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Cited by 59Fish Biology and Ecology StudiesFish biology, ecology, and behaviorEvolution and Paleontology Studies

The emerging vertebrate model species for neurophysiological studies is Danionella cerebrum, new species (Teleostei: Cyprinidae)

Open access
Britz, Ralf, Conway, Kevin W., Rüber, Lukas·2021·Scientific Reports
DOI 10.1038/s41598-021-97600-0PMC PMC8460714
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Abstract

The four described species of Danionella are tiny, transparent fishes that mature at sizes between 10–15 mm, and represent some of the most extreme cases of vertebrate progenesis known to date. The miniature adult size and larval appearance of Danionella , combined with a diverse behavioral repertoire linked to sound production by males, have established Danionella as an important model for neurophysiological studies. The external similarity between the different species of Danionella has offered an important challenge to taxonomic identification using traditional external characters, leading to confusion over the identity of the model species. Using combined morphological and molecular taxonomic approaches, we show here that the most extensively studied species of Danionella is not D. translucida , but represents an undescribed species, D. cerebrum n. sp. that is externally almost identical to D. translucida , but differs trenchantly in several internal characters. Molecular analyses confirm the distinctiveness of D. cerebrum and D. translucida and suggest that the two species are not even sister taxa. Analysis of the evolution of sexual dimorphisms associated with the Weberian apparatus reveals significant increases in complexity from the simpler condition found in D. dracula , to most complex conditions in D. cerebrum , D. mirifica and D. translucida .

AI snapshot

Written from the paper’s full text.

TL;DR

The neurophysiological model species widely studied as *Danionella translucida* is actually an undescribed species, described here as *Danionella cerebrum* n. sp., which is externally almost identical to *D. translucida* but distinct in internal skeletal characters and molecular data. Molecular analyses place *D. cerebrum* as sister to *D. mirifica*, not *D. translucida*, and reveal increasing complexity of sexually dimorphic Weberian apparatus structures across *Danionella*.

Key findings

  • *Danionella cerebrum* is distinguished from *D. translucida* by anal-fin rays 15–18 vs. 12–15, last dorsal-fin ray inserted opposite the last anal-fin ray vs. posterior to it, last anal-fin pterygiophore inserted in front of haemal spine of vertebra 22–24 vs. 19–21, a blade-like vs. axe-shaped lateral process of the second vertebra, and a bifurcated vs. single distal tip of the fused inner arms of the ossa suspensoria.
  • Molecular analyses recovered the topology (*D. dracula*,(*D. priapus*,(*D. translucida*,(*D. mirifica*,*D. cerebrum*)))); uncorrected coxI p-distances were 22.2–22.9% between *D. cerebrum* and *D. translucida*, and 10.2–10.9% between *D. cerebrum* and its closest relative *D. mirifica*. Estimated splits were ~17.9 MYA for *D. priapus* from the remaining taxa, ~13.3 MYA for *D. translucida* from *D. mirifica* + *D. cerebrum*, and ~3.2 MYA for *D. mirifica* and *D. cerebrum*.
  • Sexual dimorphism in the Weberian apparatus increases in complexity from the simpler condition in *D. dracula* to most complex conditions in *D. cerebrum*, *D. mirifica*, and *D. translucida*; *D. cerebrum* males have bony flanges on the outer arm of the os suspensorium, a connection to the lateral process of vertebra 2, and a drumming cartilage/muscle, while females lack these modifications.
  • At the type locality Hmawbi, *D. cerebrum* was abundant and co-occurred with *D. translucida* (a single c&s *D. translucida* among 28 *D. cerebrum*); at Daikme Chaung, the type locality of *D. translucida*, *D. cerebrum* was uncommon (1 out of 27 c&s *Danionella*).

Methods

  • Morphological taxonomic study using cleared and double-stained specimens; counts and measurements followed Britz et al. (2016). Meristic counts for *D. cerebrum* were based on n = 32 (MTD 39986, MTD 39987, MTD 39989), and for *D. translucida* on n = 28 (MTD 39992, MTD 39993); the holotype is BMNH 2021.8.30.1, a female 12.6 mm SL.
  • Molecular datasets comprised coxI (654 bp; 47 *Danionella* specimens), 16S rRNA (469 bp; 22 specimens), erg2b (834 bp; 10 specimens), rag1 (1422 bp; 15 specimens), and rho (894 bp; 14 specimens), with *Danio rerio* as outgroup. Maximum likelihood analyses used RAxML with 1000 bootstrap replicates; divergence times used BEAST v2.6.4 with a strict molecular clock, Yule process, and a normal calibration prior for the *Danionella* MRCA (mean 29.5 MYA), with two MCMC chains run for 200 million iterations.

Limitations

  • Stated: sound in *Danionella* has been recorded and characterized only for a single species, *D. cerebrum* (as *D. translucida*), so hypothesized links between species-specific anatomical differences and species-specific sounds remain to be tested by comparative studies.
  • Stated: *D. cerebrum* is difficult to distinguish externally from *D. translucida*, and anal-fin ray counts are challenging because posterior rays are very small and often pressed close to the body; reliable counts require cleared and double-stained specimens. The type series of *D. translucida* may have included two species, requiring verification of the holotype via photograph.
  • Stated/evident: the significance of unique adenine insertions in coxI is unknown, and those insertions were excluded from phylogenetic analyses; whether miniaturization in *Danionella* involves genome miniaturization and loss of hox/developmental genes “will need to be demonstrated.” Evident from the text: no behavioral or sound recordings are presented for the other four species, and molecular sampling is limited to the available specimens and loci analyzed.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41598-021-97600-0

Cites

27 of 27 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

21 of 54 cited sources checked · 4 supported · 2 flagged · accuracy not yet measured

  • Findingown data

    The 12 individuals of D. cerebrum and D. mirifica sequenced for coxI had unique adenin insertions at positions 95 and 624 of the coxI alignment leading to frame shifts and premature stop codons.

    “The 12 individuals of Danionella cerebrum and D. mirifica sequenced for the cytochrome coxidase subunit I (coxI) gene had unique adenin insertions at positions 95 and 624 of the coxI alignment leading to frame shifts and premature stop codons as previously reported for the gobioid Parapocryptes serperaster15, the significance of which is unknown.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [15] Rahman, M. M., Norén, M., Mollah, A. R. & Kullander, S. O. Building a DNA barcode library for the freshwater fishes of Bangladesh. Sci. Rep. 9, 9382 (2019). source

      The citation is attached to the comparison with Parapocryptes serperaster, not to the finding about Danionella. The Discussion reports a frameshift and stop codon in Pseudapocryptes elongatus; it mentions P. serperaster only as the reference genome used to locate the corresponding position. It does not report the insertion in P. serperaster. (LLM, conf=0.86)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    The larval condition of the adult skeleton of Danionella, in which the skull roof is missing and the brain is covered only by skin, has led various researchers to turn to Danionella as the adult vertebrate model organism to study neurophysiological questions by deep imaging their brain activity in vivo.

    “It is this larval condition of their adult skeleton, in which the skull roof is missing and the brain is covered only by skin, that has led various researchers to turn to Danionella as the adult vertebrate model organism to study neurophysiological questions by deep imaging their brain activity in vivo11–14.”
    Quote in the paperSubstantial claim3 of 4 sources checked
    • cites [11] Schulze, L. et al. Transparent Danionella translucida as a genetically tractable vertebrate brain model. Nat. methods 15, 977–983 (2018). source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [12] Penalva, A. et al. Establishment of the miniature fish species Danionella translucida as a genetically and optically tractable neuroscience model. bioRxiv, 444026 (2018). source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [13] Chow, D. M. et al. Deep three-photon imaging of the brain in intact adult zebrafish. Nat. methods 17, 605–608 (2020). source

      Split into 2 atoms — 0 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [14] Gokul, R. et al. Evolutionary divergence of locomotion in two related vertebrate species. bioRxiv 2021.02.11.430752 (2021).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Premisecitation

    Male Danionella have a large drumming muscle that originates from expanded bony flanges on the os suspensorium of their Weberian apparatus and inserts on a hypertrophied fifth rib.

    “a large drumming muscle that originates from expanded bony flanges on the os suspensorium of their Weberian apparatus and inserts on a hypertrophied fifth rib”
    Quote in the paperNot a substantial claim1 of 4 sources checked
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Description and Osteology sections describe body musculature and note ribs on vertebrae 5–12, but neither describes a drumming muscle or its attachments. Searches for “drumming,” “os suspensorium,” and “fifth rib” found no passage addressing the claimed anatomy; page numbers are unavailable in our copy. (LLM, conf=0.74)

      Experimental — accuracy not yet measured
    • cites [9] Britz, R. & Conway, K. W. Danionella dracula, an escape from the cypriniform Bauplan via developmental truncation?. J. Morph. 277, 147–166 (2016). source
  • Premisecitation

    In male Danionella, the gut and genital ducts are redirected so that both open between the pelvic fins.

    “These include a redirection of their gut and genital ducts so that both open in between the pelvic fins”
    Quote in the paperNot a substantial claim1 of 4 sources checked
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Description (page not specified) reports that the anus and genital papilla of male Danionella dracula lie between the pelvic fins, unlike their position in females. This supports the stated opening locations, but the paper does not describe the ducts themselves being redirected or establish the feature for male Danionella generally. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [9] Britz, R. & Conway, K. W. Danionella dracula, an escape from the cypriniform Bauplan via developmental truncation?. J. Morph. 277, 147–166 (2016). source
  • Premisecitation

    Male Danionella have a conical drumming cartilage that probably works like a drumstick on the anterior swimbladder chamber.

    “and a conical drumming cartilage that probably works like a drumstick on the anterior swimbladder chamber4–6,9.”
    Quote in the paperNot a substantial claim1 of 4 sources checked
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Description section mentions the anterior gas bladder chamber but does not describe a conical drumming cartilage or its proposed drumstick-like action. Searches of our copy for those terms and for sound production found no passage addressing that mechanism. (LLM, conf=0.75)

      Experimental — accuracy not yet measured
    • cites [9] Britz, R. & Conway, K. W. Danionella dracula, an escape from the cypriniform Bauplan via developmental truncation?. J. Morph. 277, 147–166 (2016). source
  • May combine two claims. 17
  • Classified as probably not a substantial claim. 12
  • The quote only partly states this claim. 1

  • May combine two claims.

    Premisecitation

    The four described species of Danionella are tiny, transparent fishes that mature at sizes between 10-15 mm.

    “The four described species of Danionella are tiny, transparent fishes that mature at sizes between 10–15 mm”
    • Also stated in: § Introduction · plain
      “So far, four species of the genus Danionella, maturing at sizes of 10–15 mm in length and including some of the smallest fishes and vertebrates, have been described from Myanmar and northeastern India3–6.”
    Quote in the paperSubstantial claim1 of 4 sources checked
    • cites [3] Roberts, T. R. Danionella translucida, a new genus and species of cyprinid fish from Burma, one of the smallest living vertebrates. Environ. Biol. Fishes 16, 231–241 (1986). source
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Diagnosis and the discussion of miniaturization name D. dracula and its two other species, D. translucida and D. mirifica, rather than four described species. The Material section lists a male D. dracula holotype at 16.3 mm, outside the claimed 10–15 mm range. The paper does describe Danionella as miniature, but these passages contradict the claim’s species count and size limit; they do not establish transparency for all species. (LLM, conf=0.86)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Four species of the genus Danionella, maturing at sizes of 10-15 mm in length and including some of the smallest fishes and vertebrates, have been described from Myanmar and northeastern India.

    “So far, four species of the genus Danionella, maturing at sizes of 10–15 mm in length and including some of the smallest fishes and vertebrates, have been described from Myanmar and northeastern India3–6.”
    Quote in the paperNot a substantial claim1 of 4 sources checked
    • cites [3] Roberts, T. R. Danionella translucida, a new genus and species of cyprinid fish from Burma, one of the smallest living vertebrates. Environ. Biol. Fishes 16, 231–241 (1986). source
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Introduction identifies Danionella dracula as a miniature species, and the Distribution section places it in northern Myanmar. The Diagnosis names only two other congeners; the copy does not establish four species or a northeastern Indian locality. The Material and Description sections give a 16.3 mm holotype and a known maximum of 16.7 mm, but do not establish maturation at 10–15 mm. (LLM, conf=0.87)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Species of the genus Danionella possess unique morphological novelties in males.

    “Species of the genus Danionella are further remarkable in possessing a number of unique morphological novelties in males.”
    Quote in the paperNot a substantial claim1 of 4 sources checked
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Introduction describes novel, sexually dimorphic characters in male D. dracula. The Diagnosis says its male jaw processes are absent in its congeners, D. translucida and D. mirifica, and the discussion says those species do not show the same skeletal modifications. The source therefore supports the claim for D. dracula, not for species of Danionella generally. (LLM, conf=0.90)

      Experimental — accuracy not yet measured
    • cites [9] Britz, R. & Conway, K. W. Danionella dracula, an escape from the cypriniform Bauplan via developmental truncation?. J. Morph. 277, 147–166 (2016). source

  • May combine two claims.

    Premisecitation

    The miniature adult size and larval appearance of Danionella, combined with a diverse behavioral repertoire linked to sound production by males, have established Danionella as an important model for neurophysiological studies.

    “The miniature adult size and larval appearance of Danionella, combined with a diverse behavioral repertoire linked to sound production by males, have established Danionella as an important model for neurophysiological studies.”
    Quote in the paperSubstantial claim3 of 4 sources checked
    • cites [11] Schulze, L. et al. Transparent Danionella translucida as a genetically tractable vertebrate brain model. Nat. methods 15, 977–983 (2018). source

      The Abstract (page unavailable in our copy) describes small, transparent adults with complex behaviors, including acoustic communication, and presents D. translucida as a promising model for studying adult brain function. It does not specify larval appearance or sound production by males, and it calls the fish a potential model rather than an established important one. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [12] Penalva, A. et al. Establishment of the miniature fish species Danionella translucida as a genetically and optically tractable neuroscience model. bioRxiv, 444026 (2018). source

      The Introduction describes Danionella’s miniature adult size, retained immature features, and suitability for systems neuroscience; the Discussion reports social and learning behaviors and says the fish communicate vocally. The cited passages do not establish that males specifically produce the sounds, and the paper presents Danionella as a promising new model rather than an already established important one. No page numbers are available in our copy. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
    • cites [13] Chow, D. M. et al. Deep three-photon imaging of the brain in intact adult zebrafish. Nat. methods 17, 605–608 (2020). source

      The paper describes Danionella as a small, translucent, emerging fish model and reports imaging the brains of intact adults (Abstract; Online Methods, Structural Imaging; pages not provided). It does not describe a larval appearance, male sound production, or a diverse behavioral repertoire, and it does not say those traits established Danionella as a neurophysiological model. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [14] Gokul, R. et al. Evolutionary divergence of locomotion in two related vertebrate species. bioRxiv 2021.02.11.430752 (2021).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingcitation

    In Danionella dracula, the apparatus of males is similar to that of females, as the anterior flange on the outer arm, its connection to the lateral process of the second vertebra, and the flange connecting outer and inner arms are all missing.

    “However, in Danionella dracula, the sister taxon to all other Danionella6 (Fig. 4), the apparatus of males is similar to that of females, as the anterior flange on the outer arm, its connection to the lateral process of the second vertebra, and the flange connecting outer and inner arms are all missing (Fig. 4).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The four recognized species of Danionella have been distinguished by fin-ray counts and internal anatomy.

    “The four recognized species have thus been distinguished by fin-ray counts and internal anatomy4–6”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [4] Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [5] Britz, R. Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae). Zootaxa 2277, 53–60 (2009). source
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

      The Diagnosis section distinguishes D. dracula from its congeners using fin-ray counts and internal skeletal features. But it names only two congeners, and the discussion calls them the “other two species of Danionella”; this copy therefore does not support the claim that four species were recognized. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    This highly complex vocalization apparatus has been identified as a promising organ system to study neurophysiologically.

    “This highly complex vocalization apparatus has been identified as a promising organ system to study neurophysiologically11.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [11] Schulze, L. et al. Transparent Danionella translucida as a genetically tractable vertebrate brain model. Nat. methods 15, 977–983 (2018). source

      The Abstract (page not provided) identifies acoustic communication among Danionella translucida’s complex behaviors and presents the fish as a promising model for studying adult brain function at single-cell resolution. It does not specifically identify the vocalization apparatus as highly complex or as a promising organ system for neurophysiological study. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Britz et al.6 obtained an age of the most recent common ancestor (MRCA) of Danionella of 29.5 (95% confidence interval 27.4-31.9).

    “Based on the results of Britz et al.6, who obtained an age of the most recent common ancestor (MRCA) of Danionella of 29.5 (95% confidence interval 27.4–31.9)”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Britz et al. [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In D. dracula, mature males have huge odontoid fangs that resemble teeth in their arrangement and appearance.

    “in which mature males have huge odontoid fangs that resemble teeth in their arrangement and appearance6”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [6] Britz, R., Conway, K. W. & Rüber, L. Spectacular morphological novelty in a miniature cyprinid fish, Danionella dracula n. sp. Proc. R. Soc. B. 276, 2179–2186 (2009). source

  • May combine two claims.

    Findingown data

    D. cerebrum is externally almost identical to D. translucida but differs trenchantly in several internal characters.

    “that is externally almost identical to D. translucida, but differs trenchantly in several internal characters.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Danionella cerebrum is difficult to distinguish from D. translucida alive or preserved because they look very similar and anal-fin ray count is challenging to obtain.

    “Alive or preserved, Danionella cerebrum is difficult to distinguish from D. translucida, because the two look very similar and the distinguishing count of anal-fin rays is challenging to obtain, as the most posterior fin rays are very small and often pressed close to the body rendering their number extremely difficult to count.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    At Daikme Chaung, the type locality of D. translucida, D. cerebrum was uncommon (1 out of 27 c&s specimens of Danionella) on 19 Aug 2008, but D. translucida was abundant.

    “At Daikme Chaung (Fig. 3), the type locality of D. translucida, D. cerebrum was uncommon (1 out of 27 c&s specimens of Danionella) on 19 Aug 2008, but D. translucida was abundant.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    D. cerebrum is distinguished from D. translucida by the distal tip of the fused inner arms of the ossa suspensoria bifurcated (vs. single).

    “by the distal tip of the fused inner arms of the ossa suspensoria bifurcated (vs. single, Fig. 2e,f)”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Reliable anal-fin ray counts can be easily obtained in c&s specimens and distinguish the majority of specimens of both species.

    “Reliable anal-fin ray counts, however, can be easily obtained in c&s specimens (see Fig. 2a,b) and distinguish the majority of specimens of both species”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    All water bodies in which D. cerebrum was found are turbid low altitude streams with visible flow, surface temperatures around 30 °C, pH 7.4-7.5 and soft water of 20-100 micro Siemens.

    “All water bodies in which Danionella cerebrum was found, are turbid low altitude streams (Fig. 3) with visible flow, surface temperatures of around 30 °C, pH 7.4–7.5 and soft water of 20–100 micro Siemens.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    D. cerebrum was not found at the surface, but at a depth below ca. 30 cm where the water is significantly cooler (ca. 25 °C).

    “Danionella cerebrum was not found at the surface, but at a depth below ca. 30 cm where the water is significantly cooler (ca. 25 °C).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    In other species of Danionella including D. cerebrum, the head skeleton and jaws are not sexually dimorphic.

    “while in other species of Danionella including D. cerebrum, the head skeleton and jaws are not sexually dimorphic.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    D. cerebrum was abundant at the type locality in Hmawbi on 18 Oct 2008, where it co-occurred with D. translucida, which appears to have been less common (a single c&s D. translucida among 28 D. cerebrum).

    “The species was abundant at the type locality in Hmawbi on 18 Oct 2008, where it co-occurred with D. translucida (as evidenced by c&s specimen and DNA sample), which appears to have been less common (a single c&s D. translucida among 28 D. cerebrum).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Some mature males of D. priapus lack the process connecting the os suspensorium to the lateral process of the second vertebra, and if present, it is much thinner than in the three Myanmar species of this clade.

    “Interestingly some mature males of D. priapus lack the process connecting it to the lateral process of the second vertebra and, if present, it is much thinner than in the three Myanmar species of this clade.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Female D. cerebrum do not possess these additional flanges, the drumming muscle or the drumming cartilage, and their fifth rib is smaller and only poorly ossified.

    “Females do not possess these additional flanges, the drumming muscle or the drumming cartilage and their fifth rib is smaller and only poorly ossified.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    All mature males of D. translucida, D. mirifica, and D. cerebrum show a well-developed connecting process between the os suspensorium and the lateral process, and their bony flanges on the outer and inner arm are more extensive than in D. priapus.

    “In contrast all mature males of D. translucida, D. mirifica, and D. cerebrum show a well-developed connecting process between the os suspensorium and the lateral process, and their bony flanges on the outer and inner arm are more extensive than in D. priapus”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The different loci (coxI, 16S rRNA, erg2b, rag1, rho) resulted in the same tree topology for the five species of Danionella but showed different support values.

    “The different loci resulted in the same tree topology for the five species of Danionella but showed different support values (Figs. 3, 4, Electronic Supplementary Fig. 2).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Progenesis is an evolutionary process that speeds up gonad development in relation to somatic development, so that the result is a small organism with larval features yet ripe gonads.

    “Progenesis is an evolutionary process that speeds up gonad development in relation to somatic development, so that the result is a small organism with larval features yet ripe gonads1,2.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [1] Gould, S. J. Ontogeny and Phylogeny (Harvard University Press, 1977).
    • cites [2] Hanken, J. & Wake, D. B. Miniaturization of body size: Organismal consequences and evolutionary significance. Annu. Rev. Ecol. Evol. Syst. 24, 501–519 (1993). source

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    The study of Danionella presents a promising system to understand major morphological changes.

    “We conclude by stressing that the study of Danionella presents a promising system to understand major morphological changes”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The striking structural differences in the arrangement of the Weberian apparatus in males of the different species of Danionella may equate to differences in the sounds produced by males.

    “The striking structural differences in the arrangement of the Weberian apparatus in males of the different species of Danionella may equate to differences in the sounds produced by males.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The more extensive bony flanges in D. translucida, D. mirifica, and D. cerebrum potentially provide a larger surface for the origin of the drumming muscle.

    “potentially providing a larger surface for the origin of the drumming muscle.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Danionella have a developmentally truncated neurocranium, but a precociously developing Weberian apparatus.

    “Danionella have a developmentally truncated neurocranium, but a precociously developing Weberian apparatus”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Conway et al. [10] Conway, K. W., Kubicek, K. M. & Britz, R. Extreme evolutionary shifts in developmental timing establish the miniature Danionella as a novel model in the neurosciences. Dev. Dyn. 250, 601–611 (2020). source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The small medioventrally directed process at the base of the fifth rib in male D. cerebrum potentially plays a role in the production of sound.

    “which potentially plays a role in the production of sound (see below).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    In Danionella, the Weberian apparatus aids in the perception of sound and evolved into a unique apparatus for sound production.

    “which in the latter not only aids in the perception of sound, but also evolved into a unique apparatus for sound production.”
    Quote in the paperNot a substantial claim
29 of 29

  • The paper relies on this without support.

    The external similarity between different species of Danionella has led to confusion over the identity of the model species.

    “The external similarity between the different species of Danionella has offered an important challenge to taxonomic identification using traditional external characters, leading to confusion over the identity of the model species.”

  • The paper relies on this without support.

    The four recognized species of Danionella are difficult to tell apart when alive.

    “The four recognized species have thus been distinguished by fin-ray counts and internal anatomy4–6 and are difficult to tell apart when alive.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The scaffold N50 of Danionella cerebrum was 6.5 Mb, 19-fold larger than a previous draft genome with a similar genome size.

    “The scaffold N50 of Danionella cerebrum was 6.5 Mb, 19-fold larger than a previous draft genome25 with a similar genome size (Table 1).”

    From Genomic and genetic insights into speciation and pigment pattern diversification in <i>Danio</i> fishes (2025) · cites this paper as [25]

    The Molecular results section identifies an earlier genome sequence labeled D. translucida as belonging to D. cerebrum, supporting the identity of the comparison genome. It does not report a 6.5 Mb scaffold N50, a 19-fold difference, or similar genome sizes. No page number is available in our copy. (LLM, conf=0.78)

    Experimental — accuracy not yet measured

  • Danionella dracula has recently emerged as a model organism for neurophysiological research.

    “Danionella dracula has recently emerged as a model organism for neurophysiological research ( Tatarsky et al., 2022), along with D. cerebrum ( Schulze et al., 2018), previously misidentified as D. translucida ( Britz et al., 2021).”

    From The genome sequence of the Dracula fish, Danionella dracula (Britz, Conway &amp; Rüber, 2009) (2024) · cites this paper as Britz et al., 2021

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Figure 4 specimen exceeds its lot's stated size range

    Minor

    Figure 4 lists a 16.5 mm specimen from BMNH 2009.9.9.38-43, but the Methods give 15.9 mm SL as the maximum for that lot.

  • Figure 2 specimen exceeds its lot's stated size range

    Minor

    Figure 2 lists an MTD 39992 specimen at 13.1 mm SL, while the Methods give 12.2 mm SL as the maximum for that lot.

  • Pterygiophore-position frequencies total 33 rather than 32

    Minor

    The reported frequencies for the number of anal-fin pterygiophores before the first haemal spine sum to 33 specimens, exceeding the stated D. cerebrum sample of 32.

    Reported 32 · recomputed 33

  • Anal-fin ray frequencies total 31 rather than 32

    Minor

    The frequencies for 15, 16, 17 and 18 anal-fin rays sum to 31 specimens, although Table 1 gives 32 D. cerebrum specimens for these counts.

    Reported 32 · recomputed 31

  • Figure 1 assigns D. translucida specimens to D. cerebrum

    Minor

    Figure 1 identifies MTD 39992 specimens as D. cerebrum paratypes, whereas the Methods identify that lot as D. translucida.

  • Abdominal vertebra range omits a reported count of 15

    Minor

    Table 1 gives D. cerebrum an abdominal-vertebra range of 13-14, but the description reports one specimen with 15.

6 of 6

Cites

Flagged first, then by citations

Research works printed but not linked: 4

  1. Britz, R. Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae). Ichthyol. Explor. Freshw. 14, 217–222 (2003).
  2. Hanken, J. Adaptation of bone growth to miniaturization of body size. In Bone, Volume 7: Bone Growth (ed. Hall, B. K.) 79–104 (CRC Press, Boca Raton, 1993).
  3. Kottelat, M. & Vidthayanon, C. Boraras micros, a new genus and species of minute freshwater fish from Thailand (Teleostei: Cyprinidae). Ichthyol. Explor. Freshw. 4, 161–176 (1993).
  4. Conway, K. W. Monophyly of the genus Boraras (Teleostei: Cyprinidae). Ichthyol. Explor. Freshw. 16, 249–264 (2005).

Cited by

Sorted by citations

Related

Authors
Britz, R., Conway, K. W., & Rüber, L.
Affiliations
  • Natural History Museum (GB)
  • Australian Museum (AU)
  • University of Bern (CH)
Corresponding author
Britz, Ralf
ORCID
Venue
Scientific Reports
Publisher
Springer Science and Business Media LLC
Published
2021-09-23
Volume
11
Issue
1
Pages
18942-18942
ISSN
2045-2322 (ISSN-L)
DOI
10.1038/s41598-021-97600-0
PMC
PMC8460714
OpenAlex
W3199418203
Cited by
53
References
27
Citations by year
2026: 14 · 2025: 12 · 2024: 15 · 2023: 6 · 2022: 5 · 2018: 1
FWCI
6.03
Type
journal article
Language
en
Open access
Licence
Locations
  • Scientific Reports (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, other-oa)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Bern Open Repository and Information System (University of Bern) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Zenodo (CERN European Organization for Nuclear Research) (submittedVersion, cc-by)
  • Open Access CRIS of the University of Bern
Funders
  • Texas A&M Agrilife (HATCH TEX09452; BRTC #)
  • Senckenberg Gesellschaft für Naturforschung (SGN)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Aquatic Science › Fish Biology and Ecology Studies
  • Physical Sciences › Environmental Science › Nature and Landscape Conservation › Fish biology, ecology, and behavior
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
Keywords
new species description, Cyprinidae, model organisms, neurophysiology, sound production, sexual dimorphism, Weberian apparatus, species delimitation, molecular taxonomy
MeSH terms
Animals, Cyprinidae, Female, Male, Neurophysiology, Sex Factors, Models, Animal

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-11-02.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-11-02.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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