What They Had is a 2018 movie focusing on the family whose matriarch suffers from Alzheimer’s disease. Although seemingly similar, this movie is very different from the more popular Still Alice, and, in my opinion, shows the difficulties of navigating everyday life better. The movie, directed by Elizabeth Chomko, who drew inspiration directly from her personal life, stars brilliant Hilary Swank as a worried daughter Betty who comes back home in order to care for her mother Ruth, played by Blythe Danner. Michael Shannon, playing Swank’s brother Nicky, is masterful as ever, showing his impeccable acting skills, as he clashes with their father (Robert Forster) over the possibility that their mother should continue her life in an assisted living facility.
What I like about this movie, is that it isn’t solely focused on Alzheimer’s disease, but rather on family dynamics around it; it explores how members of the immediate family deal not only with their mother, wife, and grandmother as the illness progresses but also with each other. Without revealing more of the plot, as I truly believe everyone should watch this movie, I have to praise it for tastefully and realistically conveying many symptoms of AD, such as when Ruth wanders away in the middle of the night, experiences speech difficulties or flirts with her adult son, not recognizing him.
The last scene I described isn’t brought on as a dramatic one, but rather a humorous one, albeit dark. As a matter of fact, the whole movie deals with the severity of the situation in a similar manner, but it will still bring tears to your eyes. This movie is honest, truthful, and above all, touching; I honestly can’t believe it’s not more known and as I’m writing this review, I’m quite anxious that my review isn’t presenting it in the best possible light, which it absolutely deserves. I hope my clumsy writing won’t discourage you from watching What They Had, a movie that beautifully reminded me why I chose neurodegeneration as my field of study.
If you watched What They Had, let me know if you liked the movie as much as I did. I am also sharing the trailer here as well.
Phylum Platyhelminthes, also known as flatworms, consists of four distinct classes: Turbellaria, Monogenea, Trematoda (flukes), and Cestoda (tapeworms).
Today, I want to write more about Turbellarian nervous system, which is more advanced than the one found in Ctenophora or Cnidaria. Turbellaria are small animals (up to 20 mm in size, although there is one species that can be more than half a meter long, imagine that touching your foot) found in water and wet habitats. Turbellaria have a brain, both sensory and motor neurons, and a series of sensory receptors. Although bilateral animals, not all Turbellaria have a bilateral nervous system, with some of them still having a radial system characteristic for cnidarians.
The turbellarian nervous system, made of uni-, bi-, and multi-polar neurons, can be epidermal, sub-epidermal, and sub-muscular. However, only less advanced species have the epidermal nervous system, while all the others have both subepidermal and submuscular.
When discussing the radial nervous system, it is important to mention cerebral ganglion and three pairs of nerve cords (dorsal, lateral, and ventral). These cords are connected by annular commissures. In the bilateral system, on the other hand, we have a primitive brain made of several ganglia and only two ventro-lateral cords, mutually connected by transverse commissures. There are also sensory nerves, which extend forward from the brain.
Turbellaria have a whole myriad of sensory receptors: mechano-, chemo-, photo-, and balance receptors. Mechanoreceptors can be divided into two groups, thigmoreceptors and rheoreceptors. Both of these can be found on the whole area of Turbellaria body, and both contain cilia in order to sense outside stimulus. The difference between the two is that thigmoreceptors are specialized for touch, while rheoreceptors process water flow stimuli. Chemoreceptors are located in special grooves on the head, and serve to locate food or a mate. Photoreceptors are located in ocelli (ocelli are analogue of eyes) and although they usually have only a pair on the head, some species have couple of pairs or even many ocelli on the edge of their bodies. Statocysts serve as balance organs, although only some species have them. Statocysts are chambers filled with a fluid and also contain one statolith. It is actually unknown how statocysts receive stimuli.
Schmidtea mediterranea, an adorable flatworm of Tricladida class is one of the modal organisms in genetic and molecular research, because it has diploid genome and asexual and sexual strain. These characteristics make S. mediterranea a very popular choice among the scientists, especially since the discovery of its apparent immortality. Due to an abundancy of stem cells, almost any amputated part of this flatworm can regenerate into a full organism in a span of just several days. Yes, this little organism is literally Deadpooling its way through life!
Of course, the explanation behind this mechanism is all but simple; it seems that this regeneration ability depends much on the activity of an enzyme called telomerase, and not even this works the same in asexual and sexual strains of S. mediterranea. There are also many genes involved, but since some of the genes have orthologs in human, scientists are now trying to discover if they could somehow stop aging in our species.
So, what do you think about these small creatures? Do you like them, or do they frighten you a little bit?
Unfortunately, I couldn’t find many resources online regarding their general nervous system, so most of the information is sourced from one book, which is available only in Croatian. More research is needed regarding these creatures, and some are underway, especially regarding their astonishing regenerative capabilities.
Literature & more information: Habdija et al: Protista-Protozoa, Metazoa-Invertebrata, Alfa, 2011, Zagreb Moraczewski, Czubaj & Bgkowska Organization and Ultrastructure of the Nervous System in Catenulida (Turbellaria) Zoomorphologie 87, 87-95 (1977) Tan et al: Telomere maintenance and telomerase activity are differentially regulated in asexual and sexual worms PNAS vol. 109, no. 11, 4209–4214 (2012) Handberg-Thorsager, Fernandez & Salo Stem cells and regeneration in planarians Frontiers in Bioscience 13, 6374-6394 (2008)
Hello everyone, and, after a longer break, welcome back to my blog! As the title itself suggests, I was a part of another BIUS field trip, which was again located at the Žumberak Mountains. For the adventures from the previous year, click here and here.
Quick reminder: BIUSis 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 served as editor-in-chief and I am now an adviser.
Initially, I planned to write this post as soon as I came back, back in May, but I felt rather overwhelmed by everything in my life, especially health wise. I decided to postpone all of my posts, both on this blog and social media, because I just didn’t have enough energy to dedicate myself to creating content in a way I thought I should.
If you read my previous posts about Žumberak, you already know that, despite wanting to spend my life working in a lab, I also like to explore nature. During the last field trip, I was part of the Crustacean group, and this year, I was part of a Butterfly group, although I don’t know that much about either of these topics. However, one of my main reasons to go to excursions is to learn and experience new things, connect with other people, and make great memories. And I must say, I had wonderful four days. I would also like to thank to two other members of our group, Filip and Ivan, for selflessly sharing their knowledge with me and having patience to answer all my questions!
Frist photo: Asplenium scolopendrium (hart’s-tongue fern) sprouts. Forests were full of these and, honestly, I was feeling like I was a character in a fantasy novel, surrounded by magical plants.
Second photo: A bee and a wild orchid. I must admit that I'm very proud of this photo 🙂
Third photo: Caddisflies! Every stream was full of the caddisfly larvae; you might think these are just some silly rocks, but those are actually insects of the order Trichoptera, who make these protective cases in their larval stage.
I arrived at Sunday, just a little bit before noon, and immediately joined my group; they were strolling down the road, mostly checking environment and inspecting passing butterflies. My main task was taking photos, especially if anyone caught a butterfly. The Butterfly group itself was only recently revived, after Filip showed amazing initiative and interest in butterflies, so we were all actually new to the group, trying our best to wave our little nets. Our main tasks were:
confirm the already recorded species of day butterflies
investigate and record species of night butterflies, which are not very well known in this area
I should immediately note that, despite being successful at both tasks, we noticed an alarmingly small number of butterflies and insects in general, especially for that time of the year. I am honestly not sure what is to blame; we had a weird winter that jumped right into high summer temperatures and our country is, sadly, generally not very preoccupied with the protection of nature, species, and habitats. There were also fun moments, with Ivan very decidedly running after every butterfly in sight. Also, the Botany group brought us a little caterpillar for determination, which Filip then successfully nurtured to the butterfly stage, in order to determine the species.
After returning to the camp that same day, I investigated an area around it, with my friend Paula, who used to be a leader of a Beetles group (and is now leading Marine Biology). She was, naturally, much better than me in spotting hidden insects and even caught some water newts after we stumbled upon a puddle. It was such a fun and interesting day, and my only regret was forgetting my straw-hat at home, because the sun was really too strong for my taste.
(Photo: Meloe sp, probably violaceus)
My next day was, however, my favourite experience of the whole trip, because I joined the Biospeleology group and went caving! The last time I visited a cave before this was in 2019, and I must admit, I missed it so much; that specific smell of the cave air, wearing three layers of clothes, fixing my helmet all the time, and walking through impassable terrain. Wait, scratch that last one, I never miss walking on the extremely narrow mud path through the forest, holding onto branches we are passing on the way, barely catching my breath, trying to finally reach the cave entrance. Luckily, everyone in the group was completely understanding and wasn’t imposing any type of time restrictions. Three of us were students, but we also had an expert mentor, who was so kind, patiently answering our questions.
First photo: Mia & Martina looking for spiders
Second photo: Grasshopper sp.
Third photo: A flying insect, perhaps a mosquito, starting to get... Calcified? Mineralized? I'm honestly not sure what is the right word to use here.
The cave in question is called Zidane pećine (roughly translated as Masonry caves), and it’s a cave you can access without the ropes (helmets and speleo overalls are a must). The main task of the group was to collect various insects and bugs that might live in the cave, mainly spiders. Now, the focus was on the creatures that might permanently live in the cave, and not on the ones that only sometimes enter the cave in search for a hiding place. I was, unsurprisingly, mostly taking photos: of my colleagues, cave walls, and various animals inside, which include creepy grasshoppers (not their scientific name) and bats. The cave is also apparently an archaeological site, although I can’t find any verifiable information about that, apart from one mention in a blog post which states that archaeological find dates back to the 16th century and Ottoman attacks. What locals did tell us it that the cave used to be a hiding place during the wars.
Tuesday was a bit more challenging for me; our lovely group leader Filip decided we should check out a big meadow at a higher elevation, which doesn’t sound too bad, except the sun was plaguing me badly. However, we were hopeful we might find an interesting butterfly, but barely found any butterflies at all. As it turns out, it was simply too cold for them at that particular place. We spent the rest of the day mostly hanging around the camp, until evening, when it was time for the night hunt. And yes, it was as cool as it sounds. Around 10pm, a huge group of us gathered a bit further from the camp, in order to observe, and in some instances catch, bugs that are active during the night. To accomplish this, Mladen, mentor of the Beetles group, put up two pyramids, which are made of a metal construction with a simple fabric thrown over it, and a UV light in the middle of it. (Mladen also politely measured a safe distances for me, in order not to be harmed by the UV light, although I have to admit, I purposely got quite close couple of times, in order to take pictures). One of the pyramids was erected next to the road, and another couple of hundreds meters away, near the bank of a stream. It was really fun going back and forth, and taking pictures of all the insects and spiders we found on the road. This experience was also very educational for me, not only because this was my first night hunt, but also because I was surrounded by experts who gladly shared their vast knowledge about beetles, spiders, moths, caddisflies, and mosquitoes.
My last day was Wednesday, and as a group, we honestly didn’t have much to do, due to changeable weather and very strong winds. We visited a bio-park nearby, where we saw llamas and walked next to donkeys and donkey-hybrids. It was overall a fun ordeal and we didn’t understand why are we the only visitors there. After a quick search on our phones, we realized that the park was a part of a small ecological scandal last year, so we left. The second part of the day was spent with the Crustacean group; together, we visited a beautiful creek, which was much bigger than I expected. Members of the Crustacean group were setting up traps, similar to the ones I was writing about last year, while the rest of us just walked around, amazed by the nature around us.
As I was driving home that evening, I couldn’t help but smile reminiscing about the packed experience I just had, which included not only visits to the breathtaking places, but also learning more about the tiny world around me, taking numerous photos and videos, and meeting new people.
Here you can find social media of some of the members of the Butterfly group, as well as the link to official Instagram profile of the group. I am also sharing a social media link to Paula’s Instagram, who already shared impressive photos and videos on her profile.
Pozdrav svima i dobro došli na moj blog. Ovo je zapravo prva objava koju pišem na hrvatskom jeziku, a razlog tomu je moj mali, studentski projekt koji je fokusiran na zaštićene vrste grada Zagreba i okolice. Iako su moji primarni interesi neuroznanost i molekularna biologija, smatram da je zaštita okoliša i bioraznolikosti iznimno važna, jednako kao i borba protiv klimatskih promjena, pravilno razvrstavanje otpada te prelazak na samo-obnovljive izvore energije.
Ni sama nisam sigurna kada je ideja za ovakav projekt niknula u mom umu, ali u ožujku 2020. godine, otvaranjem natječaja Studentskog Zbora Sveučilišta u Zagrebu, već sam imala konkretnu ideju kakav projekt bih htjela provesti i na koji način. Mali, studentski projekt koji bi educirao širu javnost, poglavito djecu osnovnoškolske uzrasti, o zaštićenim vrstama koje se nalaze u svijetu oko njih.
Na prvu, ovo se možda čini kao relativno dosadan projekt: malo letaka, malo otvorenih predavanja, o nekim nebitnim životinjama koje žive po šumama i rupama oko Zagreba.
Ipak, zaštićene vrste koje obitavaju u Zagrebu i okolici nisu samo životinje, već i biljke, gljive i lišajevi. I važnije, mnoge životinje koje se nalaze na listi zaštićenih životinja nisu opskurne, već bića koja srećemo toliko često, u prirodi i medijima, da možda ne bismo ni pomislili da su ugrožene i zaštićene. S nekoliko prijatelja sam raspravljala o ideji, i nakon njihovog ohrabrenja, prijavila projekt. Pandemija koronavirusa i bolesti COVID-19 me spriječila u izvođenju projekta kako sam ga inicijalno zamislila, s obzirom da se predavanja otvorenog tipa nisu mogla odvijati, pa sam taj dio projekta prebacila na snimanje edukativnog video uratka, koji je objavljen na stranicama Udruge BIUS, udruge koja je partner projekta. Iva Čupić, poznatija na Instagramu pod imenom Samsa Critters, je ilustrirala projekt svojim sjajnim crtežima, koje možete vidjeti i u letku i videu, a umjetnica Ivana Geček je obradila grafičku pripremu za tisak.
U ovom video uratku, saznajte točnu definiciju strogo zaštićenih vrsta te ukratko u određenim vrstama životinja koje se često pojavljuju na području grada Zagreba i okolice, kao i načine na koje se možete dalje informirati o zaštićenim vrstama.
Ovaj projekt nije ni velik ni poseban, ali nadam se da će educirati barem nekoliko ljudi o posebnosti biljnog i životinjskog svijeta oko njih; ako samo jedno dijete, tijekom šetnje po Medvednici, Jarunu, Savici, Bundeku ili Maksimiru, samo jedno dijete vidi malenog crvendaća i shvati da je upravo ta vrsta zaštićena, ugrožena i posebna, i da je na nama da tu vrstu zaštitimo od izumiranja, smatrat ću da je moj projekt ispunio svoj cilj o edukaciji i proširenju kolektivne svijesti o prirodnom bogastvu kojim smo okruženi.
Hello everyone and welcome to another post in the series about biological topics in movies and TV series. You can find a link to the previous post right here. My intention with these is to clarify different claims made in various movies and TV shows I watched, and also to share perhaps some surprising facts mentioned in them. If you’d like for me to watch something specific, please let me know (I’m currently preparing another post focused on the German TV show “Biohackers”). So let’s start with some extremely popular offenders.
Friends – “Lobsters mate for life” In a classical Friends episode, Phoebe claims that lobsters mate for life. They don’t. There are some animals that remain monogamous for life, such as wolves, swans, penguins, and barn owls, but lobsters are not one of them; in fact, male lobsters actually change mates frequently during the mating season.
Harry Potter and the Goblet of Fire During the famous scene in which professor Moody tortures the amblypygi (of species Damon diadema; Amblypygi belong to class Arachnida) with the Cruciatus curse, poor creature starts to squeal in pain, but can amblypyg actually make that sort of sounds? As it turns out, some species of spiders (which also belong to class Arachnida ) can tap on the surface or even vibrate (again, on certain surfaces) to make mating calls or communicate, but the type of screech depicted in the movie, under the spell or not, is physiologically impossible.
The Alienist – “Butterflies inflict pain during the coitus” While I’m still on the topic of invertebrates, let’s divulge into this one. Now, pain is the subject of many definitions, but assuming it’s just an unpleasant physical stimulus, the question is raised whether insects can actually feel it? Until recently, researchers agreed that insects can feel nociception, which is the response to life-threatening stimuli, but most agreed that they don’t feel the pain like we do. A recent study, however, showed that fruit-flies could experience a chronic pain-like state, but the science still has a long way to go to conclusively show if insects can or cannot feel pain. Do butterflies feel pain when mating? Possible, but it seems that, until more evidence comes to light, it’s highly unlikely.
Rouge – “Lions are not afraid of fire” This fun but quite forgettable B flick starring Megan Fox and a CGI lioness off-handedly mentioned that lions are, in fact, not afraid of fire. That didn’t sound right with me so I searched for it and it seems like it’s true. Apparently, not only they’re not afraid but like to check out what’s happening around the campfire. I would like to point out, however, that most of the web-sites are literally copying the same sentence about it, verbatim, and I didn’t find where it originated.
Did you notice similar misinformation or surprisingly correct information in popular movies and TV shows? Please let me know in the comments below, I love reading about movie mistakes!
Ctenophora, commonly known as comb jellies, are a rather perplexing phylum of beautiful pelagic creatures. Their evolutionary position has been debated for many years as is the origin of their nervous system (some scientists believe they are older than sponges and that sponges lost their nervous system, while others advocate the theory about the nervous system forming independently twice, once in cnidarians and once in ctenophores). Ctenophora have two nerve nets: subepidermal and less organized subgastrodermal, which recent research identifies as a mesogleal nerve net. Nerve cells from this layer communicate with muscles by synapses and affect the locomotion of the body. The subepidermal net is denser around the mouth, the pharynx, and under the comb rows (comb rows are strips that run the length of the ctenophore body and contain cilia called “ctenes”). Ctenophore neurons can be iso- and multipolar.
They have sensory cells on the whole surface of the body and those correspond to vibrations and thermal and chemical stimuli: more receptors are located around the mouth and pharynx. Ctenophora also have an apical and aboral sensory organ. Such sensory organ consists of a statocyst, a sensor that contains a statolith that balances on four groups of long cilia connected to the comb rows. These organs help the orientation of the ctenophore body. What’s extremely interesting is that ctenophores use different chemical signalling system than the ones described in the previous posts, mainly because these animals simply lack the neurotransmitters (and genes), such as serotonin, dopamine, noradrenaline, and acetylcholine; glutamate is the only neurotransmitter currently known to be present.
I gathered all this information from different resources, and some are sometimes contradictory or are generalizing conclusions about the whole phylum from the data of only one ctenophora species. This is the best overview I could manage, to show both the similarities and the differences of the ctenophora nervous system, when compared to the Cnidarian system. These lovely animals are not very well researched and I’m sure many wonderful breakthroughs about their anatomy, physiology, and their place in the evolutionary tree are to come.
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.
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!
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! BIUSis 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.
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.)
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.
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.
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.
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.