Costasiella kuroshimae – Solar Powered animals, that do indirect photosynthesis

I just got to see a different species of kleptoplastic sea slugs in the wild last month, on a kayak tour of the mangroves around Key West. Our guide scooped some lettuce sea slugs up in a plastic container (and then returned them safely). They were bigger, about 3 inches long, with a wavy/frilly green border. It made my biologist heart very happy!

We‘re all solar—powered animals.

I remember as a kid wondering if we could give humans chlorolaplasts.

This is one of those times evolution doesn't make sense to me. It's clear how a giraffe's neck evolves, the ones that could reach higher leaves in trees had an advantage. In examples like this, how does this evolve when there is no gradual change? An animal had to exist that had an offspring that somehow both absorbed the chloroplasts of the food it ate in a way that it could use (not just simple digestion), then have a place to store them, then have a mechanism to move the chloroplasts to the storage space, then have the mechanisms in their body to use the energy the stored chloroplasts create. How does that happen gradually when each step is totally useless without the others?

(please note I am not challenging the scientific truth of evolution, I simply do not understand how something like this happens)

Makes you imagine a world with high solar power density and maybe lower gravity or something where larger land animals might be realistically supplemented by solar energy as well.

That was likely a sea slug from the Nudibranchia order (they resemble lettuce sea slugs sometimes) which are a bit different from Sacoglassa order slugs like the one in TFA in that they carry symbiotic algae colonies, rather than digesting them and keeping the chloroplasts like Sacoglassa.

We‘re all solar—powered animals.

You know what they meant.

I remember as a kid wondering if we could give humans chlorolaplasts.

Somewhat related https://what-if.xkcd.com/17/

The surface is too small and you only get like 4% of the energy you need (Assuming you like being naked under full sunlight all day long. The article is for cows, but I guess the number is similar for humans.) 4% of 2400 kcal is almost 100 kcal, that is the content of a small diet treat or 2 apples.

These sea slugs can survive because they move very slowly. For a human, I think it's not enough energy to survive even if all the activity is to watch TV inside a hot swimming pool.

I believe that mitochondria and chloroplast both were originally independent single celled organisms.

So kind of funny that, chloroplast is being "stolen" again by this sea slug.

Stuff like this really makes you wonder what life might look like out in the universe.

(please note I am not challenging the scientific truth of evolution, I simply do not understand how something like this happens)

The article notes that the chloroplasts are like a larder that the slug can digest when needs be, so storage could have come well before photosynthesis was actually utilized.

Or maybe it was photosynthesis first. The chloroplasts just did their thing for a while, and slugs that digested them slower (and eventually ones that stored them) got more benefit than ones that didn't.

> please note I am not challenging the scientific truth of evolution

Evolution isn’t a matter of faith, you’re welcome to challenge it and try to poke holes in it.

They look kind of translucent to me, maybe the first of this kind of slug just had a digestive problem that didn't break down the chloroplasts, and the minimal energy through their bodies made those individuals more successful because they didn't need to eat as often as those who digested theirs. Yada yada other errors among the indegestible-chloroplast population showed further advantages when it's closer to the skin, they outcompeted their peers, etc.

Makes you imagine a world with high solar power density and maybe lower gravity or something where larger land animals might be realistically supplemented by solar energy as well.

Closer to the sun (high solar power density) and smaller (lower gravity)... I think we actually have one of those nearby?

You know what they meant.

Somewhat related https://what-if.xkcd.com/17/

These sea slugs can survive because they move very slowly. For a human, I think it's not enough energy to survive even if all the activity is to watch TV inside a hot swimming pool.

I believe that mitochondria and chloroplast both were originally independent single celled organisms.

So kind of funny that, chloroplast is being "stolen" again by this sea slug.

The article notes that the chloroplasts are like a larder that the slug can digest when needs be, so storage could have come well before photosynthesis was actually utilized.

> please note I am not challenging the scientific truth of evolution

Evolution isn’t a matter of faith, you’re welcome to challenge it and try to poke holes in it.

Stuff like this really makes you wonder what life might look like out in the universe.

Sounds like you might be interested in “The Zoologist’s Guide to the Galaxy”.

https://en.wikipedia.org/wiki/The_Zoologist%27s_Guide_to_the...

Some things on Earth (especially in the ocean) you'd think were extraterrestrial... What a gift to still be able to find such amazing animals out there.

https://www.eastoftheweb.com/short-stories/UBooks/TheyMade.s... - love this short story and its take on that question.

Isn't life on this planet also life out in the universe? It depends on your point of view.

[1] Pale blue dot - Carl Sagan https://www.youtube.com/watch?v=wupToqz1e2g

Closer to the sun (high solar power density) and smaller (lower gravity)... I think we actually have one of those nearby?

Some infinite water supply would be probably helpful there.

Sounds like you might be interested in “The Zoologist’s Guide to the Galaxy”.

https://en.wikipedia.org/wiki/The_Zoologist%27s_Guide_to_the...

Some things on Earth (especially in the ocean) you'd think were extraterrestrial... What a gift to still be able to find such amazing animals out there.

https://www.eastoftheweb.com/short-stories/UBooks/TheyMade.s... - love this short story and its take on that question.

A classic, and regularly shared here on HN :)

I really like this version of it personally: https://www.youtube.com/watch?v=T6JFTmQCFHg

Isn't life on this planet also life out in the universe? It depends on your point of view.

[1] Pale blue dot - Carl Sagan https://www.youtube.com/watch?v=wupToqz1e2g

Do you consider things that are inside a house to also be outside a house?

Some infinite water supply would be probably helpful there.

Infinite indeed, need to keep it topped off as it all boils away.

A classic, and regularly shared here on HN :)

I really like this version of it personally: https://www.youtube.com/watch?v=T6JFTmQCFHg

Do you consider things that are inside a house to also be outside a house?

Is the coffee actually in the mug or only on top of it?

All things are moving in space and time and in relation to other objects so inside or outside are relative points of view.

[1] https://en.wikipedia.org/wiki/Special_relativity

[2] Point of view is worth 80 IQ points - Alan Kay. He didn't specify the sign....

Things inside this house are indeed outside that house.

Infinite indeed, need to keep it topped off as it all boils away.

Is the coffee actually in the mug or only on top of it?

Things inside this house are indeed outside that house.

Now I think of a scifi setting, where rich people use massive ressources to feed their artificial gardens on Merkur with water from comets, so the genetically engineered solar powered green butterflies in their garden can keep flying.

(But there might be more expensive adjustments needed, like rotation speed)

All things are moving in space and time and in relation to other objects so inside or outside are relative points of view.

[1] https://en.wikipedia.org/wiki/Special_relativity

[2] Point of view is worth 80 IQ points - Alan Kay. He didn't specify the sign....

I wonder if life elsewhere in the universe is pedantic too.

(But there might be more expensive adjustments needed, like rotation speed)

I wonder if life elsewhere in the universe is pedantic too.

QED.

[1] Why people hate smart individuals: Studies reveal it's linked to your own intelligence level https://www.gq.com.au/health/wellness/studies-say-who-you-ha...

[2] On the importance of being pedantic https://medium.com/@lfloridi/on-the-importance-of-being-peda...

[3] Pedantic definition https://dictionary.cambridge.org/dictionary/english/pedantic

[4] Pedantic opinion https://www.vocabulary.com/dictionary/pedantic

QED.

[1] Why people hate smart individuals: Studies reveal it's linked to your own intelligence level https://www.gq.com.au/health/wellness/studies-say-who-you-ha...

[2] On the importance of being pedantic https://medium.com/@lfloridi/on-the-importance-of-being-peda...

[3] Pedantic definition https://dictionary.cambridge.org/dictionary/english/pedantic

[4] Pedantic opinion https://www.vocabulary.com/dictionary/pedantic

If you were so smart, you'd probably find better sources than GQ and Medium to prove your point.

From Wikipedia, the free encyclopedia

Costasiella kuroshimae

Wakatobi National Park, 2015
Scientific classification
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C. kuroshimae

| | Binomial name | | Costasiella kuroshimae

Ichikawa, 1993

| | |

Costasiella kuroshimae (also known as a leaf slug, sea sheep, or leaf sheep) is a species of sacoglossan sea slug. Costasiella kuroshimae are shell-less marine opisthobranch gastropod mollusks in the family Costasiellidae.[1] Despite being animals, they perform photosynthesis, via kleptoplasty.[2]

Discovered in 1993 off the coast of the Japanese island Kuroshima, Costasiella kuroshimae have been found in the waters near Japan, the Philippines, and Indonesia. They live in tropical climates.[3] The type locality is Kuroshima, Taketomi, Okinawa, Ryukyu Islands.[4]

They have two dark eyes and two rhinophores that emerge from the tops of their heads that look similar to sheep's ears or insect antennae.[5] They range in size from 5 to 10 mm (1⁄4 to 3⁄8 inch) in length. Their leaf-like appearance is credited to the cerata featured in rows across their body. These cerata contain digestive glands that assist the Costasiella kuroshimae in obtaining and storing food. They also aid in defense and respiration. [6]

Costasiella kuroshimae are capable of a physiological process called kleptoplasty, in which they retain the chloroplasts from the algae they feed on. Absorbing the chloroplasts from algae enables them to perform photosynthesis.[7]

Costasiella kuroshimae is a selective feeder of algae from the genus Avrainvillea,[5] from which it sequesters chloroplasts into its own cells, retaining them for short-term photosynthesis. Even in the absence of active photosynthesis, chloroplasts provide a nutrient storage or "larder" that facilitates the survival of the slug without food for an extended period of time.[8]

A frontal picture of a Costasiella kuroshimae.
Costasiella kuroshimae taken in Secret Bay Anilao dive site, Batangas, Philippines
Costasiella kuroshimae at Koh Phangan, 2014
Costasiella kuroshimae at Bali, Indonesia.
Costasiella cf. kuroshimae on Avrainvillea erecta. Locality: Lizard Island, Great Barrier Reef. The length of the slug is about

1 cm (3⁄8 in).

^ Bouchet P (2014). "Costasiella kuroshimae Ichikawa 1993". World Register of Marine Species. Retrieved 17 January 2015.
^ Christa, Gregor; B. Gould, Sven; Franken, Johanna; Vleugels, Manja; Karmeinski, Dario; Handeler, Katharina; F. Martin, William; Wagele, Heike (23 May 2014). "Functional kleptoplasty in a limapontioidean genus: phylogeny, food preferences and photosynthesis in Costasiella, with a focus on C. ocellifera (Gastropoda: Sacoglossa)". Journal of Molluscan Studies. 80 (5): 499–507. doi:10.1093/mollus/eyu026.
^ Palomares ML, Pauly D, eds. (2023). "Costasiella kuroshimae" in SeaLifeBase. March 2023 version.
^ Jensen KR (2007). "Biogeography of the Sacoglossa (Mollusca, Opisthobranchia)" (PDF). Bonner Zoologische Beiträge. 55 (3/4): 255–81. Archived from the original (PDF) on 2013-10-05.
^ a b Oceana. "Leaf Sheep." Oceana, [Date Accessed: 26 Oct. 2023], https://oceana.org/marine-life/leaf-sheep/
^ Togawa, Yumiko; Shinji, Junpei; Fukatsu, Takema; Miura, Toru (2019-10-01). "Development of Cerata in the Cladobranchian Sea Slug Pteraeolidia semperi (Mollusca: Gastropoda: Nudibranchia)". Zoological Science. 36 (5): 387. doi:10.2108/zs190057. ISSN 0289-0003.
^ Händeler K, Grzymbowski YP, Krug PJ, Wägele H (December 2009). "Functional chloroplasts in metazoan cells - a unique evolutionary strategy in animal life". Frontiers in Zoology. 6 (1): 28. doi:10.1186/1742-9994-6-28. PMC 2790442. PMID 19951407.
^ Christa, G., Wescott, L., Schaadt, T., Händeler, K., & Waegele, H. (2014). Photosynthesis in Sacoglossa: the impact of food sources, photosynthetic efficiency, and the occurrence of kleptoplasty in Costasiella ocellifera. Journal of Experimental Marine Biology and Ecology, 461, 57-61.

Sealife Collection photos

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Costasiella kuroshimae – Solar Powered animals, that do indirect photosynthesis

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