48
Short answer
Under ideal conditions, an octopus may survive several minutes on land.
Background
Octopuses have gills and hence are dependent on water for the exchange of oxygen and carbon dioxide. Gills collapse on land because of the lack of buoyancy (source: UC Santa Barbara). Octopuses have three hearts. Two of these are dedicated to move blood to the ...
20
You've found a sea anemone, a cnidarian of the Order Actiniaria. In this case, the anemone is closed and thus hiding its characteristic tentacles (likely as a form of protection while "out to dry").
I'm by no means an expert, but my guess is that you have a vertically striped species of the genus Diadumene -- likely one of many morphotypes of the species ...
12
After some more searching, I think stumbled across the answer. It appears to be an…
Eriophora ravilla:
Source BugGuide.net.
This species appears to have quite a diverse range of colors, and even thought I haven't found one that quite matches mine, the other similarities (the large abdomen, the stripe down the back, the four 'dimples', and the dark ...
11
The standard view on this is that the size of terrestrial arthropods like insects and spiders is limited by the atmospheric concentration of oxygen. This is because they rely upon diffusuion of oxygen into the 'blood' or haemolymph via a system of tubes called trachea that open on to the body surface at the spiracles. As the body grows larger the proportion ...
11
UPDATE:
Based on a comment by ArthurJFrost reminding me of the existence of a group of insects I totally forgot about, AND based on a closer examination of the cerci and what appears to be external mouthparts in the image of the OP's specimen, I think this insect might actually be a webspinner!
These insects would be also about the right size, with the ...
9
Found an octopus today which had attached itself to a rock covered in algae during high tide and had failed to swim back out with the receding tide. We found it at low tide, this means it must have been exposed for a long period of time, definately not only minutes. December in North Wales means it was wet, cold, no direct sun (but no rain). The octopus was ...
9
This is the shell of a marine mollusk called a chiton.
They are also sometimes known as sea cradles or "coat-of-mail shells", or more formally as loricates, polyplacophorans, and occasionally as polyplacophores.
In Puerto Rico, they call these animals "Quitones."
All chitons bear a protective dorsal shell that is divided into eight articulating ...
answered Mar 21 '17 at 22:40
8
It's a sea urchin (Echinoidea). It looks like a specimen of Lovenia or another genus from the heart urchin (Spatangoida) family.
What you see is just the shell without the spines.
Lovenia woodsii
Fossil sea urchin spines
Image sources:
http://www.thefossilforum.com/index.php?/collections/echinoderms/echinoids/lovenia-woodsii-r488/
http://www.fossilguy....
8
Some moth actually do use clicks for their own echolocation: "Noctuid moths (Noctuidae) are the only group of invertebrates for whom echolocation was
demonstrated":
Lapshin & Vorontsov 1998
Lapshin et al 1994.
7
There are a couple of advantages and disadvantages of possessing the eyes of octopuses.
The first advantage of the octopus eye is that it has no blind spot. This means that octopuses can see everything that is going on in their environment, and are more aware of predators and prey than some vertebrates. Also, they have many more photoreceptors than ...
7
Hard to tell because of the poor picture/video quality, but almost immediately the body shape, distinct "face", size and behavior made me think of a small invertebrate animal called a rotifer (Phylum Rotifera).
Rotifer eating protists. Photo Credit: Jacqueline Ronson, 2016
There are about 2000 species occurring worldwide within this primarily freshwater ...
answered Mar 12 '19 at 18:12
7
According to the Smithsonian:
The longest of all known polychaetes was found in Port Jackson, Australia. It was a member of the family Eunicidae, consisted of approximately 1,500 segments and was nearly 6 meters long when alive.
The Eunicidae consist of numerous species (including the super cool bobbit worm), many of which get fairly large.
Though, ...
answered Apr 14 '19 at 16:56
6
It's hard to identify from the photos provided, but I think it is Chloeia flava (a species of polycaete worm, within the phylum Annelida), also known in English as the "Golden Fireworm".
The size is roughly similar to what you describe (they are typically about 7-10 cm long). The individual you observed looks like it lives in sandy bottom environments (not a ...
6
It really depends on which type of gastropod you are talking about, since different types of snails, have different types of eyes.
Marine gastropods could only become more mobile, when their abilities of sight had improved. This happened, when the eye cup deepened and the visual opening narrowed. An effect was the result, which in historical time was ...
5
Asterosaponins are the class of compounds - they have a cholesterol like organic core.
Apparently, these saponins make pore-forming complexes with Δ5-sterols of cell membranes, and so are deadly to all usual kind of life, including bacteria and fungi. Quote:
Starfish and sea cucumber cell membranes are resistant to their own
saponines due to the ...
5
Those appear to be the eggs of a species of apple snail in the genus Pomacea, probably the introduced invasive golden apple snail (Pomacea canaliculata), but there are at least two other candidates1,2.
You can learn more about this species and the problems it causes from this Columbia University webpage.
For comparison — Figure 3 from "The identity, ...
4
Breathing during digging
And if all that wasn’t enough responsibility for these claws, they also are used for digging. While most digging crabs use their back legs to burrow backwards into the sand, the shame-faced crab uses the claws like little bulldozers, excavating the sand forward so the crab sinks downward until it is completely covered by the ...
4
Good question! I had never really though about it, so thank you!
Echinodermata have a pentaradial symmetry
Echinodermata actually don't have a radial symmetry like jellyfish do. They have a pentaradial symmetry as they systematically have 5 arms.
Parsimony
Even if Echinodermata were radially symmetric, then it would actually be unlikely that bilateral ...
4
In 1877, Lankester proposed in "Notes on the Embryology and Classification of the
Animal Kingdom" division of the group we now call Chordata into three parts:
Urochorda
Cephalochorda
Craniata
which is more or less the accepted division today, with Urochorda being called Urochordata now.
In this essay, Lankester says:
The evidence of degeneration is ...
4
They are Apple snail's eggs; check the picture:
Check this.
4
This could very well be the eggs from an apple snail (family Ampullariidae).
According to Wikipedia
Several apple snail genera (Pomacea, Pila and Asolene/Pomella) deposit eggs above the waterline in calcareous clutches. This remarkable strategy of aquatic snails protects the eggs against predation by fish and other aquatic inhabitants.
If these are in ...
answered Mar 29 '19 at 19:14
4
Yes this is a leech. It appears to be a species in the family Glossiphoniidae, or the freshwater jawless leeches. This family of leeches is relatively flattened with a poorly defined anterior sucker.
According to The Canadian Encyclopedia, there are about 45 species of leeches found in or around Canada.
Langer et al. (2018)1 provide a more limited ...
3
As others have indicated, I also haven't seen direct evidence of echolocation in insects. However, there is much evidence that the auditory system of e.g. moths can hear ultrasound generated by bats (Waters, 2003). According to Waters (2003) moths mainly use this to avoid predation. The review also contain many useful references and examples of moth ...
3
Leeches:
According to Taube (1966)$^1$:
The adults of American leeches range from about 1/4 inch to 12 inches in contracted length.
Because leeches can bloat to more than 10x their "normal" size after a meal (and can undergo up to a 300% change in length), it seems that measuring a leech at anything but their contracted state would lead to wildly too ...
answered Dec 21 '16 at 17:50
3
Why so many molluscs exhibit sinistral winding?
The estimates of the number of molluscs vary quite greatly between 50,000 and 200,000 species. Of those molluscs species, about 70'000 are Gasteropoda. Gasteropa is most diverse Mollusca phylum.
The winding you describe is present in all Gasteropoda and is often called the torsion. So the answer to why there ...
3
This is one of those speculative questions where you don't have a definite answer unless you specifically experiment and find out for yourself.
It is a known fact that earthworms breathe through diffusion. It has a thin cuticle over its body and requires moist skin which is achieved by a slimy mucous (reference). It is interesting to note that earthworms ...
3
Gooseneck barnacles
It appears to be a cluster of goose barnacles washed up onshore. This is based on the thick, distinct pedicle and the general shape of the asymmetrical valves. Without more information, that’s as accurate as I can probably get you.
3
I have finally figured out what these are, and it turns out I greatly misunderstood their relationship with snails.
These worms are annelids of the genus Chaetogaster, specifically Chaetogaster limnaei limnaei.
Source: Page 653 of "Fresh-water biology" (1918)
Ch. l. limnaei is unique in its genus in that lives on the bodies and in the shells of snails, ...
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