Hong Kong Post unveiled a series of new postal stamps this week, including a set featuring Hong Kong’s rich marine biodiversity designed by Shirman Lai . Revealing our beautiful underwater world, this six-piece issue aims to promote awareness for marine conservation in the hope of making joint efforts to preserve our precious marine life. For extra fun, the souvenir sheet features fish-shape perforations to match the overall fish silhouette. Among others the stamp features the Chinese White dolphin, stingrays, corals green sea turtles and jellyfish.
Introducing Hoilungia hongkongensis a Placozoan. What’s a placozoan? Literally it means “flat animal” and these animals represent one of the simplest multicellular life forms known. And up until this year the entire phylum (major branch of the tree of life) of Placozoans had only 1 species: Trichoplax adharens! That would be like saying that the sum of all known vertebrates was just one species.
But a team of scientists have now added Hoilungia hongkongensis making it 2!
Hoilungia – meaning sea dragon – was isolated from HK and therefore honoured with the species name hongkongensis. Don’t rush to go looking for this 1 mm across flattish blob though. Placozoans are utterly featureless and have only 5-6 different cell types – one of which is the epithelial cell which has little beating hairs that propel the animal across the sediment (slooowly) where it feeds like an amoeba by engulfing detritus. Like other featureless or cryptic species this one was identified and separated from others by genetic analysis alone. Basically there is nothing to look at.
Featured image: Bernd Schierwater (cc by 4.0)
The betuline cone (Conus betulinus) is a large predatory and venomous cone snail, related to the textile cone.
It has a heavy shell that grows to up to 17 cm in length, and is distributed across the Indo-Pacific. The snail itself is velvet black and crawls around on a broad foot hunting worms.
In Hong Kong it occurs on sandy bottoms down to 5 m and in 1985 was still regarded common, although I haven’t ever seen a live one locally (yet!)
In contrast to the textile cone, the toxicity of the betuline cone is low. The toxins of cone shells are known collectively as conotoxins and act on the ion-channels regulating cells activities as well as on neurotransmitter functions.
Bordered Seastar (Craspidaster hesperus)
Described as the new species Pseudarchaster spatuliger in 1934, it was later revised to an already known species. The diameter with arms is about 10 cm. It is a flat starfish with tapered arms. The edges of the body are bordered with large, wide plates giving it its english name. The tube feet are pointy and not tipped with suckers like other starfish. Occurs from the Bay of Bengal to China and southern Japan.
Sand-sifting Starfish (Astropecten polyacanthus)
The sand sifting starfish or comb sea star is a widespread species, found throughout the Indo-Pacific region in shallow tropical and sub-tropical seas (from the Red Sea and Zanzibar to Hawaii, and from Japan to Australia and New Zealand). The diameter including arms is up to 20 cm. The upper surface is dark purplish in colour and the underside is orange. Little pillars with flattened top on the upper surface are cream, grey or brown, sometimes making chevron patterns. Along the edges of the arms are long, sharp spines, with brown bases and pale tips. It spends its time buried in silty seabeds feeding on detritus and small invertebrates. Sometimes it also engulfs pebbles and digests the biofilm (bacterial and algal films) and small invertebrates adhering to the surface. It contains the potent neurotoxin, tetrodotoxin, also known as TTX which has no known antidote. In a case of paralytic poisoning in Japan it was found that the victim had eaten a trumpet shell, Charonia lampas, which had acquired the toxin through its food chain, thus implicating Astropecten polyacanthus.
Pentaceraster chinensis (no English common name)
A tropical starfish know from several locations including Hainan.
Luzon Sea Star (Echinaster luzonicus)
The Luzon sea star is prone to shed its arms, which then regenerate into new individuals. It is normally six-armed but often quite asymmetrical in appearance, because of it has a habit of shedding arms. Its colouring ranges from red to dark brown. It is found in the tropical and sub-tropical western Indo-Pacific region, ranging from Madagascar and the east coast of Africa to Northern Australia, Indonesia and the Philippines. It is found on both reef crests and in the intertidal zone where it feeds on bacterial and algal films that it extracts from the sediment. By shedding its arms for regeneration the species can reproduce asexually. The shed arm regenerates, growing a new disc and further arms. Up to 65 cm in diameter.
Eight-armed Luidia sea star (Luidia maculata)
The diameter with arms is 12 – 20cm and it has 5 – 9, but normally 8 arms. The arms are long, rounded and tapered to a sharp tip. The tips bear small sharp spines on the sides. The underside is pale and the grooves along the arms bear large tube feet with club-like, pointy tips. The colours and patterns on the top side are variable from greyish blue, to brown and beige, but normally have a darker star-shaped pattern in the middle, and dark irregular bars running along the arms. It ranges from SE Arabian Sea, Persian Gulf, Maldive area, Ceylon, Bay of Bengal, East Indies, north Australia, Philippine, China and south Japan. Occurs inshore at depth from 0-134 m. Observations in Hong Kong include near Kau Sai Chai in Sai Kung and near Port island. It burrows in soft sediments and eats small invertebrates including other starfish.
Distributed in SE Arabia, Maldive area, Ceylon, Bay of Bengal, East Indies, norh Australia, Philippine, China and south Japan. Lives inshore in tropical, Indo-west Pacific Ocean waters at depths from 0 – 50 m. Observed in Hong Kong from Tai Long Sai Wan, in sand substrate.
Cholcolate Chip Starfish (Nidorella armata)
Nidorellia armata is also known as the chocolate chip star which leads to confusion with Protoreaster nodosus which is also know as the cholcolate chip starfsih in english. It has a diameter of about 23 cm and lives on rocky surfaces with algae and seagrass at depths of 5 – 70 m. They feed on small invertebrates and algae which they digest externally by turning their stomachs inside out and covering their prey with it. They are found in tropical waters clinging on corals and rocky reefs.
Sand Star (Archaster typicus)
It is found in shallow waters in the western Indian Ocean and the Indo-Pacific , incouding the Maldive Islands, the Bay of Bengal, Singapore, northern Australia, New Caledonia, the Philippines, China, southern Japan and Hawaii. It usually occurs in areas of the seabed with soft sediments such as sand, silt and seagrass meadows at depths down to 60 m. Larvae settle among mangroves and the young adult individuals gradually move to seagrass and sandy habitats as they age. It eats detritus and anything edible it comes across by everting its stomach through its mouth and on to its food item. The food is then engulfed and brought inside the starfish where the stomach is returned to its normal position.