The chapter about the anatomy of the Goodeidae is based on the contribution of Abraham Kobelkowsky to the book Viviparous Fishes from Mari Carmen Uribe and Harry Grier, 2005, New Life Publications (ISBN: 0-9645058-5-1), but structured a bit differently and supplemented by more details. The original title of this paper within the book is: "General Anatomy and Sexual Dimorphism of Goodea atripinnis (Teleostei: Goodeidae)", and may be used as basis for this website with the friendly permission of Mari Carmen Uribe, to who we communicate our thanks.
This chapter is dealing exclusively with the species Goodea atripinnis, and consequently, not all things described herein can be assigned to other species, especially to the Empetrichthyinae. Nevertheless, many things are universal valid for all species or genera, and therefore this chapter should serve as a brief introduction to the anatomy of this amazing group of fish.
Following A. Kobelkowsky, we divide the chapter into the following subchapters:
1. The Skeleton
2. The Musculature
3. The Digestive System
4. The Urogenital System
5. The Circulatory System
6. The Nervous System and the Sense Organs
7. Sexual Dimorphism in Goodea atripinnis
The Musculature
The visceral musculature encompasses the muscles of the head and the gill archs. Among the visceral muscles of Goodea atripinnis, the largest muscle is the adductor mandibulae which is straight, oriented longitudinally and is subdivided into the bundles A1 and A2. It is responsible for closing the jaws. The most important muscle for opening the mouth is the sternohyoideus. Likewise, is an extensive muscle the adductor arcus palatini. It plays - together with the levator arcus palatini - an important role in expanding the oral cavity. The protractor hyoidei brings the lower jaw down.
Based on their origin and insertion the dorsal branchial arch muscles can be divided into three groups: the external branchial arch levators, connecting the branchial arches to the neurocranium, called levatores externi I to IV for the first four branchial arches. The fifth arch has the levator posterior instead, well-separated from the levatores externi. The internal branchial arch levators or levatores interni are connecting the pharyngobranchials to the neurocranium. Finally the dorsal oblique muscles, or obliqui dorsales, are interconnecting the branchial arches and pharyngobranchials. Functionally, however, there are only two categories with the following properties: The first, which consists of the external branchial arch levators alone, is active during every respiratory cycle. These muscles expand the branchial basket through gill arch abduction and, in combination with hyomandibular pumping movements, lower the floor of the buccal cavity. The results of these combined movements are: The gill arches remain evenly distributed within the expanding branchial cavities during inspiration, so that continuity of the gill curtain is maintained. Water flow resistance is reduced also. The volume of water flowing into the buccal cavity during inspiration is increased. The second category, comprising the internal branchial arch levators and the dorsal oblique muscles, contracts only during the cough and else is completely inactive. Contraction of these muscles reinforces the dorsal suspension of the gill arches by firmly anchoring the pharyngobranchials and epibranchials to the base of the skull. In this way strong, caudally directed forces which develop during the intermediate expansion of the cough can be prevented from dislocating the branchial basket. An adductores series of five muscles connect the epibranchial and ceratobranchial elements of each arch.
Concerning the three muscles of the operculum, the dilatator operculi and levator operculi muscles are relatively broad. Together with the addcutor operculi, these muscles are responsible for opening and closing of the gill cover.
Pharyngeal musculature: A large muscle that extends posterodorsally from the upper pharyngeal jaw to the vertebral column is the retractor dorsalis muscle. It inserts on the two first precaudal vertebrae and is the dominant retractor of the upper pharyngeal jaw. An elongated muscle, the pharyngohyoideus serves primarily to protract the lower pharyngeal jaw. Acting as the functional antagonist of the pharyngohyoideus, the slender pharyngoclavicularis internus mainly mediates retraction and adduction of the lower pharyngeal jaw. The pharyngoclavicularis externus muscle has an especially wide insertion on the fifth ceratobranchial and functions mainly to mediate abduction of the lower pharyngeal jaw.
The musculature of the dorsal and anal fins consists of the inclinatores anales respectively dorsales, erectores anales respectively dorsales and depressores anales respectively dorsales. Whereas erectores and depressores are used to erect or depress the associated fin, the inclinatores move the fin rays sidewise and admit the fish to perform wavelike motions of the associated fins. The inclinatores anales muscles orginate from the fascia between the skin and the axial musculature; its longitude is bigger in males, occupying the 64.3% of the distance from the fin base to the horizontal septum, whereas in females it occupies 46.9%. The erectores anales originate from the lateral face of the proximal pterygiophores and insert widely on the anterolateral part of base of the rays; those of males are wider and longer. These muscles are broader near their insertions. The upper part of the first erector is more massive than the rest of erectors and the muscle inserts by a tendon on the first anal rays. The depressores anales muscles originate from the proximal pterygiophores and insert on the posterior part of the anal rays bases; those of males are larger.
Anterior to the anal musculature, and upon the urogenital organ, the infracarinalis medius muscle originates and surrounds part of the spermatic and urinary ducts of males. In females this muscle surrounds the urinary duct and oviduct. It is thicker in males.
From the caudal musculature, the muscles flexor ventralis and flexor dorsalis are wide. They originate from the last 4 centra and hemal and neural spines, respectively. The flexor ventralis muscle inserts on the lateral bases of the ventral branched rays, whereas the flexor dorsalis inserts on the dorsal rays. The hypochordal longitudinalis muscle originates on the hypural plate and inserts on dorsal rays 4 and 5. Contractions of these 3 muscles lead to an outfanning of the caudal fin. The supracarinalis posterior and infracarinalis posterior muscles run posteriorly in the shape of small fans on the dorsal and ventral procurrent rays. They help in performing wavelike movements with the caudal fin.
The epiaxiales form the dorsalmost components of the body musculature, whereas the hypaxiales form the ventral mass of the body musculature and are situated below the horizontal septum. Coupled with the epiaxiales, the caudal components of the hypaxiales play a central role in propulsive locomotion.
The protractor hyoidei brings the lower jaw down.
Based on their origin and insertion the dorsal branchial arch muscles can be divided into three groups: the external branchial arch levators, connecting the branchial arches to the neurocranium, called levatores externi I to IV for the first four branchial arches. The fifth arch has the levator posterior instead, well-separated from the levatores externi. The internal branchial arch levators or levatores interni are connecting the pharyngobranchials to the neurocranium. Finally the dorsal oblique muscles, or obliqui dorsales, are interconnecting the branchial arches and pharyngobranchials. Functionally, however, there are only two categories with the following properties:
The first, which consists of the external branchial arch levators alone, is active during every respiratory cycle. These muscles expand the branchial basket through gill arch abduction and, in combination with hyomandibular pumping movements, lower the floor of the buccal cavity. The results of these combined movements are: The gill arches remain evenly distributed within the expanding branchial cavities during inspiration, so that continuity of the gill curtain is maintained. Water flow resistance is reduced also. The volume of water flowing into the buccal cavity during inspiration is increased.
The second category, comprising the internal branchial arch levators and the dorsal oblique muscles, contracts only during the cough and else is completely inactive. Contraction of these muscles reinforces the dorsal suspension of the gill arches by firmly anchoring the pharyngobranchials and epibranchials to the base of the skull. In this way strong, caudally directed forces which develop during the intermediate expansion of the cough can be prevented from dislocating the branchial basket.
An adductores series of five muscles connect the epibranchial and ceratobranchial elements of each arch.
Concerning the three muscles of the operculum, the dilatator operculi and levator operculi muscles are relatively broad. Together with the addcutor operculi, these muscles are responsible for opening and closing of the gill cover.
A large muscle that extends posterodorsally from the upper pharyngeal jaw to the vertebral column is the retractor dorsalis muscle. It inserts on the two first precaudal vertebrae and is the dominant retractor of the upper pharyngeal jaw. An elongated muscle, the pharyngohyoideus serves primarily to protract the lower pharyngeal jaw. Acting as the functional antagonist of the pharyngohyoideus, the slender pharyngoclavicularis internus mainly mediates retraction and adduction of the lower pharyngeal jaw. The pharyngoclavicularis externus muscle has an especially wide insertion on the fifth ceratobranchial and functions mainly to mediate abduction of the lower pharyngeal jaw.
The musculature of the dorsal and anal fins consists of the inclinatores anales, erectores anales and depressores anales. Whereas erectores and depressores are used to erect or depress the associated fin, the inclinatores move the fin rays sidewise and admit the fish to perform wavelike motions of the associated fins. The inclinatores anales muscles orginate from the fascia between the skin and the axial musculature; its longitude is bigger in males, occupying the 64.3% of the distance from the fin base to the horizontal septum, whereas in females it occupies 46.9%. The erectores anales originate from the lateral face of the proximal pterygiophores and insert widely on the anterolateral part of base of the rays; those of males are wider and longer. These muscles are broader near their insertions. The upper part of the first erector is more massive than the rest of erectors and the muscle inserts by a tendon on the first anal rays. The depressores anales muscles originate from the proximal pterygiophores and insert on the posterior part of the anal rays bases; those of males are larger.
Anterior to the anal musculature, and upon the urogenital organ, the infracarinal medius muscle originates and surrounds part of the spermatic and urinary ducts of males. In females this muscle surrounds the urinary duct and oviduct. It is thicker in males.
From the caudal skeleton, the muscles flexor ventralis and flexor dorsalis are wide. They originate from the last 4 centra and hemal and neural spines, respectively. The flexor ventralis muscle inserts on the lateral bases of the ventral branched rays, whereas the flexor dorsalis inserts on the dorsal rays. The hypochordal longitudinalis muscle originates on the hypural plate and inserts on dorsal rays 4 and 5. Contractions of these 3 muscles lead to an outfanning of the caudal fin. The supracarinalis posterior and infracarinalis posterior muscles run posteriorly in the shape of small fans on the dorsal and ventral procurrent rays. They help in performing wavelike movements with the caudal fin.
The epiaxiales form the dorsalmost components of the body musculature, whereas the hypaxiales form the ventral mass of the body musculature and are situated below the horizontal septum. Coupled with the epiaxiales, the caudal components of the hypaxiales play a central role in propulsive locomotionThe visceral musculature encompasses the muscles of the head and the gill archs. Among the visceral muscles of Goodea atripinnis, the largest muscle is the adductor mandibulae which is straight, oriented longitudinally and is subdivided into the bundles A1 and A2. It is responsible for closing the jaws. The most important muscle for opening the mouth is the sternohyoideus. Likewise, is an extensive muscle the adductor arcus palatini. It plays - together with the levator arcus palatini - an important role in expanding the oral cavity.
The protractor hyoidei brings the lower jaw down.
Based on their origin and insertion the dorsal branchial arch muscles can be divided into three groups: the external branchial arch levators, connecting the branchial arches to the neurocranium, called levatores externi I to IV for the first four branchial arches. The fifth arch has the levator posterior instead, well-separated from the levatores externi. The internal branchial arch levators or levatores interni are connecting the pharyngobranchials to the neurocranium. Finally the dorsal oblique muscles, or obliqui dorsales, are interconnecting the branchial arches and pharyngobranchials. Functionally, however, there are only two categories with the following properties:
The first, which consists of the external branchial arch levators alone, is active during every respiratory cycle. These muscles expand the branchial basket through gill arch abduction and, in combination with hyomandibular pumping movements, lower the floor of the buccal cavity. The results of these combined movements are: The gill arches remain evenly distributed within the expanding branchial cavities during inspiration, so that continuity of the gill curtain is maintained. Water flow resistance is reduced also. The volume of water flowing into the buccal cavity during inspiration is increased.
The second category, comprising the internal branchial arch levators and the dorsal oblique muscles, contracts only during the cough and else is completely inactive. Contraction of these muscles reinforces the dorsal suspension of the gill arches by firmly anchoring the pharyngobranchials and epibranchials to the base of the skull. In this way strong, caudally directed forces which develop during the intermediate expansion of the cough can be prevented from dislocating the branchial basket.
An adductores series of five muscles connect the epibranchial and ceratobranchial elements of each arch.
Concerning the three muscles of the operculum, the dilatator operculi and levator operculi muscles are relatively broad. Together with the addcutor operculi, these muscles are responsible for opening and closing of the gill cover.
A large muscle that extends posterodorsally from the upper pharyngeal jaw to the vertebral column is the retractor dorsalis muscle. It inserts on the two first precaudal vertebrae and is the dominant retractor of the upper pharyngeal jaw. An elongated muscle, the pharyngohyoideus serves primarily to protract the lower pharyngeal jaw. Acting as the functional antagonist of the pharyngohyoideus, the slender pharyngoclavicularis internus mainly mediates retraction and adduction of the lower pharyngeal jaw. The pharyngoclavicularis externus muscle has an especially wide insertion on the fifth ceratobranchial and functions mainly to mediate abduction of the lower pharyngeal jaw.
The musculature of the dorsal and anal fins consists of the inclinatores anales, erectores anales and depressores anales. Whereas erectores and depressores are used to erect or depress the associated fin, the inclinatores move the fin rays sidewise and admit the fish to perform wavelike motions of the associated fins. The inclinatores anales muscles orginate from the fascia between the skin and the axial musculature; its longitude is bigger in males, occupying the 64.3% of the distance from the fin base to the horizontal septum, whereas in females it occupies 46.9%. The erectores anales originate from the lateral face of the proximal pterygiophores and insert widely on the anterolateral part of base of the rays; those of males are wider and longer. These muscles are broader near their insertions. The upper part of the first erector is more massive than the rest of erectors and the muscle inserts by a tendon on the first anal rays. The depressores anales muscles originate from the proximal pterygiophores and insert on the posterior part of the anal rays bases; those of males are larger.
Anterior to the anal musculature, and upon the urogenital organ, the infracarinal medius muscle originates and surrounds part of the spermatic and urinary ducts of males. In females this muscle surrounds the urinary duct and oviduct. It is thicker in males.
From the caudal skeleton, the muscles flexor ventralis and flexor dorsalis are wide. They originate from the last 4 centra and hemal and neural spines, respectively. The flexor ventralis muscle inserts on the lateral bases of the ventral branched rays, whereas the flexor dorsalis inserts on the dorsal rays. The hypochordal longitudinalis muscle originates on the hypural plate and inserts on dorsal rays 4 and 5. Contractions of these 3 muscles lead to an outfanning of the caudal fin. The supracarinalis posterior and infracarinalis posterior muscles run posteriorly in the shape of small fans on the dorsal and ventral procurrent rays. They help in performing wavelike movements with the caudal fin.
The epiaxiales form the dorsalmost components of the body musculature, whereas the hypaxiales form the ventral mass of the body musculature and are situated below the horizontal septum. Coupled with the epiaxiales, the caudal components of the hypaxiales play a central role in propulsive locomotion.The visceral musculature encompasses the muscles of the head and the gill archs. Among the visceral muscles of Goodea atripinnis, the largest muscle is the adductor mandibulae which is straight, oriented longitudinally and is subdivided into the bundles A1 and A2. It is responsible for closing the jaws. The most important muscle for opening the mouth is the sternohyoideus. Likewise, is an extensive muscle the adductor arcus palatini. It plays - together with the levator arcus palatini - an important role in expanding the oral cavity.
The protractor hyoidei brings the lower jaw down.
Based on their origin and insertion the dorsal branchial arch muscles can be divided into three groups: the external branchial arch levators, connecting the branchial arches to the neurocranium, called levatores externi I to IV for the first four branchial arches. The fifth arch has the levator posterior instead, well-separated from the levatores externi. The internal branchial arch levators or levatores interni are connecting the pharyngobranchials to the neurocranium. Finally the dorsal oblique muscles, or obliqui dorsales, are interconnecting the branchial arches and pharyngobranchials. Functionally, however, there are only two categories with the following properties:
The first, which consists of the external branchial arch levators alone, is active during every respiratory cycle. These muscles expand the branchial basket through gill arch abduction and, in combination with hyomandibular pumping movements, lower the floor of the buccal cavity. The results of these combined movements are: The gill arches remain evenly distributed within the expanding branchial cavities during inspiration, so that continuity of the gill curtain is maintained. Water flow resistance is reduced also. The volume of water flowing into the buccal cavity during inspiration is increased.
The second category, comprising the internal branchial arch levators and the dorsal oblique muscles, contracts only during the cough and else is completely inactive. Contraction of these muscles reinforces the dorsal suspension of the gill arches by firmly anchoring the pharyngobranchials and epibranchials to the base of the skull. In this way strong, caudally directed forces which develop during the intermediate expansion of the cough can be prevented from dislocating the branchial basket.
An adductores series of five muscles connect the epibranchial and ceratobranchial elements of each arch.
Concerning the three muscles of the operculum, the dilatator operculi and levator operculi muscles are relatively broad. Together with the addcutor operculi, these muscles are responsible for opening and closing of the gill cover.
A large muscle that extends posterodorsally from the upper pharyngeal jaw to the vertebral column is the retractor dorsalis muscle. It inserts on the two first precaudal vertebrae and is the dominant retractor of the upper pharyngeal jaw. An elongated muscle, the pharyngohyoideus serves primarily to protract the lower pharyngeal jaw. Acting as the functional antagonist of the pharyngohyoideus, the slender pharyngoclavicularis internus mainly mediates retraction and adduction of the lower pharyngeal jaw. The pharyngoclavicularis externus muscle has an especially wide insertion on the fifth ceratobranchial and functions mainly to mediate abduction of the lower pharyngeal jaw.
The musculature of the dorsal and anal fins consists of the inclinatores anales, erectores anales and depressores anales. Whereas erectores and depressores are used to erect or depress the associated fin, the inclinatores move the fin rays sidewise and admit the fish to perform wavelike motions of the associated fins. The inclinatores anales muscles orginate from the fascia between the skin and the axial musculature; its longitude is bigger in males, occupying the 64.3% of the distance from the fin base to the horizontal septum, whereas in females it occupies 46.9%. The erectores anales originate from the lateral face of the proximal pterygiophores and insert widely on the anterolateral part of base of the rays; those of males are wider and longer. These muscles are broader near their insertions. The upper part of the first erector is more massive than the rest of erectors and the muscle inserts by a tendon on the first anal rays. The depressores anales muscles originate from the proximal pterygiophores and insert on the posterior part of the anal rays bases; those of males are larger.
Anterior to the anal musculature, and upon the urogenital organ, the infracarinal medius muscle originates and surrounds part of the spermatic and urinary ducts of males. In females this muscle surrounds the urinary duct and oviduct. It is thicker in males.
From the caudal skeleton, the muscles flexor ventralis and flexor dorsalis are wide. They originate from the last 4 centra and hemal and neural spines, respectively. The flexor ventralis muscle inserts on the lateral bases of the ventral branched rays, whereas the flexor dorsalis inserts on the dorsal rays. The hypochordal longitudinalis muscle originates on the hypural plate and inserts on dorsal rays 4 and 5. Contractions of these 3 muscles lead to an outfanning of the caudal fin. The supracarinalis posterior and infracarinalis posterior muscles run posteriorly in the shape of small fans on the dorsal and ventral procurrent rays. They help in performing wavelike movements with the caudal fin.
The epiaxiales form the dorsalmost components of the body musculature, whereas the hypaxiales form the ventral mass of the body musculature and are situated below the horizontal septum. Coupled with the epiaxiales, the caudal components of the hypaxiales play a central role in propulsive locomotion.
