AI Comparison
Chatgpt’s Answer
This crab appears to be a mud crab / mangrove crab, most likely Scylla serrata (also known as the giant mud crab or Sri Lankan crab).
How to tell:
- Large, heavy claws with dark (almost black) tips
- Broad, oval carapace with distinct spines along the front edge
- Greenish-brown shell with orange-yellow highlights on the claws
- Flattened rear legs adapted for swimming (a key trait of mud crabs)
Common names:
- Mud crab
- Mangrove crab
- Sri Lankan crab
- Black crab
Where they’re found:
- Mangroves, estuaries, and coastal waters throughout Southeast Asia, including Singapore
Notes:
- This species is edible and highly prized in seafood cuisine (e.g., chili crab, pepper crab 🦀).
- They can be very aggressive — those claws are strong enough to break shells and cause injury.
If you’d like, I can also help differentiate it from similar species like Scylla olivacea or Scylla paramamosain.
Gemini’s Answer
Based on the physical characteristics in the image—specifically the six sharp spines on each side of the carapace and the paddle-shaped rear legs—this is an Asian Paddle Crab (Charybdis japonica).
Key Identification Features
- Carapace (Shell): It has six distinct, sharp spines on either side of the shell. The overall shape is roughly hexagonal and often a dark olive or purplish-brown.
- Claws (Chelipeds): These are large and robust with prominent spines (usually five) on the upper surface. The yellow/orange underside of the claws seen in your photo is a common color variation.
- Swimming Paddles: The last pair of legs are flattened into “paddles,” which is characteristic of swimming crabs (family Portunidae).
- Legs: Note the purplish/dark blue tint on the joints and segments of the walking legs, which is typical for this species.
Why It Matters
This crab is native to East Asia (Japan, Korea, China, Malaysia) but has become a highly invasive species in other parts of the world, particularly New Zealand and Australia.
- Aggression: They are very aggressive and can out-compete native crab species for food and habitat.
- Health Warning: In some regions, they are known to carry diseases like the White Spot Syndrome Virus, which can affect local shellfish populations.
- Safety: Watch your fingers! These crabs are known for being particularly “feisty” and can deliver a painful pinch.
Where did you find this specimen? If you are in a region like Australia or New Zealand where they are considered invasive, local biosecurity agencies often request that sightings be reported. Would you like me to help you find the correct agency to report this to?
Genspark’s Answer
This is a swimming crab (family Portunidae) and it most closely matches the Blue Crab (Callinectes sapidus)—or a very close Callinectes relative (genus-level ID is solid; species-level depends a lot on where it was found). Source
Why this ID fits (visible traits)
- Paddle-shaped last legs (the rear pair are flattened like ovals): classic “swimming crab” feature. Source
- Broad, flattened carapace with a toothed/spiny side margin (the edge has multiple points/teeth). Source
- Color pattern consistent with Callinectes: olive-green/brown carapace, bluish‑purple legs, and orange/tan claws with dark tips. Source
Most likely species
- Blue crab (Callinectes sapidus) — most likely if you’re on the U.S. Atlantic or Gulf coasts. Source
Quick question to confirm the exact species
Where was this crab found (country + nearest coast/body of water)? Location is the easiest way to tell C. sapidus from other very similar Callinectes species.
Claude’s Answer
What a beautiful specimen! This is a Blue Swimming Crab (Portunus pelagicus), also commonly known as the Flower Crab or Sand Crab.Here’s what gives it away in your photo:
Shell (Carapace): Wide, flattened, olive-green with that characteristic scalloped edge and subtle spotted patterning — textbook P. pelagicus.
Claws (Chelipeds): Long, powerful, with dark purple-black tips fading to golden-orange — very distinctive of this species. The serrated edges are clearly visible.
Legs: The walking legs show that signature blue-purple iridescence, and the rear pair (not fully visible) would be paddle-shaped for swimming — the hallmark of all swimmer crabs.
Colors: The olive/bronze-green carapace with golden and blue tones is classic for this species.
Quick Facts:
| Common name | Blue Swimming Crab / Flower Crab |
| Scientific name | Portunus pelagicus |
| Family | Portunidae (swimmer crabs) |
| Habitat | Sandy/muddy coastal waters, estuaries |
| Range | Indo-Pacific, Red Sea, Mediterranean |
| Edibility | Highly prized — one of the most commercially fished crabs in Asia |
Given your location in Singapore, this is an extremely common and commercially important species — it’s the crab you’d find at a chilli crab or black pepper crab restaurant! 🦀🌶️
Do you know where this one was found?
Perplexity’s Answer
This looks like a swimming crab from the family Portunidae, most likely a species of Thalamita (often called “eyes‑wide‑apart” or red/purple swimming crabs) rather than an edible mud crab (Scylla). wildsingapore
Why this identification
- The last pair of legs are flattened like paddles, a hallmark of Portunidae swimming crabs. wildsingapore
- The carapace is relatively flat and broader than long, with lateral spines along the sides, matching Thalamita‑type swimming crabs seen on Singapore shores. tidechaser.blogspot
- The legs are purplish while the claws and carapace margins are orange‑brown, which fits descriptions of species such as the “Spiny Hands” or related Thalamita swimming crabs that have orange carapaces and purple legs. tidechaser.blogspot
How certain is this?
- Family (Portunidae, a swimming crab) – very likely. wildsingapore
- Genus (Thalamita) – probable based on body shape, colours, and habitat, but a precise species ID would usually need a close look at the frontal teeth, carapace spines, and underside, which the photo does not fully show. wildsingapore
If you want a definitive species name, you could share this photo with local shore-life groups or reference guides to Singapore’s swimming crabs; they often ask for top and underside photos taken close up. tidechaser.blogspot
TLDR
Chatgpt: Mud Crab (Scylla Serrata)
Gemini: Asian Paddle Crab (Charybdis Japonica)
Genspark: Blue Crab (Callinectes Sapidus)
Claude: Blue Swimming Crab (Portunus Pelagicus)
Perplexity: Portunidae family, Thalamita species
Me: Charybdis Hellerii (Purple-Legged Swimming Crab)