AQUACULTURE

 

Preliminary Fish Dissection

Head and Gills, March 23-27, 2007, Species Unknown

This particular specimen I opened up was obtained from a local fish market earlier today. I would say it is a Croaker, and fairly certain that was the species, but made the error of not making a note when the sales-lady told me.

I looked at one of the gills under the microscope and was surprised to see there were no parasites {at least not any of which I observed). I have been studying and learning about fish parasites and diseases, and one of the parasites' favorite hideouts apparently are the gills. Parasites, I have learned, are a common occurrence in agricultural products, though not normally in great numbers.. they still exist on the meat products which are purchased. Parasites are present on every human, including the regularly and freshly bathed, if you want to get technical about it. Parasites are a normal occurrence in both humans and livestock. The point is, the fish market I visited evidently had higher quality fish in stock and for sale, if no parasites were present in the gills, and worth mentioning, they were relatively clean gills. Of course, there may be a fallacy in my presumption because bacteria are too small to detect with the equipment I currently have access to, which would include in the event of a dangerous bacteria such as Listeria. Such questions, including those I'm still unaware exist, are what I'm seeking to get answers to, throughout future courses in college.

All photos are provided as thumbnails. By clicking on thumbnail, the high resolution version should open in another window.
Fish Dissection
Fig. 1
Fish Dissection
Fig. 2
Fish Dissection
Fig. 3
Fish Dissection
Fig. 4
Fig. 3-4. When I began this preliminary dissection (to get hands-on with the fish's organs, to know where I am going with it, and further research I will need to do) I knew I wanted to learn how the eye's components are interrelated. I've got closeup to the fish eye. I was quite surprised at the end of the evening when I finally some details about the inside-workings of a fish eye. Though I am not at all clear on how similar the structure of the human eye is in comparison with fish, this was a fascinating learning experience in itself (See the two tiny clear balls at end of this page, in the photos).
Fish Dissection
Fig. 5
Fish Dissection
Fig. 6
Fish Dissection
Fig. 7
Fish Dissection
Fig. 8
Figure 5-8, though not excessive, the slime coating the gills got my attention. Excessive "mucus" may be the side-effect and can be produced in fish, by some parasitic protozoans, and lead to suffocation of the fish. How much mucus is normal? This is, what I presume is meant by "mucus". Another feature which struck me as fascinating, was the teeth-like structures throughout the gills. I'm asking myself at this point, what purpose they serve? They are not designed to thwart parasites, but in fact can be quite painful for larger predators (like humans) who choose to handle the fish around the gills. I was also able to capture some fairly good closeup to the hair-like lining on the gills. Later, I plan to research the individual parts and correct names for parts of the gills.
Fish Dissection
Figure 9
Enlarge image to full resolution 2816 x 2112 pixels

Gills as an indicator of freshness of fish
Fresh gills: gills are a characteristic red colour and mucus is absent; spoiled gills: gills are discoloured with excessive mucus.
Fresh head: eyes are clear and concave ; spoiled head: eyes are cloudy and sunken.
From How fresh is your fish?

 

Fish Dissection
Fig. 10
Fish Dissection
Fig. 11
Fish Dissection
Fig. 12
Fish Dissection
Fig. 13
Fish Teeth - Bucal Cavity
Roof of Mouth showing bones with teeth.
Fish Teeth - Bucal Cavity
Floor of Mouth showing bones with teeth and tongue.

Illustrations adapted from Miller and Lea, 1972 Guide to the Coastal Marine Fishes of California

Fish Dissection
Fig. 14
Fish Dissection
Fig. 15
Fish Dissection
Fig. 16
Fish Gills Dissection
Figure 17
Enlarge image to full resolution 2816 x 2112 pixels
This image was created from the outside of the gills. It's purpose, for me, is presently unknown. There seems to be a row of teeth-like points on this opening in the fish' body, located outside and above the region of the gills (bent downward in photo).
Gills Dissection
Fig. 18
Gills Dissection
Fig. 19
Gills Dissection
Fig. 20
Gills Dissection
Fig. 21
Figure 18-21. More angles of the region where a row of teeth is exposed (see also Fig. 43). Black spots can be noted around some of the teeth (Fig. 19), but presumably this is due to natural pigmentation.
Fish Teeth
Figure 22
Enlarge image to full resolution 2816 x 2112 pixels
On this particular species small teeth along the roof of the mouth are not easily detected with the unaided eye. By running my finger across the upper mouth, it was abrasive and clear to the touch, small teeth were protruding from the surface skin. Presumably, the gills have these same small teeth protruding on the surface.
Both lower and upper palettes are abrasive to the touch, and do not appear to have even rows of teeth. Rows of teeth are staggered, see Figures 23 and 24. Staggered teeth are heavily protruded on lower palette of mouth, see Figure 25. Sharks also share this trait (Fig. 32), though in contrast to bony fish, sharks lack bones (made of cartilage) and lack a swim bladder.
Fish Teeth
Figure 24
Lower palette of mouth (right).
Enlarge image to full resolution 2816 x 2112 pixels
Fish Teeth
From Figure 33, staggered teeth lining upper palette.
Teeth
Fig. 23
Teeth
Fig. 25
Shark Teeth
Figure 32. Goby shark, with staggered teeth placement. (Image source: Encyclopedia of Sharks, Parker/Parker 2002, Firefly Books)
Gills
Fig. 30

Position of Gill Arches inside Gill Cavity of a bony fish (Gill cover or Operculum removed.)

Gill Rakers

Fig. 31
b. Side view of first gill arch. (A raker in the angle between the upper and lower limbs is counted with the lower rakers.)
c.Top view of cross-section of 1st gill arch.
- Illustrations adapted from Miller and Lea, 1972, Guide to the Coastal Marine Fishes of California

 

Gills
Fig. 26
Gills
Fig. 27
Gills
Fig. 28
Gills
Fig. 29

Figures 26-31. Observing the formation of eight "gill arches," evenly distributed on both sides with the right side of what I presume would be the "operculum" or covering of the gills, detached from the fish.

Gills and Teeth
Fig. 33
Gills
Fig. 34
Gills and Teeth
Fig. 35
Gills and Teeth
Fig. 36

Figures 33-34, provides magnification in structure of gills. Figures 35-36 focusing on upper palette filled with rows of staggered teeth and lower jaw.

Gills and Teeth
Fig. 37
Gills and Teeth
Fig. 38
Gills and Teeth
Fig. 39
Gills and Teeth
Fig. 40

Figures 37-40, concentrating on the lower and upper palette and how the mouth fits together.

Gills and Teeth
Fig. 41
Gills
Fig. 42
Teeth on Exterior
Fig. 43, See Figs. 18-19 notes.
Gills
Fig. 44
Tongue-eating Louse

A parasite which gobbles up a fish's tongue then acts to replace it with its own body. The bug, usually found off the coast of California, has the scientific name cymothoa exigua - was discovered inside the mouth of a red snapper bought from London.
Source: Fish Tongue Parasite

Fish Mouth and Tongue
Fig. 45
Fish Mouth and Tongue
Fig. 46
Fish Mouth and Tongue
Fig. 47
Fish Mouth and Tongue
Fig. 48

Figures 44-51, focusing on the mouth of the fish and its tongue.

Fish Mouth and Tongue
Fig. 49
Fish Mouth and Tongue
Fig. 50
Fish Mouth and Tongue
Fig. 50
Fish Mouth and Tongue
Fig. 51
Fish Mouth
Figure 52
Enlarge image to full resolution 2816 x 2112 pixels
Fully expanded mouth of a fish.

Fish suck, or at least most do when they eat, drawing food into their mouths like underwater vacuum cleaners. Still, key details of how the complicated, kinetic mix of some 60 bones and 80 muscles orchestrate activity in the head of a bony fish to suck down meals eluded biologists for decades. Given that suction feeding is found in the majority of fish species, despite wild variations in head anatomy, it must be of immense evolutionary importance. Now, using ultrasound-emitting crystals implanted in the mouth of some hungry bass, Christopher Sanford and Peter Wainwright have for the first time captured the split-second changes fish mouth cavities go through when gulping down food (p. 3445).

Suction feeding is accomplished by an explosive expansion of the cheeks, with water flowing in like air sucked into a bellows. Changes in the fish's head structure induce the sudden suction pressure, but attempts to measure the bone movements using highspeed video recordings failed, because the skull obscured the view of these moving bone structures. Since looking at the mouth from the outside wasn't working, the researchers decided to poke around inside instead.

Suction feeding in fishes is the result of a highly coordinated explosive expansion of the buccal cavity that results in a rapid drop in pressure. Prey are drawn into the mouth by a flow of water that is generated by this expansion. At a gross level it is clear that the expansion of the buccal cavity is responsible for the drop in pressure. From the positional relationships of six piezoelectric crystals we monitored the internal movements of the buccal cavity and mouth in both mid-sagittal and transverse planes. We found that peak subambient pressure was reached very early in the kinematic expansion of the buccal cavity, occurring at the time when the rate of percentage change in buccal volume was at its peak. Using multiple regression analyses we were consistently able to account for over 90%, and in the best model 99%, of the variation in buccal pressure among strikes using kinematic variables. Sonomicrometry shows great promise as a method for documenting movements of biological structures that are not clearly visible in the external view provided by film and video recordings.
From How Fish Hook Fish

Expanded Fish Mouth
Fig. 53
Expanded Fish Mouth
Fig. 54
Expanded Fish Mouth
Fig. 55
Expanded Fish Mouth
Fig. 56
Expanded Fish Mouth
Fig. 57
Expanded Fish Mouth
Fig. 58
Expanded Fish Mouth
Fig. 59
Underside of Fish Head
Fig. 60
Fish Mouth
Figure 61
Enlarge image to full resolution 2816 x 2112 pixels
Fully expanded mouth and fish' tongue.
Underside of Fish Head
Fig. 62
Expanded Gills
Fig. 63
Expanded Gills
Fig. 64
Expanded Gills
Fig. 65
Expanded Gill Arches
Figure 66
Enlarge image to full resolution 2816 x 2112 pixels
Fully expanded gills revealing teeth distributed throughout the gills.
Expanded Fish Gills
Fig. 67
Expanded Fish Gills
Fig. 68
Expanded Fish Gills
Fig. 69
Expanded Fish Gills
Fig. 70
Expanded Fish Gills
Fig. 71
Magnified Fish Gills
Fig. 72
Magnified Fish Gills
Fig. 73
Magnified Fish Gills
Fig. 74
Magnified Fish Gills
Fig. 75
Magnified Fish Gills
Fig. 76
Magnified Fish Gills
Fig. 77
Magnified Fish Gills
Fig. 78
Magnified Fish Gills
Fig. 79
Magnified Fish Gills
Fig. 80
Magnified Fish Gills
Fig. 81
Magnified Fish Gills
Fig. 82
Magnified Fish Gills
Fig. 83
Magnified Fish Gills
Fig. 84
Gill Arch
Fig. 85
Gill Arch
Fig. 86
Gill Arch
Figure 87
Enlarge image to full resolution 2816 x 2112 pixels
Close-in shot on the center of a gill arch, and the teeth-like protrusions on the underside.
Gill Arch
Fig. 88
Gill Arch
Fig. 89
Magnified Fish Gills
Fig. 90
Magnified Fish Gills
Fig. 91
Magnified Fish Gills
Fig. 92
Magnified Fish Gills
Fig. 93
Magnified Fish Gills
Fig. 94
Magnified Fish Gills
Fig. 95
Magnified Fish Gills
Fig. 96
Magnified Fish Gills
Fig. 97
Magnified Fish Gills
Fig. 98
Magnified Fish Gills
Fig. 99
Gill Arch
Fig. 100
Upper palette and teeth
Fig. 101
Teeth on Jaw
Fig. 102
Teeth on Jaw
Fig. 103
Upper Palette and Teeth
Figure 104
Enlarge image to full resolution 2816 x 2112 pixels
Close-in shot on the upper palette and staggered teeth.
Teeth on Jaw
Fig. 105
Teeth on upper palette
Fig. 106
Teeth on upper palette
Fig. 107
Teeth on upper palette
Fig. 108
Teeth on lower palette
Fig. 109
Teeth on lower palette
Fig. 110
Teeth on lower palette
Fig. 111
Lower Palette and Teeth
Figure 112
Enlarge image to full resolution 2816 x 2112 pixels
Close-in shot on the lower palette and staggered teeth.
Pore
Fig. 113
Pore
Fig. 114
Pore
Fig. 115
Pore
Fig. 116
Pore
Fig. 117
Skull and Nervous System Fragments
Fig. 118
Skull and Nervous System Fragments
Fig. 119
Skull and Nervous System Fragments
Fig. 120
Skull and Nervous System Fragments
Fig. 121
Skull and Nervous System Fragments
Fig. 122
Skull and Nervous System Fragments
Fig. 123
Skull and Nervous System Fragments
Fig. 124
Wiring of Eyes
Figure 125
Enlarge image to full resolution 2816 x 2112 pixels
Close-up to the eyes, their x-cross wiring, which connects then to the brain.
Brain of a Fish
Figure 126
This preparation shows the central and peripheral nervous system isolated from a carp.
From UC David University, Teaching Resources Center

 

Wiring of Eyes
Figure 127
Enlarge image to full resolution 2816 x 2112 pixels
Close-up to the eyes and the direct connection which exists between them.
connection between eyes
Fig. 128
connection between eyes
Fig. 129
connection between eyes
Fig. 130
connection between eyes
Fig. 131
connection between eyes
Fig. 132
connection between eyes
Fig. 133
connection between eyes
Fig. 134
connection between eyes
Fig. 135
fish eye
Fig. 136
fish eye
Fig. 137
fish eye
Fig. 138
fish eye
Fig. 139
fish eye
Fig. 140
Optic Nerve
Fig. 141
Eye Lens
Fig. 142
Eye Lens
Fig. 143

Optic Nerve
Figure 144
Enlarge image to full resolution 2816 x 2112 pixels
Close-up to the connection between the eyes. When the insulting flesh was forcibly pulled away from the eyes, thin, but very strong wire remained between both eyes.

I am lead to believe I'm looking at the exposed optic nerve and insulating myelin. The white tissue which surrounded this thin wire, must be myelin, and the thin wire itself must be the optic nerve which according to one source, "transmits electrical signal from the retina to the brain... it connects to the back of the eye near the macula... the visible portion of the optic nerve is called the optic disc." And from another source states, "Myelin is a substance that acts like insulation around a nerve. Just as insulation on a electric wire protects the wire, myelin protects nerves. When a nerve loses its insulation, the messages in the nerve slow down. This slowing affects the ability of the nerve to do its job."

Eye Dissection - Squid
Figure 145
From Squid Dissection, Mississippi State University

Eye Lens
Fig. 146
Eye Lens
Fig. 147
Eye Lens
Fig. 148
Eye Lens
Fig. 149
Eye Lens
Fig. 150
Eye Lens
Fig. 151
Eye Lens
Fig. 152
Eye Lens
Fig. 153

Eye and Lens
Figure 154
Enlarge image to full resolution 2816 x 2112 pixels
Close-up to the eye with details of the surrounding, protective tissue restraining fluid which covers the lens. Figures 142- reveal the single round lens which sets within fluid. A close up to an intact eye makes visible the important role the lens plays in the build and structure of an eye.

Eye and Lens
Figure 155
Enlarge image to full resolution 2816 x 2112 pixels
The lens separated. I must presume this gelatanous fluid surrounding the lens, likely aids in protection of the eye through buoyancy. The actual fluid which creates the dark pupil coloration is very watery. It is seen in the form of a puddle around the gel mass.

Eye Lens
Fig. 156
Eye Lens
Fig. 157
Eye Lens
Fig. 158
Eye Lens
Fig. 159
Eye Lens
Fig. 160
Eye Lens
Fig. 161
Eye Lens
Fig. 162
Eye Lens
Figure 164
Enlarge image to full resolution 2816 x 2112 pixels
The lens of fish eyes.

Comments, on this page.

 

Return to Index