Thekey differencebetween placoid and cycloid scalesis that placoid scales are triangular, rough structures present incartilaginous fish,虽然圆形尺度是圆形的,但存在于bony fish.
Theexoskeletalcovering of vertebrates is made of two types of scales. They are epidermal and dermal. Epidermal scales are well developed in vertebrates such as reptiles, birds, and mammals, while dermal scales are well developed in fish. Placoid scales and cycloid scales are two types of dermal scales. They act as protective structures against predators.
内容
1.Overview and Key Difference
2.What are Placoid Scales
3.什么是环形尺度
4.相似之处 - 板岩和环形尺度
5.Placoid vs Cycloid Scales in Tabular Form
6.摘要 - Plosoid vs Cycloid量表
What are Placoid Scales?
Plosoid尺度是微小的,三角形的牙齿样结构,覆盖了软骨鱼的皮肤。生物体达到完全成熟后不会生长。Plosoid尺度包含嵌入在鱼皮中的矩形底板。它们也被称为真皮齿,因为它们从生物体的真皮层中生长出来。就像牙齿一样,它们具有内核,其中包括结缔组织,血管和神经。牙髓腔是由一层分泌牙本质滋养的。牙本质是一种钙化材料,它形成了另一层鳞片。这些拟合在以前形成的旧秤之间。牙本质涂有一种称为玻璃体的牙釉质样物质。玻璃体比牙本质硬,并且在外胚层中产生。
Placoid scales are usually packed tightly together. They grow facing backwards and lay flat on the skin. Placoid scales are rough, and the structure is impossible to penetrate. These scales protect fish from predators. The triangular shape reduces drag and increases turbulence when swimming.
什么是环形尺度?
Cycloid scales are smooth-edged, uniform structures that cover the skin of bony fish. These scales contain two regions. The inner fibrous layer is composed of collagen, while the outer bony layer is a calcium-based frame. At a cooler temperature, cycloid scales tend to grow closely and slowly, leaving a dark band called the annulus.
细胞量表大多在晚期鱼类中发现,它们为生物体提供了外部保护。它们是灵活的,并且具有圆形轮廓。由于存在胶原蛋白,因此中心的厚度较厚。暴露于后区域的秤的一部分显示出较少的脊,并且前部区域嵌入皮肤中。环形尺度是重叠的量表,并包含生长环。随着鱼的生长,这些鳞片继续增长。这会导致量表上同心生长环的模式。
What are the Similarities Between Placoid and Cycloid Scales?
- 在鱼类中可以看到骨质和环形尺度。
- They provide external protection.
- 都是真皮。
Plosoid和Cycloid量表有什么区别?
Placoid scales are triangular, rough structures present in cartilaginous fish, while cycloid scales are round, flexible structures present in bony fish. Thus, this is the key difference between placoid and cycloid scales. Moreover, placoid scales stop growing once the fish matures with time, but cycloid scales grow with the growth of fish. Furthermore, placoid scales are tightly packed scales, unlike cycloid scales.
The below infographic presents the differences between placoid and cycloid scales in tabular form for side by side comparison.
摘要 - Plosoid vs Cycloid量表
Placoid and cycloid scales are present in fish, and they provide external protection against predators. Placoid scales have the unique feature of not growing after an organism is fully matured, while cycloid scales grow along with the growth of the organism, resulting in growth rings. The tough structure of placoid scales is a result of the presence of a calcified substance called dentine. Placoid scales are mainly present in cartilaginous fish, while cycloid scales are present in bony fish. So, this summarizes the difference between placoid and cycloid scales.
Reference:
1.“”Galleries: Cycloid Fish Scale.”尼康的显微镜.
2. Kennedy, Jennifer. “Learn Why Shark Skin Is so Rough.”ThoughtCo.
Image Courtesy:
1.“”Osteichthyes – Carassius auratus (cycloid scales detail)” By MAKY.OREL – Own work (CC0) via Commons Wikimedia
2. “Fossilized scales 2“通过Paleopermru– Own work(CC BY 4.0)via Commons Wikimedia
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