Gymnotiformes

(South American knifefishes and electric eels)

Class Actinopterygii

Order Gymnotiformes

Number of families 5

Evolution and systematics

South American freshwaters are dominated by fishes in the superorder Ostariophysi: the siluriforms, characiforms, and gymnotiforms together comprise more than 75% of all the known freshwater species in South America. Recent data based on cladistic methodology strongly indicate that Gymnotiformes and Siluriformes are sister groups within the Ostariophysi. Of the three Neotropical ostariophysan orders, the gymnotiforms have the smallest number of species. It is also the least investigated group as far as systematics and ecology are concerned. This is largely because many species are difficult to distinguish, hard to catch, especially in their preferred deep riverine benthic habitats, and finally yet importantly are of little commercial interest. The first known gymnotiform fish, now known as Gymnotus carapo, was described in 1648. In 1758 Linnaeus described four species, today known as Electrophorus electricus, Gymnotus carapo, Rhamphichthys rostratus, and Apteronotus albifrons. Our main understanding of the systematics of these fishes is based on work performed during the past 20 years. Science now recognizes 105 described and at least 32 undescribed species, grouped within 29 genera and 5 families. The family Gymnotidae includes 17 described species, the family Rhamphichthyidae 13, and the family Hypopomidae 15 species. The fishes of these families have retained the plesiomorphic pulse-type electric organ discharge. Twenty-four species are grouped in the family Sternopygidae and 43 in the family Apteronotidae; these knifefishes produce the derived tone-type electric organ discharge.

Sternopygus astrabes most closely resembles the ancestral gymnotiform phenotype. Gayet and Meunier in 1991 described the first fossil gymnotiform fish, Ellisella kirschbaumi, from the Upper Miocene (about 10 million years ago) from Bolivia. However, the morphological characteristics of E. kirschbaumi—the absence of dorsal and pelvic fins and the replacement of the caudal fin by a long bony cartilaginous rod (as seen in sternopygids) in the regenerated caudal part—indicate that knifefishes are much older than 10 million years.

Physical characteristics

The Gymnotiformes constitute a group of rather specialized fishes. In most species, the body is compressed laterally, very elongated and slender, with long caudal appendages and a long anal fin tht resembles a knife (thus the name knifefishes). The fishes lack pelvic and dorsal fins; the dorsal filament of the Apteronotidae is sometimes interpreted as a rudiment of an adipose fin, but it might also be modified muscle. The caudal fin is replaced by the caudal appendage except in the apteronotids, which possess a reduced caudal fin that is interpreted by some authors as being derived from the caudal appendage and not representing an intermediate state in the loss of a caudal fin. All gymnotiform fishes possess an extremely well-developed ability to regenerate the caudal, or hind, parts of their bodies. In the apteronotids, however, this feature is less pronounced.

The caudal appendage represents an extension at the end of the anal fin, including the axial skeleton (a bony rod in most cases), the spinal cord, the remaining soft tissues, and the electric organ. A derived feature of gymnotiform fishes is their head morphology, which apparently reflects an adaptation for specialized feeding. For example, some knifefishes possess large mouths (Gymnotus, some Apteronotus) and feed on large prey; some possess terminal mouths (Rhabdolichops, Eigenmannia) and feed on insect larvae and on plankton; some posses external teeth (Oedemognathus) and feed on scales; some posses a long curved mouth (Sternarchorhynchus) and search

for insect larvae in holes and crevices. The same variations in head morphology, related to feeding, are found in the African mormyrid fishes.

The most outstanding feature of the knifefishes is the possession of electroreceptors and electric organs in the skin. In some Rhabdolichops species, the large transparent electric cells in the tail region can be easily seen by external inspection. Electrophorus electricus is characterized by strong electric discharges up to 700 volts (V) at more than 1 ampere, or amp(A); in addition, this species can emit weakly electrical discharges for orientation. All the remaining knifefishes produce weakly electrical discharges around 1 V. The electric organs are derived from muscle, except in apteronotids, where modified spinal axons constitute the electric organ. Some species, such as Steatogenys elegans and Hypopygus lepturus, possess accessory electric organs in the head region. Larvae of some species (families Sternopygidae, Apteronotidae) differentiate larval electric organs early during their development.

Distribution

Gymnotiform fishes occur in all Neotropical river systems, from the Rio Salado in the pampas of Argentina to the Rio San Nicolas of Chiapas in Mexico. Species diversity is highest in the Amazon river system (89 species), followed by the Orinoco river system (61 species), rivers found in the Guyanas (35 species), and the Parana-Paraguay river system (26 species). Fourteen species occur in northwestern South America, twelve in southeastern Brazil and in Uruguay, nine in northeastern Brazil, seven on the Pacific slope of South America, seven in Central America, and just one species in the Rio Sali-Dulce of northwestern Argentina and on the island of Trinidad.

Largely because of their poorly understood systematics, the distribution of gymnotiforms at the species level is not well known. The most widely distributed species seem to be Gymnotus carapo, Brachyhypopomus pinnicaudatus, Apteronotus albifrons, Eigenmannia lineata, and Sternopygus macrurus. Not surprisingly, these are the species most commonly encountered in the tropical fish trade.

Habitat

Most rivers in tropical South America can be classified according to water conditions: white water (e.g., the Amazon), black water (e.g., the Rio Negro) or clear water (e.g., the Rio Tapachos). All three types are characterized by low pH values (from 7 down to 3.5) and low levels of salts and nutrients. The freshwater systems of Central America have higher levels of mineral content due to their different geology. Gymnotiform fishes occur in all three major water types. In the extremely acidic and nutrient-poor black waters of the Rio Negro, 36 gymnotiform species have been found. Knifefishes occur in small streams, large rivers, lakes, and various types of backwaters. The enormous abundance of gymnotiforms that occur in deep, main-river channels was only recently discovered (1980s): in the Orinoco River system, for example, 86% of the fish species are gymnotiforms. It is still not well understood why this predominance occurs in this type of habitat.

Some knifefishes show adaptations to habitats with low oxygen. The electric eel (Electrophorus electricus; modified buccal cavity) and the banded knifefish (Gymnotus carapo; swim bladder) can take air from the water surface, as can several species of Brachyhypopomus. The electric eel is an obligatory air breather and drowns if denied access to atmospheric air. However, as long as its skin is kept moist, it can survive for several hours out of water. A large embryonic fin fold of the gymnotiform free embryos serves as a respiratory organ during early development.

Most gymnotiform fishes tolerate temperatures between 68 and 92°F (20 and 35°C); a few species, however, have been found in colder waters. Apteronotus sp. and the glass knifefish (Eigenmannia lineata) occurred in considerable quantities in the Huallaga River (about 64.4°F or 18°C in the tropical mountain rainforest near Tingo Maria, Peru). Under experimental conditions, Sternarchorhynchus sp. did not survive below 77°F (25°C), but tolerated temperatures up to 98.6°F (37°C). For Sternopygus sp., the range was 66.2–86°F (19–30°C).

In the field, gymnotiforms can tolerate pH values of 7 (Amazon) to below 4 (black water). In captivity, the glass knifefish tolerates a pH range between 3.5 and 8.4!

Behavior

Knifefishes are nocturnal, hiding during daytime between plants, in floating meadows, in crevices and holes, and under various kinds of shelter. During the day some species, such as Rhamphichthys rostratus and Steatogenys elegans, lie flat and motionless on the bottom, imitating marbled leaves. Species of the genus Gymnorhamphichthys burrow in the sand during daytime.

Gymnotiforms move by undulating the elongate anal fin that extends along most of the ventral part of the body. In as sociation with this form of locomotion, the anal fin rays articulate directly with proximal pterygophores, providing the fin rays unrestricted mobility. The caudal, elongate portion of the body is maintained in a rigid posture by numerous intermuscular bones. This facilitates the use of the integument as a sensory sheet due to the presence of numerous electroreceptors. This mechanism is used for object location. The presence of an individual nearby with an electric organ discharge frequency of similar magnitude disturbs the object location performance of the fish: a shift in frequency occurs, which is termed the jamming avoidance response.

Feeding ecology and diet

The food of knifefishes is of indigenous origin, mostly insect larvae, annelid worms, and crustaceans. The banded knifefish predominantly feeds on shrimp and smaller fishes, as do some larger knifefishes. Electric eels are also piscivorous and include their own weakly electric relatives in their diet. Regardless of seasonal changes, Rhamphichthys marmoratus does not change its diet, which consists mostly of chironomids (Diptera) and polymitarcids (Ephemeroptera).

Ontogenetic change in the diet is documented for the banded knifefish: up to 7.9 in (20 cm) the principal food items are aquatic insects, predominantly chironomid larvae; beyond 7.9 in (20 cm) the fish prefer large insect larvae (Odonates), shrimp, and fish, preferably small characids (genera Ctenobrycon and Curimata). This change in diet coincides with the time when the banded knifefish females reach first maturity (9.8 in/25 cm, 2 years old).

Species of the genus Rhabdolichops possess well-developed gill rakers and are known to be effective plankton feeders. The knifefish Oedemognathus exodon feeds on scales of fishes. The knifefish Magosternarchus duccis, from the murky channel of the Amazon, chiefly eats the tails of other knifefishes (these do regenerate afterward).

The importance of gymnotiforms as part of the food chain is demonstrated in the case of top predators of the pimelodid family, the catfishes; fifteen commercially important pimelodid species of the Rio Apure in Venezuela include gymnotiforms in their diet. Most pimelodids feed on only one or two species; however, some pimelodids, such as Brachyplatystoma rousseauxii, feed on a maximum of five species.

Reproductive biology

Reproduction in most species occurs during the highwater season. Experimental studies have shown that gonad maturation is triggered mainly by decreasing water conductivity and increasing water level. Information on reproductive biology has been gathered from a limited number of species (8-9), but has consistently revealed diverse reproductive strategies. The electric eel breeds during the dry season in small ponds. The male builds a foam nest at the water surface between the adventitious roots of the plant Montrichardia arborescens. The eggs are deposited in the

foam nest, and at the beginning of exogenous feeding, the larvae feed on eggs of subsequent ovipositions. Juveniles are guarded up to a length of 3.9 in (10 cm). The males of the banded knifefish are mouth breeders and guard the fry afterward. The longtail knifefish (Sternopygus macrurus) is a substrate spawner and guards the eggs until hatching. Other knifefishes hide the eggs in plants, in between roots, or in crevices. All species are fractional spawners, with spawning intervals of a few days up to several weeks. Egg diameter varies between 0.08 and 0.1 in (0.2 cm and 0.3 cm). Some species live in pairs during reproduction; others form complicated social hierarchies that are based on size, motor components of aggressive behavior, and seasonal conditions. Best studied in this respect is the glass knifefish (Eigenmannia lineata).

During courtship behavior, the electrical discharges serve various purposes: males and females often produce different electrical discharge frequencies, and frequency modulations of the male discharge can trigger oviposition. Large amplitudes characterize dominant males, differences in the form of the discharge occur between males and females.

During the breeding season the males of the Rosen knifefish (Sternarchorhynchus roseni) develop external teeth; these knifefishes are very territorial and rather aggressive. The males of gymnotiforms often grow larger than the females. Males of several species of the genus Apteronotus develop longer heads than the females.

Conservation status

No gymnotiform species are listed by the IUCN.

Significance to humans

The strongly electric Electrophorus electricus was for decades a preferred animal for the study of basic bioelectric phenomena. The physiology, anatomy, and behavior of weakly electric knifefishes have been studied intensively, particularly in the context of orientation (object location) and electrocommunication. Some larger knifefishes, such as Rhamphichthys rostratus and the longtail knifefish are locally of some economical importance in fisheries.

Species accounts

List of Species

Black ghost

Apteronotus albifrons

family

Apteronotidae

taxonomy

Apteronotus albifrons Linnaeus, 1766, South America.

other common names

English: Apteronotid eel; French: Poisson-couteau; German: Amerikanischer Weißstirnmesserfisch.

physical characteristics

Size 11.8 to 19.7 in (30 to 50 cm). They are completely black, except for a yellow frontal longitudinal stripe and two whitish transversal bands at the end of the anal fin and just before the black caudal fin. The males have longer heads than the females. The species is weakly electric.

distribution

Amazon, Orinoco, Parana-Paraguay river systems; rivers in French Guiana.

habitat

Occurs near undercut banks and in wooden debris along river and stream margins, as well as in densely vegetated habitats.

behavior

Gregarious and nocturnal. During swimming movements they are not always in an upright position, often turning their body parallel to the ground.

feeding ecology and diet

Various kinds of aquatic insect larvae, as well as ants and termites. The larger fishes also eat shrimps and fishes.

reproductive biology

Breeding groups of black ghosts are composed of several males and females. As oviposition does not occur in regular intervals, single eggs of 0.1 in (0.3 cm) are deposited in holes and crevices, rather irregularly. The embryos hatch on day three, feeding starts on day 10.

conservation status

Not listed by the IUCN

significance to humans

Black ghosts are the most common knifefishes in the tropical-fish trade. They are regarded by indigenous people with superstition, as they are reputed to be inhabited by a ghost or an evil spirit.

No common name

Sternarchorhynchus curvirostris

family

Apteronotidae

taxonomy

Sternarchorhynchus curvirostris Boulenger, 1887, Canelos, Ecuador.

other common names

None known.

physical characteristics

Size from 15.7 to 19.7 in (40 to 50 cm). Their bodies are extremely compressed, with a pronounced curved snout; they lack dorsal and pelvic fins. The skin is uniformly brown. The electric organ is weak as it is derived from nerve cells (neurogenic) as opposed to muscle tissue (myogenic).

distribution

Amazon and Orinoco river systems; rivers in the Guyanas.

habitat

Channel bottom of large rivers.

behavior

Nocturnal, feeding (and probably spawning) at night. Territorial and rather aggressive.

feeding ecology and diet

Insect larvae and possibly smaller crustaceans.

reproductive biology

Probably spawn during the rainy season. Other details of their reproductive biology are not known.

conservation status

Not listed by IUCN. They are common throughout their range of distribution but at low densities.

significance to humans

None known.

Electric eel

Electrophorus electricus

family

Gymnotidae

taxonomy

Electrophorus electricus Linnaeus, 1766, South America.

other common names

French: Anguille électrique; anguille trembleuse; German: Zitteraal; Spanish: Anguilla, anguilla electrica; Portuguese: Poraquê.

physical characteristics

Electric eels are the largest of all knifefishes, up to 8 ft (2.4 m) long. They lack dorsal, caudal, and pelvic fins, and do not have scales. The color is a uniform dull olive to almost black, yellowish to orange underneath the head and throat. These fishes produce strong electric discharges up to 700 volts.

distribution

Rivers in the Guyanas; the Amazon and Orinoco river systems.

habitat

Occurs in creeks and ponds, and along the banks of lakes.

behavior

Nocturnal. They hide during the day under shelter or in holes. They are sometimes gregarious.

feeding ecology and diet

These fishes are mostly piscivorous (they stun prey with electric shocks), but they also eat amphibians.

reproductive biology

These fishes breed during the dry season in small ponds. The male builds a foam nest. The larvae first eat eggs of subsequent spawnings, then change diet to insect larvae. Piscivorous feeding starts at around 3.9 in (10 cm); the males guard juveniles up to this size.

conservation status

Not listed by the IUCN. They are common throughout their range of distribution but at low densities.

significance to humans

Electric eels have been used for basic studies on bioelectric phenomena.

Banded knifefish

Gymnotus carapo

family

Gymnotidae

taxonomy

Gymnotus carapo Linnaeus, 1758, South America.

other common names

English: Eel knifefish; gymnotid eel; cutlass fish; French: Coutelas; German: Gebänderter Messerfisch.

physical characteristics

Banded knifefishes range in size from 19.7 to 23.6 in (50 to 60 cm). They have an eel-like body shape, with a blunt head, and extend to a fine point at the tip of the tail. The anal fin originates close behind the anus and continues to the tip of the tail. These fishes are variable in color, with many dark bands, and are sometimes mottled. The bands become increasingly narrow toward the tail. Banded knifefishes are air-breathing (with swim bladder), and are weakly electric.

distribution

Tropical South America from Venezuela to Uruguay, including Trinidad.

habitat

Creeks and ponds and along the banks of lakes and rivers.

behavior

Nocturnal, hiding during daytime under various types of shelter. They are territorial, defending areas of several square yards (meters).

feeding ecology and diet

Banded knifefishes up to 7.9 in (20 cm) long eat insect larvae; afterwards odonats (dragonflies), shrimps, and fish.

reproductive biology

Banded knifefishes spawn during the rainy season. Sticky eggs are deposited in between the stalks of plants. Males build nests from plant material and guard the free embryos in their mouths until the start of exogenous feeding. The first reproduction in captivity was in 1999.

conservation status

Not listed by the IUCN. They are widespread and common but at low densities.

significance to humans

These weakly electric fishes are studied regularly for scientific purposes. They are extensively fished for and eaten in their native range.

No common name

Brachyhypopomus pinnicaudatus

family

Hypopomidae

taxonomy

Brachyhypopomus pinnicaudatus Hopkins 1991 coastal swamp in French Guiana, 3.5 km northwest of Kourou.

other common names

French: Poisson-couteau; Creole/French: Poson-sab, bloblo; Portuguese: Tuvira, itui.

physical characteristics

These fishes range in size from 4.7 to 5.9 in (12 to 15 cm). Their bodies are compressed laterally; they lack dorsal, tail, and pelvic fins. Their bodies have a light-brown or reddish background with 22–25 narrow, dark brown bands running from the base of the anal fin dorsally to the lateral line. The dorsal surface is dark brown and reticulated, with distinct contrasting borders. The tail filament is compressed in males, pointed in females. These fishes are weakly electric.

distribution

Rivers in French Guiana and southeastern Brazil; Amazon and Parana-Paraguay river systems.

habitat

Occurs along the edges of slow-moving rivers and in standing water, often in dense vegetation that becomes stagnant and partially deoxygenated.

behavior

Nocturnal, resting during the day in dense vegetation.

feeding ecology and diet

Aquatic insects and copepods (small crustaceans).

reproductive biology

Reproduction in these fishes occurs mainly during the high-water season; some populations seem to show aperiodical reproduction. Sticky eggs are deposited in crevices and holes, and in between plants. The embryos hatch on day three, exogenous feeding starts on day eight to nine; the juveniles grow quickly.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Bandfish

Rhamphichthys rostratus

family

Rhamphichtyidae

taxonomy

Rhamphichthys rostratus Linnaeus, 1766, South America.

other common names

Spanish: Bombilla (Argentina), cuchillo (Venezuela); French Guiana: Wabri.

physical characteristics

Bandfishes range in size from 3.3 to 4.9 ft (1 to 1.5 m). This most striking knifefish has a long, trunklike snout, ending in a small mouth. Otherwise, the body form is as in most knifefishes. Bandfishes lack dorsal, tail, and pelvic fins. They are medium brown in color, with blotches of dark brown and black on the back, and brown mottling on the sides. They are weakly electric.

distribution

Amazon, Parana-Paraguay, and Orinoco river systems; rivers of Guyana and northeastern Brazil.

habitat

Small and more open streams, and occasionally in large rivers.

behavior

Nocturnal. During the day they hide motionless in plants or on the bottom.

feeding ecology and diet

Bandfishes are bottom feeders; they eat oligochaets (annelid worms) and insect larvae.

reproductive biology

Bandfishes spawn during the rainy season. Data on reproduction in captivity known from one Rhamphichtys species, probably R. rostratus. About 1,000 sticky eggs are deposited in crevices; the embryos have attachment organs. Spawning intervals between three and four weeks. Juveniles show quick growth.

conservation status

Not listed by the IUCN. They are widespread and common but at low densities.

significance to humans

Bandfishes are highly regarded as a food fish in areas where they are common.

Glass knifefish

Eigenmannia lineata

family

Sternopygidae

taxonomy

Eigenmannia lineata Müller and Troschel, 1849, Lake Amucu, French Guiana.

other common names

English: Green knifefish; German: Grüner Messerfisch; Spanish: Chucho, ratón, mayupa; Portuguese: Tuvira.

physical characteristics

Female glass knifefishes are 7.9 (20 cm) long; males are 13.8 in (35 cm). Their bodies are slender and compressed, possessing only pectoral fins and the very long anal fin. Most of the fish is very transparent, except in the head region. There are three black stripes running lengthwise along the body. Glass knifefishes are weakly electric.

distribution

Amazon, Orinoco, and Parana-Paraguay river systems.

habitat

Occurs near undercut banks and in wooden debris along river and stream margins; in the open-water areas of small creeks, lagoons, and marshes; and particularly in densely vegetated habitats of river margins.

behavior

Gregarious and nocturnal. During daytime can be sometimes found in large numbers in hiding places.

feeding ecology and diet

Aquatic insect larvae and crustaceans.

reproductive biology

Glass knifefishes spawn during rainy season; breeding groups of several fish establish complicated social hierarchies. The dominant male spawns with the ripe female at night. Sticky eggs are deposited on floating plants; they hatch on day three. Exogenous feeding begins on day eight.

conservation status

Not threatened.

significance to humans

Glass knifefishes are the most intensively studied species of knifefish. They are often designated as Eigenmannia virescens. The systematics of the genus Eigenmannia is very difficult, which often leads to misidentification. The fish sold in the fish trade is in general called E. virescens (this name therefore often appears in scientific papers); however, the morphological features of this fish make it clear that it is not E. virescens but rather E. lineata.

Longtail knifefish

Sternopygus macrurus

family

Sternopygidae

taxonomy

Sternopygus macrurus Bloch and Schneider, 1801, Brazil.

other common names

English: Ghost knifefish; Spanish: Bio del rio.

physical characteristics

Longtail knifefishes range in size from 23.6 to 31.5 in (60 to 80 cm), and are among the largest knifefishes. They have a pale yellow skin, a large black humeral spot; and a pale-yellow or white longitudinal stripe along the base of the anal fin, pterygiophores, and lateral midline posteriorly. They are weakly electric.

distribution

Amazon, Orinoco, and Parana-Paraguay river systems; rivers of northeastern and southeastern Brazil.

habitat

Widely distributed in streams, trenches, ditches, and the back waters of rivers in open savanna and in plantations.

behavior

Mainly active at dusk and dawn, when the light level is low; they forage at night. They are territorial, slow-moving fishes.

feeding ecology and diet

When young, longtail knifefishes feed on small crustaceans and insect larvae. During growth, their diet changes to larger organisms such as shrimps and fishes. Adult insects are an important food item at all stages.

reproductive biology

Longtail knifefishes mature when they are 11.8–15.7 in (30–40 cm) long. Several hundred 0.1 in (0.3 cm) eggs are deposited on a substrate. The male guards the eggs, which hatch after three days. The larval stage begins at 10 days.

conservation status

Not listed by the IUCN. They are common throughout their range of distribution but at low densities.

significance to humans

Longtail knifefishes are fished for and eaten in their native range. The flesh is firm and considered to have a good flavor.

Resources

Books

Albert, J. Species Diversity and Phylogenetic Systematics of American Knifefishes (Gymnotiformes, Teleostei). Ann Arbor: Museum of Zoology (University of Michigan), 2001.

Bullock, T., and W. Heiligenberg. Electroreception. New York: John Wiley & Sons, 1986.

Gayet, M., and F. J. Meunier. Première découverte de Gymnotiformes fossiles (Pisces, Ostariophysi) dans le Miocène supérieur de Bolivie. C. R. Acad. Sci. Paris, t. 313, ser. 2, II, 1991.

Kirschbaum, F., and L. Wieczorek. Entdeckung einer neuen Fortpflanzungsstrategie bei südamerikanischen Messerfischen (Teleostei: Gymnotiformes: Gymnotidae): Maulbrüten bei Gymnotus carapo. Vol. 2. In Verhalten der Aquarienfische, edited by H. Greven and R. Riehl. Bornheim, Germany: Birgit Schmettkamp Verl., 2002.

Mago-Leccia, F. Electric Fishes of the Continental Waters of America. Vol. 29, Biblioteca de la Academica de Ciencias Fisicas Matematicas y Naturales. Caracas, Venezuela: FUDECI, 1994.

Moller, P., ed. Electrical Fishes: History and Behavior. Fish and Fisheries Series 117. London: Chapman & Hall, 1995.

Periodicals

da Silva Assunção, M. I., and H. O. Schwassmann. "Reproduction and Larval Development of Electrophorus electricus on Marajó Island (Pará, Brazil)." Ichthyological Exploration of Freshwaters 5 (1995): 1–10.

Kirschbaum, F. "Reproduction of the Weakly Electric Fish Eigenmannia virescens (Rhamphichthyidae, Teleostei) in Captivity." Behavioral Ecology and Sociobiology 4 (1979): 331–355.

——. "Electric Fishes." Aqua Geographia 1 (1992): 59–70.

Kirschbaum, F., and F. J. Meunier. "Gymnotiform Fishes As Model Systems for Regeneration Experiments." Arch. Anat. Mic. Morph. Exper. 75, no. 4 (1986): 307.

Frank Kirschbaum, PhD