See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/226578190 Ecology of Subterranean Fishes: An Overview Article in Environmental Biology of Fishes · October 2001 DOI: 10.1023/A:1011841913569 CITATIONS READS 59 107 1 author: Eleonora Trajano Universidade Federal de São Carlos (UFSCa… 90 PUBLICATIONS 1,177 CITATIONS SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, Available from: Eleonora Trajano letting you access and read them immediately. Retrieved on: 08 September 2016 Environmental Biology of Fishes 62: 133–160, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands. Ecology of subterranean fishes: an overview Eleonora Trajano Departamento de Zoologia, Instituto de Biocienciasˆ da USP, C. P. 11461, 05422-970, Sao˜ Paulo SP, Brazil (e-mail: [email protected]) Received 26 April 2000 Accepted 14 January 2001 Key words: troglobitic fishes, population ecology, fish movements, life cycle, Ancistrus Synopsis A synthesis of ecological data available for subterranean fishes throughout the world is presented, and comparatively analyzed in an evolutionary context. Methods of ecological research are described, and their potential and limitations for the study of hypogean fishes are discussed. Ecology of troglobitic (exclusively subterranean) fishes is discussed with focus on distribution areas, population densities and sizes, use of habitat and movements, life cycle and feeding. When data are available, these species are compared with their epigean relatives. Putative ecological autapomorphies of troglobitic fishes, including habitat change, adaptations to cope with food scarcity, and precocial lifestyles, are interpreted in ecological and evolutionary contexts. Species interactions among subterranean species, including cases of syntopy and predation are briefly analyzed. Non-troglobitic hypogean fishes, with their ecological importance and evolutionary role, are also addressed. Problems of classification of subterranean fishes according to the Schiner-Racovitza system (troglobites, troglophiles and trogloxenes) are discussed, and a scenario of evolution of subterranean populations is presented. Introduction among others), the majority being found in caves. Cave fishes are fairly easy to investigate in the field because Troglobites, or species restricted to the subterranean they are relatively large, generally conspicuous, and habitat, usually show a series of autapomorphies not difficult to observe and collect, as many species (troglomorphisms), including morphological, physio- have lost phobic reactions and show increased activ- logical, behavioral and ecological features, which can ity. Nevertheless, there have been few studies in this be directly or indirectly related to the hypogean life, area, partly because ecological investigations require being either adaptive or not (for a discussion of theories long-term permanence in the field and many troglobitic about character evolution in the cave habitat, see Culver fishes occur in tropical regions, sometimes in caves of et al. 1995). The most common morphological traits difficult access, where there are few local researchers. characterizing troglobites are reduction of both eyes The relatively abundant cavefish literature (about and pigmentation. Ecological traits frequently cited for 1600 references, G. Proudlove personal communica- troglobites include low population sizes, restricted geo- tion) is dominated by studies on systematics, genetics, graphic distribution, low tolerance to environmental morphology, physiology and behavior in the labora- stress, precocial life cycle features (e.g., Culver 1982, tory and focuses on few taxa, especially the blind Trajano 1997a) related to the life under permanent Mexican characins, genus Astyanax, followed by North darkness, few environmental cues, usually restricted American amblyopsids. A low proportion of these pub- space, and frequent food scarcity. lications (fewer than 4%) dealt strictly with ecology of More than 86 species of subterranean troglobitic subterranean fishes. fishes belonging to 18 families in nine orders have One can trace ecological data scattered in the been recorded throughout the world (Weber et al. 1998 literature on cave fishes, including habitat descriptions 134 and comments on habitat use, abundance, reproduction to distinguish between plesiomorphic character states and behavior, back to Eigenmann’s (1909) ‘Cave Verte- and ecological autapomorphies of troglobites, result- brates of America’, or earlier. However, detailed eco- ing from specialization to the particular conditions logical studies with population analyses started with in the subterranean habitat. Because few troglobitic the investigation of the African cyprinid, Caecobarbus species, and even fewer epigean relatives, have been geertsii, by Heuts (1952). Some years earlier, Pavan studied with focus on ecological aspects, general pat- (1946) published a population study on the Brazilian terns may be difficult to visualize. The present overview blind catfish, Pimelodella kronei, but essentially within shows how much there still is to be learned about these an evolutionary context. Among the ecological stud- fascinating animals. ies published since then, we can mention the compre- hensive study on the North American amblyopsids by Poulson (1963), also the object of recent studies by Methods of ecological studies in subterranean Means & Johnson (1995) and Brown (1996); the rare fishes: a comparative analysis ecological studies on the otherwise intensively inves- tigated Mexican blind tetras, Astyanax spp. (Mitchell Basically, three kinds of methods have been used in et al. 1977, Parzefall 1983); and a series of ecologi- studies of the ecology of subterranean fishes: extensive cal studies on Brazilian troglobitic catfishes published collections of preserved samples, direct observation in the last decade (Trajano 1991, 1997a,b, Mendes in the habitat, and capture-mark-recapture programs. 1995a,b, Trajano & Bockmann 2000). Different methods are the most useful for investigating These works included information on population different aspects of ecology, and each one has its advan- sizes and densities, fish movements and life history tages and limitations. Therefore, they must be regarded aspects besides feeding (reproduction, growth rates, as complementary. etc.). However, few authors studied feeding beyond Two methods have been applied to determine pop- general diet (as Trajano 1997b, focusing on temporal ulation sizes and densities in cave fishes: visual cen- variation and seasonality). Likewise, few publica- suses (VC) and mark-recapture (MR) techniques. In tions included a detailed description of cavefish habi- visual censuses, ‘instantaneous’ counts of the num- tats (as those by Heuts 1952, for C. geertsi, and ber of fish seen in the habitat are made from the sur- Mitchell et al. 1977, for Astyanax spp.) and habi- face or during snorkeling or SCUBA diving. These tat preferences. Mitchell et al. (1977) made the most censuses may encompass the total accessible habi- 1 thoughtful and comprehensive description of habitats tat, as done for amblyopsids (Poulson , Willis & occupied by cave fishes, listing and describing all Brown 1985, Brown & Todd 1987) and the Brazil- localities known for Mexican troglobitic Astyanax, and ian catfish, Taunayia sp. (Trajano & Bockmann 2000). detailing the geomorphology and hydrology in the so- In other cases, selected sections of the cave habi- called Huastecan Province; such a publication provides tat are inspected, such as small areas, for Astyanax a solid basis for discussion of the origin and evolu- spp. (Parzefall 1983), transects, for an undescribed tion of these populations. The modern tendency is to genus and species of Brazilian heptapterine from NE greatly abbreviate habitat descriptions, which rarely Brazil (Mendes 1995a – the species is here cited as include good maps, and information on fish microhab- Imparfinis sp.), or stream sectors, for Thai balitorids, itats based on careful field and laboratory observation Schistura oedipus and Cryptotora thamicola (Trajano, is scarce, making it difficult to get a proper notion of Borowsky, Mugue & Smart unpublished data). habitat use. Therefore, ecological aspects such as habi- Visual censuses produce estimates of minimum pop- tat change and specialization are usually overlooked. ulation densities, from which one can calculate the total Herein I present an overview of results from ecolog- population size if: (1) the total habitat area occupied by ical studies on hypogean fishes throughout the world, the fish population is known, and (2) population den- comparatively analyzing data on population sizes and sity remains constant throughout this area. These two densities, use of space (habitat, movements, species conditions are rarely met and such estimates generally syntopy), feeding and life history of different taxa, as a provide only a rough comparative notion of minimum contribution to the knowledge of fish species restricted to this special habitat. When data are available, subter- 1 Poulson, T.L. 1969. Population size, density and regulation ranean populations were compared to those of epigean in cave fishes. pp. 4–5. In: Proc. 4th International Congress of close relatives living in the same area, in an attempt Speleology, Ljubljana. 135 population sizes. We must keep in mind that VC pro- juveniles) have been included in this kind of study, duce underestimates, especially when done from