Insemination in Scoloplax

[Silurus]

Spadella, MA, C Oliveira & I Quagio-Grassiotto, 2008. Morphology and histology of male and female reproductive systems in the inseminating species Scoloplax distolothrix (Ostariophysi: Siluriformes: Scoloplacidae). Journal of Morphology 269: 1114–1121.

Abstract

The morphology and histology of male and female reproductive systems were examined in Scoloplax distolothrix. Internal insemination was documented in this species by the presence of sperm within the ovaries. Mature males and females have elongated genital papillae, exhibiting a tubular shape in males and a plain heart-shape with two median protuberances in females. The testes are two elongated structures that converge ventrally, under the intestine, towards the genital papilla. They are joined at the caudal end, forming an ovoid single chamber for sperm storage. Secretory regions were not observed. In the lumen of the testicular tubules, spermatozoa can be tightly packed along their lengths, but do not constitute a spermatozeugmata. The lumen of the sperm storage chamber and spermatic duct are filled with free spermatozoa without the accompanying secretions. The ovaries are bird-wing shaped, saccular structures that converge ventrally under the intestine, towards the genital papilla. They are joined at the caudal end, forming a tubular chamber possibly destined for oocyte storage. An oviduct with an irregular outline connects the chamber to the tubular region of the genital papilla. No distinct sperm storage structure was found in the ovaries. The unique male and female genital papillae suggest that these structures are associated with the reproductive mode in scoloplacids, representing evidence for insemination. The occurrence of free spermatozoa, without the accompanying secretions and not arranged in a spermatozeugmata can be associated with the presence of a tubular male genital papilla for sperm transfer to the female genital tract. This reinforces the idea that sperm packets are not necessary for all inseminating species. The male reproductive system in scoloplacids is very different from that in auchenipterids, a second catfish family with insemination, which indicates that the occurrence of insemination is not connected to the internal morphology of reproductive organs.

[Richard B]

Very interesting HH - am i right in thinking Scoloplax are not imported into the hobby? This is a pity as it appears a very interesting catfish indeed.

[MatsP]

I don't expect they appear commonly in the hobby, and they are tiny: 16-20mm according to the Cat-eLog.

Scoloplax

--
Mats

[Richard B]

Indeed Mats, there are 2 registered keepers, & both cat-e-log species are kept. I have not been able to find where i the world they come from but going by their "my cats" lists they might be from somewhere in South America(?)

[MatsP]

The user "loach" is from Denton, TX (according to the user-specified location) User info

The user Attu is from "SoCal" - Southern California. Calls himself "Ichtyologist" in Occupation. User info

--
Mats

[Richard B]

Cheers Mats,

Hmmm -an ichthyologist might be able to aquire species seldom seen in the hobby.....

(whenever i hear or see the placename "Denton" i can't help but think of the Rocky Horror picture show"

[MatsP]

Cheers Mats,

Hmmm -an ichthyologist might be able to aquire species seldom seen in the hobby.....

(whenever i hear or see the placename "Denton" i can't help but think of the Rocky Horror picture show"

Although that is Denton, Ohio, not Denton, Texas - the latter is north of Dallas/Fort Worth according to Google Maps.

--
Mats

[Richard B]

Cor - i stand corrected!

Actually, geography always was a weak point of mine.....

[MatsP]

Cor - i stand corrected!

Actually, geography always was a weak point of mine.....

Sure. The US has LOTS of placenames that are repeated - more so than the UK for example - probably because places where named after places here in Europe, and often the same popular place was used several times. For example, there are 10 places called Paris:
Paris, TX
Paris, Henry, TN
Paris, Edgar, IL
Paris, Bourbon, KY
Paris, Logan, AR
Paris, Monroe, MO
Paris, Mecosta, MI
Paris, Bear Lake, ID
Paris, Stark, OH
Paris, Lafayette, MS

London also occurs in 10 places too. [One of which is in Texas, and looking at the map, I think I drove through it at some point on my various travels - but it's just a small dot on the map, so I expect that I may have missed that point].

--
Mats

[Richard B]

So Planet catfish is a definitive site for info on Catfish & Geography

[lfinley58]

Hi All,

It goes back a few years, but I had maintained a group of around 10 Scoloplax (most probably S. dolicholophia) for around a year or so. I had collected these in the Brazilian Rio Negro in the vicinity of Barcelos while I was doing some volunteer work for Project Piaba. In some typical habitat areas - leaf litter - they were actually quite "common", but collecting them was another story. I had made, with Scoloplax specifically in mind, a dip net that was counter netted with nylon window screen so as you might imagine nothing escaped. Getting the leaves is easy, but going through them looking for very small fishes of the same or similar color is labor intensive. I am sure that you could get the same results just by scooping up a bucket of leaves, but the net was kind of fun to use. With the same net I was also able to catch some very small and interesting sand dwelling trichomycterid catfishes. I also found that Acestridium were easy to catch in the net (they were fairly common on certain vertical growing plants), but their rostral odontodes were small enough to get caught in the window screen making for a long process of getting them out of the net without hurting them.

I think that such small fishes are just below the radar of the local fish collectors. It takes a bit of work to collect them and no doubt the exporters are not interested in such "small fry". But who knows the future. Maybe with some of the loricariid problems (some from the Xingu come to mind) that are developing maybe there will be an increasing market for shipping such small and interesting catfishes. We can only hope that this might come to be.

Lee

[Richard B]

great info Lee, thanks for posting - good to see you on PC again.