Delve into the Fascinating Microcosm of Riccia okahandjana: A Unique and Intriguing Moss

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Exploring the Fascinating World of Riccia okahandjana S.W.Arnell Moss

Have you ever heard of Riccia okahandjana S.W.Arnell


Riccia-cavernosa-Hoffm-SEM-image-of-proximal-face-of-spore-from-Herb-GM-Dirkse-14140_Q640.jpg from: https://www.researchgate.net/figure/Riccia-teneriffae-SWArnell-SEM-image-of-proximal-face-of-spore-from-the-holotype-S_fig2_272253996

? This tiny but mighty moss, part of the Ricciaceae family, may be unfamiliar to many. But for moss enthusiasts and botanists, Riccia okahandjana is a fascinating species worth getting to know. In this blog post, we’ll dive into the details of this unique moss and explore what makes it so special.


207318.jpg from: https://inpn.mnhn.fr/espece/cd_nom/786452

Background on Riccia Mosses

Before we focus on Riccia okahandjana specifically, let’s cover some background on Riccia


Riccia-cavernosa-Hoffm-SEM-image-of-distal-face-of-spore-from-Herb-GM-Dirkse-14140_Q320.jpg from: https://www.researchgate.net/figure/Riccia-teneriffae-SWArnell-SEM-image-of-distal-face-of-spore-from-the-holotype-S_fig1_272253996

mosses in general. Riccia is a genus of thallose liverworts in the order Marchantiales. There are over 150 Riccia species found worldwide. They are small, ribbon-like or fan-shaped plants that lack leaves and stems. Instead, they have a flattened body called a thallus.

Morphology and Identification of Riccia okahandjana

Now let’s zero in on our star species. Riccia okahandjana S.W.Arnell was first described by Swedish botanist Sigfrid Wilhelm Arnell in 1963. It is a small thalloid liverwort, typically 1-3 cm long. The thallus is light green, translucent, and dichotomously branched with a distinct midrib. The thallus margins are slightly wavy.
Identifying Riccia okahandjana requires microscopic examination of its spores and scales. The spores are triangular-globular, 75-95 μm in diameter, and covered with irregular ridges. Ventral scales are present and hyaline.


Riccia_crystallina_003C.JPG from: https://cisfbr.org.uk/Bryo/Cornish_Bryophytes_Riccia_crystallina.html

Global Distribution and Habitat

Riccia okahandjana has a very limited distribution. To date, it is only known from northern Namibia in southwestern Africa. There, it grows on sandy soils in association with other bryophytes like Riccia albida and Exormotheca pustulosa. The habitat experiences summer rainfall and has sparse vegetation cover.

Ecological Roles and Adaptations

Like other Riccia mosses, R. okahandjana plays important ecological roles:

  • Helps retain moisture in the soil
  • Provides microhabitats for invertebrates
  • Acts as a pioneer species in disturbed areas
  • Contributes to nutrient cycling

To survive in its arid habitat, R. okahandjana has some key adaptations:

Riccia okahandjana Facts


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Characteristic Description
Taxonomy Class Marchantiopsida, Order Marchantiales, Family Ricciaceae
Plant Type


P1030806.JPG from: https://correzitude.fr/RICCIA.html

Thallose liverwort (bryophyte) lacking leaves and stems
Size Small, thallus 1-3 cm long
Appearance Light green translucent ribbonlike thallus with wavy margins
Known Range Endemic to northern Namibia
Habitat Sandy soils in areas with summer rainfall


Riccia%2Bsubbifurca%2BPelenna%2Blowres.jpg from: https://southwalesbryos.blogspot.com/2016/09/riccia-subbifurca-along-pelenna-forest.html

Leathery thallus, scales, rhizoids, spores



riccia-rhenana-50fb4b93a3924.jpg from: https://www.flowgrow.de/db/wasserpflanzen/riccia-rhenana

Riccia okahandjana S.W.Arnell may be a small and obscure moss, but it is a prime example of how bryophytes are adapted to survive in challenging environments. Through its unique morphology, limited distribution, and ecological roles, R. okahandjana reminds us that even the tiniest organisms can have an important story to tell.
The next time you’re in northern Namibia, keep your eyes peeled for this gem of a moss! And consider this: what other miniature marvels of the plant kingdom have yet to be fully appreciated and understood?

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