Exercise 28. Revision of the diseases. Match symptoms to the disease.

bovine babesiosis	lethargy, loss of appetite, coughing, difficulty breathing, diarrhea, jaundice, blindness, eye problems
coccidiosis	fever, eyes and gums are pale with anemia, they are also jaundiced, red-colored urine, constipation (in later stages), late-pregnant animals may abort; in severe cases – incoordination, paralysis, coma, followed by death
toxoplasmosis	diarrhea, big weight loss, emaciation, depression, dehydration, pale mucous membrane; in some cases, neurologic symptoms – muscular tremor, convulsions of head and neck

UNIT 7

ARTHROPODS AND DISEASES CAUSED BYARTHROPODS

 

TEXT A

ARTHROPODS

VOCABULARY LIST TO TEXT A

antennae n (pl)	[æn'teniː]	усики
appendage	[ əˈpen.dɪdʒ ]	конечность
Arachnids n (pl)	[ə'ræknɪds]	паукообразные
Arthropoda n (pl)	['ɑːθrɔpədə]	членистоногие
botfly n	['bɔtflaɪ]	овод
calcium carbonate	['kælsɪəm] ['kɑːb(ə)neɪt]	карбонат кальция
compound eye	['kɔmpaund][aɪ]	сложный глаз
Crustaceans n (pl)	[krʌs'teɪʃ(ə)n]	ракообразные
(double nerve) cord n	['dʌbl][nɜːv][kɔːd]	двойной нервный тяж
dramatic adj	[drə'mætɪk]	существенный
extinct adj	[ɪk'stɪŋkt]	вымерший
flea n	[fliː]	блоха
fly n	[flaɪ]	муха
fuse v	[fjuːz]	здесь: сливаться (воедино)
gill n	[gɪl]	жабра
gnat n	[næt]	мошка
grasshopper n	['grɑːsˌhɔpə]	кузнечик
habitat n	['hæbɪtæt]	местообитание
hard ticks	[hɑːd] [tɪks]	«твердые» (иксодовые) клещи
harden v	['hɑːd(ə)n]	отвердевать
hemocoel n	[ˈhiməsil]	гемоцель
horse-fly n	[hɔːsflaɪ]	слепень
marine adj	[mə'riːn]	морской
metamorphosis n	[ˌmetə'mɔːfəsɪs]	метаморфоз
mite n	[maɪt]	(чесоточный) клещ
molt v	[məult]	линять
mosquito n	[mɔs'kiːtəu]	комар или москит
mouthparts n (pl)	['mauθˌpɑːts]	ротовой аппарат
Myriapods n (pl)	[mɪrɪəˈpədz]	многоножки
olfactory adj	[ɔl'fækt(ə)rɪ]	обонятельный
preference n	['pref(ə)r(ə)n(t)s]	предпочтение
single basic body plan n	['sɪŋgl] ['beɪsɪk]['bɔdɪ][plæn]	единый план строения тела
(soft) ticks	[sɔft] [tɪks]	«мягкие» (аргасовые) клещи
spiracle n	['spaɪərəkl]	дыхальце (у насекомых)

 

The phylum Arthropoda (meaning “jointed feet”) is the largest and most varied in the animal kingdom. It includes over one million described species. This represents approximately three-quarters of all known biological organisms, living or extinct. Countless arthropods remain undescribed (not yet named and studied), and the actual number of living species could be as high as ten million or more. Arthropods are found in literally every known marine (ocean-based), freshwater, and terrestrial (land-based) ecosystem, and vary tremendously in their habitats, life histories, and dietary preferences.

Despite the remarkable variety of arthropod species, all share aspects of a single basic body plan. All arthropods possess a stiff exoskeleton (external skeleton) composed primarily of chitin. In some species lipids, proteins, and calcium carbonate may also contribute to the exoskeleton. The external skeleton offers organism protection as well as support for the body. The exoskeleton is incapable of growth, and is molted (shed) repeatedly during the growth of the animal. Molting allows for rapid growth until the newly secreted exoskeleton hardens.

Arthropod bodies are divided into segments. However, a number of segments are sometimes fused to form integrated body parts such as head, thorax and abdomen. Arthropods also have appendages(attachments) with joints. In early primitive arthropods each body segment was associated with a single pair of appendages. However, in most species some appendages have been modified to form other structures, such as mouthparts, antennae, or reproductive organs.

Some arthropods have highly developed sense organs: principal and secondary eyes to see (spider), Johnston’s organ to maintain balance (butterfly and bee), olfactory sensillum to smell (fruit fly), Haller’s organ to detect hosts (tick), tympana organ to hear (grasshopper). Most species have paired compound eyes. Arthropods have an open circulatory system that consists of a tube that is the heart and an open hemocoel, in which blood pools. Arthropods also have a complete gut with two openings, the mouth and the anus.

Gas exchange in the phylum occurs in various ways. Some species have gills, while others employ tracheae. The tracheal respiratory system consists of external openings called spiracles. They are linked to a system of branched tubules, which allow respiratory gases to reach internal tissues. Arthropods have a brain as well as a nerve ring around the area of the pharynx. A double nerve cord extends backwards along the ventral surface of the body, and each body segment is associated with its own ganglion (mass of nerve cells). In most arthropod species, the sexes are separate. Fertilization usually occurs internally, and most species are egg laying. While some species exhibit direct development, in which eggs hatch as miniature versions of adults, other species pass through an immature larval stage and undergo a dramaticmetamorphosis before reaching adult form.

Arthropods include Insects (having 3 pairs of legs), Arachnids (having 4 pairs of legs), Crustaceans (having 5 pairs of legs) and Myriapods (having up to 750 legs). Insects and Arachnids are of veterinary concern.

Insects include fleas, mosquitoes, flies, botflies, horse-flies, gnats and others. Arachnids include spiders, scorpions and Acari (Acarina). The last ones, in turn, include various ticks and mites. Ticks are divided into so-called hard ticks (Ixodidae) and soft ticks (Argasidae). They are about 0.5 cm while mites are microscopic.

A surprisingly large number of various diseases are transmitted by insects and other arthropods, either mechanically, by carrying infective material on their biting mouthparts, or by the fact that they act as intermediate hosts for the complete development of certain disease-producing organisms. Some diseases of animals can be transmitted only through the instrumentality of specific arthropod hosts. This knowledge is of great importance and practical value, because it enables veterinarians and livestock sanitation centers to control and in many cases to eradicate a number of animal diseases by attacking or destroying arthropods responsible for their transmission.

Apart from being vectors and transmitting significant number of different diseases, both insects and acari bother animals biting or literally eating them. They may causediseases like mange, dermatitis, gastrophilosis, etc.

EXERCISES TO THE TEXT

Exerise 1. a) Make up collocations using words from both columns.

primitive	exoskeleton
jointed	importance
complete	arthropods
great	gut
stiff	feet

b) Fill in the gaps with the collocations from above.

1.The phylum Arthropoda (meaning “…”) is the largest and most varied in the animal kingdom.

2. All arthropods possess a …(external skeleton) composed primarily of chitin.

3. In early …each body segment was associated with a single pair of appendages.

4. Arthropods also have a …with two openings, the mouth and the anus.

5. This knowledge is of … and practical value, because it enables veterinarians livestock sanitationcenters to control, and in many cases to eradicate a number of diseases of animals by attacking or destroying arthropods responsible for their transmission.