Category: Uncategorized
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How I came to own a copy of Trembley’s Memoires
In 1744, Jean and Herman Verbeek of Leiden published a book by the Swiss scholar Abraham Trembley entitled “Mémoires, pour servir à l’Histoire d’un Genre de Polypes d’Eau douce, a bras en forme de Cornes.” In English the title is “Memoirs, for the History of a Genus of Freshwater Polyps, with Arms in the Form…
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Ectoderm and Endoderm
Have you ever wondered about the origin of the use of the terms Ectoderm and Endoderm for the two epithelial layers of the hydra polyp? They were coined by George James Allman in a monograph he published in 1871. The citation for the monograph is: George James Allman (1871). A Monograph of the Gymnoblastic or…
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Stretching the Hypostome
In 1982, Jennie O’Hern and Howard Lenhoff published a paper (O’Hern and Lenhoff, 1982) describing their study on the relationship between the diameter of the hypostome and the number of tentacles in the Hydra head. O’Hern was an undergraduate student at UC Irvine in the Lenhoff lab who subsequently went to medical school at Johns Hopkins and practiced…
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The Biggest Hydra
People are fascinated by the largest of something. Hydra is no exception. The largest Hydra species is Hydra oxycnida, a member of the Oligactis clade. H. oxycnida was first described by Schulze (Schulze, 1914). Adult polyps of this species can be as long as 3 cm when extended. Compared to some other Hydra species, the distribution of H. oxycnida is relatively restricted. It has been collected only in…
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The multiheaded mutant of Hydra viridissima
When he was a faculty member at the University of Miami and an HHMI investigator, Howard Lenhoff found a green Hydra polyp in an aquarium at a tropical fish store. He took this polyp to his laboratory and founded a line with it, which he called Chlorohydra viridissima Florida strain 1961, with 1961 presumably indicating the year in which…
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Some thoughts on Hydra medium
The origins of Hydra Medium The first description of a defined medium for culturing Hydra in the laboratory was published by Loomis in 1953 (Loomis, 1953). This medium contained calcium chloride, sodium bicarbonate, and sodium chloride in deionized or distilled water. The story of how this medium was developed is an amusing one, and is told by Howard Lenhoff in…
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Is Hydra magnipapillata still a valid Hydra species name?
No, it is not. H. magnipapillata was first described by Takeo Ito (Ito, 1947) from specimens he collected in 1943 and 1944 from multiple locations in Japan. One wonders why he was wandering around Japan looking for Hydra in the middle of World War II. Phylogenetic studies (Martínez et al., 2010) have since shown that H. magnipapillata is a member of the Eurasian Vulgaris clade…
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Cannibalism in Hydra?
Hydra appears not to be cannibalistic. Hydra polyps of the same species do not consume each other, even when they are starving. One Hydra polyp will sometimes swallow another one when both polyps grab the same bunch of brine shrimp in the laboratory. But the swallowed polyp will eventually be egested unharmed. A paper was published on this topic in…
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Why 18 degrees?
Have you ever wondered why everyone cultures Hydra at 18 °C? I have. Hydra does not live at a constant temperature as does E. coli. In the wild, the temperature that Hydra is exposed to varies by geographic location, season, and where Hydra is in the water column. Hydra has been found at the bottom of Lake Superior (Nalepa et al., 1987), where the temperature is 4…
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To what animal clade does Hydra belong?
Hydra is a member of the animal phylum Cnidaria (formerly Coelenterata). It is classified as follows: Phylum Cnidaria Class Hydrozoa Subclass Hydroidolina Order Anthoathecata Suborder Aplanulata Family Hydridae Genus Hydra The genus Hydra was established by Linnaeus in 1758 (Linnaeus, 1758). In 1914, Paul Schulze (Schulze, 1914) added two additional hydra genera – Pelmatohydra, and Chlorohydra. However Pelmatohydra and Chlorohydra are no longer valid taxa. Pelmatohydra is now Hydra oligactis,…
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