Teeth of Plecostomus

     One of the species of the Plecostomus family, Plecostomus cordovae was examined by Theodore H., focusing on the needle-like teeth of pleco fish. The teeth of Plecostomus cordovae are uniform tubes of dentine which contains no enamel, flattened at the tip. The entire set of teeth in each dentary and premaxilla lies in a deep trough in the bone while each tooth attaches by a movable joint just under the overhanging rim of the trough when the tooth is developed completely, as shown in Figure 1.

i., integument of mouth; p.m., premaxilla; t., tooth.

Figure 1: (Left) Ventral aspect of head of Plecostomus cordovae; (Right) Cross-section of premaxilla of Plecostomus cordovae showing development of series of teeth.

     The teeth are piled in vertical series within the jaw, in which the teeth at the bottom being buds in the first stage of development, and those toward the exterior growing progressively more complete and more angular until the last and oldest in the series emerges ready for use. The teeth that break off are replaced by the one below. The dentine is covered by two layers of columnar cells, one outside and another inside the tooth as shown in figure 2. The columnar layer within continues down to the bottom of each papilla and up the adjacent surface of the overlying cap during the earlier stages of the tooth papilla. These layers appear to be identical in the papilla and in the surrounding cap, which suggests that both layers contribute to the deposit of the tooth. It is worth to note that the increase in thickness at the tip is due to the lengthening of individual cells instead of the multiplication of layers.

           

     For more fully developed teeth, the cells within the dentine column become nearly cut off from those outside, as the need to carry materials to the tooth must exist as well as the observed groups of erythrocytes. A capillary passes close to the base of each tooth while sending a loop up into it. Distally the dentine within the tip is transparent, thin and filled with minute canals crossing it as many different angles.

     A series of zones exists along the face of the cavity in which the teeth arise, from bottom to the top. Narrow and nearly straight tip of the teeth formed in the bottom zone; the first segment of the shaft formed in the second zone, preceded by an angle; another segment marked by an opposite bend in the third zone and the final rounded base for articulation with the bone when the tooth is in position for use in the fourth zone. Hence, the growing teeth push those above gradually outward from the bottom of the trough; different effects occur as they come to different levels. Although their nature and factor are unknown, the effects are probably due to a sequence of changes in the secreting tissues. The complete tooth is a lifeless shell as the tissues become less compact within the teeth, eventually shrink away, leaving large gaps and scattered group of cells.

c., columnar cells; cap., capillary; d., dentine; e., erythrocytes

Figure 2: Microscopic section of earliest stages in tooth development of Plecostomus cordovae

Our NEXT POST discussed on how the SUCTION of the Plecostomus' mouth INSPIRED better MEDICAL DEVICES!!!

Reference

http://www.jstor.org/stable/1436721?seq=1#page_scan_tab_contents

Dermal Plates of the Armored Catfish - Pterygoplichthys Pardalis

The Pleco fish, also commonly called the suckermouth fish, was also called by another name which is the armored catfish. The term “armoured” was given primary because the Place fish has a rather tough skin surface at the top of the fish. Because of that, Ebenstein (2015) have carried out a research on the dermal plates of this so called armored catfish. In her research paper, Ebenstein analysed the dermal plates of the Amazonian fish Pterygoplichthys pardalis (Pleco fish) which then characterized it into the structural, chemical and nanomechanical properties. Among the analysis performed by Ebenstein, the most significant discovery was from the scanning electron microscope (SEM) that reviewed that the dermal plates have a sandwich-like structure, it is made up of an inner porous matrix surrounded two external dense layer (Ebenstein et al., 2015).

            For most fishes, their outer skin layer are covered by scales. These scales found on their body are much like the other college-based natural structure such as bones, teeth and mineralized materials (Torres et al., 2008). On the contrary, the armored catfish does not have scales compared to the majority of the fishes, but instead have a rather distinct type of dermal elements such as odontodes, teeth, dermal denticles (like sharkskin) or dermal plates as Ebenstein described it in her research paper. However, a little was known about the structural, chemical and mechanical properties of this dermal plate until Ebenstein’s research in 2015.

            Based on the results obtained in the research of Ebenstein, she discussed that the dermal plates from the Pterygoplichthys pardalis are not flat like those of elasmoid fish scales, but have a 3-dimentional “V” shape as shown in Figure 1. It was measured that the dermal plates are around 15 mm in length and 1.5 mm in thickness (Ebenstein et al., 2015). The internal surface of the plates that are not exposed to water is actually smooth, whereas the external surface has a rough surface due to the presence of tubercles (see Figure 1). The tubercles are referred to as dermal denticles that are tooth-like element. On the other hand, the sharkskin is also referred to as dermal denticles but microscopic observation showed that the structure is not the same as those of the armored catfish.

Figure 1. Dermal plate of armored catfish Pterygoplichthys pardalis 

It was also reported that the tubercles on the dermal plates provided the armored catfish against penetration resistance as well as hydrodynamics (Ebenstein et al., 2015). With that said, the penetrating tooth of the catfish’s predator such as aquatic snakes, freshwater turtles or other predatory fish would have to indent the tubercles first before penetrating the external layer of the dermal plate. When the predator tooth penetrate on its dermal plate, the outer dense layer act as a shield to resist penetration while the inner matrix will deform to absorb the shock from the forces of the predator teeth during the attack, thus this help to increase the toughness of the dermal plate to prevent the fracture and penetration of the soft inner tissue beneath the dermal plates (Ebenstein et al., 2015).

Apart from that, it was also analysed that the tubercles also modify the viscous drag forces of the flowing water, surface shear stress and skin friction of the Pterygoplichthys pardalis (Ebenstein et al., 2015). So even though the dermal denticles of the armored catfish is different from that of the sharkskin, it was debated that both their dermal denticle served the same purpose of reducing drag as they swim.

Apart from structural analysis using SEM, Ebenstein also studied on the chemical properties on the dermal plates of Pterygoplichthys pardalis using FTIR, DSC and XRD that reviewed on the composition of the dermal plates, these results can be referred in the research paper as they are not the main discussion of this literature topic.

Thus, to conclude this literature review, the Pterygoplichthys pardalis does not have scales but rather a dermal plates that has a 3-dimasional “V” shape structure. The main findings from Ebenstein reviews that the tubercles on the external surface of the dermal plate served to provide protection for the Pterygoplichthys pardalis against predator in its habitat and also reviewed that it also modify the water flow across the surface of the fish which provided hydrodynamics.

Be sure to CHECK OUT our NEXT POST where we share how the skin of the fish INSPIRED the development of a NEW TYPE of BODY ARMOUR!!!

Reference

1. Ebenstein, D., Calderon, C., Troncoso, O.P. and Torres, F.G., 2015. Characterization of dermal plates from armored catfish Pterygoplichthys pardalis reveals sandwich-like nanocomposite structure. Journal of the Mechanical Behavior of Biomedical Materials, 45(February), pp.175–182.
2. Torres, F.G. et al., 2008. Characterization of the nanocomposite laminate structure occurring in fish scales from Arapaima Gigas. Materials Science and Engineering C, 28(8), pp.1276–1283.

Habitat and Diet of the Hypostomus Plecostomus

Living environment

The natural habitat of the Pleco fish consisted of streams, rivers and also ponds. The Pleco fish however do preferred slow moving waters which have shelters during the day as they are nocturnal. They tend to seek shelters such as driftwoods and aquatic plants. Thus, one should provide the aquarium with suitable shelter or a ‘hiding place’ if they plan to adopt a Pleco fish. With some inside of the living environment of the Pleco fish, the group have provided the shelters in the form of the short PVC pipes. It was observed that the Pleco adopt themselves well in the PVC pipes and can be found residing inside the pipe most of the time. Providing a hiding place also reduces the stress as well as the aggression of the Pleco fish. Figure 1 and Figure 2 show the PVC pipe as shelter.

Figure 1. PVC pipe as shelter

Figure 2. Pleco fish inside PVC pipe

Diet

Pleco fish exhibit a diverse diet as there are omnivores. Their range of diet include algae, other plant material, insects and even small crustaceans which they can find in the wild.  Fellow Pleco fish owners are advised to provide a similar range of diet in their aquariums. The best choice of food for the Pleco fish are ones which can sink to the bottom, therefore, the group have purchased sinking fish pellets for them.  Figure 3 below shows the fish pellet fed to the Plecos.

Figure 3. Sinking pellets

Although this fish pellets are rich in proteins, but are fairly low in fibre content. To provide a substantial amount of fibre in their diet, fruits and vegetables can be regularly fed to them, but bear in mind not to fed them acidic fruits or vegetables. Many of the website and blogs visited have reviewed that zucchinis are one of the favourite foods of the Pleco fish. We have try feeding the Plecos with zucchinis and they absolutely love it. Besides getting the source of fibre through fruits and vegetables, a common recommendation from websites and blog are to provide the Plecos with driftwoods.

Reference

1. Oscar Fish.com, 2016, Pleco Dietary Needs... Supplementary Food [Online]. Available at: http://www.oscarfish.com/article-home/fish/99-pleco-dietary-needs.html [Accessed: 30 May 2016].
2. Seymor, M., 2014, Common Pleco - The Care, Feeding and Breeding of Common Plecos - Aquarium Tidings [Online]. Available at: http://aquariumtidings.com/common-pleco/ [Accessed: 30 May 2016].

Position of Pleco Mouth

     If you observed closely, different species of fish will have different mouth position. The mouth position of fish, whether it is angled up, ahead or down actually correlates with the trophic ecology of the fishes. The majority of fishes have terminal mouth regardless of trophic habits, which means that their mouth opens forward.  Any deviation from the terminal location of the fish's mouth will usually indicate that their different feeding habitat.

     Compared to other fishes, the Pleco's mouth is positioned on the bottom , which means their mouth open downwards when feeding. This type of fish mouth characterizes the fish as algae eaters or bottom feeders. Fishes with such mouth are termed inferior or subterminal, where most of them belonged to the catfish species.

     One amazing fact about inferior mouth fish is that they too can feed on food that is floating on the water surfaces. Believe it or not, they can position themselves in an upside-down position if the food does not sink to the bottom.

     The video below showed a rare video of our Pleco feeding upside-down on the cucumber we feed them every day. YOU REALLY HAVE TO SEE TO BELIEVE IT!! NO JOKE!!!

Reference

1. Helfman, G., Collette, B., Facey, D and Bowen, B., 2009,  The Diversity of Fishes: Biology, Evolution, and Ecology, 2edn, Wiley.

The Anatomy of Pleco

Figure1. Anatomy of Pleco

Dorsal Fin

The dorsal fin is located at the top of the Pleco fish. This fin supports the balancing of the fish and also allowed the fish to swim in a straight path. Dorsal fin also plays an important role in stabilizing the fish against rolling in the water. A unique feature of the Pleco fish is that it has a huge dorsal fin compared to other aquarium fish. The dorsal fin of juvenile Pleco is usually folded (closed) when they are stationary. When the juvenile Plecos are resting on the wall of the aquarium or any surfaces, their dorsal fin is always closed to minimize turbulence from water currents. As they reach adulthood, the dorsal fin can be seen to remain open at all times. This could possibly because the larger body mass of the adult Pleco can help to maintain balance even when the dorsal fin remains open.

Pectoral Fin

The pectoral fins are located just below the Pleco grills as do most fishes. Main functions of these fins are to facilitate the swimming capabilities of the fish. These fins also allowed the Pleco to hover or glide in water. Generally, the pectoral fins are always moving in most fishes to keep them stable in the water. But it has been a week that we observed our Plecos, their pectoral fins remained immobile most of the time if they are not swimming around the aquarium. This is because they spent a majority of the time attaching to surfaces, so their pectoral fins remained still to induce minimal movement.

Pelvic Fin

The pelvic fins are situated at the bottom of the Pleco fish just in front of the anal fin. Like most other fished, Pleco fish used these fins to change the direction of their motion in water while also stabilizing themselves. Besides that, the Pleco uses the pelvic fins for breeding purpose. For Plecos fishes, the male species will be the one caring for their offspring. He will guard the eggs, occasionally turns them over with his mouth and wait for it........ he will supply oxygen to the eggs by fanning them with his pelvic fins. The video below captured the precious moment where the male Pleco is fanning the eggs. It is soooo adorable!!!

Caudal (Tail) Fin

The caudal (tail) fin as it name suggest is located at the back of the Pleco fish. This is one of the most important fin of any fished as it is the main fin which allows them to propel forward. This is the only fin of the Pleco (other fishes as well) that is connected with the spine of the fish. In some species of fish, the caudal fin can easily distinguish the sex of the fish, a good example is Guppies. Just like the dorsal fin of juvenile Plecos, the caudal fin is usually closed and open only if the Plecos are in motions. Similarly, the caudal fin remained open at all times they reached adulthood 

Anal Fin

The anal fin is exactly what the name state, where the fin is located near the anal cavity which is between the pelvic fins and caudal fin. Anal fin also aids the Pleco in swimming on a straight path. For some fishes, the anal fin plays an important role for spawning.

Eye

The eye of the Pleco is unique compared to most of the species of aquarium fishes. The Pleco has an eye structure called the “iris operculum” which enables them to monitor the amount of light entering their eye during the day. Plus it also helps them to disguise their eye-spot. The iris of the Pleco was also referred to as the “omega iris” because as the operculum is closed the pupil of the Pleco actually resembles the Greek letter Omega.

References

http://www.monsterfishkeepers.com/forums/threads/pleco-anatomy.29321/
http://hubpages.com/animals/all-about-algae-eaters
http://www.tropical-fish-success.com/fish-anatomy.html

https://www.youtube.com/watch?v=0ASUfZnIoBk