The common Surinam toad or star-fingered toad (''Pipa pipa'') is an purely aquatic species of frog in the family ''
Pipidae'' with a widespread distribution in
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
. The species is known for incubating its eggs in honeycombed chambers in the skin of the mother's back, releasing fully formed froglets after a period of 4-5 months. It is an
ambush predator
Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey ...
that lies in wait in the water for prey to come into range, which it then captures using
suction feeding
Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identifi ...
.
Description
''P. pipa'' is a strictly aquatic
frog
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...
and the largest member of its
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
. The species has an exceptionally depressed body, almost entirely flat and with a broad, flat, triangular head. It is without a tongue.
The body is similar in appearance to a mottled brown leaf. The feet are broadly webbed with the front toes having small, star-like appendages. Males can grow up to 154 mm long, whereas females can reach up to 171 mm. Females can be distinguished not only by their length but also by their ring-shaped
cloacas, visible when they are ready to breed.
The skin color is mostly light brown with some darker spots on the back, providing good camouflage
Nostrils are terminal, eyes very small, and the
tympanum is missing. The limbs are in a laterally sprawled position in the plane of the body, and the fingertips are modified into four small lobes.
Absence of a tongue prevents the species from capturing prey with that organ like most other frogs, and instead suction capture is used.
The skull is hyperossified and the cranial and postcranial bones are heavily modified compared to other anurans. While the eyes are relatively small and narrow, the species has a
lateral line system and
neuromast
The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...
organs which are assumed to help it locate prey and predators.
The Surinam toad lacks dermal
antimicrobial peptides that may inhibit disease agents such as
chytridiomycosis
Chytridiomycosis ( ) is an infectious disease in amphibians, caused by the chytrid fungi '' Batrachochytrium dendrobatidis'' and '' Batrachochytrium salamandrivorans''. Chytridiomycosis has been linked to dramatic population declines or extinc ...
and
Ranavirus
''Ranavirus'' is a genus of viruses, in the family ''Iridoviridae''. There are six other genera of viruses within the family ''Iridoviridae'', but ''Ranavirus'' is the only one that includes viruses that are infectious to amphibians and reptile ...
, which could make it slightly more susceptible to disease.
Habitat and distribution
The species lives under submerged litter in slow flowing watercourses, stream backwaters, ponds, and pools from flooded forests.
It has the largest geographic distribution for its genus and is found in much of
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
, including
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
and
Ecuador
Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ' ...
, particularly within the
Amazon rainforest.
It is so strongly adapted for an aquatic lifestyle that on land it is helpless and scarcely able to move.
Diet
The species is an
omnivorous
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
ambush hunter. Its diet consists mostly of
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s, such as worms, insects, crustaceans and small fish.
Field caught ''Pipa pipa'' have been found with
erythrinid fish species, other small ''Pipa pipa'',
catfish
Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive ...
,
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s and amphibian skin in their stomachs.
One study found that
Cyclopoida
The Cyclopoida are an order of small crustaceans from the subclass Copepoda. Like many other copepods, members of Cyclopoida are small, planktonic animals living both in the sea and in freshwater habitats. They are capable of rapid movement. Thei ...
made up 67%,
Diptera larvae 7.3%, and
Heteroptera 6.3% of prey. The skin fragments that were found in their stomach are an indication that these frogs commit cannibalism or eat their own skin which is common among amphibians. Based on these results, ''P. pipa'' is an
opportunist
Opportunism is the practice of taking advantage of circumstances – with little regard for principles or with what the consequences are for others. Opportunist actions are expedient actions guided primarily by self-interested motives. The term ...
that will eat anything that falls into the water or that the species may occasionally forage in land.
Feeding behavior
The Surinam toad can catch prey by
entraining
Entrainment may refer to:
* Air entrainment, the intentional creation of tiny air bubbles in concrete
* Brainwave entrainment, the practice of entraining one's brainwaves to a desired frequency
* Entrainment (biomusicology), the synchronization ...
and ingesting large volumes of water and by limiting fish escape with its fingers. It uses a
bidirectional suction mechanism where the amount of water ingested is influenced by the ability for the frog to actively increase its body volume. When it captures prey, its
buccopharyngeal cavity (the cavity connecting the mouth and the pharynx) is very distensible and can expand substantially. It has the ability to use its entire trunk to rapidly enlarge its buccopharyngeal cavity and expand into the lower end of the trunk. Additionally, its major organs such as the
hyoid
The hyoid bone (lingual bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies between the base of the mandible and the third cervical vertebra. ...
and
larynx,
heart
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
,
lungs,
liver
The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
,
esophagus
The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
, and
stomach
The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...
are arranged to move a third of the length of the body which gives space for expansion of the buccopharyngeal cavity. The fish that are captured are located in the middle of the body instead of the stomach. This modification allows for ''Pipa pipa's'' unique inertial
suction feeding
Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identifi ...
.
The species may be the only
tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
that can enlarge its entire trunk during suction feeding. Additionally, it has been found that ''P. pipa'' can modulate the timing of most elements of its prey capture process. For instance, it can asymmetrically or asynchronously move its jaw during the capture and manipulation of its prey.
The forelimbs are used to grasp and shove the prey into the mouth. Prior to capture of its prey, the forelimbs are held in a forward-flexed position so that each hand is positioned in front of the head. During prey capture, the forelimbs are extended and drawn towards the mouth. If the prey item is encountered during this movement, it is grabbed and pushed into the mouth. Otherwise it is sucked into the mouth without any use of the limbs. These frogs have a high degree of dexterity compared to other
''pipid'' species.
Reproduction
The mating period of these frogs is during the fall and winter seasons. These frogs call usually during the morning and mid-afternoon hours.
Males of this species do not attract females with croaks, instead producing a sharp clicking sound by snapping the
hyoid bone in their throats. The clicking sound resembles metallic noises. The average rate of these clicks is four clicks per second, consisting of blocks of 10 to 20 seconds per period.
Thereafter, the male will grab the front legs of the female in
amplexus
Amplexus (Latin "embrace") is a type of mating behavior exhibited by some externally fertilizing species (chiefly amphibians and horseshoe crabs) in which a male grasps a female with his front legs as part of the mating process, and at the same ...
, causing the clochea and the skin of the female to swell.
The partners rise from the floor while in amplexus and flip through the water in arcs. The couple will swim around in the water until they have to swim to the surface to breathe. Afterwards, they will swim back down to the bottom of the water. There the male will lay on his back, with the female on top of him on her stomach. During the amplexus, the female's back is gradually swelled to a puffy condition. The male and female
cloacae are brought close together, and many eggs are transferred anteriorly to the female's swollen dorsal
epidermis.
The eggs, each around 6.5 mm in diameter, then become implanted into the female's dorsal
epidermis. During the first day the eggs on the female's back will sink into the skin and by evening will be set into the back of the female. Two days later, the yolks of most of the eggs are beneath the skin level and only parts of the jelly and outer membranes of the eggs are visible on the backs above. The coverings over the eggs will remain in the wild until the brood emerges.
The embryos develop through to the
tadpole
A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found ...
stage inside these pockets but do not emerge as tadpoles, instead remaining in their chambers until complete development to toadlet stage. The young toads grow a tail during their growth, but these will only be temporary because they will need the tail for inhaling oxygen. After 12 to 20 weeks, the young toads will hatch as small toads, looking identical to their parents. It takes a while for them to grow bigger since they are only 25 mm long when they are born. Once they have emerged from their mother's back, the toads begin a largely solitary life. After giving birth to the new toads, the mother slowly sheds the thin layer of skin used for birth and can begin the cycle again.
Pipa pipa 1.jpg, The gray shape is the Surinam toad.
Surinam toad (DFdB).jpg, A Surinam toad with eggs embedded in the skin
Pipa pipa big.jpg, Museum specimen
Pipa pipa whole body.jpg, Museum specimen: closeup
Mating competition
When two males encounter each other during the
mating season
Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and ch ...
, there is a possibility that the two males will fight. The toads nearly press their snout to the chest or throat of the other male. During the
conflict
Conflict may refer to:
Arts, entertainment, and media
Films
* ''Conflict'' (1921 film), an American silent film directed by Stuart Paton
* ''Conflict'' (1936 film), an American boxing film starring John Wayne
* ''Conflict'' (1937 film) ...
, both males make single clicks to each other, which resembles the sound that they normally use during the breeding. If the toads have eye contact, they make a rapid series of these clicks. This process shows no visible movement of the vocal system. After some time, they will return to swimming, but will never lose contact with one another. One toad swims above the other very closely, touching his enemy with only the front limbs. The fight between males may be long-lasting. Eventually, one of the males bites the other male and this is supposed to be the end of their encounter, although they do not always give up the fight. It may happen that the male that loses the battle does not give up and disturbs the
breeding pair itself, even during reproduction.
Conservation
Although the species is classified as
Least Concern
A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...
by the
IUCN, it is subject to habitat loss and habitat fragmentation caused by agricultural expansions.
Due to the deforestation and human encroachment on the Amazon rainforest, the species has been found in regions where it would not normally be encountered, such as terrestrial locations. This highlights the importance of preserving the endangered habitats that these frogs live in.
Captivity
![Pipa pipa 2](https://upload.wikimedia.org/wikipedia/commons/a/ad/Pipa_pipa_2.jpg)
In the aquarium, the species prefers plants and rocks to hide behind. Low light conditions are required. Because the Surinam toad excretes high amounts of
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
, water changes have to be frequent.
Cultural significance
In a letter to Catherine Clarkson the poet
Samuel Taylor Coleridge
Samuel Taylor Coleridge (; 21 October 177225 July 1834) was an English poet, literary critic, philosopher, and theologian who, with his friend William Wordsworth, was a founder of the Romantic Movement in England and a member of the Lake ...
writes “I envy dear Southey's power of saying one thing at a time in short and close sentences, whereas my thoughts bustle along like a Surinam Toad, with little toads sprouting out of back, side, and belly, vegetating while it crawls”.
The Surinam toad is commonly cited as an example of a
trypophobia trigger.
References
External links
*
*
''Pipa pipa'' at
Animal Diversity Web
Animal Diversity Web (ADW) is an online database that collects the natural history, classification, species characteristics, conservation biology, and distribution information on thousands of species of animals. The website includes thousands ...
{{Taxonbar, from=Q220414
Pipa (frog)
Amphibians of Bolivia
Amphibians of Brazil
Amphibians of Colombia
Amphibians of Ecuador
Amphibians of Guyana
Amphibians of Peru
Amphibians of Suriname
Amphibians of Trinidad and Tobago
Amphibians of Venezuela
Amphibians described in 1758
Taxa named by Carl Linnaeus