb
Endocrine-like Signaling in Cnidarians: Current Understanding and Implications for Ecophysiology
Evolution of sensory structures in basal metazoa