Characteristics of orders-9-NUDIBRANCHIA,10-RHODOPACEA,11-PYRAMIDELLACEA ,12-PARASITA of subclass OPISTHOBRANCHIA

Order 9:-NUDIBRANCHI

 1)They do not have or are naked

 2) They do not have internal gill or ctenidium an
    osphradium

 3) Mantle and mantle cavity is absent in them

 4) They respire by secondary branchiae which are usually

     arranged in circlet around the anus.


    Examples:-Doris, Tritonia, Armina, Eolis.   

Armina

 
Eolis 

Eolis

Order10:-RHODOPACEA 

  1) They are vermiform snail.

  2) They are without external appendages.

  3) They have nephridia of protonephridial type.

       Example:-Rhodope.  

Rhodope.

Order11:PYRAMIDELLACEA
  1) They have spirally twisted shell
  2) They have long invaginable proboscis.
  3) They do not have operculum.
  4) They do not have gills and radula. 
       Examples:-Turbonilla, Odostomia

Turbonilla,

Odostomia

Order12:- PARASITA

 1) They are endoparasitic gastropods found in the interior 
  of holothurians.

  2) They are extremely degenerated snails. 
Examples:-Entoconcha, Thyonicola

Entoconcha

Thyonicola

       






























   












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Characteristics of orders-6-PHILILNOGLOSSACEA,7-SACCOGLOSSA,8-NOTASPIDEA of subclass OPISTHOBRANCHIA

Order6:- PHILILNOGLOSSACEA

             1) They are minute naked snail.

         2) They do not have head appendages.

         3) They do not have gills..

           4) They have visceral mass separated from the foot   

                only by a shallow groove.

                Example:- Philinoglossa.

Philinoglossa

Order7:- SACCOGLOSSA

               1)They may be with or without shell.

             2) They have suctorial type of Pharynx.

             3) They have closed type of sperm duct.

             4) They have Parapodia and cerata.

                Example:- Oxynoe.

oxynoe

oxynoe

Order8:-NOTASPIDEA

1)They may or may not have shell.

2) They donot have Parapodia.

3) They have bipectinate gills and ospharadium on the right side.

4) They have mantle but devoid of mantle cavity.

   Examples:-Tylodina, Pleurobranchus.

Pleurobranchus.

                     















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Characteristics of orders-3-ANASPIDEA,4-PTEROPODA,5-ACOCHILIDIACEA of subclass OPISTHOBRANCHIA

Order3:- ANASPIDEA

1) They are mostly found in tropica; and subtropical 
     waters.

2) They have small shell more or less covered by 
     mantle.

3) They have well developed Parapodial lobes.

4) The anterior end of these animals bears a pair of  

     tentacles ,a pair of rhinophores and a pair eyes.

5) The sperm duct opens to the penis located    
     anteriorly after running through the body length.

     Examples:-Aplysia, Akera.

Aplysia californica

Aplysia

                 

Alkera

                    



Order4:- -PTEROPODA

1) They include Pelagic snails with or without   
    shell.

2) They swim by a pair of lateral expansions.

                            3) They are protandrous , hermaphrodite with   
                                an  open sperm  groove.

                               Examples:-Spiratella, Cavolina, Peraclis, Clione.

                          

Spiratella

Cavolina

   

            











Order5:- ACOCHILIDIACEA

     

1)They are minute without shell or naked snail.

2) They have gills ,parapodia and visceral sac  

     projecting  behind the foot.

3) They may be monoecious or dioecious.

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Characteristics of order1-ONCHIDIACEA and order2-CEPHALASPIDEA of subclass-OPISTHOBRANCHIA

Order1-ONCHIDIACEA

1) They are slug-like, naked or without shell.

2) They have mantle which is projected widely beyond  

    the foot.

3) They have head with a pair retractile tentacles each  

     tipped with an eye.

4) Pulmonary sac ,anus and female gonopore located at 

     the posterior end.

5) They have male gonpore placed posteriorly.

  Examples:-Onchidium, Onchidella.

Onchidella nigricans

Onchidella celtica

 

     

Order2-CEPHALASPIDEA 

1) They generally have shell but may be partly or wholly

    enclosed by mantle.

2) They may or maynot have Parapodial lobes.

3) They have head with tentacular shield.

Examples:-Acteon, Hydatina, Bulla

Bulla peasiana

Acteon tonatilis 

Hydatina

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Characteristics of subclass 2-OPISTHOBRANCHIA of Gastropoda

1) They are exclusively marine gastropods.

    2) They have reduced type of shell and when present 

         often covered with mantle or pedal folds.

    3) They do not have operculum usually.

    4) They have single gill or often replaced by secondary 

         branchiae in the form of dorsal outgrowth.

        5)They have heart with one auricle posterior to the

            ventricle.

        6)They have mantle cavity rotated to right side or often

             lost due to detorsion.

                7)They have nervous system concentrated due to

                    detorsion.

                8) They are hermaphrodite.

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Characteristics of order3 –Stenoglossa of subclass-PROSB RANCHIA

1)They have shell with more or  elongated siphonal canal.

2)They have radula which consist of rows with two or three teeth in each rows.

  Examples: Murex, Magilus, Buccinum, Meulongena,Conus and Teregera.

 Conus geographus

Parts of Conus geographus

Murex

Magilus

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Characteristics of order2 –Mesogastropoda of sub class PROSOBRANCHIA

1)    They are the Prosobranchia with siphon, penis  and 
        non –calcified Operculum.

2)    They have radula of taenioglossare type with 7 teeth   
        in each row.

3)    They have one monopectinate gill.

4)    They have heart with one auricle.

5)    They have one ospharadium and  nephridium.

6)    They have nervous system concentrated without pedal cords.

Examples:-Viviparus, Ampullarius, Pila, Valvalata, Truncatella, Littorina, Hydrobia, Jonthina,Cypraea.

Viviparus

Ampullarius 

Ampullarius gigas

   
        

Cypraea

Hydrobia

Littorina

Littorina

Cypraea.

Cypraea.



 

         

Characteristics of order –Archaeogastropoda of sub class PROSOBRANCHIA

1) They are the Prosobranchia without proboscis, siphon,penis  

    and prosrratic glands.

2) Operculum is also present in many forms with few exception.

3) They have one or two bipectinate internal gills.

4)  They have heart mostly with two auricles.

5)  They usually have two osphradia.

6)  They have two nephridia.

7)  They have nervous system which is not concentrated and usually with two pedal cords.

8) They discharge the sex cells directly into the sea by the right nephridia.
Examples:-Haliotis, Fissurella, Acamaea, Patella, Trochus, Asteraea. Turbo.
        

Fissurella volcano

Patella

Trochus snail

                                                    

Characteristics of subclass of Mollusca-PROSOBRANCHIA

1)    They are mostly marine ,few freshwater or terrestrial forms.

2)    They have visceral mass twisted.

3)    They have mantle cavity which opens anteriorly in front of the visceral mass.

4)    They generally have conical and spirally coiled  shell with an operculum.

5)    They have distinct head with snout bearing a pair of tentacle and a pair of eyes.

6)    They have muscular foot that forms the ventral part of the body.

7)    They may have ctenidia or gills and if present are situated in the front of the heart.

8)    Sexes are separate

Characteristics of Mollusca’s class-GASTROPODA

1)    They are marine, freshwater, terrestrial and few parasitic on echinoderms. 

2)    They have unsegmented, asymmetrical  body with a univalve, spirally coiled shell. 

3)    They have distinct head with tentacles, eyes and mouth. 

4)    They have foot which is ventral, broad, flat and muscular forming the creeping sole and often bearing dorsally a hard piece, the operculum on its posterior end. 

5)    They have visceral mass spirally coiled exhibiting torsion. 

6)    Mantle is a collar-like fold of body wall, lining the body whorl leaving a space, the mantle cavity ,between itself and the body. 

7)    They have Buccal cavity containing an odontophore with radula bearing rows of chitinous teeth. 

8)    They have digestive system consisting of a muscular pharynx, long oesophagus, stomach, long coiled intestine and anteriorly placed anus. 

9)    Most of them respire through gills(ctenidia ) ,some of them through the wall of the mantle cavity and many by lungs. 

10) They have open circulatory system with heart enclosed Pericardium

11) They have excretory organs  consisting of metanephridia which are paired in primitive forms and reduced to a single nephridia in most forms.
12)They have nervous system comprising of distinct cerebral and pleural besides buccal, pedal, parietal and visceral ganglia.

13)Most of them have sexes in two bodies(dioecious) but few have both the sexes in same body.

14) The development  includes trochophore and veliger larval stage.