Difflugia species
Fig. 1: a D. pyriformis after Perty, 1849; b D. oblonga after Ehrenberg, 1858; c-d Pyriform tests

 

Difflugia pyriformis group

 

Perty (1849, 1852) described Difflugia pyriformis (Fig. 1a) the shell of which is 140-200 µm long, pyriform or sometimes irregular in shape, and with a rough surface. Since then this species has been subject of many discussions and misinterpretations. Authors considered it being identical with D. oblonga Ehrenberg 1832 (Fig. 1b) and even modified the original description of the latter to fit that of D. pyriformis.

 

Pyriform or pear shaped tests are not rare, but differ in shape and size, ranging from about 60 till over 600 µm. It’s not likely that all these shells belong to one species. However it’s extremely difficult to distinguish between species solely based on light microscopical characters. DNA sequencing can be very helpful here. Traits which might be important to distinguishing between species are:

  • length and breadth of the test
  • L/B ratio
  • diameter of the aperture
  • construction of the pseudostome
  • presence or absence of symbiotic algae
  • relative length of the neck
  • structure of the nucleus
  • cyst formation
  • food

As long as we don’t have sufficient matches between DNA sequences and morphological characters it is nearly impossible to know which species belongs to a specific test.

Difflugia species

 

Difflugia pyriformisup to 483 um: one or more species?

 

Difflugia pyriformis, 284-307 µm – Lemmer, Netherlands
Recent posts

Cryptodifflugia collum

Cryptodifflugia collum, after Chardez, 1971 Cryptodifflugia collum  (Chardez, 1971) Bobrov et Mazei, 2017 Difflugiella collum Chardez, 1971 Diagnosis: Shell globose, transparent, hyaline, chitinous, aperture topped

Read More »

Cryptodifflugia brevicolla

Cryptodifflugia brevicolla, after Golemansky, 1979 Cryptodifflugia brevicolla  Golemansky, 1979 Diagnosis: Shell ovate, laterally compressed, with clearly expressed chitinous collar around an aperture, neck circular in

Read More »

Cryptodifflugia bassini

Cryptodifflugia bassini, after Bobrov, 2001 Cryptodifflugia bassini  Bobrov, 2001 Diagnosis: Shell small, axially symmetrical, circular in transverse section, flattened in longitudinal section, widely elliptical. Aperture

Read More »

Cryptodifflugia apiculata

Cryptodifflugia apiculata, after Cash, 1904 Cryptodifflugia apiculata  (Cash, 1904) Page, 1966 Difflugiella apiculata  Cash, 1904 Diagnosis: Shell ovoid, not compressed laterally, chitinous, smooth, transparent, colorless,

Read More »

Cryptodifflugia angusta

Cryptodifflugia angusta, after Schönborn, 1965 Cryptodifflugia angusta  (Schönborn, 1965) Page, 1966 Difflugiella angusta  Schönborn, 1965 Diagnosis: Shell small, organic, elongated-ovate, not transparent, yellow-brown, covered with

Read More »

Cryptodifflugia angulata

Cryptodifflugia angulata, after Playfair Cryptodifflugia angulata Playfair, 1917 Diagnosis: Shell small, oval, transparent, lateral sides flattened, fundus rounded-conic, widest shell part in the middle, lateral

Read More »