解剖やイトヨ鰓スケルトンのフラットマウント
Summary
The branchial skeleton, including gill rakers, pharyngeal teeth, and branchial bones, serves as the primary site of food processing in most fish. Here we describe a protocol to dissect and flat-mount this internal skeleton in threespine sticklebacks. This method is also applicable to a variety of other fish species.
Abstract
The posterior pharyngeal segments of the vertebrate head give rise to the branchial skeleton, the primary site of food processing in fish. The morphology of the fish branchial skeleton is matched to a species’ diet. Threespine stickleback fish (Gasterosteus aculeatus) have emerged as a model system to study the genetic and developmental basis of evolved differences in a variety of traits. Marine populations of sticklebacks have repeatedly colonized countless new freshwater lakes and creeks. Adaptation to the new diet in these freshwater environments likely underlies a series of craniofacial changes that have evolved repeatedly in independently derived freshwater populations. These include three major patterning changes to the branchial skeleton: reductions in the number and length of gill raker bones, increases in pharyngeal tooth number, and increased branchial bone lengths. Here we describe a detailed protocol to dissect and flat-mount the internal branchial skeleton in threespine stickleback fish. Dissection of the entire three-dimensional branchial skeleton and mounting it flat into a largely two-dimensional prep allows for the easy visualization and quantification of branchial skeleton morphology. This dissection method is inexpensive, fast, relatively easy, and applicable to a wide variety of fish species. In sticklebacks, this efficient method allows the quantification of skeletal morphology in genetic crosses to map genomic regions controlling craniofacial patterning.
Introduction
多様性の信じられないほどの量は、特に魚類の中で、脊椎動物のうち、頭部骨格に存在します。多くの場合、この多様性は、異なる給餌戦略1を容易に– 4を 、そして外部と内部の両方の頭蓋顔面パターン形成に大きな変更を伴うことができます。鰓スケルトンは魚の喉の内部に位置し、口腔の大部分を取り囲みます。鰓骨格は鰓をサポート前部4そのうちの5連続的相同セグメントで構成されています。一緒にこれらの5つのセグメントは、魚や彼らの食糧5との間のインタフェースとして機能します。鰓耙、咽頭歯、および鰓骨などの形質の多数の変動は、食品のさまざまな種類の効率的な採餌に貢献しています。
トゲウオは、北半球全体の淡水湖や小川植民地化先祖の海洋形後の適応放散を受けました。食生活の変化海の小さな動物プランクトンから淡水でより大きな獲物には、いくつかの頭蓋顔面の特性6の劇的な栄養変化をもたらしました。多くの研究は、トゲウオ7で外部頭蓋顔面の違いに焦点を当ててきたが– 13、重要な頭蓋顔面の変更は内部鰓スケルトンで繰り返し進化します。形態学的に異なるトゲウオ集団との間の肥沃なハイブリッドを作成する機能は、鰓スケルトンへの進化の変化の遺伝的基礎をマッピングするための絶好の機会を提供します。
生態学的意義の一つ栄養特性は、鰓耙、鰓骨の前部と後部の顔を並べると獲物のアイテムをフィルタリングするために使用されている定期的な皮膚、骨のパターニングです。一般的に小さな獲物のアイテムを餌に魚がより長く、より密に間隔を置い鰓が大きい獲物14,15を餌に魚に比べ耙持っている傾向があります。鰓耙の変化が報告されている両方のwithinと種間14-19、および鰓放蕩者のパターニングの側面は、栄養ニッチとフィットネス16に貢献しています。数十年にわたる研究が盛んthreespineトゲウオで17鰓放蕩者の数と長さの変化を報告している– 21;しかし、これらの研究は、一般的に鰓耙の最初の行に焦点を当てます。最近の研究は、1または単一の鰓の放蕩者が理解するために行以上のことを学ぶことの重要性を強調23、長さ24間隔鰓スケルトン22,23を横断し、鰓放蕩者で単一の行全体で鰓放蕩者数の遺伝的制御にモジュール性を示しています鰓放蕩者の減少の発生遺伝的基盤。
生態系と生物医学の両方の重要性の第二の栄養特性は、咽頭歯のパターニングです。魚類における歯は咽頭歯として知られている、両方の口腔顎にし、鰓スケルトンに配置することができます。口腔歯は、pのために主に使用されています27 –咽頭歯は咀嚼と獲物操作25のために使用されている間レイキャプチャします。両方のセットは、共有発達機構を介して形成し、相同28発達と考えられています。このようなゼブラフィッシュ、不足口腔および背側咽頭歯29のようないくつかの種は、他の種は、複数の歯付きceratobranchialsを持ってpharyngobranchials、時にはbasihyal歯と30を hypobranchialsながら、それによって興味深いモジュール性が発生します。トゲウオでは、咽頭歯は前部と後部31を pharyngobranchials上の第五ceratobranchialと背に腹側に発見されました。トゲウオ供給上のキネマティクスは、口腔顎は主に獲物捕獲および咽頭顎に咀嚼を残して吸引送り9を容易にするために使用されることを示します。シクリッドでは、下咽頭顎形態は劇的32,33が変化し、適応および栄養ニッチ34と相関することが示されています。マルチPLE淡水トゲウオ集団は腹側咽頭歯数23,35,36の劇的な増加を進化させてきました。最近の研究は、この進化した歯利得の発達の遺伝的基礎は淡水トゲウオ36の2つの独立して誘導された集団における大部分は別個のものであることを示しました。哺乳動物の歯とは違って、魚は成人期37を通じて継続的に自分の歯を再生成します。これらの前述の高い歯付淡水集団の両方が再生36の遺伝的基礎を研究するまれな脊椎動物のシステムを提供すること、加速歯の交換レートを進化させてきました。
淡水トゲウオで繰り返し進化してきた第三の栄養特性は長く、それぞれ38 epibranchialとceratobranchial骨、上下の顎の鰓弓の分節同族体、です。長い鰓の骨が大きく口腔を与え、おそらくより大きな獲物アイテムはcできるようにするために適応されていますonsumed。また、他の魚で、epibranchial骨は背側咽頭歯プレート25のうつ病のために重要です。鰓耙と咽頭歯と同じように、鰓骨は、内部および容易に視覚化または定量化することは、困難です。
ここでは、分析する詳細なプロトコルを提示し、重要な頭蓋顔面形質の様々な簡単に可視化および定量化を可能にする、鰓骨格をフラットマウント。このプロトコルは、トゲウオの解剖を説明しているが、これと同じ方法は、他の魚の様々に取り組んでいます。
Protocol
Representative Results
Discussion
The branchial skeleton is a complex set of bones in the throat of a fish that manipulates, filters, and masticates food items on their way to the esophagus. Many interesting trophic traits including the patterning of gill rakers, pharyngeal teeth, and branchial bones vary across and within species. The majority of these traits are difficult to near impossible to accurately measure with the branchial skeleton in situ (e.g., gill raker length, branchial bone length). This flat-mounting protocol places all…
Disclosures
The authors have nothing to disclose.
Acknowledgements
This work was funded in part by NIH R01 #DE021475 to CTM and an NSF Graduate Research Fellowship to NAE. Thanks to Miles Johnson for assistance with imaging and Priscilla Erickson for critical reading of the manuscript.
Materials
| Sodium Hydroxide (KOH) | EMD | PX1480-1 | |
| Glycerol | Sigma-Alderich | G7893-4L | |
| 10% Neutral Buffered Formalin (NBF) | Azer Scientific | NBF-4-G | |
| Alizarin Red S | EMD | 116-12 | |
| Microscope Cover Glasses 22x60mm | VWR | 16004-350 | |
| 100x10mm Glass Petri Dish | Kimble Chase | 23064-10010 | To dissect samples on |
| Sylgard 184 Silicone Elastomer Kit | Ellsworth Adhesives | 184 SIL ELAST KIT 0.5KG | Can be poured into glass or plastic petri dishes to make dissecting plates |
| Modeling Clay | Sargent Art | 22-4000 | 1lb cream |
| Scintillation Vials (case of 500) | Wheaton | 66021-668 | Borosilicate Glass with Screw Cap |
| Forceps-Dumont #5 Inox (Biologie tip) | FST | 11252-20 | Dumostars are an alternative |
| Dissecting Scissors | FST | 15003-08 | Alternate sizes are available depending on size of sample |
| Dissecting Microscope | Leica | S6E with KL300 LED | Many other models work nicely, having a flat base helps |
| Microcentrifuge Tubes 1.7mL | Denville | C-2170 | |
| Cardboard slide tray | Fisher | 12-587-10 |
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