Pengertian, Ciri-ciri, Klasifikasi, dan Peranan Mollusca

Mollusca

Moluska (filum Mollusca, dari bahasa Latin : Molluscus = lunak, merupakan hewan triploblastik selomata yang bertubuh lunak. Ke dalamnya termasuk semua hewan lunak maupun tanpa cangkang, seperti berbagai jenis siput, kiton, kerang-kerangan serta cumi-cumi dan kerabatnya.

Moluska merupakan filum terbesar kedua dalam kerajaan binatang setelah filum Arthropoda. Saat ini ada 35 ribu jenis dalam bentuk fosil. Moluska hidup di laut, air tawar, payau dan darat. Dari palung benua di laut sampai pegununggan yang tinggi, bahkan mudah saja ditemukan di sekitar rumah kita.

Moluska dipelajari dalam cabang zoology yang disebut malakologi (malacology).

Ciri-ciri Mollusca :

•         Merupakan hewan triploblastik

•         Tubuh bertipe simetri bilateral

•         Tubuh tidak bersegmen

•         Memiliki mantel yang dapat membuat cangkang dari kalsium karbonat dan kelenjar lendir

•         Sistem pencernaan sempurna

•         Sistem saraf terdiri atas ganglion otak, ganglion padat, dan ganglion viseral (organ dalam)

•         Sistem peredaran darah terbuka, kecuali cephaloda

•         Alat ekskresi berupa ginjal

•         Alat pernapasan berupa insang, pulmonum, epirdemis, atau mantel

•         Tidak semua bersifat hermafrodit

•         Pembuahan dilakukan secara eksternal

Daur Hidup Mollusca

Klasifikasi Mollusca

•         Kelas Amphineura

Tubuh Amphineura berbentuk pipih dan oval, contohnya Chyton. Hewan tersebut memiliki fase larva yang disebut trokofor. Kamu dapat menemukan hewan tersebut pada batuan sepanjang tepi pantai yang dangkal.

•         Kelas Scaphoda

Kelas Scaphoda memiliki cangkang berbentuk gading yang pada ujungnya terdapat lubang atau mantel. Hewan sebagian besar hidup di laut tersebut dilengkapi tentakel untuk menyampaikan makanan berupa protozoa ke dalam mulut. Contohnya, siput gading (Dentalium entale).

•         Kelas Gastropoda

Kelas Gastropoda memiliki perut yang juga berfungsi sebagai kaki. Kaki tersebut selalu basah oleh lendir yang dihasilkan kelenjar lendir (Glandula pedalis) di bawah mulut.

Tubuh Gastropoda dilindungi oleh cangkang yang berbentuk seperti kerucut. Cangkang tersebut tersusun dari tiga lapisan, berturut-turut dari arah luar lapisan periostrakum, lapisan prismatik, dan lapisan mutiara (nakreas).

Tubuh gastropoda terdiri dari atas kepala, leher, kaki dan alat-alat dalam. Pada kepala terdapat dua pasang antena, yang pendek berfungsi sebagai indra pembau (kemoreseptor), sedangkan pada ujung antena yang panjang terdapat bintik mata. Bintik mata berfungsi panjang terdapat bintik mata.

Bintik mata berfungsi untuk membedakan intesintas cahaya. Pada bagian kaki terdapat sepasang statosis atau alat keseimbangan. Bekicot termasuk hewan hermafrodit, tetapi tidak dapat melangsungkan pembuahan sendiri. Kedua sel kelamin dibentuk di dalam ovotestis. Contohnya, bekicot, siput dan siput telanjang.

•         Kelas Pelecypoda

Kelas Pelecypoda memiliki kaki berbentuk kapak. Kelompok tersebut disebut juga kelas Lamellibranchiata karena memiliki insang yang berlapis-lapis, atau kelas Bivalvia karena memiliki sepasang cangkang. Contoh Bivalvia adalah tiram (Mytilus sp., Osterea sp.), remis (Buccinus sp.) dan kerang mutiara (Melengrima margaritivera)

Di dekat mulut terdapat palp yang berfungsi sebagai alat peraba untuk bergerak, dan untuk menangkap makanan. Bivalvia tidak memiliki kepala. Tubuhnya dilindungi oleh sepasang cangkang yang dihubungkan dengan ligamen. Pembukaan dan penutupan cangkang diatur oleh otot aduktor.

•         Kelas Cephalopoda

Kelas Cephalopoda memiliki kaki yang terdapat di kepala. Kaki tersebut berfungsi sebagai alat gerak dan penangkap mangsa. Kulit tubuhnya mengandung zat kromatofor sehingga dapat berubah warna sesuai dengan lingkungannya. Contohnya, cumi-cumi (Logilo palii), sotong (Sepia officinalis), gurita (Octopus), dan nautilus (Nautilus pompilus). Nautilus merupakan satu-satunya sefalopoda yang bercangkang.

Sefalopoda memiliki beberapa lengan yang berevolusi dari kaki, misalnya cumi-cumi memiliki 10 lengan, sedangkan gurita memiliki 8 lengan. Pada ujung lengan terdapat cakram penghisap Pergerakan hewan tersebut dikemudikan oleh otot berbentuk cerobong di bagian kepala. Pergerakan ke arah depan dan belakang dilakukan oleh sirip pendayung di sebalah kanan dan kiri tubuh.

Sefalopoda memiliki sistem peredaran darah ganda yang tertutup. Darahnya berwarna biru karena mengandung tembaga. Hewan tersebut bersifat gonokoris.

Peranan Mollusca

Manusia telah memanfaatkan moluska sebagai bahan makanan (cumi-cumi, sotong, kerang dan siput) dan perhiasan (kerang dan tiram). Selain itu, serbuk cangkang kerang laut berpotensi sebagai obat maag.

Tidak semua moluska menguntungkan bagi manusia. Bekicot dan keong dalam jumlah banyak dapat menjadi hama makanan. Cacing hati yang menginfeksi manusia memanfaatkan siput air sebagai inang sementara.

Similes

Similes

1.      Similes showing qualities of creatures :

as agile as a monkey

as blind as a bat

as brave as a lion

as bright as a lark

as busy as a bee

as calm as a cat

as crafty as a fox

as devoted as a mother

as fast as a deer

as fast as a hare

as fat as a pig

as feeble as a child

as fierce as a lion

as frisky as a lamb

as gentle as a dove

as gentle as a lamb

as graceful as a swan

as hairy as a gorilla

as happy as a king

as happy as a lark

as harmless as a dove

as heavy as an elephant

as hungry as a hunter

as hungry as a wolf

as industrious as a beaver

as like as two herrings

as loyal as an apostle

as mad as a hatter

as mad as a march hare

as meek as a lamb

as obstinate as a mule

as playful as a kitten

as playful as a puppy

as plump as a partridge

as poor as a church mouse

as proud as a peacock

as quiet as a mouse

as sick as a dog

as silly as a sheep

as slippery as an eel

as slow as a snail

as slow as a tortoise

as sober as a judge

as strong as a horse

as strong as an ox

as sure-footed as a goat

as swift as a deer

as swift as a hare

as swift as a hawk

as tall as a giant

as tenacious as a bulldog

as tender as a chicken

as tender as a shepherd

as thick as thieves

as timid as a mouse

as timid as a rabbit

as wise as an owl

as wise as Solomon

as white as a ghost

2.      Similes showing special qualities of things

as bitter as gall

as black as coal

as black as soot

as bold as brass

as bright as a button

as brittle as glass

as brown as a berry

as clean as a whistle

as clear as a bell

as clear as crystal

as cold as ice

as cool as cucumber

as dead as a doornail

as deaf as a doorpost

as dry as a bone

as fat as butter

as fit as a fiddle

as flat as a pancake

as fresh as a daisy

as fresh as paint

as good as gold

as green as grass

as hard as horn

as hard as iron

as hard as nails

as heavy as lead

as hot as a furnace

as light as a feather

as neat as a new pin

as old as the hills

as quick as lightning

as regular as the clock

as right as rain

as safe as houses

as safe as the bank

as sharp as a needle

as sharp as a razor

as quiet as the grave

as smooth as glass

as soft as butter

as soft as down

as soft as putty

as sound as a bell

as sour as vinegar

as steady as a rock

as straight as an arrow

as sturdy as an oak

as sweet as honey

as thin as a rake

as tough as leather

as warm as wool

as weak as a water

as white as a sheet

as white as a snow

as ugly as sin

as unpredictable as the weather

as easy as A.B.C

as large as life

as pale as death

English Grammar - Collective Nouns

Collective Nouns

1.      A collective noun is used for a group of people, things or animals which are considered as a whole.

2.      Example :

·         PEOPLE AND ANIMALS

an army of soldiers                      

a band of musicians                     

a bench of magistrates                   

a board of directors                     

a brood of chickens                      

a choir of singers                        

a class of scholars                       

a company of actors                     

a crew of sailors                         

a drove of cattle                         

a flock of birds                          

a flock of sheep                         

a gaggle of geese                       

a gang of labourers                      

a gang of thieves                        

a herd of buffaloes                      

a herd of cattle                          

a litter of kittens

a nest of rabbits

a pack of rascals

a pack of wolves

a plague of insects

a pride of lions

a pod of whales

a shoal of fish

a staff of servants

a staff of teachers

a stud of horses

a swarm of bees

a swarm of insects

a team of horses

a team of oxen

a troop of monkeys

a troupe of dancers

·         THINGS

a batch of bread                               

a bouquet of flowers                           

a bunch of grapes                       

a bundle of rags                         

a clump of trees                         

a cluster of diamonds                    

a cluster of stars                        

a clutch of eggs                         

a collection of pictures                   

a flight of aeroplanes              

a flight of steps                          

a forest of trees                         

a library of books

a pack of cards

a set of china         

a set of clubs          

a set of tools

a string of beads

a string of pearls

a suit of clothes

a suite of furniture

a suite of rooms

a fleet of motorcars

a fleet of cars

a fleet of ships