side by side images - Joel Sartore

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INV004-00068

Two nerite snails (Neritina semiconica) at Dvůr Králové Zoo.

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INV004-00067

Two tiger nerite snails (Neritina gagates) at Dvůr Králové Zoo.

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INS002-00473

Two garden fruit chafers (Pachnoda aemula) at Dvůr Králové Zoo.

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INS002-00472

Two garden fruit chafers (Pachnoda aemula) at Dvůr Králové Zoo.

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BIR064-00298

Two Zanzibar red bishops (Euplectes nigroventris) at Dvůr Králové Zoo. The male is more colorful than the female.

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BIR064-00297

Two Zanzibar red bishops (Euplectes nigroventris) at Dvůr Králové Zoo. The male is more colorful than the female.

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BIR049-00138

Two cape sparrows (Passer melanurus) at Dvůr Králové Zoo. The male has black chest and face.

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INS006-00419

Two Costa Rican redleg tarantulas (Megaphobema mesomelas) from a private collection. The male is smaller.

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FIS039-00136

Limia dominicensis at Plzen Zoo in the Czech Republic. This species is from Hispaniola. The smaller of the two is a young male, with color. The female is plain and much larger.

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FIS039-00133

Limia melanogaster at Plzen Zoo in the Czech Republic. This species is from Hispaniola. The male is smaller and with color, on bottom. Female is on top.

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FIS039-00130

Endangered Varatraza panchax (Pachypanchax varatraza) at Plzen Zoo in the Czech Republic. This species is from Madagascar.

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FIS039-00129

Endangered Varatraza panchax (Pachypanchax varatraza) at Plzen Zoo in the Czech Republic. This species is from Madagascar.

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FIS039-00128

Limia perugiae at Plzen Zoo in the Czech Republic. This species is from Hispaniola. The female is on top, with less color. The male is below.

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FIS039-00127

Limia perugiae at Plzen Zoo in the Czech Republic. This species is from Hispaniola. The female is on top, with less color. The male is below.

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FIS039-00124

Gold-ring danio (Danio tinwinii) at Plzen Zoo in the Czech Republic. These animals are from Myanmar.

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FIS039-00123

Gold-ring danio (Danio tinwinii) at Plzen Zoo in the Czech Republic. These animals are from Myanmar.

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FIS039-00119

Gournara (Tropidophoxinellus hellenicus) at Plzen Zoo in the Czech Republic. These animals are from Greece.

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FIS039-00118

Gournara (Tropidophoxinellus hellenicus) at Plzen Zoo in the Czech Republic. These animals are from Greece.

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FIS037-00008

A cape kurper (Sandelia capensis) at Plzen Zoo, in the Czech Republic. This animal was originally from South Africa.

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Xenotoca doadrioi CR (earlier known as Xenotoca sp. San Marcos) at the Plzen Zoo in the Czech Republic. These animals were originally from San Marcos, Mexico. The male is on the left. The female is on the right.

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BIR039-00270

Two Western bluebills (Spermophaga haematina) from a private collection in St. Augustine, Florida. The male has more color, with vivid red on chest. The female is in front.

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INS025-00024

Thai rainbow millipedes (Tonkinbolus dollfusi) at Petra Aqua.

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INS025-00023

Thai rainbow millipedes (Tonkinbolus dollfusi) at Petra Aqua.

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FIS041-00312

Two cave molly (Poecilia mexicana) at Zoo Plzeň. This species is a cave dweller from Mexico that gives live birth. The male is smaller.

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FIS041-00311

Two cave molly (Poecilia mexicana) at Zoo Plzeň. This species is a cave dweller from Mexico that gives live birth. The male is smaller.

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FIS032-00016

Two Balsas splitfins (Ilyodon whitei) at Zoo Plzeň. This species is from Mexico. The larger fish is male, the other female.

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FIS032-00014

Two Balsas splitfins (Ilyodon whitei) at Zoo Plzeň. This species is from Mexico. The larger fish is male, the other female.

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FIS028-00085

A male and female ray-finned fish at Zoo Plzeň. The species is undescribed, though it resembles Tawi Atair garra (Garra dunsirei).

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FIS028-00084

A male and female ray-finned fish at Zoo Plzeň. The species is undescribed, though it resembles Tawi Atair garra (Garra dunsirei).

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BIR049-00126

Two 20-day-old fledgling Florida grasshopper sparrows (Ammodramus savannarum floridanus) at White Oak Conservation Center, Yulee, Florida.

These birds are part of a captive breeding program for this critically endangered bird, a few of which still live in the vanishing prairies of central Florida. There are nearly 100 adults, nestlings and hatch year birds here now at White Oak. This is likely more than are left in the wild now.

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ANI110-00279

A pair of critically endangered San Martin fringe-limbed tree frogs (Ecnomiohyla valancifer) at the Amphibian Foundation in Atlanta Georgia. The male is larger with big front arms.

The Amphibian Foundation is an Atlanta-based nonprofit dedicated to the conservation of amphibians in the Southeast United States and across the globe.

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BIR064-00240

Two male saffron finches (Sicalis flaveola brasiliensis) at the Membeca Lagos Farm, near Rio de Janeiro, Brazil.

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BIR064-00239

Saffron finches (Sicalis flaveola brasiliensis) at the Membeca Lagos Farm, near Rio de Janeiro, Brazil. The female is more brown, the males more brilliant yellow.