Brachyhypopomus batesi Crampton, de Santana, Waddell & Lovejoy, 2017

Family:  Hypopomidae (Bluntnose knifefishes)
Max. size:  12 cm TL (male/unsexed); 12.1 cm TL (female)
Environment:  benthopelagic; freshwater; pH range: 4.5 - 6
Distribution:  South America: Central Amazon and upper rio Negro in Brazil and Colombia.
Diagnosis:  Anal soft rays: 159-173. Brachyhypopomus batesi can be distinguished from other species of the genus Brachyhypopomus by the following combination of characters: anal fin with 165-179 rays (vs. 180-293 in B. alberti, B. beebei, B. belindae, B. bennetti, B. brevirostris, B. bullocki, B. diazi, B. gauderio, B. hendersoni, B. janeiroensis, B. jureiae, B. occidentalis, B. palenque, B. verdii, and B. walteri); presence of scales in entire middorsal region, although sparse and hard to see in some specimens (vs. absence in middorsal region of anterior third of body in B. benjamini and B. provenzanoi); absence of accessory electric organ over the opercular region (vs. presence in B. bombilla, B. menezesi, and B. regani; head depth at occiput 61.0-67.9% HL, (vs. 71.4-94.6% in B. cunia, B. draco, B. flavipomus, B. hamiltoni, and B. pinnicaudatus); and absence of scattered conspicuous black or charcoal flecks on flanks (vs. presence in B. sullivani) (Ref. 116763).
Biology:  The type series was sampled from the lower, seasonally flooded reaches of low-conductivity blackwater rainforest streams that flow into lago Tefé, and lago Amanã (large blackwater ria lakes of similar conductivity to the streams). Mostly found in marginal root mats or submerged leaf litter along stream edges. The recorded water parameters at the time of sampling were the following: conductivity 10-30 μScm-1, dissolved oxygen 2.0-5.2 mgl-1, temperature 24.3-27.0°C, and pH 4.5-6.0. During the high water period, this species disappears from the flood-swollen lower stream reaches which is possibly due to declining dissolved oxygen levels, and apparently moves upstream to terra firme stream reaches above the seasonal river-floodplain flood influence. Breeds during the early rising-water period, which in the Tefé region corresponds to the rainy season. Occurrence of this species outside the sampling area of type series localities are all recorded from low-conductivity blackwater rainforest streams. In the region of the type locality, Brachyhypopomus batesi co-exists in geographical sympatry and ecological syntopy with the following species occurring in terra firme stream: B. beebei, B. brevirostris, B. sullivani, and B. walteri. It is also allotropic in distribution with B. belindae, B. bennetti, B. flavipomus, B. hamiltoni, B. hendersoni, B. pinnicaudatus, and B. regani. In the rio Negro, it occurs in geographical sympatry with B. beebei, B. brevirostris, B. bullocki, B. hendersoni, B. regani, B. sullivani, and B. Walteri. Feeds on aquatic insect larvae (primarily Chironomidae), and other small aquatic invertebrates (Ref. 116763).
IUCN Red List Status: Not Evaluated (N.E.) Ref. (130435)
Threat to humans:  harmless


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