Sundasalanx microps ROBERTS, 1981

Etymology

Sundasalanx: from ‘Sundaland’, the continental landmass of Southeast Asia south of the Isthmus of Kra, plus the generic name Salanx.

microps: from the Ancient Greek μικρός (mikrós), meaning ‘small, little’, and ὄψ (óps), meaning ‘eye’.

Classification

Order: Clupeiformes Family: Sundasalangidae

Distribution

Type locality is ‘Kapuas River at Kampong Nibung, Borneo, 0°39’N, 112°10.5’E’.

Habitat

Sundasalanx species tend to inhabit turbid, slow to moderately flowing water over substrates of silt, sand, or mud in the lower parts of river basins, but apart from observational evidence that they may migrate towards the surface at dusk, little else is known of their ecology.

Maximum Standard Length

15 – 20 mm.

Aquarium SizeTop ↑

Base dimensions of 45 ∗ 30 cm or equivalent should be the minimum considered.

Diet

Likely to require small planktivorous food such as Artemia nauplii in the aquarium. The gut contents of wild specimens include small aquatic invertebrates and segmented worms.

Behaviour and CompatibilityTop ↑

Unconfirmed, but likely to be a gregarious, schooling species and a poor competitor.

Sexual Dimorphism

Unrecorded, but males of the congeners S. malleti and S. megalops are distinguished from females by possessing a more intense dark marking on the lower caudal-fin lobe.

Reproduction

Unknown.

NotesTop ↑

This species does not seem to have appeared in the aquarium trade and is likely to prove very difficult to transport.

The genus Sundasalanx is distributed throughout much of Southeast Asia and currently comprises seven species which have primarily been distinguished on the basis of oral and dental morphology, gill rakers and eye size. S. microps possesses 0-3 small conical teeth on ceratobranchial 5, 0-2 minute gill rakers on the first arch and a small eye measuring less than 4 % of SL.

The grouping was originally considered related to the osmeriform family Salangidae, commonly known as icefishes or noodlefishes, but was later moved to the family Clupeidae by Siebert (1997) who considered it to represent a miniaturised clupeiform. The latter placement, but not the former, has been supported by subsequent authors therefore the family Sundasalangidae is presently considered a valid assemblage within Clupeiformes.

Adults in all species are sexually mature at a size of less than 20 mm SL and evolved via a process known as miniaturisation.  They resemble larval forms of their larger ancestor and are often referred to as ‘developmentally truncated’ or ‘paedomorphic’.

References

1. Roberts, T. R., 1981 - Proceedings of the California Academy of Sciences (Series 4) v. 42 (no. 9): 295-302
   Sundasalangidae, a new family of minute freshwater salmoniform fishes from southeast Asia.
2. Britz, R. and M. Kottelat, 1999 - Ichthyological Exploration of Freshwaters 10(4): 337-344
   Sundasalanx mekongensis, a new species of clupeiform fish from the Mekong basin (Teleostei: Sundasalangidae).
3. Ishiguro, N. B., M. Miya, J. G. Inoue, and M. Nishida, 2005 - Journal of Fish Biology 67(2): 561-569
   Sundasalanx (Sundasalangidae) is a progenetic clupeiform, not a closely‐related group of salangids (Osmeriformes): mitogenomic evidence.
4. Kottelat, M., 2013 - The Raffles Bulletin of Zoology Supplement 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibliography of the fishes known to occur in freshwaters, mangroves and estuaries.
5. Parenti, L. R. and K. K. P. Lim, 2005 - The Raffles Bulletin of Zoology Supplement 13: 175-208
   Fishes of the Rajang Basin, Sarawak, Malaysia.
6. Roberts, T. R., 1989 - Memoirs of the California Academy of Sciences No. 14: i-xii + 1-210
   The freshwater fishes of western Borneo (Kalimantan Barat, Indonesia).
7. Siebert, D. J., 1997 - Bulletin of the Natural History Museum London (Zoology) 63(1): 13-26
   Notes on the anatomy and relationships of Sundasalanx Roberts (Teleostei, Clupeidae), with descriptions of four new species from Borneo.
8. Tan, H. H. and M. Kottelat, 2009 - Ichthyological Exploration of Freshwaters 20(1): 13-69
   The fishes of the Batang Hari drainage, Sumatra, with description of six new species.