Chapter 4: Honey Bee Anatomy

Transcription

1 Chapter 4: Honey Bee Anatomy University of Florida Department of Entomology & Nematology Dr. Jamie Ellis Created by: Jason Graham, Catherine Nalen, Jamie Ellis External Morphology Honey bees, like all insects, have segmented exoskeletons which: - protect their vital organs from the environment - provide areas of attachment for muscles and connective tissue External Morphology The honey bee is covered in small branched plumose (branched) hairs, even between the facets of the compound eyes. Bees are distinguished from other Hymenoptera by these plumose hairs. Caron,1999 These hairs - have sensory capabilities - enhance pollen collection/transportation ability - help protect the exoskeleton keeping it free of debris. 1

2 Head Much like with the human head, the honey bee head is made for sensory input and processing of information. Zachary Huang, University of Michigan The ocelli, compound eyes, mandibles and antennae are all hard-wired directly to the honey bee brain. Dade1994 Eyes Honey bees have three ocelli (simple eyes) which respond to changes in light and darkness, possibly leading to flight stability. The two compound eyes are each made up of 6,000 facets which see a mosaic of the view before them. Bees can see further into the ultra violet end of the color spectrum than humans but not as far into the red spectrum. Eyes Tautz, 2008 Many flowers have complex UV color patterns to guide the bees to the center 2

3 Antennae This close-up of a honey bee antenna shows the sensory hairs and oval plates that act as both mechanoreceptors and chemoreceptors. Dade, 1994 Caron, 1999 Each antenna is a hollow tube containing the large antennal nerve, minute extensions of the tracheal system, and small muscles that move the segments upon one another - Snodgrass (1910). Images: Caron, 1999; Winston, 1991 Mouthparts Honey bees mouthparts can chew (mandibles) and suck (proboscis). Mandibles: paired "teeth" that can be opened and closed to chew, manipulate wax, clean other bees, or bite other bees or pests Zachary Huang, University of Michigan Proboscis: sucking in liquids such as nectar, water and honey, exchanging food with other bees (trophallaxis), and for removing water from nectar Thorax The thorax is the center for locomotion in the honey bee. It is the point of attachment for all six legs and both pairs of wings. It is divided into the prothoracic, mesothoracic and metathoracic segments. 3

4 Prothorax The prothorax is the first thoracic segment and is where the forelegs are attached. There is no wing attachment on the prothorax. Mesothorax The mesothorax is the second and middle thoracic segment. This is the point of attachment for the forewings and the middle pair of legs. Metathorax The metathorax is the third and final thoracic segment. This is the point of attachment for the hind legs and hind wings. Dade,

5 Wings Dade, 1994 The fore and hind wings of the honey bee are held together by hamuli which occur on the hind wing and act similar to Velcro. Each vein in the wing has a name and wing venation is a key character used to differentiate European from African honey bees. Legs The honey bee legs are modified for the function they best serve. Huang, MSU The forelegs have notches for cleaning antennae. The spine of the middle legs is used to pry pollen or resin. The hind leg is modified for collecting and transporting pollen. Legs 5

6 Abdomen The abdomen is the center for most of the vital organs in the honey bee. Note that the first abdominal segment is in front of the wasp waist fused with the thorax. Dade, 1994 All segments from the waist down are collectively termed the gaster. Honey bees secrete wax from wax glands on the ventral abdominal segments. Abdomen Z. Huang, MSU Stinger The honey bee sting is a modified ovipositor used for defense instead of for laying eggs. The worker honey bee s sting is barbed and stays beneath the skin after the doomed bee flies away. Attached to the embedded sting are nerves, muscles and glands which continue to work in the absence of the rest of the bee. 6

7 Stinger Internal Morphology The internal anatomy of the honey bee is a network of organ systems and muscles. Digestive system Nervous system Circulatory system Reproductive system Respiratory system Endocrine system Digestive System The digestive system also called the alimentary canal is responsible for food intake, nutrient uptake and excretion. The alimentary canal includes the: Esophagus salivary glands crop midgut Malpighian tubules ileum rectum 7

8 Esophagus and Crop Food enters the honey bee digestive tract through the esophagus. Glandular secretions aid in food digestion. These secretions originate in glands such as the salivary glands. From the esophagus, food enters the crop. The crop (or honey stomach ) is used to carry nectar from the flowers to the hive. Midgut Food enters the midgut through a valve called the proventriculus. Most digestion and absorption occurs in the midgut. The inner wall of the midgut is lined with a membrane, likely to protect the cells from damage by the gut contents. The Malpighian tubules act as kidneys, absorbing liquid nitrogenous wastes and passing them ultimately to the rectum. Hindgut The alimentary canal is completed by a short small intestine (ileum) and a large intestine (rectum). They compose the hindgut where food digestion is completed. Undigested food residues are reformed into feces in the rectum and eliminated through the terminal anus. Feces of adult bees contain almost intact, empty pollen grain shells. 8

9 Z. Huang, MSU Nervous System The nervous system of the honey bee consists of a brain and a ventral nerve cord extending from the head to the end of abdomen. The brain is mostly the sensory center, receiving stimuli from the eyes and antennae, and transmits the nervous impulses to the motor centers of the ventral nerve cord. Seven ganglia occur in various locations throughout the body. Most locomotion is controlled by the ganglia, not the brain. A beheaded bee can walk and sting (though not fly). Z. Huang, MSU 9

10 Circulatory System The honey bee has an open circulatory system; the main pumping organ of this system is the dorsal blood vessel. The dorsal aorta runs from the abdomen to the head. The blood (hemolymph) of the honey bee is not responsible for oxygen delivery. Its primary function is the distribution of digested food material and transfer of carbon monoxide and waste products. Reproductive System The mature reproductive cells of the male are called spermatozoa, and the female eggs or ova. Ovaries of the queen are paired, each with a bundle of ~150+ ovarioles. Workers also have paired ovaries, but the number of ovarioles depends on colony conditions. Zachary Huang, University of Michigan Queens have a spermatheca while worker bees do not. Reproductive System Ovarioles of a fertile queen are large and fill almost all of the abdominal cavity. The eggs can be fertilized by spermatozoa stored in the spermatheca When an egg is ready to be discharged, the follicle opens, the egg passes down the oviduct. Only eggs intended to develop into female larvae are fertilized. Eggs that will become males are not. 10

11 Reproductive System: Drone Testes are composed of tubules in which sperm are produced and Immature Drone mature. At sexual maturity (12-13 days post emergence), the testes are reduced. Mature Drone The endophallus is everted on mating while a pair of copulatory claspers grip the queen during copulation. While mating, the endophallus breaks off, is left in the queen, and the drone dies. Respiratory System Honey bees have external respiratory openings called spiracles. There are 3 pairs on the thorax and 7 pairs on the abdomen. They access the trachea. Zachary Huang, University of Michigan Tracheal tubes on the midgut of a worker bee. The trachea arms widen to form air sacs. The small branches and tubes (trachea and tracheoles) emerging from the sacs extend to the tissues. Bees can accelerate the passage of air into their bodies by contracting these sacs, thus speeding the oxygenation of the tissues. Endocrine System Four basic functions of endocrine system: 1) Wax production 2) Communication [internal (hormones) and external (pheromones) communication] 3) Defense 4) Food processing 11

12 Endocrine System Hypopharyngeal glands produce the food fed to young larva and are the largest glands in the worker bee. Well developed in nurse bees. Mandibular glands provide components of the bee saliva and royal jelly. They are the most developed in queens. Salivary glands occur in the head and thorax. They aid in the digestion of food. Zachary Huang, University of Michigan Endocrine System Zachary Huang, University of Michigan Wax glands on the fourth through seventh ventral abdominal segments secrete wax in liquid form onto wax plates. The wax then hardens into wax scales that are used by workers to construct comb. The Nasonov scent gland produces a pheromone that attracts other bees. The sting gland releases alarm pheromones which are used to alert other bees and mark an enemy. Larval Honey Bees Larva are almost totally inactive. They are blind and without functional legs. Their mouthparts are only capable of sucking up semi-fluid food. The alimentary canal is not complete until the first defecation of the larvae which occurs at about 10 days old. 12

13 Additional Reading: 1. Caron, D.M Honey Bee Biology and Beekeeping. Wicwas Press, Cheshire, CT. 363 pp 2. Dade, H.A Anatomy and Dissection of the Honeybee. The Alden Press, Oxford, UK. 158 pp. 3. Goodman, L Form and Function in the Honey Bee. International Bee Research Association, Cardiff, UK. 220 pp. 4. Snodgrass, R.E (1993 reprint) Principles of Insect Morphology. Cornell University Press, Ithaca, NY. 667 pp. 5. Winston, M.L The Biology of the Honey Bee. Harvard University Press. 294 pp. 13