Plagiomnium cuspidatum

Close up image of P. cuspidatum showing sharply toothed edge and noticeable midrib (dark linear area)

P. cuspidatum has sharp-toothed leaf margins, as its common names suggest, and can be identified from other members of the Plagiomnium genus by their leaves which measure to about 2.5–3.5 mm in length and have a tip that is tapered more gradually than other Plagiomnium species, a leaf base that runs all the way down onto the stem, and leaf cells that are elongated and clearly not arranged in diagonal rows.[4] P. cuspidatum is often characterized as a small moss with shoots ranging from 1.5-4 cm tall and leaves roughly around 3 mm long.[5][4] Leaves of P. cuspidatum gradually taper towards the tip, more so than other species in the genus.[4] Leaf margins are sharply toothed and are absent in the lower half of the leaves while the midrib is obvious.[4][7] Leaves are arranged in pseudo whorls- where the arrangement of leaves appear to originate at the same level but do not.[5]

Up close view of P. cuspidatum's leaves and stems

Using a x20 hand lens, the small cells can be seen to not be in diagonal rows and no longer than wide.[4][7] The non-fertile stems can be one of two descriptions: erect or curved. When aggregated together, the plant forms a green cushion-like structure. When dry, the leaves darken and begin to curl.[7]

Capsule and conical lid

P. cuspidatum do not reproduce asexually but are dioicous – having antheridia and archegonia on separate plants – and synoicous- having archegonia and antheridia on the same plant.[8] From the foot of the plant, there can be multiple seta that raises the capsules above the plant. Capsules are frequent have a conical lid. Spores range from 18-40μm and are numerous inside the capsule.[4][8]

It can be used as a planting medium in bioactive terrariums, aquariums, and paludariums too due to its anti-microbial and antifungal properties.[6] Its ability to retain high humidity levels and grow in mats or carpets, which provides great cover for the tank's "clean-up crew", also make it perfect for the hobby.

In many bryophytes, there have been antibacterial, antiviral, and antioxidant properties associated with certain species.[14] P. cuspidatum is able to produce substances that can inhibit bacteria and fungi. But due to these substances being unstable, they have not been able to be used in the medical field but have garnered some attention for its potential use.[14] The instability of the substance stems from the substance being produced while the moss is under stress and a variety of species produce a variety of substances.[14] It has been seen that P. cuspidatum showes resistance to methicillin-resistant Staphylococcus aureus, commonly known as MRSA.[15] Also, the extracts of P. cuspidatum studied have shown promising antiproliferative activities against cancer cell lines in which 50% inhibition or more was achieved when testing on cervical, ovarian, and breast cancer cell lines.[15] The extracts of P. cuspidatum, flavonoids, have been a topic of interest. Flavonoids are polyphenolic secondary metabolites that are commonly consumed in human diets.[15] A few of the major flavonoids of P. cuspidatum are saponarine, luteolin, and apigenin-7-O-neohesperidoside.[15]