ANATOMICAL DIRECTIONALITIES FOR SUNFISHES

The four most basic anatomical directionalities are dorsal, posterior, ventral and anterior. These are somewhat like the cardinal directions (north, east, south and west). The anatomical directionalities allow for understanding where a feature is being described on a fish and are often used for comparing the position of a feature against another feature. These descriptors are applicable to ALL FISHES in the world as well as to most other animals in zoology.

The adjacent video shares a bit more information on this topic.


THINK OF IT LIKE THIS: Let’s say you ask someone for directions to McDonald’s. They might say, “The McDonald’s is two blocks west of the Starbucks.” From this information, assuming you knew the location of the Starbucks, you would have a very good idea of what direction to walk for your burger and fries. Similarly, in this sunfishes guide I might be describing the location of a color on a species. I might say, “A bright blue ‘bowl’ exists ventrally in the eye.” Of course you know where the eye is—but without knowing what “ventrally” means, it will leave you wondering where exactly the blue is in the eye.

LEFT-RIGHT AXIS (LATERAL AXIS)

Each sunfish has two mostly symmetrical lateral sides, a left side and a right side. In the images above, the left side of the fish is visible. The pectoral fin in the image above is the left pectoral fin and the eye is the left eye, etc..

PROXIMODISTAL AXIS

Distal describes what is away from the body or body part in reference.

Proximal describes what is near the body or body part in reference.

It’s always easiest to think of your own anatomy when remembering distal and proximal. If you look at your hand and stick out your fingers you’ll see your fingernails on the distal end of your fingers. Your knuckles make up the proximal end of your fingers.

If you look at the soft rays in the fins of sunfishes you’ll notice that they start as one ray and then branch. The branching of rays occurs distally, or away from the body.

ANTEROPOSTERIOR AXIS

Anterior describes the direction towards to the front. The anterior region of a sunfish is also the cranial region where the head, mouth and snout exist. In the supporting image, it is correct to say that the most anterior edge of the upper lip is marked with a “1”.

Posterior describes the direction towards the rear. The posterior region of a sunfish is also called the caudal region as that is where the caudal fin, or tail fin, is located. In the supporting image, it is correct to say that the posterior edge of the maxillary is marked with a “2”.

DORSOVENTRAL AXIS

Dorsal describes the direction towards the back, or spinal region. Both the soft rayed and spinous dorsal fins are dorsally seated on lepomids. In the supporting image, it is correct to say that the premaxillary is dorsal to the dentary.

Ventral describes the direction towards the belly. The breast, belly, pelvic fins, anal fin, anus and urogenital opening are all located on the ventral region of sunfishes. In the supporting image, it is correct to say that wavy blue streaks exist both ventrally and anteroventrally to the eye.