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BillT

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Viewing 15 posts - 136 through 150 (of 154 total)
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  • in reply to: Hello, and some biotope-setup questions. #350408

    BillT
    Participant

    The entire word “süßwasser tang” meaning freshwater kelp, “süß” actually meaning sweet

     

    I like word explanations.

    Interestingly, in american (if not more widespread) aquaculture the term “sweetwater” can be used for good quality freshwater. Also many place names.

    in reply to: Seriously Fish App? #350406

    BillT
    Participant

    Based upon my personal usage, I would like the following features in an app:

    • species profiles

    • wide range of aquarium tools (I am thinking calculator type things like volume conversions, dilutions, chemical interaction ratios {how much sodium thiosulfate to inactivate an given amount of chlorine}, toxic ammonia at given pH/tamps, etc.)

    • Although I probably would not use it, phone photos to the website would also make sense to me.

     

    These are things I would be likely to want to use when walking around the fish room. Other things I would be more likely to access from my laptop in a more leisurely manner.

     

    I use iOS and would be using an iPad, so I would vote for iOS.

    in reply to: Brackish Water Question #350297

    BillT
    Participant

    Usually brackish water refers to water resulting from the mixing of the local freshwater and seawater.

    The salinity can vary due to the variability of the mixing.

    The ions and their ratios will probably be dominated by those of seawater.

    in reply to: Can Shrimps Get Velvet (or Other Fishy Diseases)? #350262

    BillT
    Participant

    Not a shrimp to fish link, but a crayfish to frog link.

     

    The fungus killing frogs in many places around the world can infect and sicken crayfish which can also act as a disease reservoir for frogs:

    http://www.pnas.org/content/110/1/210

     


    BillT
    Participant

    Wow. That’s a great picture in that link Oaken.

    Seems like a good trait to keep an eye out for.

     


    BillT
    Participant

    Great pictures.This appears to be more complex than I thought.

    The stripe you might be calling greenish in D. dracula I would call yellowish, maybe. It may be surrounding of the spinal cord.

    I have attached another picture of one of the Danionella translucida. I got these fish through a friend Joel Sohm who some how convinced Herbert Axelrod to fund in some way Tyson Roberts to get a bunch for researchers bunch on a collecting trip. This makes me think these are really D. translucida. They also have a short body axis (fitting with being a smallest freshwater fish). This was some time in the 1990’s, I think before the other members of the genus were known. I got some because Joel knew the PI of the lab I was in, Scott Fraser. At the time they were the smallest known freshwater fish and we were interested in non-invasively looking at the internals of a live vertebrate. It worked well except for the are I was most interested, in the hindbrain (which I did my thesis on in zebrafish).

    Getting to a point here: In this picture you can see an obnoxious (to me) yellow coating over the brain (behind the eye and in front of the spinal cord). The spinal cord in this animal is the translucent white stripe that ends at the upper right side of the picture. It maybe that the color is an extension of this yellow brain covering. However see comments below.

    You can see what I would call birefrigence green just below where the skin exits the the picture at the top. Also a spot just below the vertebrae, behind the gills.This picture was shot through a microscope, probably with a 40x objective and Nomarski optics (fancy phase contract). The black background is the dark field of the microscope illumination.

    All these apparent colors will be affected by the illuminating light and the background.

    The vertebrae are the clearish (but in areas shiny) things lined up directly underneath the spinal cord. The black spots are individual pigment cells. You can see blood vessels especially in the gills. The heart should be medial at the back of the gills, maybe the darker red area.

     

    Danionella-translucida-1.jpg

     

    When I got around to ordering some D. translucida from a commercial source a few years ago, at first I assumed they were the right sps. Eventually they seemed too long in proportion to their other dimensions so I knocked one out and took some pictures with a digital microscope I could plug into my laptop (no longer in a lab). This scope was a bit difficult to focus and get the illumination right, but not bad for $200-300.

    I figured it was mirifica based upon the ventral medial pigment stripe which I read about somewhere in a paper. I think this was before dracula was described, not sure about priapus. This fish was dead by this time which is why I don’t like knocking them out. It is turning opaque. This fish does seem to have pigment stripes dorsally, which is confusing. This also shows what seem to be more than one pigment stripe dorsally. This would indicate priapus according to your list above.

    The next picture shows the anal fin (before I realized the rays would be good to count). It has a lot of fin rays, my guess is about 18 (which puts it in your mirifica range) but it is not the perfect picture for this.

    It also has a yellow stripe in the tail region which fades away above the body cavity. This stripe extend over the spinal cord but also below to cover the vertebrae in this view and into the tail. So much for the spinal cord covering explanation.

    There are other possibly relevant pieces of anatomy in this area. The longitudinal pigment cells stripes down the dorsal-ventral middle of the tail are probably along the lateral line nerve which innervate neuromasts (clusters of haircells that are lateral line sensory cells; not to be mistaken for the lateral line seem macroscopically in scales). This nerve usually runs between the dorsal and ventral blocks of the muscle segments. in zebrafish a different kind of muscle develops between these two muscle blocks. Slow muscle instead of fast muscle. It might look different perhaps because of having more mitochondrial or something. You should be able to see two lines from either side, but in places there are three. Perhaps one is at the midline. it might be along a midline blood vessel.

     

    Danionella-maybe-mirifica.jpg

    Danionella-maybe-mirifica-anal-fin.jpg

     

    I suppose it is possible that here are not yet described species being distributed commercially which could increase the difficulty of identifying these guys.

     


    BillT
    Participant

    If the greenish lateral stripe is iridescent (which is what it looks like in some pictures I have seen) I would bet that it has something to do with birefringence of light interacting with the muscle fibers. If it is due to birefringence, it may not be a reliable defining trait unless there is some difference between these species that only allows it to happen in one of them.

     

    Birefringence a process similar to the iridescent color of structural pigments but it can occur with light passing through the fish. The muscle actin or myosin fibers are periodically spaced at a molecular level (like guanine crystals). Each could reflect of refract the light resulting in a variety of light paths varying by certain wavelengths or fractions of wavelengths. This could then result through constructive or destructive interference in light from the different lights paths summing up to produce colors when looking at a particular place in the fish. Different angles can produce different colors in some cases because the length of the light path differences due to the trigonometry of the situation. This is seen a lot through microscopes in larval zebrafish.

    A shiny oil slick on water that shows different colors in different places or with different angles of light is a good example of this phenomenon. Light reflects off of the top and bottom of the oil layer, producing two different length light paths which looking at the same place that interfere to make a color. The light path differences, the nature of the interference, and the colors produced would vary with the angles of illumination, viewing, and local thickness of the layer of oil.


    BillT
    Participant

    That is interesting Stefan. I suppose he should know the species if any one does. Do you know the specific features he used to ID them?

    I suppose a good picture of the front of the head could show the “teeth” but that might be a difficult shot to get but simpler in a dead specimen.

    I have over the years knocked out these fish for various purposes, but they have shown a disturbing tendency to not wake up after that. Since I don’t usually have a lot of them I try to take pictures of swimming fish in a photo box.

     

    I feed these fish heavily on brine shrimp nauplii, Water worms (like microworms), Moina, and a commerical baby fish powder (100 µm particle size). The females get surprisingly and obviously fat. This is the main way I tell the sexes apart.

    I got a bunch of Danionella in once that had some disease I think was velvet but I do not feel sure about that identification. The fish got less transparent and more of an opaque white in areas. They looked thin in the abdominal area, about the same thickness as the head and tail. Eventually many started dying so I nuked the tank with bleach.

     


    BillT
    Participant

    Oaken, the more I get dainonins and look at them closely, the more I am convinced of the truth of your words about naming actions of people in the supply chain between the fish in the wild and the people keeping them in their tanks.

     

    By the way, I looked at the pictures in the topic: Danionella dracula Britz, Conway Rüber, 2009 – from Myitkyina, Myanmar

    based upon Matt’s post about other threads on Danionellas. Although I have never had the priapus species, the second picture in that post indicates to me that it is a priapus not a dracula species fish. You can see a little thing projecting downward in front of the anal fin. Based on what I have read, this is what I would expect to see in this species.

     

    It would be nice if there more detailed and easily comparable pictures of these fish available. I would like to make an easily useable picture guide to ID’ing these fish. I guess good cartoons could suffice as an alternative. However, to see a lot of these details in fish that I have, I find a decent picture is a great help. Many small details can not be easily viewed in a small, moving, unmagnified fish.

     

    Below is a picture I took many years ago (in the 1990’s I think) of a Danionella translucida that we got in a lab I was in. Its not a great image, partly because it is a scan of a picture on a photographic projection slide (no good digital cameras back then) and the whites are now kind of blown out. But it was taken through a compound microscope at low mag and shows the short body axis of this species. This is a female that was knocked out and viewed on a microscope slide with a cover slip held up at the sides to keep from crushing the fish. You can see a series of clear blobs below clear air bladder. These are the eggs. At high mag you can see the nuclei in the oocytes (egg cells). I never got these fish to breed, but I did not know what I know know.

     

    These fish are great potentially research animals because you can see so much inside the bodies of live adults. However, the difficulty in breeding them makes it problematic. One of my “missions from god”.

     

    Danionella-translucida.jpg

    BillT
    Participant

    Very interesting behavior.

    I don’t think your pictures all that bad for pictures in a tank. These are difficult fish to photograph.

    I have some Danionella which have bred, but I have never seem it.

    In Pete Cottle’s Danios and Devarios book there is an discussion of Danionella breeding. The person who wrote it thinks they like to dive into a gravel (not sand) substrate to lay their eggs. I had been keeping them for a while in a bare bottom tank with a java moss and a lot of acrylic yarn mops with no breeding success. After reading the above account, I added some trays with various sizes of gravel and some marbles at different levels int he tank (30 G). After a while I got about 100 offspring over a period of a few weeks.

     

    These look like two males to me or a male and a female maybe but the female does not look like it is carrying eggs.

    When my Danionella are carrying eggs it is really obvious. The females are about 1.5 times the top to bottom thickness of the males. I use an intense little flashlight to look at them and sometimes the light glints off the eggs in the females body.

     

    I am not sure what species they are but I don’t think they are priapus since the males should have a small projection projection going down in front of the anal fin. The pictures seem good enough to show this and I can’t see it.

    I doubt they are translucida because they have a shorter body axis. I had these in a lab I worked in once.

    If they are dracula they should have two little downward pointing teeth on the upper jaw. I can’t see these, but I don’t know if they would be visible in this kind of picture.

    Among described Danionella species I am aware of, that leaves mirifica. They are supposed to have a line of pigments cells on the ventral midline. Not easy to see. I did this once by knocking a fish out, but it did not wake up. There cold however be other not yet described species. I think it is rare for any Danionella species sold in the US to be correctly identified by the people selling them.

     

    The green line is probably birefringence due to light reflecting off of muscle fibers similar to the light reflecting off of layers of structural pigments that give some fish an iridescent sheen. You can get this in really clear small fish with the light at the right angle. I have never seen as darkly pigmented Danionella as your dark one.

     


    BillT
    Participant

    BillT
    Participant

    There is a Xiphophorus Stock Center in Texas, set up for research purposes.

    This is the webpage for their fish images which also has a contact for making requests for images.

    I have no idea what their policy is, but it would not surprise me if public education is within the scope of what they are funded for. Since Seriously Fish is (I assume) non-profit and seems to me to be the best purveyor of solid fish information for the public, I would guess they would be happy to let you use their images unless there were other things like copyright constraints going on.

    in reply to: Happy Darwin Day! #350125

    BillT
    Participant

    DNA was discovered the year I was born 1953. DNA day is coming up. The structure of DNA was first published on April 25, 1953, 60 years ago. The molecule that ties it all together.

     

    a DNA song:

    http://www.youtube.com/watch?feature=player_detailpage&v=3glTqNLUUN4

    in reply to: Danio cf putaoensis “mini putao danio” #350088

    BillT
    Participant

    Yes. The coloration does look like a D. devario. A stumpy one.

    in reply to: Danio cf putaoensis “mini putao danio” #350085

    BillT
    Participant

    These fish are now about 2 and a half weeks older than the previous pictures. They have more color in their fins and a darker stripe in their tail.Some of them are also getting fatter, hopefuly with eggs.

    older-mini-Putao-Danio.jpg

Viewing 15 posts - 136 through 150 (of 154 total)

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