Hydrozoa Collection (page 3)

Periphylla periphylla, helmet jellyfish
Coloured drawing by Edward Adrian Wilson (1872-1912), made on 1 August 1902 during the Discovery Expedition to the Antarctic, 1901-1904. Jellyfish found in the McMurdo Strait

Brown Hydra (Hydra oligactis) adult, filter feeding with tentacles extended, attached to piece of gravel underwater, Belvedere, Bexley, Kent, England

Green Hydra (Chlorohydra viridissima) adult, in process of asexual reproduction by budding off new animal, attached to piece of gravel underwater, Belvedere, Bexley, Kent, England

Hydra (Hydra viridis) two, with tentacles extended, Italy, june

Portuguese Man of War (Physalia physalis) floating on ocean surface, Azores, august

Hydra (Hydra viridis) with tentacles extended, Italy, june

Portuguese man-of-war (Physalia physalis) at the waters surface. This organism is a colony composed of many specialised polyps, groups of which form its structures

Hydroid (Campanularia flexuosa), LM
Hydroid (Campanularia flexuosa). Light micrograph (LM) of a colonial hydroid, showing gonozooid (reproducing) and gastrozooid (feeding) polyps, attached to a central stolon (stalk)

Porpita umbela hydrozoan, light micrograph. This is a small specimen of this colonial marine organism, which consists of a collection of specialised polyps

Obelia hydrozoan medusa, light micrograph
Obelia hydrozoan medusa. Dark-field light micrograph of a medusa (young polyp) from the Obelia geniculata hydroid. The circular shallow semi-bell has solid tentacles on the rim

Hydrozoan medusa (Gonionemus vertens), Japan

Hydrozoa (Ectopleura larynx). Hydrozoa are a type of cnidarian and are related to corals and sea anemones. Photographed in the White Sea, Russia

Hydromedusa. Medusa stage of a Halitholus sp. hydrozoan. Hydromedusae are the sexually reproductive stage of hydrozoan cnidarians

Portuguese men-of-war, artwork
Portuguese men-of-war. Artwork of a group of Portuguese men-of-war (Physalia utriculus) in the open ocean. Each Portuguese man-of-war is not one organism, instead being a colony of hydrozoan animals

Historical microscope, artwork
Historical microscope. 18th Century artwork of a microscope designed to observe aquatic organisms. This device was invented by the Swiss naturalist Abraham Trembley (1710Ôé¼" 1784) in 1747

Lyretail anthias and coral
Lyretail anthias. Female lyretail anthias, or goldies, (Pseudanthias squamipinnis) with fire coral. Photographed in the Red Sea, Egypt

Hydrozoan colony. Close-up of the tentacled feeding structures of a hydrozoan (Tubularia larynx) colony. Hydrozoa are a type of cnidarian and are related to corals and sea anemones

Nudibranch eating hydrozoa
Nudibranch (Flabellina verrucosa) eating hydrozoa (Eudendrium sp.). Nudibranchs are shell-less marine molluscs that live in seas around the world

Fish eggs. Close-up of fish eggs (white spheres) on a hydrozoan colony (plant-like) with skeleton shrimps (translucent). Hydrozoa are a type of cnidarian that are related to corals and sea anemones

Hydrozoan colony and amphipods. Amphipod (Stenothoe marina) crustaceans sheltering amongst the tentacled feeding structures of a hydrozoan (Tubularia larynx) colony

Hydrozoan (Tubularia indivisa). Hydrozoa are a type of cnidarian and are related to corals and sea anemones

Predators feeding on a hydroid colony
Predators feeding on a hydrozoa colony. Colony of Tubularia larynx hydrozoa that has been destroyed by nudibranchs (Coryphella sp)

Pontohi pygmy seahorse amongst hydroid colony. Pontohi pygmy seahorses (Hippocampus pontohi) have only recently been described (as of 2010)

Nudibranch (Cratena peregrina) Sardinia, Italy. (RR)
Alan James / SplashdownDirect

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Hydrozoa, a fascinating class of marine animals, encompasses a diverse range of species that inhabit oceans worldwide. From the venomous Portuguese man o war drifting along the shores of Tenerife in the Canary Islands to the mesmerizing Hydromedusa with its intricate tentacles found deep beneath the surface near the mid-Atlantic ridge, Hydrozoa never fails to captivate. The Portuguese man o war (Physalia physalis) is an iconic representation of Hydrozoa's beauty and danger. Its vibrant colors and long tentacles make it both alluring and deadly. Incredibly, there are creatures like the Man-of-war fish (Nomeus gronovi) that live within these perilous tentacles, displaying an astonishing resistance to their toxin. Not only do some organisms coexist with Hydrozoa but others even prey upon them. The Blue dragon seaslug (Glaucus atlanticus), immune to their venom, feasts on Indo-Pacific Portuguese man-of-war washed ashore during mass strandings. This unique adaptation allows them to thrive while other creatures succumb. Hydra viridissima, commonly known as green hydra, can be found in garden ponds across Derbyshire in the UK. These small yet captivating creatures add a touch of enchantment to any aquatic environment they inhabit. Venturing into deeper waters reveals more wonders within this class. Crystal jellyfish (Aequorea victoria) gracefully float through Trondheimsfjord in Norway's Atlantic Ocean depths. Their translucent bodies emit an ethereal glow that illuminates their surroundings with an otherworldly radiance. From vibrant Red Sea coral reefs teeming with Scalefin anthias fish to top-down views of Indo-Pacific Portuguese Man-of-War colonies stretching across South Africa's coastline—these images showcase just how diverse and awe-inspiring Hydrozoa truly is.