Classification / Names
Common names | Synonyms | Catalog of Fishes(genus, species) | ITIS | CoL | WoRMS | Cloffa
Actinopteri (ray-finned fishes) > Atheriniformes
(Silversides) > Phallostethidae
Etymology: Neostethus: Greek,neos = new + Greek, stetho, stethion = brest; literal = to prick a little breast (Ref. 45335); geminus: From the Latin geminus for twin or double referring to the close morphological similarity of the new species to its inferred sister species, Neostethus bicornis, and to the paired or double ctenactinia in both species..
Environment: milieu / climate zone / depth range / distribution range
Freshwater; brackish; benthopelagic. Tropical; 27°C - ? (Ref. 95599)
Asia: Brunei Darussalam.
Size / Weight / Age
Maturity: Lm ?  range ? - ? cm
Max length : 2.6 cm SL male/unsexed; (Ref. 95599)
Morphology | Morphometrics
soft rays: 15 - 16;
Vertebrae: 35 - 37. Neostethus geminus is most closely related to N. bicorni. Both species differ from all congeners by having two elongate curved ctenactinia (vs. one elongate and one short ctenactinium) in mature males and a brown blotch on the pelvic-fin rays of the proctal side of immature males, and a fleshy, hood-like fold in females that includes the anus and genital and urinary pores. Neostethus geminus is distinguished from N. bicornis in being smaller (reaching no more than 2.57 cm SL vs. 3.1cm SL), and having a relatively compact priapium with a foreshortened, broad aproctal axial bone that meets but does not overlap the pulvinular appendage (vs. a relatively elongate priapium with a long and narrow aproctal axial bone that overlaps the pulvinular appendage medially); thin, nearly translucent, broad papillary bone expanded distally into a tab (vs. a short papillary bone), and females with a thickened fleshy, hood-like fold that includes the anus, genital pore and urinary pore (vs. a thin fold of skin), and a thickened ridge just posterior to the fold and separated from it by a gap (vs. lacking a ridge and a gap) (Ref. 95599).
At the type locality, this species was collected together with other fishes: Ambassis sp., Scatophagus argus, Tetraodon leiurus, Gobiopterus brachypterus, and Brachygobius doriae and Neostethus borneensis. The brackish water was clear and brown (Ref. 95599).
Life cycle and mating behavior
Maturity | Reproduction | Spawning | Eggs | Fecundity | Larvae
Parenti, L.R., 2014. A new species of Neostethus (Teleostei; Atherinomorpha; Phallostethidae) from Brunei Darussalam, with comments on northwestern Borneo as an area of endemism. Raffles Bull. Zool. 62:175-187. (Ref. 95599)
IUCN Red List Status (Ref. 125652)
Threat to humans
Common namesSynonymsMetabolismPredatorsEcotoxicologyReproductionMaturitySpawningSpawning aggregationFecundityEggsEgg development
ReferencesAquacultureAquaculture profileStrainsGeneticsAllele frequenciesHeritabilityDiseasesProcessingNutrientsMass conversion
Estimates based on models
Phylogenetic diversity index (Ref. 82805
= 0.5002 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00389 (0.00180 - 0.00842), b=3.12 (2.94 - 3.30), in cm total length, based on all LWR estimates for this BS (Ref. 93245
Trophic level (Ref. 69278
): 3.0 ±0.4 se; based on size and trophs of closest relatives
Fishing Vulnerability (Ref. 59153
): Low vulnerability (10 of 100) .
Climate Vulnerability (Ref. 125649
): (0 of 100) .