Research Article |
Corresponding author: Ana Maria Leal-Zanchet ( zanchet@edu.unisinos.br ) Academic editor: David Gibson
© 2015 Stella Teles de Souza, Ana Laura Nunes Morais, Lívia Medeiros Cordeiro, Ana Maria Leal-Zanchet.
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:
de Souza ST, Morais ALM, Cordeiro LM, Leal-Zanchet AM (2015) The first troglobitic species of freshwater flatworm of the suborder Continenticola (Platyhelminthes) from South America. ZooKeys 470: 1-16. https://doi.org/10.3897/zookeys.470.8728
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Brazilian cave diversity, especially of invertebrates, is poorly known. The Bodoquena Plateau, which is located in the Cerrado Biome in central Brazil, has approximately 200 recorded caves with a rich system of subterranean water resources and high troglobitic diversity. Herein we describe a new troglobitic species of Girardia that represents the first obligate cave-dwelling species of the suborder Continenticola in South America. Specimens of the new species, which occur in a limestone cave in the Bodoquena Plateau, in the Cerrado biome, are unpigmented and eyeless. Species recognition in the genus Girardia is difficult, due to their great morphological resemblance. However, the new species can be easily recognized by a unique feature in its copulatory apparatus, namely a large, branched bulbar cavity with multiple diverticula.
New cave-dwelling species, subterranean diversity, Brazilian savannah, planarians, triclads
Despite a significant development of the speleobiology in Brazil over the last two decades, species diversity of Brazilian cave fauna has been highly underestimated (
The Bodoquena Plateau, in central Brazil (Mato Grosso do Sul), has approximately 200 recorded caves with a rich system of subterranean water resources from the phreatic level (
The diversity of freshwater triclads of the suborder Continenticola in the Neotropical region is considered to be low, and most of the species belong to the Dugesiidae genus Girardia Ball (
Triclad diversity in South American subterranean habitats is largely unknown.
Specimens were collected from the limestone cave “Buraco do Bicho”, located at 266 m a.s.l. in the karst area of Bodoquena Plateau (20°33’50”S and 56°43’50”W), Mato Grosso do Sul, Brazil (Fig.
Type-locality of Girardia multidiverticulata: 1 location of the “Buraco do Bicho” cave, in Bodoquena Plateau, Mato Grosso do Sul, Brazil, showing the range of limestone outcrops and the adjacent “Serra da Bodoquena” National Park 2 schematical drawing of the “Buraco do Bicho” cave from where the flatworms were sampled 3 cave entrance (arrow).
The flatworms were directly sampled from a lake (10 m2) in the cave, at a depth of 25 m from the narrow entrance of the cave (Figs
Live specimens were photographed in the field and in the laboratory (Figs
Girardia multidiverticulata: 4 photograph of a live specimen in ventral view soon after sampling 5 photograph of a live specimen, in ventral view, fed at the laboratory 6 photograph of a preserved specimen in ventral view. The tip of the pharynx is protruded (arrow) through the mouth. Scale bar for the Fig.
Type-material was deposited in the following reference collections: Museu de Zoologia da Universidade do Vale do Rio dos Sinos, São Leopoldo, Rio Grande do Sul, Brazil (MZU), and the Helminthological Collection of Museu de Zoologia da Universidade de São Paulo, São Paulo, São Paulo State, Brazil (MZUSP).
The flatworms were maintained in a permanently dark laboratory under a temperature of 24 °C for three years. They were kept in small tanks and fed weekly with live Artemia salina.
a: anterior tip; bc: bulbar cavity; br: brain; ca: copulatory apparatus; cb: copulatory bursa; cbc: bursal canal; cg: cyanophil glands; ceg: cement glands; cf: circular muscle fibers; ci: cilia; cm: circular cutaneous musculature; cs: cyanophil secretion; de: dorsal epidermis; di: diverticula of the bulbar cavity; eg: erythrophil glands; ej: ejaculatory duct; em: external pharyngeal musculature; es: esophagus; fa: female atrium; g: gonopore; go: gonoduct; i: intestine; im: internal pharyngeal musculature; in: insunk nuclei; lf: longitudinal muscle fibers; lm: longitudinal cutaneous musculature; lu: pharyngeal lumen; m: mouth; ma: male atrium; mm: muscles; n: nerve cord; o: ovary; om: oblique cutaneous musculature; ov: oviducts; pb: penis bulb; pg: penis glands; ph: pharynx; phg: pharyngeal glands; php: pharyngeal pouch; pp: penis papilla; r: rhabdites; rg: rhabditogen glands; s: sperm; sd: sperm duct; sg: shell glands; sv: spermiducal vesicle; t: testes; ve: ventral epidermis; vi: vitellaria; xg: xanthophil glands.
Holotype. MZUSP PL.1573: “Buraco do Bicho” cave, Bodoquena Plateau, Mato Grosso do Sul (MS), Brazil, July 2011, coll. L. M. Cordeiro & R. Borghezan, sagittal sections on 18 slides.
Paratypes. “Buraco do Bicho” cave, Bodoquena Plateau, MS, Brazil, July 2011, coll. L. M. Cordeiro & R. Borghezan. MZU PL.00184: sagittal sections on 61 slides; MZU PL.00185: sagittal sections on 8 slides; MZU PL.00186: transverse sections on 16 slides.
The species name refers to the multiple diverticula of the bulbar cavity.
Blind and unpigmented Girardia species characterized by a branched bulbar cavity with multiple irregular diverticula.
Live specimens unpigmented and eyeless (Figs
Measurements, in mm, of specimens of Girardia multidiverticulata, sp. n. DG: distance of gonopore from anterior end; DM: distance of mouth from anterior end. The numbers given in parentheses represent the position relative to body length. * Measurements after fixation; ** Measurements after histological processing; -: not measured.
Holotype MZUSP PL.1573 | Paratype MZU PL.00184 | Paratype MZU PL.00185 | Paratype MZU PL.00186 | |
---|---|---|---|---|
Length* | 16 | 20 | 12 | 14 |
Length** | 12.5 | 15 | 9 | 12 |
Width* | 2 | 3 | 2 | 3 |
DM | 9 (72%)* | 9 (60%)** | 6 (67%)** | - |
DG | 11 (88%)* | 10.5 (70%)** | 7 (78%)** | - |
Epidermis (Figs
Cutaneous musculature (Figs
Sensory organs. The auricular sensory organs are lined with densely ciliated, low cuboidal epithelium, with insunk nuclei. Few secretory cells open through this epithelium. The cutaneous musculature is very thin at the level of the sensory organs.
Digestive system (Figs
Male reproductive system (Figs
Girardia multidiverticulata, holotype in sagittal section (21–23); paratypes MZU PL.00186 in transverse section (24) and MZU PL.00184 in sagittal section (25–26): 21 detail of the copulatory bursa and its canal 22 detail of the proximal part of the female atrium 23 gonoduct 24 protruded penis papilla 25–26 male copulatory organs.
Numerous testicular follicles, 100–200 µm in diameter in the holotype, arranged in one irregular row on each side of the body. They are situated mainly ventrally (Fig.
Sperm ducts lined with a ciliated, cuboidal epithelium, becoming flattened in the spermiducal vesicles; they are coated with a circular muscle layer (3 µm thick in the holotype). The large penis bulb consists of a loose connective tissue containing abundant gland necks of penis glands and interwoven muscle fibers (Figs
Female reproductive system (Figs
Vitellaria well developed (Fig.
Ovovitelline ducts lined with ciliated, cuboidal epithelium with insunk nuclei and covered mainly by circular muscle fibres (2–3 µm thick in the holotype). Copulatory bursa lined with non-ciliated, columnar epithelium composed of cells with erythrophil secretion and cells with heavily stained, cyanophil secretion; it is covered by a thin muscle coat constituted by interwoven longitudinal and circular muscle fibres (5–8 µm thick in the holotype). The bursa of the holotype contains sperm and cyanophil secretion in its lumen (Figs
Known only from the type-locality (“Buraco do Bicho” cave), Bodoquena Plateau, Mato Grosso do Sul, Brazil.
In paratype MZU PL.00186 with contracted body, the penis papilla protrudes into the gonoduct and the bulbar cavity formes two main proximal chambers and one large distal one (Fig.
There was a density of about 5 to 10 flatworms per m2 in the lake that constitutes the type-locality of G. multidiverticulata. Other invertebrates, such as the spelaeogriphacean Potiicoara brasiliensis Pires, the amphipod Megagidiella sp. and an undetermined species of troglomorphic oligochaete, were also observed. The water level did not vary between June and August 2011, when field work was performed. The recorded values of temperature and conductivity were 23.1 °C and 0.55 mS.cm-1, respectively.
Flatworms maintained in the laboratory reproduced sexually and produced stalked egg capsules. Usually 2 to 3 specimens hatched from each egg capsule.
Due to the lack of eyes and body pigmentation, the troglobitic Girardia multidiverticulata differs from the majority of its congeners, which are pigmented, epigean organisms. It can be differentiated from the hipogean Girardia mckenziei (Mitchell & Kawakatsu) from Chiapas, Mexico, which has a smaller body length, dorsal surface with a slight, microscopic pigmentation and minute eyes (
Regarding the reproductive system, G. multidiverticulata has large, mainly ventral testes that occupy most of the dorso-ventral space of the body height, a large, branched bulbar cavity with multiple diverticula, and a stubby penis papilla. This combination of characteristics cannot be found in other species of Girardia from epigean or hipogean environments. The epigean species G. anderlani (Kawakatsu & Hauser) from the vicinity of São Leopoldo, southern Brazil, also has a large bulbar cavity, but with only two main chambers. In addition, this species has mainly ventral testes in two or three longitudinal rows and a conical and asymmetrical penis papilla (
Concluding, in comparison to other species of Girardia, most of which with very similar reproductive systems, the troglobitic G. multidiverticulata shows a unique feature in its copulatory apparatus, namely a large and branched bulbar cavity with multiple diverticula. Additionally, the new species has a combination of other characteristics of its external and internal morphology that differentiate it from its congeners.
We thank Prof Dr Eleonora Trajano (Universidade de São Paulo - USP, Brazil) for providing the laboratory conditions to keep live specimens. We acknowledge Rodrigo Borghezan (USP, Brazil), who first noticed the troglobitic planarians, for his help with field work and the technician Rafaela Canello (UNISINOS, Brazil) for her help in histological preparation. We also thank the Brazilian Research Council (CNPq) for the grants 477712/2006-1 and 143379/2009-7, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for grants and fellowships in support of this study. We acknowledge MSc Emily Toriani and MSc Edward Benya for the English review of the text. We gratefully thank Dr Leigh Winsor, Australia, for suggestions regarding anatomical descriptors. We are grateful to Prof Dr Masaharu Kawakatsu, Japan, and an anonymous reviewer for their valuable suggestions on an early draft of the paper.