A tadpole (also called a pollywog) is the larval stage in the life cycle of an amphibian, particularly that of a frog or toad. They are usually wholly aquatic, though some species have tadpoles that are terrestrial. When first hatched from the egg they have a more or less globular body, a laterally compressed tail and internal or external gills. As they grow they undergo metamorphosis, during which process they grow limbs, develop lungs and reabsorb the tail. Most tadpoles are herbivorous and during metamorphosis the mouth and internal organs are rearranged to prepare for an adult carnivorous lifestyle.
Having no hard parts, it might be expected that fossil tadpoles would not exist. However, traces of biofilms have been preserved and fossil tadpoles have been found dating back to the Miocene. Tadpoles are eaten in some parts of the world and are mentioned in folk tales and used as a symbol in ancient Egyptian numerals.
Tadpole to frog
The name "tadpole" is from Middle English taddepol, made up of the elements tadde, "toad", and pol, "head" (modern English "poll"). Similarly, "pollywog" / "polliwog" is from Middle English polwygle, made up of the same pol, "head", and wiglen, "to wiggle".
Tadpoles are young amphibians that usually live in the water, though a few tadpoles are semi-terrestrial (Indirana beddomii and Thoropa miliaris) and terrestrial (Indirana semipalmata and Adenomera andreae). During the tadpole stage of the amphibian life cycle, most respire by means of autonomous external or internal gills. They do not usually have arms or legs until the transition to adulthood, and typically have a large, flattened tail with which they swim by lateral undulation, similar to most fish.
As a tadpole matures, it most commonly metamorphosizes by gradually growing limbs (usually the back legs first, followed by the front legs) and then (most commonly in the case of frogs) outwardly absorbing its tail by apoptosis. Lungs develop around the time of leg development, and tadpoles late in development will often be found near the surface of the water, where they breathe air. During the final stages of external metamorphosis, the tadpole's mouth changes from a small, enclosed mouth at the front of the head to a large mouth the same width as the head. The intestines shorten to accommodate the new diet. Most tadpoles are herbivorous, subsisting on algae and plants. Some species are omnivorous, eating detritus and, when available, smaller tadpoles.
Tadpoles vary greatly in size, both during their development and between species. For example, in a single family, Megophryidae, length of late-stage tadpoles varies between 33 millimetres (1.3 in) and 106 millimetres (4.2 in). The tadpoles of Pseudis paradoxa grow to 25 centimetres (9.8 in), the largest of any frog.
Despite their soft-bodied nature and lack of mineralised hard parts, fossil tadpoles (around 10 cm in length) have been recovered from Upper Miocene strata. They are preserved by virtue of biofilms, with more robust structures (the jaw and bones) preserved as a carbon film. In Miocene fossils from Libros, Spain, the brain case is preserved in calcium carbonate, and the nerve cord in calcium phosphate. Other parts of the tadpoles' bodies exist as organic remains and bacterial biofilms, with sedimentary detritus present in the gut. Tadpole remains with telltale external gills are also known from several of the Labyrinthodont groups.
Some tadpoles are used as food. Tadpoles of megophryid frog Oreolalax rhodostigmatus are particularly large, more than 10 cm (3.9 in) in length, and are collected for human consumption in China. In India, Clinotarsus curtipes are collected for food, and in Peru at least Telmatobius mayoloi tadpoles are collected for food and medicine.
Despite the name, ol-chaeng-ee guksu, Korean "tadpole noodles" refers to a type of noodle made from pureed corn.
Mythology and history
According to Sir George Scott, in the origin myths of the Wa people in China and Myanmar, the first Wa originated from two female ancestors Ya Htawm and Ya Htai, who spent their early phase as tadpoles (rairoh) in a lake in the Wa country known as Nawng Hkaeo.
In the Ancient Egyptian numerals, a hieroglyphic representing a tadpole was used to denote the value of 100,000.
Mnyama anayeitwa pollywog (kwa Kiingereza: tadpole) ni mnyama anayeitwa amphibian, hasa yule anayeitwa toad. Kwa kawaida wao huishi tu majini, ingawa spishi fulani zina vifaranga wanaoishi ardhini. Wanapofunguliwa kutoka kwenye yai huwa na mwili wenye umbo la mviringo, mkia uliofinyangwa upande mmoja na miiba ya ndani au ya nje. Wanapokua, wao hubadilika-badilika, na wakati huo wao hukua viungo, huendeleza mapafu, na kunyonya mkia. Vipepeo wengi hula mimea na wakati wa mabadiliko ya umbo la mwili, mdomo na viungo vya ndani vinarekebishwa ili kujitayarisha kwa ajili ya maisha ya watu wazima wanaokula nyama. Kwa kuwa hazina sehemu ngumu, huenda ikatarajiwa kwamba visukuku vya kale havingekuwapo. Hata hivyo, alama za filamu za kibiolojia zimehifadhiwa na visukuku vya mnyama-mwitu vimepatikana vikianzia Miocene. Katika sehemu fulani za ulimwengu, wadudu hao hula na wanatajwa katika hadithi za watu na hutumiwa kama ishara katika tarakimu za kale za Misri. Jina "tadpole" linatokana na neno la Kiingereza cha Kati taddepol, linalotokana na maneno tadde, "toad", na pol, "head" (kwa Kiingereza cha kisasa "poll"). "Kama ilivyo kwa Kiingereza, pollywog ni neno la Kiingereza la kati polwygle, linalotokana na pol, ""kichwa,"" na wiglen, ""kuzunguka.""" Vipepeo ni amfibia wadogo ambao kwa kawaida huishi majini, ingawa vipepeo wachache ni nusu-wa-ardhi (Indirana beddomii na Thoropa miliaris) na ardhi (Indirana semipalmata na Adenomera andreae). Wakati wa hatua ya tadpole ya mzunguko wa maisha ya amfibia, wengi hupumua kwa njia ya gills za nje au za ndani zenye kujitegemea. Wao huwa hawana mikono au miguu hadi wanapokuwa watu wazima, na kwa kawaida huwa na mkia mkubwa, ulio tambarare ambao wao huogelea kwa kuelea upande, sawa na samaki wengi. Kadiri nyigu anavyozidi kukua, kwa kawaida yeye hujifanyiza kwa kukua hatua kwa hatua kwa viungo (kwa kawaida miguu ya nyuma kwanza, ikifuatiwa na miguu ya mbele) na kisha (kwa kawaida katika kesi ya vyura) huchukua mkia wake kwa apoptosis. Pumu huanza kupanuka wakati wa ukuzi wa miguu, na mara nyingi wadudu hao hupatikana karibu na uso wa maji, ambapo hupumua hewa. Katika hatua za mwisho za mabadiliko ya sura, mdomo wa tadpole hubadilika kutoka mdomo mdogo uliofungwa mbele ya kichwa kuwa mdomo mkubwa wenye upana sawa na kichwa. Matumbo hupunguzwa ili kukabiliana na lishe mpya. Vipepeo wengi hula mimea na mimea. Spishi fulani hula kila kitu, wakila vitu vilivyoharibiwa na, inapopatikana, wadudu wadogo. Vipepeo hutofautiana sana kwa ukubwa, wakati wa ukuzi wao na kati ya spishi. Kwa mfano, katika familia moja, Megaphryidae, urefu wa tadpoles katika hatua ya mwisho hutofautiana kati ya milimita 33 na milimita 106 (inchi 4.2). Pseudopod paradox ni aina ya chura anayekua kwa urefu wa sentimita 25 na ni mkubwa kuliko chura mwingine yeyote. Licha ya asili yao laini na ukosefu wa sehemu ngumu za madini, tadpoles za fossil (karibu urefu wa sentimita 10) zimepatikana kutoka kwa tabaka za Miocene ya Juu. Wao ni kuhifadhiwa kwa nguvu ya biofilms, na miundo imara zaidi (mkojo na mifupa) kuhifadhiwa kama filamu ya kaboni. Katika visukuku vya Miocene kutoka Libros, Hispania, kifuniko cha ubongo kimehifadhiwa katika kaboniati ya kalsiamu, na kamba ya neva katika fosfati ya kalsiamu. Sehemu nyingine za miili ya vifaranga hao zipo kama mabaki ya kikaboni na biofilms za bakteria, na mabaki ya matope yanapatikana katika matumbo. Mabaki ya mnyama anayeitwa tadpole mwenye matete ya nje yanajulikana pia kutoka kwa vikundi kadhaa vya Labyrinthodont. Baadhi ya vifaranga hutumiwa kama chakula. Mnyama anayeitwa Oreolalax rhodostigmatus ni aina ya chura anayeitwa megaphryid, ambaye kwa kawaida hupatikana nchini China. Katika India, Clinotarsus curtipes hukusanywa kwa ajili ya chakula, na katika Peru angalau Telmatobius mayoloi tadpoles hukusanywa kwa ajili ya chakula na dawa. Licha ya jina, ol-chaeng-ee guksu, Kikorea "tadpole noodles" inahusu aina ya noodle iliyotengenezwa kutoka mahindi yaliyochuja. "Kulingana na Sir George Scott, katika hadithi za asili za watu wa Wa nchini China na Myanmar, Wa wa kwanza walitokana na mababu wawili wa kike, Ya Htaum na Ya Htai, ambao walitumia awamu yao ya mapema kama tadpoles (rairoh) katika ziwa katika nchi ya Wa inayojulikana kama ""Naung Hkao.""" Katika hesabu za kale za Misri, heroglifiki iliyowakilisha mnyama-mwitu ilitumiwa kuashiria thamani ya 100,000.