coelomate asked you: 

Soooooo, for the first time in my life, I am virtually smitten. Your art is wonderful! I don’t know why I love it, just that I do. Keep it up. And, I guess this is for questions, so here goes nothin’: What’s your favourite type of candy?

This is a nice message, thanks for taking the time to write it. As for candy, thats kind of a big question. I have a major sweet tooth. First of all some of these things i mention may not be things outside of australia so just bare that in mind and don’t just think i’m making up exotic sweets. I’m a little bit addicted to starburst rattlesnakes in that i need them all the time to survive. I love gummi bears, nerds are pretty rockin, zappos, fizzers… I also love chocolate but it has to be a pretty specific kind, dark chocolate is OKAY but only a lil bit and I like white chocolate as well. 

I got a taste for both kettle corn and chocolate covered pretzels when I was in America but neither of those things exist here, so I have a fairly constant yearning. I did actually find a shop that sells chocolate covered pretzels here but its kind of expensive in comparison to the giant bags you could get for like 2 dollars in New York. 

I kinda went on a bit there… ANYWAYS thanks for the message.

Questions: ANSWERED (most certainly.) 

Watch on

Science Live: Colossal Squid

Coelomate: This is an organism who contains a coelom, a fluid filled cavity that humans have which is divided from the mesoderm in embryonic development. 

September 10
Tree of life
  • diagram
  • Taxonoms
    • Phylum platyhelminthes
      1. flat worms
      2. characteristics
        1. bilaterally symmetrical ii. dorso-ventrally flattened iii. acoelomates (don’t have coelom, lack body space other than a gut)
    • Class Trematoda: all parasitic
    • Subclass Digenea (“2 beginnings”): in life cycle, there are at least two hosts in the life cycle (definitive host & >=1 intermediate host)
      • the first intermediate host is always going to be some kind of snail/molusk
      • commonly known as “flukes”
  • General life cycle

    • image

  • Adult morphosis

    • acoelomate
    • body is solid (parenchyma)
      1. 2 cell types: fixed cells, stem cells
      2. collagen fibers
      3. functions of parenchyma
        1. fills space betwene body wall & gut ii. provides attachment points iii. internal organs embedded iv. passage of nutrients, water, and gases
    • lack circulatory, skeletal, respiratory organ systems
    • that means: respiratory relies on different methods: diffusion, so they are flat
    • digestive tract: blind gut: have a mouth, no anus
      • the mouth takes in food and expells waste
      • mouth surrounded by an oral sucker
    • pharynx: muscular, glandular enzymes
    • esophagus
    • cecum: bifurcates and may be branched
    • ventral sucker: muscular attachment
    • nervous system:
      • flat worms,
      • cerebral ganglian on the anterior end of worm (kind of like a brain, really just cluster of nerves),
      • sensory endings (do not respond to light or gravity),
      • chemoreceptors,
      • tangoreceptors
    • reproduction: sexual, most species are monoecious (hermaphrodites) except schistosomes, capable of self fertilization, but mainly cross fertilize
    • Tegument: outer surface of worm, living, complex
      • syncytium: you have a multinucleated tissue with no cell boundaries
      • 3 regions
        1. glycocalyx (outermost):
          • glycoproteins,
          • invaginations (more surface area & absorption),
          • hydrolytic enzymes,
          • defense (shields from digestive enzymes and antibodies)
        2. digital cytoplasm: anucleate,
          • membranous bodies
            • multilamellar vessicles & discoid bodies
            • synthesis of substances that maintain glycocalyx
        3. muscle layers: circular & longitudinal
        4. proximal cytoplasm (=cytan region wtf idk)
          • nuclei & organelles
          • produces substances to maintain distal cytoplasm
          • connected to distal cytoplasm by cytaplasmic connectives (channels)
          • image

      • Glucose uptake by teguments
        1. adult schistosomes: live in bloodstream of definitive host, an environment very rich in glucose
        2. specific glucose transporters (GTP): integral membrane proteins in all organisms
          • transports glucose across hydrophobic membranes
          • moves across by carrier-mediated diffusion (facilitated diffusion), therefore independent of metabolic energy, down concentration gradient
        3. schistosome tegument is surrounded externally by a lipid bilayer and surrounded internally by basal membrane
        4. schistosomes GTPs: synthesized by membranous bodies localized in tegument (not found in worm’s intestinal tract)
            * means entry of glucose into worm occurs thru tegument and *not* thru gut 
          • SGTP1 in basal membrane
          • SGTP4 in lipid bilary
        5. movement of glucose to internal tissues
          • most tissues are syncytial which allows for diffusion
              * **syncytial**: A multinucleated mass of cytoplasm that is not separated into individual cells.
        6. glycogen keeps glucose concentration inside the worm low (that way outside will alwyas be higher so it’ll always diffuse yay)
  • Food-bourne trematodiases
    • Definitive host becomes infected by ingesting parasite along with food
    • once inside definitive host
      1. intestinal flukes
      2. liver flukes (usually in liver, bile duct, or gall bladder)
      3. lung flukes

Clanorchis sinensis

  • Oriental liver fluke that infects 19 x 10^6 people
Life cycle


  • Adult worms in bile duct
  • erosion of bile duct lining
  • thickening and blocking of bile duct
    • hepatomegaly (liver englargement)
  • degree of pathology depends on the intensity of infection
    • if intensity <100 worms, individuals usually asymptomatic
    • if 100 - 1000: may start to feel something (nausea, pain, discomfort, diarrhea)
    • if >1000: fever, abdominal pain, jaundice

Fascida hepatica

  • sheep liver fluke
  • usually in cattle and sheep
  • resevoir host: non-human definitive host, source of infection to humans
  • liver rot
  • human infection: 2 - 17 x 10^6 cases
    • rare in US
    • worldwide cattle & sheep production
    • more cattle/sheep, more infection
Life cycle
  • intermediate host: snail
  • metacercaria encyst on plants (plants are not hosts)
  • watercress
  • definitive host eats vegetation
  • inside host: tortuous migration o__o
    • metacercaria ingested by DH
      • excysts in SI
        1. juvenile penetrates intestinal wall
        2. migrates through abdominal cavity (of cow)
          • many of them don’t get to point #3 due to loss of energy
        3. penetrates glisson’s capsule (membrane tissue that surrounds the liver)
          • rejects diaphragm
        4. juveniles develop in liver, get bigger, feed, and THIS causes damage to liver —> liver rot !!!
        5. migration to the bile duct (at this point, adult worms) 


Digestive tract
  • oral sucker: powerful suction, draws a plug of host tissue into the sucker that breaks the capillaries in the tissue, blood into pharynx
  • gastrodermis
    • single layer of epithelial cells
    • lines digestive tract
    • surface lamellae (protrusians)
  • cyclical transformation of gastrodermis:
    1. absorptive phase (what happens as blood is coming in): surface lamellae (long, nuemrous), golgi inactive, few secretery bodies, absorb blood ii. secretory phase: blood absorbed needs to be broken down
      • lots of secreotry bodies in cells
      • function: produce enzymes to break down blood
      • golgi are now active, lots of mitochondria, high rate of metabolism iii. the events in one cell are not synchronized with adjacent cells
  • juveniles may not make it and may end up in weird places (ie ulcers in ectopic sites)
  • responsible for acute fascioliasis (what occurs as juveniles migrate to liver while they are feeding and growing)
    • liver starts to swell up: hepatomegaly (severe symptoms in ~8 weeks)
  • infection could enter into chronic fascioliasis (result of presence of adult worms in bile duct) ~12 weeks
    • blockage, inflammation, secrete proline (stimulates collagen deposits and fibrous tissue production) —> getting hardened and inflexible and worms blocking the bile duct
      • leads to pipestem fibrosis
  • end result: less bile can move thru bile duct
    • creates a back-pressure on to the liver
    • constant pressure —> atrophy
      • cirrhosis refers to chronic disease of liver, functional liver cells being lost
      • jaundice: more bilirubin in blood.
  • Fascioliasis: emerging disease in many countries
    • one that has appeared in a population for the first time OR one that previously existed but is now rapidly re-increasing in its incidence
  • environmental change —> snail habitats

Paragonimus Westermani

  • oriental lung fluke
Life cycle
  • figure 10-10, kind of similar to fascida)
  • 1st intermediate host: snail
    • cercaria exits the host. cercaria is microcercous (small, doesn’t have a tail, but a “knob-like tail”)
      • cannot swim, can crawl… but they’re in an aquatic environment.
  • 2nd intermediate host: crabs & crayfish (metacercaria)
  • definitive host: humans
    • there are also many resevoir hosts (nonhuman dh) ie: cats, dogs, pigs, monkeys, lions (so many hosts, hard parasite to control!)
  • once parasite gets into the definitive host, excyst in small intestine and juvenile penetrates thru the intestinal wall
  • embed themselves into the abdominal wall within a week
  • migrate in abdominal cavity
  • penetrate diaphragm
  • enter into the lungs and adult worms develop here
  • juveniles as they migrate, could end up in ectopic sites (weird places)
    • stuck in abdominal wall, brain, heart
  • lung: necrosis
  • symptoms: cough, chest pain, blood in sputum (cough blood)

Metagonimus yokagawai & Heteraphyes heterophyes

  • very similar so clump them together woo
Life Cycle
  • 1st intermediate host: snail
  • 2nd intermediate host: fish (metacercaria develops)
  • definitive host: humans (ingest fish)
  • resevoir host: fish-eating mammals (lots, so hard to control)
  • morphology: smallest of the human trematodes (less than 2mm l/w/h each)
  • adult worms live in small intestine of the definitive host
    • because they are so small, they are usually not a problem
    • unless they are in very large numbers in that human
    • cumulative effect: cause inflammation or ulceration
  • pathology is a reuslt of the eggs
    • adults: burrow into the intestinal muccosa where they produce eggs
    • can erode tissue then eggs enter blood of DH
    • eggs can then reach ectopic sites (ie heart, brain, spinal chord)
      • can result in neurological disorders

Diagnosis of trematoda infection

  • How are the eggs of worms exiting (lol eggsiting) the DH?)
    1. most live in intestine, liver, bile duct (even P.w. (lungs))
      • eggs in feces, 1000 of eggs per day
      • potential for environmental contamination
    2. look for eggs in the patients’ feces
  • Direct wet smear (~2mg of feces mixed with drop of saline —> microscope slide —> examine)
    • problem: 2mg is a very small amount, there’s a large chance you’ll miss eggs in that huge piece of shit u__u
    • if infection is low, may not find eggs
    • huge probability for false negatives
  • formalin-ethyl acetate sedimentation concentration
    1. concentration: (fecal) allows for detection of small numbers of eggs that might be missed by a direct smear
    2. formalin: preserves specimen
    3. ethyl-acetate extracts debris and fat from fecal material, get rid of things that’ll obscure your view of stuff
    4. method:
      1. mix ~4g feces with formulin (yay more than 2mg, greater chance of finding eggs)
      2. strain thru gauze
      3. add saline to result mixture
      4. centrifuge the mixture and discard the supernatant
      5. add more formulin & ethyl acetate
      6. centrifuge again and discard the supernatant (eggs won’t be in there)
      7. end with sedimend and if there are eggs, this is where they will be
      8. examine small amounts with a microscope
  • identification of eggs
    1. operculum “lid”
    2. size of egg
    3. look for any species specific features
      • C sineusis:
        • image

      • P Westerwani eggs in feces and sputum (wut)


  • Praziquantel (“PZQ”)
    • wide range of trematodes & cestodes (very effective against flat worms)
    • been around since 1970s, lots of research, very safe
    • not embryo-toxic, not mutagenic, not carcinogenic
  • what happens when exposure to PZQ
    1. rapid sustained muscular contraction —> paralysis
      • worm can’t attach and gets flushed out
    2. tegumental destruction
      • tegument on surface, defends against host antibodies and such
      • now that it’s damaged, parasite antigens are exposed and host can start fighting and getting rid of it
    3. these responses are linked to disruption of voltage-gated Ca2+ channels in the tegument
  • Fascida hepatica exception: doesn’t work with PZQ
    • probably because it has a very thick tegument (not easily destroyed or damage not as significant to survival)
    • Triclabendazole (TCBZ) is effective though (1980s).
      • greatest effect on migrating juveniles
      • effects:
        1. swelling of tegument of juveniles (damaging ion pumps)
        2. mitochrondria swells up (effect on metabolism)
        3. microtubule inhibitor (results in disrupt of fromation of cytoskeleton)
          • cytoskeleton is important in assisting with movement and, specifically, disrupts the movement of vessicles to the distal cytoplasm
    • Bithionol


  • kill the adult worms (drug treatment), so there won’t be any eggs
    • take dat arrow out in life cycle
    • but if we’re trying to avoid drug treatment…
  • don’t use night-soil (human feces as fertilizer)
    • less environmental contamination
    • sanitation
  • snai control
    • why don’t we just go and remove all of them
      • … but that’s not easy
    • mulluscicides
      • copper sulfate, sodium pentachloro-phenate: both have environmental issues
      • ectoxicity
    • recolonization
      • one snail can start an entire population lol because of self-fertilization
  • fascida hepatica (specific treatments)
    • boil plant material before consumption
    • watercress
      • Nasturtium officinale in h2o, peppery leaves, good in salads
  • M Yokagawai & H heterophyes & C sinensis : all have 2nd IH as fish
    • Don’t use night soil to fish farming ponds
    • fish preparation
      • metacercariae can survive salting, pickling, drying, smoking
      • problem where raw fish is a delicacy
      • problem where cooking fuel is not available
  • Paragonimus westermani (lung fluke)
    • 2nd intermediate host: crabs / crayfish
    • same idea as the fish, need to cook it properly to get rid of metacercariae
    • asian: “drunken crab”
      • immerse in rice wine for 12 hours and eat them… metacercariae survives
    • crab juices: squashed until juices flow out of it, used for medicinal purposes, metacercariae survives
  • Control of reservoir hosts (nonhuman definitive hosts)
    • domestic animals

Parasite Transmission

Host Environment
  • Advantages: constant conditions (nothing like changing weather)
  • Problems: host dies (get out asap)
    • how to identify or get out?
  • Transmission: movement from host to ensure survival of subsequent generations
  • Contaminative: food or water contamination with infective stage
    • passive process: Chance encounters between host and parasite
    • success depends on abundance of infective stages
    • gastrointestinal parasites: if infective stage in feces of host
    • "sit and wait" … for the next host to come along and ingest you
      • long time, resist environemntal conditions, ex: eggs & cysts (thick walls, nutrient storage, low metabolic rate)
  • Sexual transmission
    • transmission without exposure to the external environment
    • no specialized transmission stage, don’t need nutrient stores etc, just go from one host to another
    • ex: Trichomonas vaginalis (protozoan, humans, male usually asymptamatic, females develop trichomonad vaginitis)
  • Congenital transmission (thru birth)
    • infection develops egg or embryo or at time of birth
    • vertical transmission (going from mother to offspring)
    • ex: Toxoplasma gandii (protozoan, wide range of hosts, crosses over placenta, infect embryo, affinity for nerves tissue (brain development), causes hydrocephaly (fluid in brain))
      • children born with very large head due to hydrocephaly
  • Active transmission
    • free-living infective stage
    • actively searches for and invades host
    • parasite gets off its lazy ass and does shit
    • requires: reliable availability of hosts, identify host, stored energy
  • Vector transmission
    • vector: actively transmits the parasite from host to host
    • mechanical vector: parasite does not undergo development
      • ex: flies pick up eggs or cysts in fecal material and brings eggs or cysts from feces to food
    • biological: parasite does undergo development
    • blood-dwelling parasites … how are the infective stages getting out? that’s how vectors help out
      • ex: Plasmodium (malaria): mosquitoes. get one host to another thru mosquitoes because they live in blood.
  • Manipulation of host behavior
    • trophic levels
      • ex: prey —> predator (moving up trophic level)
    • PITT: parasite-increased trophic transmission
      • effect of a parasite on a host which increases the chances of host being ingested
      • effects could include: behavior of host, physical characteristic of host
      • ex: Leuchocloridium paradoxum
        • image

        • tentacles of snail enlarge and become brightly colored and pulsate
        • next host in life cycle: birds. they eat the snails

Photo Credit: Pieria

Leeches are segmented worms. Like other oligochaetes, such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from other oligochaetes in significant ways. For example, leeches do not have bristles and the external segmentation of their bodies does not correspond with the internal segmentation of their organs. Their bodies are much more solid as the spaces in their coelom are dense with connective tissues. They also have two suckers, one at each end.

The majority of leeches live in freshwater environments, while some species can be found in terrestrial and marine environments, as well. Most leeches are hematophagous, as they are predominantly blood suckers that feed on blood from vertebrate and invertebrate animals. Almost 700 species of leeches are currently recognized, of which some 100 are marine, 90 terrestrial and the remainder freshwater taxa.

Leeches, such as the Hirudo medicinalis, have been historically used in medicine to remove blood from patients. The practice of leeching can be traced to ancient India and Greece, and continued well into the 18th and 19th centuries in both Europe and North America. In modern times, the practice of leeching is much rarer and has been replaced by other contemporary uses of leeches, such as the reattachment of body parts and reconstructive and plastic surgeries and, in Germany, treating osteoarthritis.

Most leech species do not feed on human blood, but instead prey on small invertebrates, which they eat whole. To feed on their hosts, leeches use their anterior suckers to connect to hosts for feeding. Once attached, leeches use a combination of mucus and suction to stay attached and secrete an anticoagulant enzyme, hirudin, into the hosts’ blood streams. Though certain species of leeches feed on blood, not all species can bite; 90% of them feed solely on decomposing bodies and open wounds of amphibians, reptiles, waterfowl, fish, and mammals. A leech attaches itself when it bites, and it will stay attached until it becomes full, at which point it falls off to digest. Due to the hirudin secreted, bites may bleed more than a normal wound after the leech is removed.

Did you know? 

* The body of leeches is composed of 34 segments. Their body is brown or black in color. 
* Leeches have 32 brains. Due to similarity with the nervous system of humans, leeches are often used in the investigations of brain disorders. 
* Leeches have suckers on both ends of their body.