Overview

Comprehensive Description

[[ Genus Micralestes ZBK ]]

Discussion. Recent collections in the region allow us to document the presence of six Micralestes ZBK in the stretch of the lower Congo River from Pool Malebo to Boma near the river’s mouth, and as an aid for field identification we provide here an illustrated key to those species.

1A Teeth with numerous small cusps, first inner row premaxillary tooth with 10-12 cusps (Key Fig. 1A). Inner row tooth pair on dentary usually multicuspid (Key Fig. 3A). Dorsal fin with distinctive black apical patch (Key Fig. 2A) .................................................................................................................. M. acutidens ZBK

1B Teeth with fewer cusps, first inner row premaxillary tooth with 6-8 cusps (Key Fig. 1B). Inner row tooth pair on dentary invariably unicuspid (Key Fig. 3B). Dorsal fin without black apical patch (Key Fig. 2B) ................................................................................................................................................................ 2

2A 23-28 scales in longitudinal series from opercle to point of caudal flexure (Key Fig. 2A) ........................ 3

2B 29-33 scales in longitudinal series (Key Fig. 2B) .................................................................... M. lualabae ZBK

3A Outer row premaxillary teeth small and tricuspid or quadricuspid (Key Fig. 1A) .....................................4

3B Outer row premaxillary teeth prominent, conical, or weakly shouldered, unicuspids (Key Fig. 1B) .......... ............................................................................................................................................... M. holargyreus

4A Median cusp of symphyseal teeth on dentary less than twice the height of adjacent cusps (Key Fig. 3A). 24-28 scales in longitudinal series from opercle to point of caudal flexure. Adipose fin black distally, pale proximally (Key Fig. 2A) ............................................................................................................................ 5

4B Median cusp of symphyseal teeth on dentary elongate and more than twice the height of adjacent cusps (Key Fig. 3B). 23-24 scales in longitudinal series from opercle to point of caudal flexure. Adipose fin black (Key Fig. 2B) ...................................................................................................................... M. stormsi ZBK

5A Relatively gracile, body depth 3.8-4.2 times into standard length. Adipose eyelid restricted posteriorly to orbital margin (Key Fig. 2A) ...................................................................................................... M. humilis ZBK

5B Relatively deep-bodied, body depth 3.0-3.8 times into standard length. Adipose eyelid extending posterodorsally over postorbital region (Key Fig. 2B) .............................................................................. M. schelly

Most of these species have widespread distributions encompassing most of the Congo basin and often also much of the rest of Central Africa (Poll, 1967). While we have not undertaken a revision of this genus and related taxa, a task that is ongoing, it is worthy of note that despite intensive collection and surveys in the region Micralestes holargyreus remains known only from the short stretch of the lower Congo River from Boma to Matadi, and M. schelly is only known from a single site in the vicinity of Inga. These two taxa are considered here to be lower Congo River endemics.

  • Melanie L. J. Stiassny, Victor Mamonekene (2007): Micralestes (Characiformes, Alestidae) of the lower Congo River, with a description of a new species endemic to the lower Congo River rapids in the Democratic Republic of Congo. Zootaxa 1614, 17-29: 24-27, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:EFFDCA90-CD71-40DA-B0D1-5E2030D2D945
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[[ Genus Micralestes ZBK ]]

Roberts & Stewart (1976) in their work on the fishes of the lower Congo River reported the presence of two Micralestes ZBK in their collections: M. acutidens ZBK (Fig. 1A) and M. humilis ZBK (Fig. 1C). Recent collections in the region also include specimens of M. lualabae ZBK (Fig. 1D), M. stormsi ZBK (Fig. 1E) and M. holargyreus (Fig. 1B). In addition to these, a collection made in the vicinity of Inga revealed the presence of a population of diminutive alestid that appears most closely to resemble Micralestes ZBK but that are not assignable to any described Micralestes ZBK or to any other species dwarf African alestid.

  • Melanie L. J. Stiassny, Victor Mamonekene (2007): Micralestes (Characiformes, Alestidae) of the lower Congo River, with a description of a new species endemic to the lower Congo River rapids in the Democratic Republic of Congo. Zootaxa 1614, 17-29: 18-18, URL:http://www.zoobank.org/urn:lsid:zoobank.org:pub:EFFDCA90-CD71-40DA-B0D1-5E2030D2D945
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Physical Description

Diagnostic Description

Discussion. Recent collections in the region allow us to document the presence of six Micralestes in the stretch of the lower Congo River from Pool Malebo to Boma near the river’s mouth, and as an aid for field identification we provide here an illustrated key to those species.

 

1A Teeth with numerous small cusps, first inner row premaxillary tooth with 10-12 cusps (Key Fig. 1A). Inner row tooth pair on dentary usually multicuspid (Key Fig. 3A). Dorsal fin with distinctive black apical patch (Key Fig. 2A) .................................................................................................................. M. acutidens

 

1B Teeth with fewer cusps, first inner row premaxillary tooth with 6-8 cusps (Key Fig. 1B). Inner row tooth pair on dentary invariably unicuspid (Key Fig. 3B). Dorsal fin without black apical patch (Key Fig. 2B) ................................................................................................................................................................ 2

 

2A 23-28 scales in longitudinal series from opercle to point of caudal flexure (Key Fig. 2A) ........................ 3

 

2B 29-33 scales in longitudinal series (Key Fig. 2B) .................................................................... M. lualabae

 

3A Outer row premaxillary teeth small and tricuspid or quadricuspid (Key Fig. 1A) .....................................4

 

3B Outer row premaxillary teeth prominent, conical, or weakly shouldered, unicuspids (Key Fig. 1B) .......... ............................................................................................................................................... M. holargyreus

 

4A Median cusp of symphyseal teeth on dentary less than twice the height of adjacent cusps (Key Fig. 3A). 24-28 scales in longitudinal series from opercle to point of caudal flexure. Adipose fin black distally, pale proximally (Key Fig. 2A) ............................................................................................................................ 5

 

4B Median cusp of symphyseal teeth on dentary elongate and more than twice the height of adjacent cusps (Key Fig. 3B). 23-24 scales in longitudinal series from opercle to point of caudal flexure. Adipose fin black (Key Fig. 2B) ...................................................................................................................... M. stormsi

 

5A Relatively gracile, body depth 3.8-4.2 times into standard length. Adipose eyelid restricted posteriorly to orbital margin (Key Fig. 2A) ...................................................................................................... M. humilis

 

5B Relatively deep-bodied, body depth 3.0-3.8 times into standard length. Adipose eyelid extending posterodorsally over postorbital region (Key Fig. 2B) .............................................................................. M. schelly

 

Most of these species have widespread distributions encompassing most of the Congo basin and often also much of the rest of Central Africa (Poll, 1967). While we have not undertaken a revision of this genus and related taxa, a task that is ongoing, it is worthy of note that despite intensive collection and surveys in the region Micralestes holargyreus remains known only from the short stretch of the lower Congo River from Boma to Matadi, and M. schelly is only known from a single site in the vicinity of Inga. These two taxa are considered here to be lower Congo River endemics.

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Melanie L. J. Stiassny

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Roberts & Stewart (1976) in their work on the fishes of the lower Congo River reported the presence of two Micralestes in their collections: M. acutidens (Fig. 1A) and M. humilis (Fig. 1C). Recent collections in the region also include specimens of M. lualabae (Fig. 1D), M. stormsi (Fig. 1E) and M. holargyreus (Fig. 1B). In addition to these, a collection made in the vicinity of Inga revealed the presence of a population of diminutive alestid that appears most closely to resemble Micralestes but that are not assignable to any described Micralestes or to any other species dwarf African alestid.

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Melanie L. J. Stiassny

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records:53
Specimens with Sequences:43
Specimens with Barcodes:37
Species:11
Species With Barcodes:11
Public Records:9
Public Species:7
Public BINs:6
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Barcode data: Micralestes sp. NM2010

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

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Statistics of barcoding coverage: Micralestes sp. NM2010

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
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Statistics of barcoding coverage: Micralestes cf. pabrensis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Barcode data

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Wikipedia

Micralestes

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