aqua International Journal 25(3)
Volume 25, Issue 2 – 15 April 2019
Volume 25, Issue 2 – 15 April 2019
Tyson R. Roberts: Alestion rapax¸ a new genus and species of miniature paedomorphic characiform fish with large conical teeth from the Lower Congo basin (Ostariophysi, Alestidae), pp. 82-102
Alestion rapax, an entomophagous new genus and species of Alestidae, scaleless and largely translucent in life, possibly most closely related to Hydrocynus, is described from nine reproductively inactive specimens 12.0-16.8 mm standard length collected from a single locality in the Kwilu drainage near Moerbeke in the lower Congo basin in 1973. Eye large, body elongate and laterally strongly compressed. A number of its characters, such as a midventral fin fold, partly actinotrichous pectoral and caudal-fin rays, lack of scales and adipose eyelid may be neotenic or paedomorphic, while others are highly specialized. Circumorbital bones, including antorbital and lacrimal, absent. Dorsal-fin rays 10, its base entirely posterior to vertical through end of pelvic-fin base (dorsal fin rays usually 10 in Hydrocynus, its dorsal fin base above pelvic-fin base, its dorsal fin origin in front of or above vertical through pelvic fin origin). Anal-fin rays 14 (15-18 in Hydrocynus). Vertebrae 25-26+13-14=39-40 (versus 29-36+15-18=45-54 in Hydrocynus). Mouth slightly upturned, lower jaw with a large fleshy mentum. Apparently two rows of enlarged conical teeth on premaxillary near symphysis of jaws (nearly forming a single row) and two rows of somewhat larger teeth on dentary near symphysis. Outer row of dentary with three teeth and inner row with a single tooth as in alestids with multicupsid jaw teeth generally. Tooth replacement alternating from side to side of the jaw as in alestids and many neotropical characins having complex multicuspid teeth. Premaxillary of largest specimen with a single tricuspid replacement tooth, its small secondary cusps subapical (rather than basal, as in tricuspid teeth of very small Hydrocynus). Feeds on small aquatic insect larvae of the dipteran family Chironomidae.
Stefano Valdesalici: A new annual killifish: Moema funkneri (Cyprinodontiformes: Rivulidae) from the Bolivian Amazon, pp. 103-110
A new annual killifish species, Moema funkneri, is described from a seasonal pool in the Río Grande drainage, a tributary of Río Mamoré, Amazon basin, Bolivia. The new taxon is similar to M. heterostigma and M. ortegai/M. quiii by males possess oblique rows of red brown dots on flanks. It differs from all known congeners by the combination of the aforementioned color pattern, short pectoral fins, presence of almost dark yellow anal fin, broad orange margin on ventral and posterior portions of caudal fin, and a relatively high number of scales in the lateral line, transverse series, and circumpeduncular series.
Stefano Valdesalici and Giuseppe Amato: Nothobranchius derhami (Cyprinodontiformes: Nothobranchiidae), a new species of seasonal killifish from western Kenya, pp. 111-124
Nothobranchius derhami, new species, is described from seasonal habitats in the Nyando River system, belonging to the Lake Victoria basin, western Kenya. Nothobranchius derhami belongs to the N. ugandensis species group and is distinguished from all other members of the genus by the following characters in males: flank light blue with red scale margins; dorsal portion of the head red, lower jaw light blue; caudal fin plain red; pectoral fin hyaline; anal fin light blue proximally to creamy white distally, with series of red dots; dorsal fin almost red proximally with few white to light blue dots, subdistal white to light blue stripe; dorsal fin with black margin, anal fin with dark red to black margin, 15-17 dorsal and anal fin rays, 27-29 scales in the median lateral series, 10-12 transverse scale rows, and 14-16 circumpeduncular scales. In view of the very restricted distribution of N. derhami, it is suggested that its conservation status according to the IUCN Red List of Threatened Species guidelines would be Vulnerable (D2).
|Dimensions||26.6 × 23.2 × 0.5 cm|