The following photographs are of dead Carcinoscorpius rotundicauda (Mangrove horseshoe crab) found alongside a stream which runs across the mudflat at Tung Chung, Lantau, Hong Kong on 23 September 2010.
The horseshoe crabs hanging in the mangrove bush are a male and female, possibly a mating pair which were swimming up the stream to spawn in the mangroves that line the stream. The animal lying on its back is a dead female C. rotundicauda.
Streams are critical to the ecology of C. rotundicauda, because they use stream courses to navigate across beaches to reach the mangrove stands where they spawn. C. rotundicauda has also been observed to spawn in the lower reaches of streams in Hong Kong.