Research Article |
Corresponding author: Ana Leal-Zanchet ( zanchet@edu.unisinos.br ) Academic editor: David Gibson
© 2014 Ana Leal-Zanchet, Stella Souza, Rodrigo Ferreira.
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:
Leal-Zanchet A, Souza S, Ferreira R (2014) A new genus and species for the first recorded cave-dwelling Cavernicola (Platyhelminthes) from South America. ZooKeys 442: 1-15. https://doi.org/10.3897/zookeys.442.8199
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Species diversity of Brazilian cave fauna has been seriously underestimated. A karst area located in Felipe Guerra, northeastern Brazil, which is a hotspot of subterranean diversity in Brazil, has revealed more than 20 troglobitic species, most of them still undescribed. Based on recent samplings in this karst area, we document the occurrence of the suborder Cavernicola (Platyhelminthes) in South American hypogean environments for the first time and describe a new genus and species for this suborder. Hausera Leal-Zanchet & Souza, gen. n. has features concordant with those defined for the family Dimarcusidae. The new genus is characterized by two unique features, viz. an intestine extending dorsally to the brain and ovovitelline ducts located dorsally to the nerve cords, which is complemented by a combination of other characters. The type-specimens of Hausera hauseri Leal-Zanchet & Souza, sp. n. are typical stygobionts, unpigmented and eyeless, and they may constitute an oceanic relict as is the case of other stygobiotic invertebrates found in this karst area in northeastern Brazil.
Troglobitic species, subterranean diversity, freshwater flatworms, triclads
Species diversity of Brazilian cave fauna has been seriously underestimated (
The triclad infraorder Cavernicola Sluys, 1990 was proposed to encompass five species of the family Dimarcusidae Mitchell & Kawakatsu, 1972 and now constitutes one of the three triclad suborders (
After erecting the taxon Cavernicola and since the description of Novomitchellia sarakawana (Kawakatsu & Chapman, 1983), no new species have been described for the family Dimarcusidae. In addition, the only known Cavernicola species from South America is R. evelinae, without records from subterranean habitats. Based on recent samplings in the Felipe Guerra karst area, northeastern Brazil, we provide here the first documentation of the family in South American hypogean environments by describing a new genus and species for this family.
Specimens were collected from the Crotes cave, a limestone outcrop located in Felipe Guerra (5°33'38.87"S; 37°39'31.80"W), Rio Grande do Norte, Brazil (Figs
Type-locality of Hausera hauseri Leal-Zanchet & Souza, sp. n.: 1–2 location in Rio Grande do Norte, Brazil, showing the range of limestone outcrops from the Apodi Group in detail (black) and the location of the Crotes cave (star) 3–4 surroundings of the main cave entrance (3) and aerial view of the region (4) indicating the cave contours (red/yellow line), main entrance (white arrow) and secondary gallery (red arrow); 5 perennial stream representing the sampling site.
During the field work, the specimens were photographed and fixed in ethanol 70%. Fixed specimens were analysed and photographed with a stereomicroscope. They were dehydrated and embedded in Paraplast. This material was sectioned at 5−7 µm and stained with hematoxyline/eosine or Goldner’s Masson (
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).
a: anterior tip; bc: bulbar cavity; br: brain; cg 1: cyanophil glands 1; cg 2: cyanophil glands 2; ci: cilia; cm: circular musculature; de: dorsal epidermis; eg: erythrophil glands; ej: ejaculatory duct; fgd: female genital duct; gic: genito-intestinal canal; i: intestine; in: insunk nuclei; lm: longitudinal musculature; m: mouth; ma: male atrium; o: ovary; ov: oviducts; pb: penis bulb; ph: pharynx; php: pharyngeal pouch; pp: penis papilla; r: rhabdites; rg: rhabditogen glands; s: sperm; sd: sperm duct; sg: shell glands; sv: seminal vesicle; t: testes; ve: ventral epidermis; vi: vitellaria; xg 1: xanthophil glands 1; xg 2: xanthophil glands 2.
Hausera hauseri Leal-Zanchet & Souza, sp. n. Monotypic
Dimarcusidae without eyes and without a copulatory bursa; female genital duct communicating with the intestine; ovovitelline ducts without caudal dichotomy, uniting to form a common ovovitelline duct; follicular testes; sperm ducts separately penetrating the penis bulb.
Felipe Guerra (Crotes cave), Brazil
The new genus is dedicated to the late Prof Dr Josef Hauser SJ as acknowledgement of his great enthusiasm for the study of freshwater flatworms. Gender: feminine.
The specimens of H. hauseri show features concordant with the definition of the family Dimarcusidae, viz. common oviduct or diverticulum oriented perpendicular to the horizontal bursal canal or female genital duct, penis bulb provided with glandular elements, ovaries generally located at some distance posterior to the brain, vasa deferentia (= sperm ducts) uniting to extra-bulbar common vas deferens or penetrating separately the penis bulb and testicular follicles fused or discrete (
It is worth mentioning that the specimens of H. hauseri have a connection with the intestine that could be confused with a copulatory bursa in which the branch of the intestine immediately posterior to the bursa may stain differently from other parts of the posterior intestinal branches. In all examined specimens, the connections with other parts of the posterior intestinal branches could be traced, leading to the conclusion that a bursa is absent in H. hauseri.
Similarly to Rhodax, Hausera gen. n. does not have a copulatory bursa. Other diagnostic characters of Rhodax, however, such as presence of eyes, fused testes, sperm ducts uniting before penetrating the penis bulb and ovovitelline ducts with a caudal dichotomy do not occur in Hausera gen. n. Similarly to Opisthobursa, the sperm ducts separately penetrate the penis bulb in the new genus, but the latter lacks a bursa, in contrast to the genus Opisthobursa.
Holotype. MZUSP PL. 1562: coll. R. Ferreira, 22 March 2011, Crotes cave, Felipe Guerra, RN, Brazil – sagittal sections on five slides.
Paratypes. Crotes cave, Felipe Guerra, RN, Brazil. MZU PL.00142: coll. R. Ferreira, 22 March 2011 – sagittal sections on 10 slides; MZU PL.00148: coll. R. Ferreira, 22 March 2011 – transverse sections on 9 slides; MZU PL.00149: coll. R. Ferreira, 05 June 2010 – anterior region: transverse sections on 12 slides, posterior region: sagittal sections on 20 slides.
Hausera hauseri can be distinguished from other species in the Dimarcusidae by (1) the numerous testicular follicles arranged in two irregular rows next to the margins of the body, extending from the level of the ovaries to the posterior end of the body; (2) the ovoid bulbar cavity with a posteriorly directed diverticulum into which the sperm ducts open; (3) a short and narrow transition region between the bulbar cavity and the ejaculatory duct; (4) the ovovitelline ducts arising from the lateral surface of the ovaries.
Live specimens unpigmented and eyeless (Fig.
Hausera hauseri Leal-Zanchet & Souza, sp. n.: 6–7 photograph of live specimens in dorsal view, one of them (6) with intestine containing food and the pharynx visible 8 photograph of a preserved specimen (paratype MZU PL.00142) in dorsal view; grains of sand are seen over the dorsal surface. Scale bar for the figs 6–7 not available.
Measurements, in mm, of specimens of Hausera hauseri Leal-Zanchet & Souza, sp. n. after fixation. 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 done after histological processing.
Holotype MZUSP PL. 1562 | Paratype MZU PL.00142 | Paratype MZU PL.00148 | Paratype MZU PL.00149 | |
---|---|---|---|---|
Length | 4.5 | 7 | 5 | 7.5 |
Width | 1.5 | 2 | 2 | 1.5 |
Length* | 4.2 | 6.7 | 4.7 | 7.2 |
DM* | 2.7 (64%) | 5 (75%) | 2.6 (55%) | 5.5 (76%) |
DG* | 3.6 (86%) | 5.5 (82%) | 3.4 (72%) | 6 (83%) |
Epidermis (Figs
Hausera hauseri Leal-Zanchet & Souza, sp. n.: holotype (9–10; 12) and paratype MZU PL.00148 (11). 9–10 dorsal (9) and ventral (10) surfaces of the body in sagittal section 11 detail of the cephalic region in transverse section showing a sensory organ (rectangle) 12 sagittal section of the pharynx.
Cutaneous musculature (Figs
Sensory organs (Fig.
Pharynx (Fig.
Intestine (Figs
Male reproductive system (Figs
Hausera hauseri Leal-Zanchet & Souza, sp. n.: paratype MZU PL.00148 (13; 15–16) and holotype (14; 17) 13 transverse section of the body 14 sagittal section of the posterior tip 15–17 copulatory apparatus in transverse section (15–16) and sagittal section (17). The arrow indicates the diverticulum of the bulbar cavity.
Sperm ducts lined with a ciliated, cuboidal epithelium, underlain by a circular muscle layer. The large penis bulb consists of a loose connective tissue with weak interwoven muscle fibres (Figs
Female reproductive system (Figs
Hausera hauseri Leal-Zanchet & Souza, sp. n.: holotype (19; 22) and paratype MZU PL.00148 (20–21; 23–24). 19 cephalic region in sagittal section 20 detail of the ovary and ovovitelline duct in transverse section 21–22 detail of the copulatory apparatus in transverse section (21) and sagittal section (22) 23–24 cephalic region in transverse section. The arrow indicates a slit in the ventral surface of the body.
Ovovitelline ducts lined with ciliated, cuboidal epithelium, receiving the secretion of shell glands in their most posterior sections (Figs
The new species is dedicated to the late Prof Dr Josef Hauser SJ.
Known only from the type-locality, Felipe Guerra (Crotes cave), Brazil.
Vitellaria well-developed in paratype MZU PL.00148 and poorly developed in paratypes MZU PL.00142 and PL.00149. In paratype MZU PL.00148, the anterior region of the body is subcylindrical in transverse section (Fig.
There are no genera within the Dimarcusidae into which we could comfortably include the species herein described; thus, the new genus Hausera is here proposed. Besides the combination of characters discussed above, the new genus is characterized by two unique features within its family: intestinal branch extending dorsally to the brain and ovovitelline ducts located dorsally to the nerve cords. According to
The type-locality of H. hauseri, a karst area located in Felipe Guerra, is unique in comparison with other karst areas in Brazil. Most limestone formations in Brazil are located in inner portions of the country, which in the past must have prevented marine groups from colonizing these caves. In contrast, the Felipe Guerra karst is located near the sea, and its limestone outcrops are at low altitude, which has allowed different invertebrates to colonize the caves during sea level rises in the past. Accordingly, many stygobiotic species found there represents oceanic relicts. They have evolved from marine ancestors trapped in the caves after isolation by events of introgression and regression of the ocean in the area, probably during the Terciary Period. This is the case of stygobiotic amphipods (
We thank Jocy Cruz, Diego Bento, José Iatagan Freitas, Uilson Campos and Darcy Santos (from CECAV- Rio Grande do Norte) for their invaluable help during expeditions into Rio Grande do Norte caves and Geilson Goes and Maria Gorete Goes and their family for their hospitality in Felipe Guerra. We acknowledge the entire staff of the CEBS (Centro de Estudos em Biologia Subterrânea - UFLA) for their efforts in the collections and Ana Laura Nunes and Rafaela Canello (UNISINOS) for their help in histological preparation. We thank Emily Toriani for the English review of the text. We also thank the Brazilian Research Council (CNPq), under grants 477712/2006-1, 301061/2011-4 and 309334/2012-8, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for grants and fellowships in support of this study. We are grateful to Prof Dr Masaharu Kawakatsu, Japan, and an anonymous reviewer for their valuable suggestions on an early draft of the paper.