RELATIONSHIPS OF SUNDASALANX 



15 



samples, albeit relatively large ones. Roberts (1984) suggested a 

 more detailed investigation of the colour pattern of different 

 populations of Sundasalanx was needed since every population 

 seemed to exhibit its own distinctive pattern, and implied that the 

 observed variation might be intra- rather than interspecific. Pre- 

 served materials studied here indicate that Sundasalanx species 

 share a basic colour pattern, but some species differ in certain 

 aspects and it varies with size and between sexes. Sex and size are 

 the two factors that appear to influence colour pattern most. Larger 

 specimens have more strongly developed colour patterns and males 

 have more vivid patterns than females or juveniles. 



In life Sundasalanx is transparent except for the silvery cover 

 around the eyeballs, which decomposes to reveal black pigment 

 around the eye if specimens are conserved in formalin. Close 

 examination, however, of preserved specimens reveals an extensive 

 colour pattern (Figs 2,11,13-15). A small black spot is present 

 behind the eye in the prootic region (best seen in Fig. 14), associated 

 with the posterodorsal surface of what is herein identified as a 

 prootic bull a. This spot was observed in all species examined except 

 5. praecox, studied materials of which were largely depigmented. 

 Pigment deposition on the dorsal surface of the prootic bulla during 

 development has been observed in other clupeoids (Hoss & Blaxter. 

 1982), and is possibly a general feature of the group. Absence of 

 prootic bulla pigmentation in S. praecox is likely an artefact of 

 preservation. 



A dark prepectoral mark, consisting of 1-5 melanophores, is 

 present just anterior to the pectoral fin in most individuals examined 

 (present in all large individuals; seen best in Figs 11, 13) of all 

 species except S. praecox. The extent of the mark appears to vary 

 interspecifically with the mark in Barito River species consistently 

 larger than that of species examined from elsewhere. In species with 

 a smaller mark it consists of one or two melanophores on the 

 dorsolateral surface of the connective tissue sheath surrounding the 

 sternohyoideus just anterior to the origin of the muscle on the 

 cleithrum. Species with a larger mark possess up to three more 

 melanophores on the rear wall of the gill chamber, dorsal to those on 

 the sternohyoideus. 



Elements of a mid-ventral line of melanophores are present in all 

 species (Fig. 2). A midventral gular streak, dividing the sterno- 

 hyoideus muscle mass into right and left sides, is present in all 

 species. A midventral line of melanophores from behind the com- 

 partment in which the heart lies to the caudal fin, as described for 

 southern peninsular Malaysia materials by Roberts ( 1 984), is present 

 in all species except S. praecox. In the region of the body cavity the 

 melanophores are associated with the ventral finfold or its remnants. 

 In the region of the anal fin, ventral midline pigmentation consists of 

 melanophores located between each anal-fin pterygiophore, one per 

 interpterygiophore space (best seen in Fig. 15): behind the anal fin 

 the line is continued as a midventral series of melanophores situated 

 between the ventral ends of myotomes of the caudal peduncle 

 myotomes. 



A line of melanophores is present on each side of the body at the 

 ventral edge of myotomes in the region of the body cavity in all 

 species examined (Figs 11, 13-15). The line begins immediately 

 behind the shoulder girdle and ends at the anus, with the frequency 

 of melanophores usually greater than one per myotome, but less than 

 two per myotome. The line is continuous except in the region 

 immediately dorsal to the pelvic fins, from which melanophores are 

 absent. 



In all species examined, a dark spot consisting of a single melano- 

 phore is located just anterior to the insertion of the pelvic fins (Figs 

 2, 1 1, 13-15), below the course of the myotomal line. An additional 

 spot is located near the anterior end of the basipterygium of 5. 



Fig. 2 Schematic representation of the melanophore pattern of 

 Sundasalanx in ventral view (anterior to left); A = gular streak of 

 midventral line, B = midventral line of the ventral fin fold, C = 

 myotomal line, D = melanophores of cleithral mark associated with the 

 sternohyoideus. E = cardiac compartment melanophores (present only in 

 males of 5. microps, S. mesops, S. megalops. and 5. platyrhynchus), F = 

 basipterygium melanophore (present in all species examined). 



praecox. Males of S. malleti with mature, or maturing, testes show 

 additional pigmentation of the pelvic-fin girdle, with a ring of 

 melanophores encircling the basipterygium. 



The lower caudal-fin lobe is marked by a broad swath of 

 melanophores in all species except possibly 5. praecox. This lower 

 caudal-fin lobe swath is especially intense in materials identifiable 

 as male (Fig. 14). A few scattered melanophores were observed on 

 the upper caudal-fin lobe of a few individuals. 



The posterior half of the compartment in which the heart lies is 

 marked with melanophores (Fig. 2) in males of S. microps, S. 

 mesops, S. megalops, and S. platyrhynchus, even in quite small 

 individuals. Examination of larger specimens in which it is obvious 

 that maturation of the testes has begun shows the mark is present 

 only in males; specimens with maturing or mature ovaries lack the 

 mark, as do all of the smallest specimens. The juxtaposition of the 

 anterior end of the myotomal lines to the pigmentation of the cardiac 

 compartment creates a very distinctive M-shaped ventral mark just 

 posterior to the pectoral girdle in males of those species with cardiac 

 compartment pigmentation (Fig. 2). 



Soft anatomy 

 Gut 



The gut of Sundasalanx is straight, with three sections clearly 

 distinguishable under gross microscopical examination of cleared 

 and stained specimens (Fig. 3). Length of gut measures approxi- 

 mately 62% of SL in the largest cleared and stained specimen 

 examined (24 mm SL).The first section, approximately 20% of total 

 gut length, is characterised by longitudinal folds, continuous through- 

 out its length. No obvious distinction between oesophagus and 

 stomach is apparent, although the posterior part of this section is 

 somewhat greater in diameter than the anterior part. The pneumatic 

 duct exits from the dorsal side of the posterior half of the stomachal 



Fig. 3 Gut and gas bladder of Sundasalanx malleti (anterior to left); A = 

 anterior section of gut (oesophagus/stomach), B = middle section of gut 

 (anterior part of intestine), C = parapelvic bones, D = middle section of 

 gut (posterior part of intestine), E = posterior section of gut, F = gas 

 bladder, G = pneumatic duct, scale bar = 3 mm. 



