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Danionella priapus, a new species of miniature cyprinid fish from West Bengal, India (Teleostei: Cypriniformes: Cyprinidae)

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Ralf Britz at Senckenberg Natural History Collections Dresden
Ralf Britz
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Danionella priapus, a new species of sexually dimorphic miniature cyprinid from the Brahmaputra drainage in India, is distinguished from the other three species in the genus by the presence in adult males of a conical projection of the genital papilla situated between funnel-shaped pelvic fins, the number of analand pectoral-fin rays, and the position of insertion of the last anal-fin pterygiophore. It differs further from D. translucida and D. mirifica in details of the colour pattern, from D. dracula and D. mirifica in number of procurrent caudal-fin rays, from D. translucida in number of vertebrae and from D. dracula in several skeletal characters. Like the other species in the genus, D. priapus shows a developmentally truncated skeleton that is associated with several evolutionary morphological novelties. The present distribution of the Danionella species may be the result of a vicariance event in the early Miocene, when the tectonic uplift of eastern Tibet and the Indo-Burman ranges lead to the interruption of the palaeo-connection between the Tsangpo (Brahmaputra) and the upper Irrawaddy Rivers.
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Accepted by R. Pethiyagoda: 8 Oct. 2009; published: 30 Oct. 2009 53
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2009 · Magnolia Press
Zootaxa 2277: 53–60 (2009)
www.mapress.com/zootaxa/Article
Danionella priapus, a new species of miniature cyprinid fish from West Bengal,
India (Teleostei: Cypriniformes: Cyprinidae)
RALF BRITZ
Department of Zoology, The Natural History Museum, Cromwell Road, London, SW75BD, United Kingdom.
E-mail: r.britz@nhm.ac.uk
Abstract
Danionella priapus, a new species of sexually dimorphic miniature cyprinid from the Brahmaputra drainage in India, is
distinguished from the other three species in the genus by the presence in adult males of a conical projection of the
genital papilla situated between funnel-shaped pelvic fins, the number of anal- and pectoral-fin rays, and the position of
insertion of the last anal-fin pterygiophore. It differs further from D. translucida and D. mirifica in details of the colour
pattern, from D. dracula and D. mirifica in number of procurrent caudal-fin rays, from D. translucida in number of
vertebrae and from D. dracula in several skeletal characters. Like the other species in the genus, D. priapus shows a
developmentally truncated skeleton that is associated with several evolutionary morphological novelties. The present
distribution of the Danionella species may be the result of a vicariance event in the early Miocene, when the tectonic
uplift of eastern Tibet and the Indo-Burman ranges lead to the interruption of the palaeo-connection between the Tsangpo
(Brahmaputra) and the upper Irrawaddy Rivers.
Key words: miniature fishes, developmental truncation, evolutionary novelty, vicariance
Introduction
Species of the genus Danionella are completely transparent, miniaturized cyprinids. Three species have been
known so far, all distributed in Myanmar: D. translucida Roberts, 1986, from the Bago Yoma in southern
Myanmar, and D. mirifica Britz, 2003 and D. dracula Britz et al., 2009, from the Myitkina district in northern
Myanmar. All species of Danionella show a highly developmentally truncated skeleton, but exhibit at the
same time astonishing morphological novelties (Britz et al., 2009). The same is true for a Danionella species
from the Jorai River in West Bengal, material of which I received recently. A detailed investigation revealed
that this Indian species is new to science and the present paper serves to make a name available for it and
report its unusual characters.
Danionella priapus, sp. nov.
(Figs. 1–4)
Danionella sp.: Jorai River, Britz et al., 2009
Type material. Holotype: BMNH 2009.9.9.1, male, 14.4 mm SL; India, West Bengal, Jalpaiguri District,
Brahmaputra drainage, Jorai River, a tributary of the Sankosh at Laskarpara, outskirts of Barobisha town. 26°
28' 52.3''N, 89° 49' 29.8''E; M. Das, 2 Apr 2008.
Paratypes: BMNH 2009.9.9.2-37 (36), 11.8–16.0 mm SL; data as for holotype. BMNH 2009.9.9.38–43
(6), cleared and double stained, 13.6–15.9 mm SL; data as for holotype.
BRITZ54 · Zootaxa 2277 © 2009 Magnolia Press
FIGURE 1. Lateral view of Danionella priapus: a. BMNH 2009.9.9.1, holotype, male, 14.4 mm SL; b. BMNH
2009.9.9.2-37, paratype, female, 15.0 mm SL. Note presence of eggs and larval preanal fin fold in female, and difference
in size and shape of pelvic fins and in position of anus and genital papilla between male and female.
FIGURE 2. Difference in pelvic-fin structure in Danionella priapus: a holotype, BMNH 2009.9.9.1, male, 14.4 mm SL,
close-up of modified pelvic fins and conically projecting genital papilla; b, BMNH 2009.9.9.2-37, paratype, female, 15.0
mm SL, close-up of pelvic fins and preanal fin fold.
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DANIONELLA PRIAPUS, A NEW CYPRINID FROM INDIA
FIGURE 3. Dorsal and ventral view of colour pattern of head and anterior body in Danionella priapus, holotype,
BMNH 2009.9.9.1, male, 14.4 mm SL.
BRITZ56 · Zootaxa 2277 © 2009 Magnolia Press
Diagnosis. Danionella priapus is distinguished from its congeners, D. dracula, D. translucida and D.
mirifica, by the presence in adult males of a conical projection of the genital papilla situated between the
pelvic fins, which form a funnel-like structure (vs. genital papilla not developed as a conical projection and
pelvic fins not funnel-shaped), by possessing 8 pectoral-fin rays (vs. 6–7) and 20–21 anal–fin rays (vs. 12–14
in D. dracula, 12–16 in D. translucida, and 17–19, rarely 20 in D. mirifica), and by having the last anal-fin
pterygiophore inserted in front of haemal spine of vertebra 27 or 28 (vs. 21 or 22 in D. translucida, 23–25 in
D. mirifica, and 22–24 in D. dracula). It differs further from D. translucida and D. mirifica in the presence of
a median and two paramedian rows of pigment cells on the dorsal side of the body (vs. pigment rows absent).
It is further distinguished from D. dracula and D. mirifica by 7–8 dorsal caudal procurrent rays (vs. 5–6) and
6–8 ventral procurrent rays (vs. 4–5). In addition it differs from D. dracula in having two upper jaw bones (vs.
one); edges of jaw bones entire, without processes (vs. dorsal face of dentary and ventral face of upper jaw in
males each with a single row of 6–13 odontoid processes, anterior most large and canine-like); presence of
maxillary-mandibular cartilage (vs. absence); absence of membrane bone flanges on basipterygium (vs.
presence); and 9+9 principal caudal fin rays (vs. 7–8 + 7–8). It differs also from D. translucida in having 15–
16 abdominal (vs. 13–14) and 22–23 caudal (vs. 19–20) vertebrae and a well developed lateral stripe
extending from ear capsule to caudal peduncle (vs. a row of few melanophores midlaterally, restricted to
posterior part of body).
Description. Morphometric information, based on 15 specimens, is presented in Table 1. Known
maximum size 16.0 mm SL. Head and eye large, mouth supraterminal (Fig. 1). Body laterally compressed,
elongate; dorsal fin short, situated opposite posterior half of long anal fin. Caudal fin furcate, with remnants of
larval fin fold in front of its dorsal and ventral margins. Remnant of pre-anal larval fin fold present in females
only (Fig. 1b). Anus and genital papilla of adult males located between pelvic fins, in females at normal
position in front of anal fin. Genital opening of adult males located at tip of short, conical projection at
proximal end of funnel-like structure formed by pelvic fins being fused along their midline (Figs. 1a, 2).
Pseudotypanum present in body musculature at lateral side of anterior gas-bladder chamber, rendering its
pigmented surface visible (Fig. 1). Body muscles greatly thinned out at lateral side of posterior gas bladder
chamber. Scales absent. Lateral-line canals and pores on head and body absent.
Skull, hyopalatine arch, gill arches, and endoskeletal shoulder girdle mostly cartilaginous with
perichondral ossifications giving skeleton overall larval appearance. Numerous bones and cartilages absent:
kinethmoid (and kinethmoid cartilage), preethmoid, vomer, dermethmoid, nasal, parietal, intercalar,
extrascapular, infraorbitals 2–5, ectopterygoid, metapterygoid, urohyal, hypobranchials 1–3, sclerotic bones,
posttemporal, postcleithrum, mesocoracoid, pectoral radials 3–4 (and pectoral radial cartilages 3–4), pelvic
radials 1–3 (and pelvic radial cartilages 2–3), supraneurals 2 and 5–9 (and supraneural cartilages 5–9), middle
and distal radials in dorsal and anal fins, epineurals, epipleurals, uroneural 2, and scales. Ceratobranchial 5
heavily ossified, bearing 4–5 tri- to quadricuspid teeth plus the tips of one or two replacement teeth. Outer arm
of os suspensorium sexually dimorphic, being enlarged and hyperossified in males and in confluence with
lateral process of second vertebra via anterior process and with inner arm of os suspensorium below tripus via
broad median flange. Males with a relatively large conical nodule of cartilage between fifth rib and outer arm
of suspensorium, its proximal surface approaching swimbladder wall.
Vertebrae totalling 37 (2) or 38 (4), abdominal vertebrae 15 (3) or 16 (3); caudal vertebrae 22 (5) or 23 (1).
Ribs present on vertebrae 5 to 14. Dorsal-fin rays ii,6,i (5) or ii,7,i (1). First dorsal-fin ray pterygiophore
inserted behind neural spine of vertebra 21 (3) or 22 (3), and last in front of neural spine of vertebra 25 (2) or
26 (4). Anal-fin rays ii,17,i (2) or ii,18,i (4). Number of anal-fin pterygiophores in front of first hemal spine: 0
(2), 1 (2) or 2 (2). Last anal-fin pterygiphore inserted in front of neural spine of vertebra 27 (3) or 28 (3).
Principal caudal-fin rays 9+9 (6) plus 7 (5) or 8 (1) dorsal and 6 (2), 7 (1) or 8 (3) ventral procurrent rays.
Pectoral-fin rays 8 (6) and pelvic-fin rays 5 (6).
Colouration. Pigmentation in alcohol specimens restricted to several rows of melanophores (Figs. 1, 3):
mid-lateral row along horizontal septum from shoulder girdle to hypural plate; ventral row from in front of
and slightly above anal-fin base along ventral larval fin fold to end of hypural plate; row along anal-fin base;
Zootaxa 2277 © 2009 Magnolia Press · 57
DANIONELLA PRIAPUS, A NEW CYPRINID FROM INDIA
mid-dorsal row starting behind head with several enlarged melanophores forming small blotch and extending
usually halfway between head and anterior base of dorsal fin, rarely to anterior dorsal-fin base; paired dorsal
paramedian rows from head to base of caudal fin; dorsal-fin base row; abdominal mid-ventral row from
ventral tip of cleithrum to anus; several melanophores on otic capsule; melanophores capping dorsal and
dorso-lateral face of gasbladder chambers and their connecting duct and lining peritoneum covering gonads;
streaks of melanophores lining anterior edge of lower cleithrum, ventral edge of opercle and preopercle,
branchiostegal rays and fin rays in dorsal, anal and caudal fins and anterior two or three rays of pectoral fin;
and several larger melanophores near symphysis of lower jaw. Head with supraoccipital blotch formed by
several large contiguous melanophores, with numerous large scattered melanophores between supraoccipital
blotch and epiphyseal bar, with a preepiphyseal blotch, and a few prenasal melanophores.
In life, body colourless and largely translucent (Fig. 4), except for melanophore patterns described above,
a thin yellowish-greenish line running along body at level of neural tube; golden chromatophores forming ring
around pupil, capping swimbladder chambers and connecting duct.
Distribution. The species is known only from the type locality, Jorai River in West Bengal, India (Fig. 5).
Etymology. The species name priapus is derived from the greek , the god of fertility of Greek
mythology. It was inspired by the conical projection of the genital papilla in males, which—at a superficial
level—is reminiscent of the penis of mammals. A noun in apposition.
TABLE 1. Selected morphometric information on 15 specimens (7 males, 8 females) of Danionella priapus, including
the holotype.
Holotype Paratypes
Male Males Females
Range Mean St. Dev Range Mean St. Dev
Standard length (SL) 14.4 12.5–14.1 13.7–15.0
In % of SL
Head length 17.4 17.4–20.0 18.3 0.9 19.0–20.7 19.8 0.7
Predorsal-fin length 70.1 68.7–70.4 69.4 0.7 68.7–71.0 70.1 0.8
Prepelvic-fin length 30.6 29.8–32.8 30.8 1.1 34.0–35.6 34.8 0.5
Preanal-fin length 52.1 51.1–52.1 51.5 0.4 53.3–54.8 54.2 0.6
Snout to anus 29.9 29.1–32.0 30.1 1.0 51.4–52.7 51.9 0.4
Body depth at dorsal-fin origin 13.2 13.1–15.2 14.1 0.7 14.4–16.0 15.4 0.5
Caudal-peduncle depth 7.6 7.5–8.5 8.0 0.3 7.5–8.9 8.0 0.5
Caudal-peduncle length 18.8 17.9–21.6 19.6 1.4 18.1–21.3 19.6 1.1
Length of dorsal-fin base 9.7 9.7–11.3 10.7 0.5 10.3–11.7 10.9 0.5
Length of anal-fin base 30.6 28.4–30.7 29.5 0.9 26.0–28.3 27.4 0.7
Length of pelvic fin 8.7 7.2–8.7 7.4 0.3 6.3–8.3 7.0 0.6
In % of HL
Eye diameter 44.0 40.0–44.0 40.8 1.5 35.0–39.3 37.3 1.3
Snout length 16.0 16.0–16.7 16.1 0.3 17.9–21.4 20.0 1.2
BRITZ58 · Zootaxa 2277 © 2009 Magnolia Press
FIGURE 4. Live colouration of male (above) and female (below) Danionella priapus. Specimens not preserved. Note
eggs in body cavity of female.
FIGURE 5. Distribution of the four species of Danionella in India and Myanmar.
Discussion
Species of the genus Danionella are among the smallest fishes with reported maximum sizes of 12 mm in D.
translucida (Roberts, 1986), 14.1 mm in D. mirifica (Britz, 2003), and 16.7 mm in D. dracula (Britz et al.,
Zootaxa 2277 © 2009 Magnolia Press · 59
DANIONELLA PRIAPUS, A NEW CYPRINID FROM INDIA
2009). With the largest specimen in the type series measuring 16 mm, D. priapus is one of the larger species in
the genus.
Danionella priapus is easily distinguished from its congeners by the conically projecting genital papilla
and the funnel-shaped pelvic fins of males, and by its 8 pectoral-fin rays, but also by its longer anal fin, which
consists of 20–21 rays, a number that is never reached in D. translucida and D. dracula, and only rarely in D.
mirifica (only in 1 out of 20 specimens, see Britz, 2003). The three rows of dorsal-pigment pattern of the body
of D. priapus are also diagnostic, as neither D. translucida nor D. mirifica shows any dorsal body
pigmentation. Danionella dracula usually has only a single short row of melanophores, but occasionally
individuals may have a denser covering with melanophores that resembles the condition in D. priapus.
Britz et al. (2009) argued that D. dracula with its massive tooth-like jaw projections, but otherwise larval
skeleton, exemplifies in a compelling way the link between evolution of morphological novelties and
progenetic paedomorphosis via heterochronic change in developmental timing. Danionella priapus can
certainly be mentioned in this context too, as it combines a developmentally truncated skeleton with highly
modified anatomical structures. While males of all Danionella species have their anus and genital opening
shifted anteriorly between the pelvic fins, the conical projection of the genital papilla of male D. priapus is not
only unique among the Danionella species, but also does not seem to be present in any other cypriniform. The
pelvic fins are modified in some Danionella species, like D. dracula, but the funnel-like formation of these
fins in D. priapus is highly unusual, if not unique, among cypriniforms. It seems extremely surprising to find
such a variety of highly specialized and modified anatomical structures among only four species of closely
related and highly miniaturized fishes. This is even more astonishing when at the same time living Danionella
translucida, D. mirifica, D. dracula, and D. priapus are superficially very similar and easily confused.
As already stressed by Britz et al. (2009: 2183) for D. dracula, it seems, however, that precisely this
evolutionary process of developmental truncation may have also facilitated the evolution of the conically
projecting genital papilla and funnel-shaped pelvic fins of D. priapus “by freeing large parts of the anatomical
structures from developmental constraints, dissociating developmentally linked pathways and creating a
greater potential for more dramatic changes”.
It is still unclear if these greatly modified anatomical structures in D. priapus are part of an unusual
reproductive strategy and further studies will have to clarify this.
Despite their external similarity the evolutionary gap between D. priapus from the Brahmaputra drainage
in India and its sister group, D. mirifica plus D. translucida from the Irrawaddy/Sittang drainages in
Myanmar, is quite significant, if expressed as time since divergence. In the time tree published by Britz et al.
(2009), the earliest split in the genus is that of D. dracula from the other Danionella species at 29.5 million
years ago (95% confidence interval 27.4–31.9). The next split is that of D. priapus from its sister group, the
remaining Myanmar species, at around 22.6 million years ago (with a 95% confidence interval of 20.7–24.6
mya) at the Oligocene-Miocene boundary. This is a similar time frame as recovered in Rüber et al.’s (2004)
molecular phylogenetic analysis of the family Badidae for pairs of sister groups in the Bramaputra and
Irrawaddy/Sittang drainages: Dario dario vs. D. hysginon; Badis pyema+B. corycaeus vs. B.kanabos+B.
badis+B. sp. ‘‘Assam’’+B. assamensis+B. blosyrus; Colisa labiosa vs. other Colisa spp.; and Ctenops nobilis
vs. Parasphaerichthys spp. The present occurrence of D. priapus is thus consistent with a vicariant event
caused by the uplifting of eastern Tibet and the Indo-Burman ranges, which interrupted the hypothesized
palaeo-connection of the Tsangpo River with the Irrawaddy River in the early Miocene (see Rüber et al., 2004
for a comprehensive discussion).
Comparative material
Danionella translucida: NRM 32233 (5), paratypes, cleared and double stained; Myanmar, Pegu Division.
Sittang River basin, Dayame Chaung 1 mile from Daik-U. NRM 32234 (3), paratypes, cleared and double
stained; same data as NRM 32233. NRM 32235 (12), paratypes; same data as NRM 32233.
BRITZ60 · Zootaxa 2277 © 2009 Magnolia Press
Danionella mirifica: USNM 372847, holotype; Myanmar, Kachin State: hill stream, 8 miles from
Kamaing on road to Tanai. USNM 372848 (36), paratypes; same data as holotype. USNM 372849 (20),
paratypes, cleared and double stained; same data as holotype.
Danionella dracula: BMNH 2008.1.1.1, holotype; Myanmar: Kachin state: stream at Sha Du Zup
between Mogaung and Tanai. BMNH 2008.1.1.2-99 (98), paratypes; same data as holotype. BMNH
2008.1.1.100-119 (20), cleared and double stained; same data as holotype.
Acknowledgements
I am grateful to Andrew Rao, Malabar Tropicals, Calcutta, and Keith Lambert, Wildwoods, Crews Hill, who
made the specimens of D. priapus available. I also thank Sven Kullander (NRM), Jeff Williams (USNM) and
Oliver Crimmen (BMNH) for access to material under their care. The manuscript benefited from comments
by Sven Kullander and an anonymous reviewer.
References
Britz, R. (2003) Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae).
Ichthyological Exploration of Freshwaters, 14, 217–222.
Britz, R., Conway, K.W. & Rüber, L. (2009) Spectacular morphological novelty in a miniature cyprinid fish, Danionella
dracula n. sp. Proceedings of the Royal Society B, 276, 2179–2186.
Roberts, T. (1986) Danionella translucida, a new genus and species of cyprinid fish from Burma, one of the smallest
living vertebrates. Environmental Biology of Fishes, 16, 231–241.
Rüber, L., Britz, R., Kullander, S.O. & Zardoya, R. (2004) Evolutionary and biogeographic patterns of the Badidae
(Teleostei: Perciformes) inferred from mitochondrial and nuclear DNA sequence data. Molecular Phylogenetics and
Evolution, 32, 1010–1023.
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Barbucca heokhuii, new species, is described from the Kahayan drainage in central Borneo. It is distinguished from the other species of the genus by its miniature size (the largest known specimen is 21.5 mm SL), a truncate to rounded caudal fin, an incomplete lateral line, and a distinctive colour pattern made, among others, of five pairs of irregular bars on the flank, narrower than interspaces, many of which may be dissociated into several small blotches. It occurs in syntopy with B. diabolica. Sexual dimorphism is reported for the first time for a member of the family; in males, the 2nd to 4th branched pectoral rays are thicker than the others and with a patch of small tubercles along their posterior edge.
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... Eukaryota; Metazoa; Eumetazoa; Bilateria; Deuterostomia; Chordata; Craniata; Vertebrata; Gnathostomata; Teleostomi; Euteleostomi; Actinopterygii; Actinopteri; Neopterygii; Teleostei; Osteoglossocephalai; Clupeocephala; Otomorpha; Ostariophysi; Otophysi; Cypriniphysae; Cypriniformes; Cyprinoidei; Danionidae; Danioninae; Danionella; Danionella dracula Background Danionella dracula (Figure 1) is a miniature, transparent freshwater fish from streams around Sha Du Zup, Kachin State, in northern Myanmar with a maximum recorded size of 16.7 mm standard length . It forms the sister group of the other four miniature species of Danionella: D. translucida (Roberts, 1986), D. mirifica (Britz, 2003), D. priapus (Britz, 2009) and D. cerebrum (Britz et al., 2021). Danionella dracula separated from its closest relatives about 29.5 mya . ...
The genome sequence of the Dracula fish, Danionella dracula (Britz, Conway & Rüber, 2009)
Article
Full-text available
  • Apr 2024
We present a genome assembly from an individual Danionella dracula (the Dracula fish; Chordata; Actinopterygii; Cypriniformes; Danionidae; Danioninae). The genome sequence is 665.21 megabases in span. This is a scaffold-level assembly, with a scaffold N50 of 10.29 Mb.
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... Adults of this species are up to 13 mm long and are considered among the smallest living vertebrates (Britz et al., 2021). Previous studies suggest that miniaturization in the genus Danionella occurred due to paedomorphism in bone development (Britz, 2003(Britz, , 2009Britz and Conway, 2015). Despite having a small brain, D. cerebrum displays a rich behavioral repertoire, including shoaling, schooling, and sound production (Schulze et al., 2018). ...
Characterization of the vocal behavior of the miniature and transparent fish model, Danionella cerebrum
Article
  • Jan 2024
  • J ACOUST SOC AM
Danionella cerebrum has recently been proposed as a promising model to investigate the structure and function of the adult vertebrate brain, including the development of vocal–auditory neural pathways. This genetically tractable and transparent cypriniform is highly vocal, but limited information is available on its acoustic behavior and underlying biological function. Our main goal was to characterize the acoustic repertoire and diel variation in sound production of D. cerebrum, as well as to investigate the relationship between vocal behavior and reproduction. Sound recordings demonstrated high vocal activity, with sounds varying from short sequences of pulses known as “bursts” (comprising up to 15 pulses) to notably longer sounds, termed “long bursts”, which extended up to 349 pulses with over 2.7 s. Vocal activity peaked at midday and it was very low at night with only a few bursts. While the number of pulses was higher during the daytime, the interpulse interval was longer at night. In addition, calling time was positively associated with the number of viable eggs, suggesting that acoustic communication is important for reproduction. These preliminary findings reveal the potential of using D. cerebrum to investigate vocal plasticity and the implications for sexual selection and reproduction in a novel vertebrate model for neuroscience.
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... Danionella is a genus of bony fish that is part of the Cyprinidae family. Danionella fish belong to the subfamily group Danioninae or danionin, which includes also the common Roberts [32], Danionella mirifica [73], Danionella dracula [74] and Danionella priapus [75]. However, in 2021, a new Danionella species was described, called Danionella cerebrum, which had been confounded for a long time with Danionella translucida [33]. ...
Study of behavioral and neuronal maturation during development on Danionella cerebrum and comparative study with Danio rerio
Thesis
  • Sep 2022
Locomotion is essential for motile animal to adapt to their environment. This ability to navigate is modulated by the sensory information animals are continuously integrating from their environment in order to find food or mates and avoid predators. Both locomotion and information integration are part of the sensorimotor program that is controlling animal exploratory behavior. In fish, these operations are already functional at early development stage and evolve with animal development. In this thesis, we explored how stereotyped stimuli are integrated and influence locomotion, and we also investigate how the underlying neuronal circuit of locomotion change through animal development. We used larvae zebrafish to answer the first question. Our involvement in developing a new vertebrate model Danionella cerebrum (DC), allowed us to initiate the exploration of the second question. Sensorimotor program requires the integration of multisensory stimulation that necessitates processing time. To study this, we combined two reflexes already described independently in larvae zebrafish, the optomotor response and the acoustic startle response. We confirmed that larvae are delaying their first movement when exposed to a visual stimulus, and we showed that this visual information did not bias the escape direction triggered by an acoustic signal. Our laboratory was involved in developing a new vertebrate model for neuroscience, the miniature fish DC. With its small size, around 15 mm at adulthood, its optical transparency from larval to adult stage, its wide behavior repertoire and its close phylogenetic relation with zebrafish, this fish is suitable for whole-brain functional imaging with a single cell resolution at different developmental stages. We created a specific fish facility in our university and we established raising and feeding protocols based on already existing knowledge. During a collaborative study, we took benefits of the phylogenetic proximity between zebrafish and DC to propose a comparative study between those two larvae. We especially focused on the spontaneous locomotion and long-term exploration. We showed that despite their different swimming patterns, both species have similar long-term exploration. To explore in more details this, we decided to model both trajectories with simple models. We are also interested in understanding how light affects the locomotor program of DC. In parallel, neuronal calcium activity was recorded with light-sheet microscope in larvae to determine neuron populations that are correlated with swimming activity. It has been published that both species have in common brain region that are recruited during swimming behaviors. Thanks to its different locomotion, we highlighted neuronal populations in DC that are firing when the fish is not swimming. We also demonstrated that it is possible to record whole-brain calcium activity in juveniles DC with the same protocol and setup used for larvae, which will allow following the maturation of the locomotor neuronal circuit and to identify mechanisms involved in brain evolution through the development. This thesis work is part of a global effort to establish DC as an interesting model for neuroscience. Further studies in our laboratory will aim at comparing the simple exploration models defined for zebrafish and DC larvae to have an insight on the evolution strategies which create divergent behaviors in close species. We will also follow modification on the simple model developed for larvae DC and on the locomotor neuronal circuit, in juvenile fish to reveal some mechanisms involved in maturation through development.
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... Goldman, 2021;UN Human Rights Council, 2018). Like other members of its genus, D. dracula exhibits developmental truncation, as they retain many larvae-like traits as adults ( pedomorphosis) and only reach 12-18 mm in standard length (Britz, 2003(Britz, , 2009Britz et al., 2009Britz et al., , 2021Britz and Conway, 2016;Conway et al., 2021;this report). Their especially small size combined with their transparency as both larvae and adults (e.g. ...
Acoustic and postural displays in a miniature and transparent teleost fish, Danionella dracula
Article
  • Aug 2022
Acoustic behavior is widespread across vertebrates, including among fishes. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio), which are hypothesized to be sonic based on the presence of a hypertrophied muscle associated with the male swim bladder. Males produce bursts of pulsatile sounds and a distinct postural display–extension of a hypertrophied lower jaw, a morphological trait not present in other Danionella species—during aggressive, but not courtship interactions. Females show no evidence of sound production or jaw extension in such contexts. Novel pairs of size-matched or -mismatched males were combined in resident-intruder assays where sound production and jaw extension could be linked to individuals. In both dyad contexts, resident males produced significantly more sound pulses than intruders. During heightened sonic activity, the majority of highest sound producers also showed increased jaw extension. Residents extended their jaw more than intruders in size-matched, but not -mismatched contexts. Larger males in size-mismatched dyads produced more sounds and jaw extensions compared to their smaller counterparts, and sounds and jaw extensions increased with increasing absolute body size. These studies establish D. dracula as a sonic species that modulates putatively acoustic and postural displays during aggressive interactions based on residency and body size, providing a foundation for further investigating the role of multimodal displays in a new model clade for neurogenomic and neuroimaging studies of aggression, courtship, and other social interactions.
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... Goldman, 2021;UN Human Rights Council, 2018). Like other members of its genus, D. dracula exhibits developmental truncation, as they retain many larvae-like traits as adults ( pedomorphosis) and only reach 12-18 mm in standard length (Britz, 2003(Britz, , 2009Britz et al., 2009Britz et al., , 2021Britz and Conway, 2016;Conway et al., 2021;this report). Their especially small size combined with their transparency as both larvae and adults (e.g. ...
Acoustic and postural displays in a miniature and transparent teleost fish, Danionella dracula
Preprint
  • Nov 2021
Individuals can reveal their relative competitive ability or mate quality through acoustic communication, varying signals in form and frequency to mediate adaptive interactions including competitive aggression. We report robust acoustic displays during aggressive interactions for a laboratory colony of Danionella dracula, a recently discovered miniature and transparent species of teleost fish closely related to zebrafish (Danio rerio). Males produce bursts of pulsatile, click-like sounds and a distinct postural display, extension of a hypertrophied lower jaw, during resident-intruder dyad interactions. Females lack a hypertrophied lower jaw and show no evidence of sound production or jaw extension under such conditions. Novel pairs of size-matched or mismatched males were combined in resident-intruder assays where sound production and jaw extension could be linked to individuals. Resident males produce significantly more sound pulses than intruders in both dyad contexts; larger males are consistently more sonic in size-mismatched pairs. For both conditions, males show a similar pattern of increased jaw extension that frequently coincided with acoustic displays during periods of heightened sonic activity. These studies firmly establish D. dracula as a sound-producing species that modulates both acoustic and postural displays during social interactions based on either residency or body size, thus providing a foundation for investigating the role of these displays in a new model clade for neurogenomic studies of aggression, courtship and other social interactions.
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Fishes of West Bengal: Review and Annotated Checklist
Article
  • Jul 2023
An updated systematic inventory of the fish faunal variety from the state of West Bengal, comprising 894 species represented by 36 orders and 152 families, has been produced following an extensive review of the literature. Diversity-wise, order Acanthuriformes, has 19 families and 120 species, is the top order of both freshwater and marine fishes. Cypriniformes, which has 7 families and 117 species, is the second most diverse order and the most diverse order in freshwater. Cyprinidae, makes up 6% of the entire fish population in West Bengal, is the family with the most diversity. Marine fishes showed the highest diversity in Gobiidae and Carangidae with 5.6% and 4.8% respectively. 221 species are fully freshwater species, whereas 297 species are marine. The rest of the species are associated with fresh water, brackish and marine habitats. According to the IUCN red list status, 8 species belong to the critically endangered category, 18 belong to the endangered category, 30 species belong to the vulnerable category and 37 species belong to the near threatened category. The conservation status of 239 fish species found in West Bengal has not yet been determined by IUCN. The present study is the first attempt to provide a comprehensive data of fish faunal diversity occurring from all the habitats present in West Bengal, which will ultimately help in the management of the prospects of fisheries resources from West Bengal as well as provide support for the effective conservational planning process.
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Danionella mirifica, a new species of miniature fish from Upper Myanmar (Ostariophysi: Cyprinidae)
Article
Full-text available
  • Jan 2004
  • ICHTHYOL EXPLOR FRES
Danionella mirifica, new species, is distinguished from its only congener D. translucida in having a more elongate body (body depth 12.2-14.8 % SL vs. 18.5-24.4 % SL), 36-37 vertebrae (vs. 32-33), 17-20 anal-fin rays (vs. 12-14), a single ventromedian row of large melanophores between pelvic fins and tips of cleithra (vs. paired ventral paramedian rows of smaller melanophores between pelvics and tips of cleithra), and in lacking scattered small melanophores on ventrolateral side of abdomen (vs. presence of these melanophores). Although slightly larger than D. translucida, D. mirifica is still one of the smallest freshwater fishes. (address for correspondance); Lehrstuhl für Spezielle Zoologie, Auf der Morgenstelle 28, D-72076 Tübingen, Germany.
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Spectacular morphological novelty in a miniature cyprinid fish, Danionella Dracula n. sp
Article
Full-text available
Danionella dracula is a new species of sexually dimorphic, miniature and highly developmentally truncated cyprinid fish. Compared with its close relative, the zebrafish Danio rerio, it lacks 44 bones or parts thereof and represents one of the most developmentally truncated vertebrates. Absence of the majority of bones appears to be due to developmental truncation via terminal deletion. In contrast to these larval-like features, D. dracula also shows several hyperossifications. Uniquely, among carp-like fishes, male D. dracula have a series of long, pointed odontoid processes on the jaws greatly resembling the jaw dentition of teleosts with true teeth. The anterior-most process in each jaw is extended as a canine-like fang projecting through the epithelium. True jaw teeth are absent from all 3700 species of cypriniforms and were lost at least in the Upper Eocene. It remains to be investigated, however, whether the conserved pathways to regulate tooth development in cypriniforms have been used in D. dracula to form and pattern the odontoid processes. This new species represents a remarkable example linking progenetic paedomorphosis via heterochronic change in developmental timing to the evolution of morphological novelties.
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Evolutionary and biogeographic patterns of the Badidae (Teleostei: Perciformes) inferred from mitochondrial and nuclear DNA sequence data
Article
Full-text available
  • Oct 2004
We reconstructed phylogenetic relationships of the family Badidae using both mitochondrial and nuclear nucleotide sequence data to address badid systematics and to evaluate the role of vicariant speciation on their evolution and current distribution. Phy-logenetic hypotheses were derived from complete cytochrome b (1,140 base pairs) sequences of 33 individuals representing 13 badid species, and using three species of Nandidae as outgroups. Additionally, we sequenced the nuclear RAG1 (1,473 base pairs) and Tmo-4C4 (511 base pairs) genes from each of the badid species and one representative of the outgroup. Our molecular data provide the first phylogenetic hypothesis of badid intrarelationships. Analysis of the mitochondrial and nuclear nucleotide sequence data sets resulted in well-supported trees, indicating a basal split between the genera Dario and Badis, and further supporting the division of the genus Badis into five species groups as suggested by a previous taxonomic revision of the Badidae. Within the genus Badis, mitochondrial and nuclear phylogenies differed in the relative position of B. kyar. We also used our molecular phylogeny to test a vicariant speciation hypothesis derived from geological evidence of large-scale changes in drainage patterns in the Miocene affecting the Irrawaddy- and Tsangpo-Brahmaputra drainages, in the southeastern Himalaya. Within both genera, Badis and Dario, we observed a divergence into Irrawaddy- and Tsangpo-Brahmaputra clades. Using a cytb substitution rate of 8.2 x 10(-9) (substitutions x base pair(-1) x year(-1), we tentatively date this vicariant event at the Oligocene-Miocene boundary (19-24Myr). It is concordant with a hypothesized paleo connection of the Tsangpo river with the Irrawaddy drainage that was most likely interrupted during Miocene orogenic events through tectonic uplifts in eastern Tibet. Our data, therefore, indicate a substantial role of vicariant-based speciation shaping the current distribution patterns of badids.
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Danionella translucida, a new genus and species of cyprinid fish from Burma, one of the smallest living vertebrates
Article
  • Aug 1986
Danionella translucida, a new genus and species of danioin cyprinid fishes, is described from Burma. Females are mature at 10–11 mm standard length, and the largest known specimen is only 12 mm. Ripe eggs are few in number and relatively large, 0.4–0.6 mm in diameter. Adults are scaleless and largely transparent, with a complex pattern of large melanophores on the ventral surface of the abdomen. Specializations observed in skeletal preparations include the danioin notch in the medial surface of the mandibles; a large maxillo-mandibulary cartilage; a cartilage (epibranchial 5?) uniting the branchial arches 4 and 5; pharyngeal bones with a single row of 4 tricuspid teeth; and pectoral, pelvic, and caudal fins with fewer rays than reported or observed in any other members of the family Cyprinidae.
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