The New Mexico spadefoot toad (''Spea multiplicata'') is a
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
American spadefoot toad
The Scaphiopodidae are a family of American spadefoot toads, which are native to North America. The family is small, comprising only eleven different species.
The American spadefoot toads are of typical shape to most fossorial (or burrowing) fr ...
found in the
southwestern United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
and
Mexico
Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
. Like other species of spadefoot toad, they get their name from a distinctive
spade
A spade is a tool primarily for digging consisting of a long handle and blade, typically with the blade narrower and flatter than the common shovel. Early spades were made of riven wood or of animal bones (often shoulder blades). After the a ...
-like projections on their hind legs, which enable them to dig in sandy soils. ''Spea multiplicata'' can be identified by its wedge-shaped spade. Some sources also refer to the species as the Mexican spadefoot toad, desert spadefoot toad or southern spadefoot toad.
Description
The New Mexico spadefoot toad has a length of with a round body and relatively short legs. They weigh between . They are green, to grey, to brown, usually reflecting the soil color of their native
habitat
In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
, often with black and orange colored speckling on their back, and a white underside. They have large
eye
An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system.
In higher organisms, the ey ...
s, with vertical
pupil
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black becau ...
s.
Behavior
Like all species of spadefoot toad, the New Mexico spadefoot toad is
nocturnal
Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite.
Nocturnal creatur ...
and secretive. If handled, these frogs might emit a
peanut
The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), goober pea, pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large ...
like odor, which can cause tearing and nasal discharge if in close contact with the face. Spending most of its time buried in the ground, the spadefoot emerges during periods of summer rainfall to feed on
insect
Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
s and to breed. Breeding takes place in temporary pools left by the rain.
Eggs laid in large masses, often hatch in as little as 48 hours. Females prefer to breed with sympatric males to produce hybrid tadpoles that can develop even faster.
The
tadpole
A tadpole or polliwog (also spelled pollywog) is the Larva, larval stage in the biological life cycle of an amphibian. Most tadpoles are fully Aquatic animal, aquatic, though some species of amphibians have tadpoles that are terrestrial animal, ...
s are forced to metamorphose quickly, before the water dries up. This process can be as quick as 8 days after hatching.
Phenotypic plasticity
''S. multiplicata'' tadpoles exhibit
phenotypic plasticity
Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompa ...
. In most cases the tadpoles will have an omnivore diet, feeding on detritus and plankton. Tadpoles that ingest
fairy shrimp, when present, may express a novel carnivore
phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...
. Features of this carnivore phenotype include enlarged jaw muscles and mouthparts that can aid in capturing and consuming prey.
This novel phenotype increases the rate of development, helping the tadpoles to escape drying pools more rapidly. Slower and smaller omnivore forms of New Mexico spadefoot tadpoles are more likely to be preyed upon by carnivore morphs of the same species. Scientists have recently produced a draft genome of the New Mexico spadefoot toad. They found that although its genome is on the smaller side compared to most other
anurans
A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough skin texture due to ...
, there have been several duplications of the key developmental gene ''
nodal'', which may be part of the reason spadefoots are able to develop so quickly and show so much phenotypic plasticity.
Taxonomy
The species was once classified as a
subspecies
In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
of the western spadefoot toad, ''
Spea hammondii'', but distinctive
morphological characteristics led researchers to reclassify it as its own species. The New Mexico spadefoot toad is also known to
hybridize with the Plains spadefoot toad, ''
Spea bombifrons'' in the areas where their
ranges overlap, making distinguishing the species from each other difficult.
Conservation threats
The New Mexico spadefoot toad has been the subject of research related to the possible effects of climate change (specifically changes in rainfall and temperature) on reproduction and development. The impact of water loss at different tadpole stages was studied in the lab in two sets of experiments. Both experiments studied how water loss affected tadpole development,
corticosterone
Corticosterone, also known as 17-deoxycortisol and 11β,21-dihydroxyprogesterone, is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands. In the very rare case of congenital adrenal hyperplasia due ...
levels, spleen size and cellularity, and overall body size. Overall, compared to control tadpoles who experienced no water loss, tadpole groups that experienced steady water loss had a faster rate of
metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...
, but no consistent differences in corticosterone levels, spleen size or cellularity, or overall body size. This study concluded that while water loss will cause increased rates of development in spadefoot tadpoles, this does not necessarily result in changes in body size in adult spadefoot.
Another potential effect of
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
could be on the spadefoot toad's calling behavior, used by males to attract mates, which is temperature dependent.
Researchers examined the relationship between the calling of spadefoot toads and temperature by compiling climate records of temperature and precipitation over a 22-year period. Interestingly, although air temperatures increased over time in the spadefoots’ habitat, the water temperature of their breeding ponds has mostly declined, which can be explained by fluctuations in rainfall temperatures. Generally, faster and higher calls by males result in greater reproductive success. Once researchers corrected call rates for temperature, spadefoot call duration decreased while pulse and call rates increased over time. These findings show that climate change does not always have a direct effect on temperature-dependent traits. Instead, it can cause changes in species’ microenvironments that can have a greater impact on animal traits.
Trivia
*The New Mexico spadefoot toad was designated as the official
State Amphibian of
New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
in 2003.
References
Herps of Texas: ''Spea multiplicata''Amphibian Species of the World: ''Spea multiplicata''*Peterson Field Guide - Western Reptiles and Amphibians 3rd Edition
External links
*
*
{{Taxonbar, from=Q2274578
Spea
Amphibians of Mexico
Amphibians of the United States
Fauna of Northern Mexico
Fauna of the Southwestern United States
Biota of New Mexico
Symbols of New Mexico
Amphibians described in 1863
Taxa named by Edward Drinker Cope