Sodwana pygmy seahorse (Hippocampus nalu)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Syngnathiformes · Family: Syngnathidae · Genus: Hippocampus.

Accepted name: Hippocampus nalu · Authority: Short, Claassens, Smith, De Brauwer, Hamilton, Stat & Harasti, 2020 · Taxonomic status: accepted · AphiaID: 1437127.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=1437127 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (FishBase)

Measured values published by FishBase for Hippocampus nalu. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 2.200000047683716 cm · Depth range: 12–17 m · Habitat zone: demersal · Body shape: other · Vulnerability index: 10 of 100 · Fishery importance: of no interest · Aquarium trade: never/rarely.

FishBase notes: This species remains undetected because of its cryptic behaviour and diminutive size. It is observed in flat sandstone-based coral reefs comprising of low pinnacles, shallow drop offs, and sandy gullies, with the latter being exposed to strong currents. It was found loosely associating with short algal turf, used as a holdfast, which was growing on sand-covered coral bedrock separated by sandy gullies (around 2 meters wide). Ambient seawater temperature averaged ca. 24 °C during the dives, which were conducted in October of 2018. Collectors experienced strong swells on the exposed reefs of 2 Mile Reef during data collection. The holotype and paratype appeared to be a mated pair, found within approximately 60 cm distance of each other on the two dives. Behaviour of the pair was observed prior to collection which was very similar to congeners H. pontohi and H. japapigu . Several individuals, including a small juvenile (ca. 1.0 cm SL), were found in the gullies and observed to be associated with low-growth algal turf. The juvenile, retained the dark colouration of a recently settled juvenile pygmy seahorse (Ref. 122372).

Source: FishBase species summary (SpecCode 69401) — https://www.fishbase.se/summary/Hippocampus-nalu.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Conservation status (IUCN Red List)

The IUCN Red List assesses Hippocampus nalu Short, Claassens, Smith, de Brauwer, Hamilton, Stat & Harasti, 2020 as Near Threatened (code NT). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 250584311) — https://www.iucnredlist.org/species/250584311/0; GBIF IUCN Red List category endpoint (taxonKey 10886876) — https://api.gbif.org/v1/species/10886876/iucnRedListCategory. Accessed 2026-09-23.

Description and natural history (Wikipedia)

The discovery of the species, which inhabits the waters of Sodwana Bay in South Africa, was revealed by an international team of researchers in May 2020. This small pygmy seahorse is the first known pygmy seahorse that lives in the water around Africa. When a diver from the region gave a tip to the researchers, a team of the researchers later discovered this pygmy seahorse. The team that made this discovery arrived in South Africa to look for the pygmy pipehorse and unintentionally found this new species.

Hippocampus nalu is quite similar to H. pontohi and H. japapigu in appearance and colouration, with adults having a honey-brown coloured skin with an overlay of white irregular reticulation and a reddish tail, and juveniles having a darker colouration. Like most syngnathids, their colouration helps them to camouflage with their surrounding habitat, as well as with algae. The Hippocampus nalu's highly different spine morphology along the superior trunk ridge also differentiates the species from its fellow pygmy seahorse. Being a pygmy seahorse, H. nalu is very small, with juveniles being ~10 mm long and adults growing up to a length of 2 centimetres.

This species is currently only known to occur in shallow coastal waters, at depths between 12 and 17 meters that contain flat sandstone-based coral reefs and short algal turfs.

Source: Wikipedia: Hippocampus nalu — https://en.wikipedia.org/wiki/Hippocampus_nalu (CC BY-SA 4.0). Accessed 2026-09-23.