Luciosoma spilopleura

Luciosoma: from the Latin lucius, meaning 'a fish (probably the pike)', and Ancient Greek σῶμα (sôma), meaning 'body', in reference to the elongate, pike-like body shape in members of this genus.

spilopleura: from the Ancient Greek σπίλος (spílos), meaning 'spot', and πλευρά (pleurá), meaning 'side', in reference to the lateral row of spots on the flank in this species.

Can be considered endemic to Indonesia since it is known only from Sumatra and Kalimantan, the Indonesian portion of Borneo. On Sumatra it has been recorded from the Batang Hari and Musi river systems in the southern half of the island, while on Borneo it is known from the upper Kapuas River in West Kalimantan (Kalimantan Barat) province and the Mahakam drainage in East Kalimantan (Kalimantan Tengah).

Type locality is 'Lahat, Palembang Province, Sumatra, Indonesia', which corresponds to the Lematang River, a tributary within the larger Musi watershed in what is currently Lahat regency, South Sumatra (Sumatera Selatan) province, Sumatra, Indonesia.

According to Roberts (1989) this species displays a preference for smaller, fast-flowing headwater streams with substrates of rocks, stones, and gravel, although juveniles have been collected from the Kapuas mainstream around floating houses and among flooded marginal vegetation (Kottelat & Widjanarti, 2005)[5].

L. spilopleura is poorly known in general and is not present in the ornamental trade, although its name has been widely misapplied to other Luciosoma species for decades. Its congeners are mostly marketed as 'apollo shark', 'shark minnow', or similar, and often labelled with incorrect scientific names.

Luciosoma spilopleura is used very commonly, for example, but that species may never have been collected for aquaria. Similarly, L. pellegrinii is scarcely known in the aquarium trade since it is native to an area where very few commercial collections take place, but its name is misapplied on a regular basis.

Those which are traded are only suitable for the largest private aquaria, with subadults of L. setigerum, L. bleekeri, and an unidentified fish with a distinctive colour pattern (see below) traded on a regular basis.

Identification of the fish pictured here is based on Bleeker (1855, 1860) and Roberts (1989), plus drawings by Bleeker, thus L. spilopleura can be distinguished from other members of the genus by the following combination of characters: head moderately pointed; presence of numerous densely-arranged tubercles on tip of snout and entire ventrolateral surface of mandible; anterior pelvic-fin ray not extended into a filament (sometimes slightly prolonged); lateral row of vertically-elongate dark spots on the flank, extending between posterior of opercle and caudal peduncle; caudal-fin with a median dark stripe and submarginal stripes on both upper and lower lobes.

Oijen and Loots (2012)[2] provided a translation of this species' section in Bleeker (1860) and he described its colour pattern thus: upper part of the body green, lower part silver; iris pink or yellow; on both flanks 13 oblong-round bluish-violet spots placed in a longitudinal row; fins yellowish or pink-hyaline; caudal fin pink with 3 longitudinal blackish-violet bands, middle band on the middle of the rays, side bands starting on the short side rays of the fin and ending on the posterior margin of the fin inside the tips; dorsal and anal fin around the middle with a longitudinal, darkish band.

There is a fish of unknown geographical origin which matches the majority of diagnostic features for L. setigerum with the exception that the dark lateral stripe is absent in the anterior portion of the body and is not composed of interconnected spots. It is relatively common in the aquarium trade and included here as L. cf. setigerum until a confirmed identity is established.