Tarantulas exhibit a diverse range of appearances. Understanding their physical characteristics reveals a fascinating array of adaptations. Examining their overall body structure, specific anatomical features, and varied colors provides insight into these unique arachnids.
Overall Body Plan
A tarantula’s body consists of two primary fused sections: the prosoma (cephalothorax) and the opisthosoma (abdomen). These parts are connected by a narrow pedicel, allowing the abdomen a wide range of motion. Eight legs extend from the cephalothorax, along with two shorter, leg-like pedipalps used for sensing and manipulating food.
Tarantulas have body lengths ranging from 5 to 11 cm, with leg spans from 8 cm up to 30 cm for the largest species like the Goliath birdeater. They possess a robust, bulky build and are covered in various types of hair. This hairiness serves multiple purposes, including sensory perception and insulation.
Key Anatomical Details
Tarantulas have eight eyes, arranged in groups, though their vision is poor. These eyes are grouped into pairs, with two larger eyes positioned centrally on their head. The remaining smaller eyes help detect movement in their surroundings.
Their fangs are part of structures called chelicerae, located below their eyes. Tarantula fangs point downwards and fold like a pocket knife when at rest, extending outward to deliver a bite. Many New World tarantula species also possess urticating hairs, tiny barbed bristles on their abdomen. These hairs can be flicked off as a defensive mechanism, causing irritation.
Silk is produced by spinnerets, located on the underside of the tarantula’s abdomen. While most spiders have six spinnerets, some tarantulas may have two, four, or eight, and they can move independently or together. These segmented organs extrude silk for various uses, including lining burrows, creating egg sacs, and tripwires.
Colors, Patterns, and Variations
Tarantulas display a wide range of colors and patterns. Their coloration includes vibrant hues of blue, green, purple, red, orange, yellow, and pink. These colors can appear as solid shades, intricate patterns, or metallic sheens on different parts of their body and legs. For example, the electric blue tarantula exhibits brilliant blue and purple hues due to light reflecting on its setae, not pigmentation.
Diversity in appearance extends to variations within a species, sometimes influenced by geographical region or age. Sexual dimorphism is an aspect for many tarantula species, meaning males and females can look different. Females are often larger and more robust than males, who may appear more slender with longer legs. In some species, males might also display duller coloration compared to the more vibrant females.