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Brief Summary
This video explores the fascinating symbiotic relationship between fig trees and fig wasps, focusing on Ficus racemosa and Ficus hispida in Thailand. It details the unique pollination process, the anatomy of the figs and wasps, and the complex life cycle within the fig. The video also touches on the challenges faced by the wasps, including predators and competition, and the presence of other organisms like nematodes and non-pollinating wasps within the fig ecosystem.
- Fig trees have a unique pollination process involving fig wasps.
- Ficus racemosa and Ficus hispida have species-specific relationships with fig wasps.
- The life cycle within the fig involves pollination, oviposition, larval development, and emergence of both male and female wasps.
Introduction to Fig Trees and Fig Wasps
Fig trees have been important in human diet and culture for millennia, producing fruit without apparent flowering by concealing their flowers within the figs. Over 750 species exist across the tropics and subtropics, providing food for numerous birds and mammals. This is made possible by a symbiotic relationship with fig wasps, insects that are scarcely a millimeter in length.
Ficus racemosa and its symbiotic pollinator wasp Ceratosolen fusciceps
Ficus racemosa is a large tree, 25-40 meters tall, usually found near rivers, bearing 2-7 fig crops a year. The figs grow in dense clusters along the trunk and boughs, reaching up to 5 cm across and turning orange-red when ripe. This fig species is pollinated by the wasp Ceratosolen fusciceps.
Female Wasp Enters the Fig
The female fig wasp enters the fig through a small opening called the ostiole. She forces her way in using her wedge-shaped head, flattening her antenna scapes into grooves. The tight gap squeezes out moisture from her body, and she loses her wings and antennal flagella in the process.
Ficus hispida and its mutualistic pollinator wasp Ceratosolen solmsi
Ficus hispida is pollinated by Ceratosolen solmsi. These wasps have shorter ovipositors. The female wasps must enter the figs quickly to avoid predators like hunting ants.
Wasp Ovipositing and Forming Galls
Once inside the fig cavity, the female wasp lays a single egg beside the ovule of each flower, injecting a secretion to induce gall formation. She uses tooth-like structures on her legs and extended mandibles to pull herself through the bracts. The fig tree benefits from this by having its reproductive needs met.
Wasp Actively Pollinating Stigmas
Unlike passive pollination, Ficus racemosa and Ficus hispida are actively pollinated by their wasps. The wasps use specialized pollen pockets on their thorax to collect and dab pollen onto the stigmas while laying eggs.
Ficus racemosa Monoecious Anatomy
Ficus racemosa is monoecious, producing figs with both pollen and seeds. The flowers are densely packed with ovaries at varying depths, and the stigmas form a single large synstigma. Ceratosolen fusciceps females lay eggs in shorter styled flowers, leaving the lower ovaries to develop into seeds. The fig tree can limit the number of entering wasps to ensure seed production.
Ficus hispida Dioecious Anatomy
Functionally dioecious fig trees like Ficus hispida separate seed and wasp production on different trees. Female wasps cannot distinguish between male and female figs by smell. In male figs, they find short-styled female flowers suitable for oviposition, while in female figs, the flowers are unsuitable, leading only to seed production.
Male Offspring Emerge and Mate
After about 30 days, adult wasps begin to emerge. The golden, wingless males emerge first, using their mandibles to chew out of their galls. They then mate with the female wasps, many of whom are their sisters, by channeling their abdomens into the galls.
Apocrypta Male Wasps
Slender males of non-pollinating Apocrypta fig wasps navigate watery areas within the fig. They have tubes on their abdomens that act like snorkels, and their spiracles are surrounded by water-repellent hairs to help them breathe.
Female Offspring Emerge and Gather Pollen
Female wasps widen the holes left by the males and emerge from their galls. They gather pollen from the anthers using their front tarsi, stuffing it into their thoracic pollen pockets. Ceratosolen solmsi females collect pollen at a rate of about one stroke per second.
Juvenile Nematode Worms Emerge
Juvenile nematode worms also emerge, attaching themselves to female fig wasps to travel to another fig. Too many nematodes can shorten the wasp's life and reduce its ability to disperse.
Male Wasps Tunnel Out
The male wasps create a tunnel for the females to leave the fig, usually through or near the ostiole. Emerging males attract predators like ants, which are drawn by the odor of the wasps and the mature fig. The males are more likely to be eaten, distracting the ants and allowing the females to escape and seek receptive figs.
Chalcid Non-Pollinating Female Wasps
Chalcid non-pollinating fig wasp females, which are parasitoids, also emerge. They have long ovipositors and lay their eggs through the fig wall. These wasps are longer-lived than the pollinators and seek receptive figs to deposit their offspring.
