Research Article |
Corresponding author: Daniela Santos Martins Silva ( danielasantos.biology@gmail.com ) Academic editor: Fernando Montealegre-Z
© 2017 Daniela Santos Martins Silva, Josip Skejo, Marcelo Ribeiro Pereira, Fernando Campos De Domenico, Carlos Frankl Sperber.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Silva DSM, Josip Skejo, Pereira MR, De Domenico FC, Sperber CF (2017) Comments on the recent changes in taxonomy of pygmy unicorns, with description of a new species of Metopomystrum from Brazil (Insecta, Tetrigidae, Cleostratini, Miriatrini). ZooKeys 702: 1-18. https://doi.org/10.3897/zookeys.702.13981
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The tribe Cleostratini Bolívar, 1887 sensu Storozhenko, 2016 does not represent a monophyletic taxon because it gathers various Tetrigidae genera with various types of horn and prolongation of frons or vertex. Prolongation of these structures is present in morphologically and biogeographically distant groups. We do not regard Miriatrini Cadena-Castañeda & Cardona, 2015 synonymous with Cleostratini because the genus Miriatra Bolívar, 1906 belongs to a group of genera distant from Cleostratus Stål, 1877. There is no adequate diagnosis for proposed groups of genera forming tribes Cleostratini or Miriatrini. Miriatrinistat. resurr. are monotypic and include only Miriatra, Cleostratini are monotypic as well. Apteromystrum Storozhenko, 2016 syn. n. is regarded synonymous with Metopomystrum, M. apterum comb. resurr., M. amazoniensis comb. resurr. and Miriatra brevifastigiata (Cadena-Castañeda & Cardona, 2015), comb. n. are not Metopomystrum member. Herein a new species of pygmy unicorn, Metopomystrum muriciense Silva & Skejo, sp. n., is described from Atlantic Forest remnants in northeast of Brazil, collected on the Estação Serra do Ouro (municipality of Murici, Alagoas state). Distribution data, morphological characterization, and an identification key to Metopomystrum species are also presented.
Apteromystrum , Atlantic Forest, fastigium, pygmy grasshopper, taxonomy
Members of the family Tetrigidae are distributed all over the world (
The subfamily Metrodorinae is not a monophyletic, but polyphyletic group established for practical identification (
The subfamily Cleostratinae was established by Bolívar in 1887 as ‘sectio Cleostratae’ for a single genus Cleostratus Stål, 1877, unique among Tetrigidae in having antennal grooves and the median ocellus placed between the compound eyes and an extremely produced frons. Recently,
The genus of pygmy unicorns Metopomystrum Günther, 1939 (
Our aims are (1) to describe a new species of pygmy unicorn from Atlantic Forest in the state of Alagoas, Brazil, by providing distribution data, morphological characterization and an identification key for species of the genus, (2) to test if there are relevant differences between Metopomystrum and Apteromystrum regardless of the presence of wings and (3) to discuss taxonomic and evolutionary aspects of Cleostratinae, Cleostratini, and Miriatrini.
Sampling and study area. The specimen of the new species of pygmy unicorn was collected by the “Biota de Orthoptera do Brasil” research group, 21–23 January 2013 at the Estação Serra do Ouro, municipality of Murici (state of Alagoas, Brazil) (coordinates 9°14.54'S, 35°50.2'W), with a pitfall trap containing ethanol fuel killing solution.
Microscopy and photography. External morphological characteristics were examined using a Zeiss Stemi 2000 stereomicroscope and photographed with Zeiss Stereo Discovery V20 stereomicroscope. Photographs were taken with the multidimensional acquisition function with AXIO VISION software, which allows capturing a series of pictures at different focal planes. The resulting images were then combined into a single picture using the Extended Focus Z function. The image plates were prepared in image editing software. Photographs of lateral and dorsal view of the holotype were taken, as well as more detailed photographs of important morphological characters (antennal segments, frontal costa, fastigium, vertex, maxillary palp, lateral lobes of the pronotum, sternomentum, abdomen (lateral and ventral profile), forelegs, hind femur, supranal plate, cerci, and subgenital plate.
Terminology. Morphological terminology follows
Distribution map and depository of type specimen. Distribution map (Fig.
Distribution data for hitherto described species of the genus Metopomystrum.
Species | Type series (holotype sex, locality, depository) | References |
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Metopomystrum amazoniensis comb. resurr. | 1♀, Colombia: Amazonas, PNN Amacayacu (Universidad Distrital Francisco José de Caldas, Colección de Entomología y Aracnología, Bogota, Colombia) |
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Metopomystrum apterum comb. resurr. | 1♂, Brazil Northeast: Bahia, Freire* (Museum für Naturkunde, Berlin, Germany) |
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Miriatra brevifastigiata comb. n. | 1♂ (nymph), Colombia: Antioquia, Envigado (Universidad Distrital Francisco José de Caldas, Colección de Entomología y Aracnología, Bogota, Colombia) |
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Metopomystrum lilianae | 1♂, Colombia, Colombia: Santander, Puerto Parra, Campo Capote, Borojó (Universidad Distrital Francisco José de Caldas, Colección de Entomología y Aracnología, Bogotá, Colombia) | |
Metopomystrum pehlkei | 1♂ Colombia: Tolima, Hacienda Pehlke, Städtisches Museum Stettin, Szczecin, Poland |
The species Metopomystrum brevifastigiata Cadena-Castañeda and Cardona, 2015 is not member of Metopomystrum nor Apteromystrum, but its holotype represents a male nymph of Miriatra sp. The holotype of M. brevifastigiata lacks antegenicular teeth on the hind femora which implies that it is not an adult animal. Head and pronotal morphology is also rather different from Metopomystrum and Apteromystrum species and represents a typical set of characters defining Miriatra. Thus, the new combination Miriatra brevifastigiata (Cadena-Castañeda and Cardona, 2015) comb. n. should be used when referring to this specimen. This species is very close to Miriatra producta (Bolívar, 1887) and the differences should be checked when adults will be found.
It is evident that comparison of Metopomystrum and the new genus Apteromystrum in
= Apteromystrum Storozhenko, 2016, syn. n.
Metopomystrum pehlkei Günther, 1939 by original designation.
Five species, all in northern part of South America (Brazil, Colombia), namely (1) M. amazoniensis (Colombia: Amazonas), (2) M. apterum (Brazil: Bahia), (3) M. lilianae (Colombia: Santander), (4) M. muriciense Silva & Skejo, sp. n. (Brazil: Alagoas), and (5) M. pehlkei (Colombia: Tolima).
Head. Frontal costa bifurcation situated above the paired lateral ocelli, between the compound eyes, so the frontal costa is long and evident before bifurcation, scutellum narrower than scapus, antennal grooves situated at the level of the lower margins of the compound eyes, paired lateral ocelli situated between the compound eyes, head and eyes exserted above pronotum, eyes protruding, so the vertex is not visible in lateral view, antennae 15-segmented, filiform, with cylindrical segments and smooth margins, fastigium narrower than the compound eyes, lateral carinae of the vertex continuous, not elevated, median carina of the vertex very weak, almost absent, anterior margin of the vertex rounded or acute, fastigium of the vertex projecting forwards and forming a horn longer than combined length of a compound eye and frontal costa above its bifurcation, dorsum of the horn with deep depression formed of joined fossulae, frontal ridge in lateral view with weak excision between the compound eyes.
Pronotum. slender in appearance, anterior margin truncated, prozonal carinae present, parallel or slightly diverging, extralateral carinae indistinct, median carina continuous from the anterior margin to the posterior apex, pronotal projections lacking, humeral angle wide, obliquely rounded, interhumeral carinae indistinct, interscapular area in winged species narrow with parallel margins, in wingless species as wide as mid femur, lateral area wider in wingless species, humero-apical, humeral and lateral carinae continuous, not armed or tuberculated, paranota triangular, lateral lobes of the pronotum directed slightly sidewards, with rounded apex lacking ventrolateral spine, dorsum of pronotum between the carinae smooth, pronotal apex truncated or acute.
Legs. Fore and mid femora not significantly compressed, fore femora with straight to slightly undulated dorsal and ventral margins, not armed with teeth or spines, mid femora not compressed, carinated above, with straight to slightly undulated dorsal and more undulated ventral margins, hind femora with smooth dorsal and ventral margins, dorsal margin with genicular and antigenicular teeth in hind knee, transverse ridges in the external surface well visible, not armed with lappets or spines, hind tibiae and tarsi not flattened or widened.
From other genera previously assigned to Cleostratini or Miriatrini, and from all the South American Metrodorinae genera (Allotettix Hancock, 1899; Amorphopus Serville, 1838; Chiriquia Morse, 1900; Cota Bolívar, 1887; Cotys Bolívar, 1887; Crimisus Bolívar, 1887; Eomorphopus Hancock, 1900; Hancockiella Cadena-Castañeda & Cardona, 2015; Metrodora Bolívar, 1887; Miriatra Bolívar, 1906; Otumba Morse, 1900; Platythorus Morse, 1900; Plesiotettix Hancock, 1907; Scabrotettix Hancock, 1907 and Trigonofemora Hancock, 1906). The genus Metopomystrum can be separated by the following set of characters: head exserted above the pronotum, frontal costa long above the bifurcation, antennal grooves situated at the level of the lower margins of the compound eyes, antennae 15-segmented, filiform, paired lateral ocelli situated between the compound eyes, median carina of the vertex weak, indistinct, not projecting forwards and not compressed, fastigium of the vertex with deep depression, lateral carinae of the vertex continuous, pronotum flat, without projections and protuberances, lateral pronotal lobes directed sidewards, having rounded apices, femora without teeth or lappets, fore and mid femora not compressed and flattened.
Holotype 1♂, in alcohol. Original label: “Brasil, Alagoas, Murici, Estação Serra do Ouro (9°14.54'S, 35°50.2'W), 21–23/i/2013. C. Sperber e equipe leg.” “[licença Sisbio n° 37717]” (
Brazil: Alagoas state, municipality of Murici, Estação Serra do Ouro, the holotype was caught in forest leaf litter [coordinates 9°14.54'S, 35°50.2'W].
The species name refers to the municipality of Murici.
This species can be distinguished from other species of Metopomystrum by the following set of characters: (i) long and acute fastigium, directed forwards, slightly upwards in its apex, (ii) forehead, genae and posthumeral spots in the pronotum yellowish, (iii) tegmina, alae and tegminal sinus absent, (iv) lateral lobes of the pronotum directed slightly sidewards, with rounded apex and yellowish band, (v) sternomentum necklace-shaped, brown with yellowish spots.
The species can easily be separated from winged Colombian species (M. lilianae and M. pehlkei) by the horn morphology, fastigium having a rounded anterior margin in those species, while it is acute in M. muriciense Silva & Skejo, sp. n., and it is directed upwards in those species, while forwards in M. muriciense Silva & Skejo, sp. n. Metopomystrum lilianae and M. pehlkei are winged species, with visible tegmina, narrower than the maximum width of the mid femora, and tegminal sinus, hence narrow infrascapular area which is wide and evident in apterous M. muriciense Silva & Skejo, sp. n. From the apterous Colombian species M. amazoniensis, the new species can be separated by the straight horn, not directed upwards as in M. amazoniensis. However, the two species only share morphology of the anterior margin, laterally vertex being narrower in M. muriciense Silva & Skejo, sp. n. than in M. amazoniensis. The occipital area in M. muriciense Silva & Skejo, sp. n. is much longer than in Colombian species of the genus. The species is morphologically most similar to M. apterum, also from Brazil, with which it shares numerous morphological features, differing however in horn (projection of the fastigium of the vertex) direction-forwards and slightly upwards in M. muriciense Silva & Skejo, sp. n., while slightly downwards in M. apterum. In M. muriciense Silva & Skejo, sp. n. the vertex is narrower and more acute than in M. apterum.
Head. In lateral view (Figs
Pronotum. Brachypronotal (because of lack of wings it can be also regarded nanopronotal, organs of flight not visible), reaching abdominal apex. In lateral view (Figs
Wings. Flightless species, tegmina and wing not visible, reduced and covered by infrascapular area of pronotum, not functional. (Note: to check if wings are present pronotum needs to be broken. We did not want to break the pronotum since there is only one specimen, the holotype). Sternomentum (Fig.
Legs (Figs
Abdomen (Figs
Metopomystrum muriciense Silva & Skejo, sp. n.: A Male holotype, habitus, lateral view B pronotum, lateral view, with infrascapular area marked in red lines C distal portion of pronotum with yellowish posthumeral spots and pronotum tip with serrate edge and many yellowish spots, dorsal view D abdomen and hind femur, ventral view E subgenital plate, dorsal view F terminalia, lateral view. Scale bar: 5.0 mm.
Unknown.
Body length from the tip of the fastigium projection to the end of the abdomen 10.8; fastigium length 1.03; vertical eye diameter 0.96; horizontal eye diameter 0.67; vertex width 0.41; pronotum length 8.12; pronotum lateral lobes maximal width 1.86; infrascapular area length 5.54; fore femur length 1.61; fore femur width 0.62; fore tibia length 1.63; mid femur length 1.99; mid femur width 0.59; mid tibia length 1.48; hind femur length 5.11; hind femur maximal width 1.67; hind tibia length 4.08; proximal hind tarsal segment length 0.51; mid hind tarsal segment length 0.04; distal hind tarsal segment length 0.50.
1 | Fastigium of the vertex and frontal costa forming horn with rounded apex in dorsal view, in frontal and lateral view horn projecting above the eyes for more than one half of a compound eye height. Tegmina and wings visible and surpassing abdominal apex. [Colombia] | 2 |
– | Fastigium of the vertex and frontal costa forming horn with acute apex in dorsal view, in frontal and lateral view horn projecting above the eyes for less than one half of a compound eye height. Tegmina and wings not visible, infrascapular area visible in their place. | 3 |
2 | Horn directed forwards and upwards at about 30o in relation to the vertex between the eyes and pronotal disc. Tegmina and pronotum unicoloured [Colombia: Tolima] | Metopomystrum pehlkei Günther, 1939 |
– | Horn directed strongly upwards at about 45º in relation to the vertex between the eyes and pronotal discus. Ventral margin of tegmina and dorsal margin of pronotum yellowish. [Colombia: Santander] | Metopomystrum lilianae Cadena-Castañeda & Cardona, 2015 |
3 | Horn directed upwards, elevated in relation to pronotal disc for about one third of a compound eye height, in lateral view horn wide and with rounded apex, scutellum two times narrower than scapus, eyes in lateral view triangular. [Colombia: Amazonas] | Metopomystrum amazoniensis Cadena-Castañeda & Cardona, 2015, comb. resurr. |
– | Horn directed almost completely forwards, only slightly elevated above a compound eye, in lateral view horn thin and with triangular apex, scutellum three times narrower than scapus, eyes in lateral view rounded. [Brazil] | 4 |
4 | Horn directed forwards, slightly upwards, vertex narrow and acute in dorsal and lateral view | Metopomystrum muriciense Silva & Skejo, sp. n. |
– | Horn directed forwards, slightly downwards in its apex, vertex wider and more rounded in dorsal and lateral view | Metopomystrum apterum Günther, 1939 comb. resurr. |
Within Miriatrini and Cleostratini, Metopomystrum is the only genus comprising winged and wingless species. The problem of division of genera by the presence or lack of wings is widespread in Tetrigoidea taxonomy (e.g.,
Metopomystrum muriciense Silva & Skejo, sp. n. is the only known species of the genus that has small posthumeral spots. Metopomystrum species have very diverse coloration and probably colour varies within a species. A lot of Tetrigidae species are known to have huge colour pattern variation within and among populations (e.g.,
Information on habitat and distributions are lacking for the majority of species of the family Tetrigidae. Metopomystrum is not exception. This genus was erected by
The genus has a large gap in the known distribution between Colombia and Brazil (Fig.
The group proposed by
Africa and islands of the Indian Ocean: members of Rhynchotettix Hancock, 1907 (Madagascar, Metrodorinae) is unique genus in having toothed lateral lobes of the pronotum, directed outwards and forwards. Pseudomitraria has the frontal carina with part of the scutellum forming the horn, in a very unusual way.
Asia and Islands of SE Asia, Wallacea, Papua, and Oceania: Rostella Hancock, 1913 (Asia, Metrodorinae) resembles Pseudomitraria and Metopomystrum in the way the horn is formed in lateral view. However, Rostella, contrary to Metopomystrum, has a wide scutellum and is in pronotal morphology related to Metrodorinae and Scelimeninae (not Scelimenini) of Asia, such as Spadotettix Hancock, 1910; Indomiriatra Tinkham, 1939 and Eucriotettix Hebard, 1930. Spadotettix (India, SE Asia, Metrodorinae) does not have a produced vertex, its length usually being less than half of the eye height, as in Tetrix subulata (Linnaeus, 1758), among others. Morphologically, Spadotettix is more similar to Indomiriatra, formerly assigned to Spadotettix. Indomiriatra (India, Metrodorinae) and Spadotettix have a more produced vertex and stronger angles of the lateral lobes of the pronotum. Both genera are similar to certain members of Coptotettix Bolívar, 1887 (Tetriginae) and Criotettix Bolívar, 1887 (Scelimeninae), in broken median carina (discontinuous, with flattened parts) of the pronotum and with species with or without laterally projecting lobes, varying even within populations of one species Indomiriatra provertex could be regarded as a large species of Spadotettix. Thyrsus Bolívar, 1887 (Oceania) shares with Birmana Brunner von Wattenwyl, 1893 (Myanmar) and Clinophaestus Storozhenko, 2013 (Thailand) (last two Tripetalocerinae, Clinophaestini) interesting morphological characters-nymphs of all these genera have flattened antennal segments, the number of antennal segments is eleven, apical ones are reduced, the preapical, medial and sometimes the basal antennomeres are widened, and their hind-femora are very robust. Thyrsus is not related to Miriatrini in any sense, probably neither to Cleostratus. Members of the genus Cleostratus Stål, 1877 are unique in having the frons projecting as a horn, and the bifurcation of the frontal costa being above the compound eyes. Therefore it is left as single genus in Cleostratini since no other species of Tetrigidae exhibit a similar way in which the frons is projecting. Thus, Cleostratini, even monotypic, represent a more logical taxon than to group it with Miriatra.
Rhopalotettix, Pseudomitraria and Spadotettix are good examples that it is possible to find high variability of vertex prolongation among species of the same genus. This character is present in other Tetrigidae groups, like Clinotettix Bey-Bienko, 1933 (Tetriginae), whose members have a longer vertex than members of Spadotettix.
We conclude (1) that Cleostratini and Miriatrini stat. ressur. are not synonymous, because Cleostratus and Miriatra belong to morphologically and biogeographically different pygmy grasshopper groups, despite both of them having a horn, (2) that a prolonged horn occurs in different evolutionary groups of pygmy grasshoppers, and (3) that a prolonged horn is not an adequate character useful in Tetrigidae suprageneric taxonomy.
The study has benefited from grant aid and facilities from CNPq/ Edital Universal (Proc n° 461854/2014-7), CNPq/Programa SISBIOTA Brasil (Edital MCT/ CNPq/ MMA/ MEC/ CAPES/ FNDCT e FAPEMIG-Ação Transversal/FAPs 166 nº 47/2010, Proc. n° 563360/2010-0) and CNPq/ PROTAX (Proc. n° 440664/2015-2) and FAPEMIG APQ-04154-15. We thank Dr. Cristiano Lopes Andrade for microscopic facilities. We are grateful to Dr. Josef Tumbrinck (Germany) who reviewed the paper and gave us valuable comments. Authorization for collection activities for scientific purposes (MMA/ICMBio/SISBIO) n° 37717. Finally, we thank the anonymous reviewers for their comments on the manuscript.