UNIT 17 BENEFICIAL NON-CHORDATES structure Introduction Objectives Broad Categorisation of beneficial nature of non-chordates on-chordates used as food Phylum Arthropods as source of food Phylum Mollusca.as source of food Non-chordates yielding food-Honey Composition of honey Kinds of honey bees How is honey produced Non-chordates yielding Industrial Products Silk Lac Beeswax Shells Pearls Precious corals Sponges Dyes and pigments Medicinal uses of Non-chordates Non-chordates useful in agriculture Non-chordates improve fertility of soil Non-chordates as pollinators Non-chordates as destroyers of pests Non-chordates as components in food chains and as scavengers Summary ~erminalquestions Answers 17.1 INTRODUCTION 'In Unit- 16 you have studied the harmful non-chordates and have seen that some of the worst disease-producers and food-destroyers are non-chordates. In this Unit you pill realise aat some non-chordates are beneficial to man. It is not the intention here to point out how they constitute significant links in the natural cycles including the food chains, or how they serve as research material in the hands of scientists but we will make a sqrvey as to how some of these we find extremely useful in a variety of other.ways. This unit will familiarise you with the variety of ways in which non-chordates are of benefit to man, directly and indirectly. Objectives After studying this unit you will be able to : categorise the ways in which the non-chordates are beneficial to humans, i describe the usefulness of non-chordates as sources of food, list the various industrial products of non-chordates and briefly describe the manner I in which these are produced by them, I cite examples of non-chordates that have been used as sources of medicines and as 1 objects of decoration, I iii I point out how they are useful agriculture. 17.2 BROAD CATEGORISATION OF BENEFICIAL NATWRE OF NON-CHORDATES I Many non-chordates are beneficial to humans in numerous ways This beneficial nature can be either direct or indirect. The direct usefulness may include their utilization as food 1 or as a source of prodi.e+s thzt fulfil human needs. The indirect benefits are the result of I their activites whirh in turn contribute to human welfare. The list below aims to classify broadly how the non-chordates are usehl to humans. Adaptation and Behavioural Pattern A. Directly beneficial 1. Used as food 2. The food they gather is used as food for human consumption. 3. They produce useful substances 4. Used in medicine 5. Used as.objects of beauty and decoration B. Indirectly beneficial 1. Useful in agriculture 2. They clean the environment and thus serve as scavengers. ' We shall now examine each of the above points in detail and survey the contributions of different non-chordates to human welfare. 17.3 NON-CHORDATES USED AS FOOD - - - - - - - - Among non-chordates only arthropods and molluscs contain edible species. 17.3.1 Phylum Arthropoda as Source of Food Though some primithe tribes are known to eat insects like termites and grasshoppers, well-recognised edible species are limited to crustaceans. CRUSTACEANS Though many crustaceans are edible, only the larger ones are of commercial significance. Most shrimps are small and are hence not of much commercial value. But prawns, lobsters and crabs are larger and are hence exploited commercially. All these come under order Decapoda. These are of great food value and are an important source of earning especially foreign exchange. The main export products are frozen prawns, canned ' prawns, dried prawns, prawn pickles, frozen crab meat and canned crab meat. 1. Prawns and Shrimps Prawns and shrimps have cylindrical or compressed body and the abdomen is large with q . peculiar bend (Fig. 17.1). The carapace has a well developed rostrum. Thoracic legs are slender, anterior ones being chelate. These swim in water. Prawns are considered a delicacy throughout the world. There are various species of prawns that inhabit the sea, freshwater reservoirs, rivers and estuaries. The following are some important species of prawns that are commercially exploited: Penaeus indicus (Indian prawn) found in coastal regions only; Penaeus monodon and Metapenaeus monoceros (Giant tiger prawn) found in fresh as well as salt watets; Macrobrachium malcomsonii : inhabit fresh and brackish water; Macrobrachium scabriculum : seen in fresh water only; and Macrobrachium rosenbergii: The giant fresh water prawn. Carapace Fig. 17.1: A Shrimp Crangon, side view Penaeus indicus is the commoneit Indian prawn which constitutes the bulk of the catch. It grows upto 20 cm in length. P. monodon grows even longer upto 30 cm. Metapenaeus monoceros is one of the most suitable species to be cultured in India and other tropical countries. For fresh water culture the giant prawn Macrobrachium rosenbergii is the most suitable. Prawn culture or farming is rapidly growing in various countries like Philippines, Japan, U.S.A., Taiwan, as well as India where ponds, tanks, paddy fields, estuaries and coastal sea waters are being.converted into prawn raising areas. 2. Lobsters Lobsters are large heavy bodied marine crustaceans. They have straight dorsoventrally flattened body, with heavier legs. Their first pair of walking legs are strongly chelate (chelipeds) for capturing prey. They are adapted for creeping or crawling. Homarus americanus (Fig. 17.2) the American lobster, may grow to a length of 60 cm and weigh over 20 kg. The European lobster Homarus gammarus is smaller. Scyllarus is the Spanish lobster. Panulirus is the Indian lobster. Fig. 17.2: A lobsterHomarusamericanu.~. 3. Crabs Crabs are chiefly marine crustaceans with short body and flattened broad carapace (cephalothorax) usually as wide as It is long. They have a small abdomen that curls forward and is held tightly beneath the cephalothorax. The chelipeds are modified as grasping pincers (Fig. 17.3). Crabs crawl on the surface when crawling rapidly they move sideways. Many crabs are treated as delicacy in mahy parts of the world. Porrunus sanguinolentus, P. pelagicus and Chatybdis cruciata are some edible Indian crabs. Fig. 17.3: A cr.b 17.3.2 Phylum Mollusca as Source of Food Many molluscs are edible, Scallops, mussels, clams, oysters, snails, squids and octopuses are examples. Ostrea is perhaps the best known edible oyster Crassostrea madrapemis (the Indian backwater oyster), Crassostrea cucullata (the rock oyster) and C. discoidea (disc oyster) are Indian edible oysters. They are marine bivalves. Several fresh water mussels such as Unio and Anodonta are also eaten. The common edible European mussel are Mytilus edulis and the closely related M. galloprovincialis. They are also cultivated in the sea either on poles, or on the seabed or from fixed frames or from freely floating structures in the sea. h@tilus viridis and M. edulis are the Indian species. The important molluscan beds in India are along the west coast and the Palk strait and the Gulf of Adaptation and Eehaviourrl Pattern Mannar. The gastropods are not of much significance as a source of food, though some species are eaten by poorpeople. So are cephalopods also in India, thou@ they are caught from the east coast for export. Sepioteuthis arctipinnis is such an Indiaq species. SAQ 1 i. Which two non-chordate phyla provide the largest variety of edible forms ? ...................................................................................................... ii. List any four crustaceans that are commonly eaten. ...................................................................................................... ,iii. Mention if the following statements are true (T) or false (F). (a) Prawn culture is a growing industry. (b) Shrimps are chiefly marine forms. (c) No insects are eaten in any part of the world. (d) All fiesh water mussels are avoided as food. (e) Primitive human races often include insects like beetles, grubs and caterpillars in their food. (f) Shrimps can grow to a size of 30 cm in length. 17.4 NON-CHORDATES YIELDING FOOD - HONEY - - - - - - - - - - We have all tasted honey at some time or the other in our lives and are familiar with the honey bees. The honey bees are insects (order Hymenoptera). Social life has attained a high degree of perfection in these insects and their social organisation and behaviour will be dealt with separately under the unit Behavioural Patterns. These honey bees produce honey and store it in their hive and use it for themselves and for their young ones. Man discovered it and started gathering honey long back. In the early days they squeezed out the honey from the hives of the bees that lived in wild state. Even today many tribal people collect honey like this fiom'forests. Later, they devised vaious types of apiaries and domesticated the honey bees. The practice of bee keeping is now very common almost throughout the world and is designated as apiculture. In India, the Khadi and Village Industries Commission is encouraging bee keeping on a large scale. Tamil Nadu, Kerala, Karanataka, Jammu and Kashmir and Himachal Pradesh are major honey producing states in India. 17.4.1 Composition of Honey Honey is an aromatic viscid product. It is sweet ada highlynutritious food. It is a product modified by the honey bees from plant nectar, and is consumed in many ways, as a spread, and is used in making drinks, candies, cakes, and is also used as a medicine. Honey is an instant source of'energy. Its solid constituents are mostly monosaccharides which are readily absorbed into the blood. The rich vitamin and mineral contents further enhance the nutritive value of honey. Chemical composition of honey: The composition of honey varies and the composition of an average sample of honey shows the following table: Sugars Fructose - 40-50% Glucose - 32-37% Sucrose - 2% Maltose - traces Polysaccharides Dextrins - 1- 12% Beneficin\ Non-ckordates Vitamins - Abundant A,B and C vitamins Minerals - Traces of iron, copper, manganese, magnesium, sodium, potassium, calcium, si,lica and phosphates.