Synodontis dhonti and S. irsacae

[lfinley58]

Hello all.

I'd like to make a few brief comments regarding S. dhonti and S. irsacae based on the recent revision of the Lake Tanganyikan Synodontis species by Wright and Page.

1. S. dhonti - This species is somewhat problematic in that of the 312 specimens of Synodontis that were examined only one S. dhonti, the 395 mm TL type specimen, was found. So the revision provides no information on what smaller specimens may look like. There is also conflicting information on some aspects of this one specimen. In a table providing quick characteristics for the various species it is noted that S. dhonti has "Triangles on rayed fins" "Present". But under the discussion of the species it is noted that "All rayed fins uniformly brownish". Possibly the note of the triangles may be based on the original description, but I do not have this immediately at hand for comparison.

2. S. irsacae - This species was described in 1959 but the author (Matthes) rather quickly placed it in synonomy with S. dhonti in 1962. Wright and Page, in their paper, resurrect this species and note numerous differences that distinguish it from S. dhonti. Matthes, in his second opinion, had considered this fish as the young of S. dhonti. So basically S. irsacae is a smaller species (maximum size given in Wright and Page is 190 mm TL and 157 mm SL). There are a number of differences given, some of which are difficult to work with on most aquarium photos (presence of an axillary pore in S. dhonti versus the absence of same in S. irsacae, the morphology of the premaxillary toothpad (actually some of the photos on this site may be helpful with this last aspect). But generally this species is recognized in the hobby, as noted by Dinyar and Sidguppy (in a very recent posting), as the "dwarf dhonti." For a sample photo that is, in my opinion, easily associated with this species I would suggest that you look at image number 12 of S. dhonti in the Cat-elog. Many of the other photos in this section do appear to be something else. Unfortunately my time schedule does not allow for a full examination of these. As soon as my plate of must do things is clear I do plan to revisit this topic. Maybe someone else will also contribute additional thoughts to this thread.

Lee

[lfinley58]

Hi all,

A quick follow up on S. dhonti: I checked the original description of this species and unfortunately Boulenger (1917) provides very little information in regards to the coloration. What is provided is "Brown above and beneath; caudal yellowish, blackish on the outer rays". So, as to where the mentioned conflict regarding the coloration of the rayed fins noted in Wright and Page comes from, I do not know.

Lee