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Humidophila undulata

Lowe et al. 2014      Category: Symmetrical biraphid

Humidophila schmassmanni


Hydrosera whampoensis

LM scalebar = 10 µm = 80 pixels.


Contributor: Rex Lowe - February 2015
Length Range: 9-11 µm
Width Range: 2.7-3.0 (broadest point), 1.9-2.4 (center) µm
Striae in 10 µm: 28-30


Valves are distinctly undulate, with a deep constriction in the central valve and sub-apically inflation. Apices are weakly rostrate to cuneate, with rounded ends. The axial area is linear to slightly lanceolate. The central area is nearly circular and slightly enlarged due to the shorter central striae. Areolae are transapically elongated. Under SEM, the proximal raphe ends terminate in laterally expanded, T-shaped depressions. The distal raphe ends terminate in T-shaped or anchor-shaped depressions. Internally, small pseudosepta are present at both apices.

Original Description

Author: Lowe et al. 2014
Length Range: 6.5-15.2 µm
Width Range: 2-2.3 (center) µm
Striae in 10 µm: 29-31

Original Description

Valves distinctly undulate with a relatively deep constriction in the middle of the valve leading to sub-apical inflations and terminating in weakly rostrate to cuneately rounded valve apices. Valve dimensions (n=25): length 6.5‒15.2 µm, width 2‒2.3 µm at the constricted center. Axial area linear to slightly lanceolate, gradually tapering toward the apices. Central area almost circular, slightly enlarged due to the shorter central striae. Striae 29‒31 in 10 µm, each composed of one transapically-elongated areola. Near the central area areolae shorter, almost circular. Mantle areolae continuing around the valve apices without any interruption near the apex. Proximal raphe endings terminating in a laterally expanded T-shaped depressions. Distal raphe endings terminating in T- to anchor-shaped depressions, often curved toward the valve center. Internally, small pseudosepta present at both apices.

Original Images

Cite This Page:
Lowe, R. (2015). Humidophila undulata. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Humidophila undulata

Contributor: Rex Lowe

Reviewer: Pat Kociolek


Lowe, R.L., Kociolek, J.P., Johansen, J.R., Van de Vijver, B., Lange-Bertalot, H. and Kopalová, K . (2014). Humidophila gen. nov., a new genus for a group of diatoms (Bacillariophyta) formerly within the genus Diadesmis: species from Hawai’i, including one new species. Diatom Research 29(4): 351-360. 10.1080/0269249X.2014.889039

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

NADED ID: none

Autecology Discussion

This species is widespread on volcanic wet walls of the Hawaii’n Islands. The largest populations are on Oahu, where H. undulata is occasionally found in small streams.