The Northern Stargazer: Romance Is Dead.
It may not be the brightest star in the ocean, but the northern stargazer is a remarkable organism; with some very unique and interesting adaptations. The northern stargazer, Astroscopus guttatus, is well adept to spending life buried in the sand, waiting to ambush its prey. It has evolved unusual and most shocking uses for its extraocular muscles. A. guttatus, is unique among teleosts, as it alone is the only marine species which has an electric organ.
This species of stargazer is distributed around the western Atlantic Ocean, ranging from New York to North Carolina, the northern stargazer is native to The Bahamas. Being a benthic dweller, the northern stargazer spends a lot if its life buried within the sandy surf zones and deeper sand – mud environments of inshore waters. The northern stargazer usually resides at depths of approximately 36m.
The Easy Life:
A. guttatus is quite lazy, spending most of its life lying under the sand waiting for the moment to ambush its unsuspecting prey. It is well adapted to life under the seabed – with modified pectoral fins that act as shovels, allowing this fish to bury itself within seconds, which can be seen in the video. One would expect living in such an environment would mean getting sand in all sorts of places, but does this matter to the northern stargazer? No. The eyes and nostrils of this teleost are somewhat strategically positioned on the top of the head, so that they are always above the sand surface when the rest of the body is hidden in plain sight.
Starry – eyed:
The eyes of the northern stargazer are unusual and very important; as A. guttatus is primarily a visual
predator. The eyes are capable of protruding outwards for a short period of time. This feature allows the ambush predator to gaze over the immediate vicinity and scope for any nearby prey. The stargazer fills the opercular cavity behind each eye with fluid thus causing the eyes to proptose.
Breathing Under Water:
Being buried under the sand proves difficult when it comes to breathing, as the gills are covered however the northern stargazer has adapted to overcome this problem. Unlike other teleost fish that use their gills to “breathe” the northern stargazer uses nostrils to do so. Similar to the eyes, the nostrils are located on the top of the head so that they don’t get buried within the sand. Fleshy comb – like fringes also help protect the nostrils from particles of sand from being breathed in.
An Intriguing Date:
The northern stargazer has a few tricks to entice prey to come closer before it strikes them down. One of which is using the unique gill slits to discharge water, causing the sand to mimic the action of a small critter moving. To the unaware victim, this movement of water and particles of sand will intrigue them and encourage them to go investigate further; tricking them into thinking there is a potential for food and ushering the oblivious fish into the striking zone of A. guttatus.
Once the prey item in in close proximity, the northern stargazer will start to put an end to the enticement with its an ocular tease. As the prey is approaching, A. guttatus will use its protruding eyes and move them in a semi circle to deceive the prey into thinking there is a tiny organism burrowing in that location. Being curious creatures, the prey will come closer to investigate further, in doing so the organism must swim over the body of the northern stargazer towards the contralateral eyes. Once the northern stargazer has its prey where it wants them, it will strike forwards and upwards, engulfing the whole of the prey; as the opening of the mouth induces a vacuum, sucking in the prey. As one would say, curiosity killed the cat.
Everyone loves to be shocked with romance, but the northern stargazer takes this quite literally, with studies showing that this species of teleost uses an electric organ to stun potential prey and predators. However, it is uncertain whether the discharge of this organ is primarily used for prey capture. It has been shown that the electric organ discharges during the process of prey capture, may be to confuse the prey item; as the discharge itself, does hold enough punch to actually kill an organism as the current is too weak.
The northern stargazer is like no other teleost fish, as it possesses an electric organ which can hold a punch of up to 50 volts. The electric organ is made up of 4 extraocular muscles; the analogue for the superior, medial and temporal recti, and the superior oblique. During the larval stages of the fish the electric organ does not exist. The electric organ only starts to develop when the larvae metamorphose, and the eyes migrate from their lateral position on the larvae to the dorsal surface of the head. This occurs when the organism starts to show the mannerisms of a benthic dweller.
However, the 4 muscles which are involved in the development of the electric organ later in the life cycle, are 6 times the size of normal muscle cells. The electric organ is unique to the northern stargazer as it is histologically different than those of other electric fish. It is made up of around 200 layers, with the outer layers primarily made up of the 4 extraocular muscles.
All in all, it is safe to say that the act of deception and teasing is the chosen tactic of the northern stargazer. Romance however, not so much, so one shouldn’t be fooled by its name.