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June 13, 2008

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Eat the parents

June 13, 2008
World Science staff

A bi­zarre prac­tice in which some crea­tures eat their own moth­ers’ skin has turned up in more than one spe­cies—sug­gest­ the strat­e­gy is at least 100 mil­lion years old, re­search­ers say.

Ma­ter­nal skin-eating was first re­ported found in a worm-like am­phib­i­an known as Bou­len­ge­ru­la tai­ta­nus. Now sci­en­tists say they have ob­served it in a sec­ond, si­m­i­lar an­i­mal, Siph­o­nops an­nu­la­tus. 

Syphonops annula­tus, as shown in an 1849 print by Charles Or­bi­gny.
The two are dis­tantly re­lat­ed cae­cil­ians, mem­bers of an or­der of trop­i­cal am­phib­i­ans that re­sem­ble earth­worms but have ver­te­brate char­ac­ter­is­tics such as jaws and teeth. 

The odd feed­ing tech­nique is called der­matophagy, from the Greek words for skin-eating.

It’s “is an un­usu­al form of pa­ren­tal in­vest­men­t,” not­ed the in­ves­ti­ga­tors in a re­port on the find­ings, pub­lished in the June 11 on­line is­sue of the re­search jour­nal Bi­ol­o­gy Let­ters. In both spe­cies, they added, the strat­e­gy is so in­grained that the moth­ers’ skin and the off­springs’ teeth are spe­cial­ized to prac­tice it ef­fec­tive­ly.

In brood­ing fe­males, the skin turns in­to a fat­ty tis­sue that pro­vides a rich supply of nu­tri­ents for the de­vel­op­ing off­spring, they wrote. The young­sters use their spe­cial­ized teeth to peel and eat the out­er lay­er, said the re­search­ers, Mark Wilkin­son of Lon­don’s Nat­u­ral His­to­ry Mu­se­um and col­leagues.

The “de­tailed si­m­i­lar­i­ties” in der­matophagy be­tween the spe­cies im­plies it was pre­s­ent in their ev­o­lu­tion­ary com­mon an­ces­tor, the sci­en­tists wrote. That an­ces­tor probably lived at least 100 mil­lion years ago, they added. The es­ti­mate is based on stud­ies of the di­ver­sifica­t­ion of am­phib­i­an lin­eages and on the con­ti­nen­tal separa­t­ion of Af­ri­ca and South Amer­i­ca, where the first and sec­ond skin-eating cae­cil­ians were found, re­spec­tive­ly. The ear­li­er find­ings ap­peared in the April 13, 2006 is­sue of the jour­nal Na­ture. 

The newer dis­cov­ery sug­gests ma­ter­nal der­matophagy may be wide­spread in re­lat­ed lin­eages of cae­cil­ians, Wilkin­son and col­leagues said.

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A bizarre practice in which some creatures eat their own mothers’ skin has turned up in more than one species—suggesting the strategy is at least 100 million years old, researchers say. Maternal skin-eating was first reported found in a worm-like amphibian known as Boulengerula taitanus. Now scientists say they have observed it in a second, similar animal, Siphonops annulatus. The two are distantly related caecilians, members of an order of tropical amphibians that resemble earthworms but have vertebrate characteristics such as jaws and teeth. The odd feeding technique is called dermatophagy, from the Greek words for skin-eating. It’s “is an unusual form of parental investment,” noted the investigators in a report on the findings, published in the June 11 online issue of the research journal Biology Letters. In both species, they added, the strategy is so ingrained that the mothers’ skin and the offsprings’ teeth are both specialized to practice it effectively. In brooding females, the skin turns into a fatty tissue that provides a rich supply of nutrients for the developing offspring, they wrote. The youngsters use their specialized teeth to peel and eat the outer layer of this skin, said the researchers, Mark Wilkinson of London’s Natural History Museum and colleagues. The “detailed similarities” in dermatophagy between the species implies it was present in their evolutionary common ancestor, the scientists wrote. That ancestor probably lived at least 100 million years ago, they added. The estimate is based on studies of the diversification of amphibian lineages and the continental separation of Africa and South America, where the first and second skin-eating caecilians were found, respectively. The earlier findings appeared in the April 13, 2006 issue of the journal Nature. The newer discovery suggests maternal dermatophagy may be widespread in related lineages of caecilians, Wilkinson and colleagues said.