Where is pectoral fin

Occasionally the fin is too long to be used, as in the "lyretail" breeds of Xiphophorus helleri. Hormone treated females may develop gonopodia. These are useless for breeding. One finds similar organs having the same characteristics in other types of fish, for example the andropodium in the Hemirhamphodon or in the Goodeidae.

The male shortly inserts the organ into the sex opening of the female, with hook-like adaptations that allow the fish to grip onto the female to insure impregnation. If a female remains stationary and her partner contacts her vent with his gonopodium, she is fertilized. The sperm is preserved in the female's oviduct. This allows females to, at any time, fertilize themselves without further assistance of males.

Male cartilaginous fish have claspers modified from pelvic fins. These are intromittent organs, used to channel semen into the female's cloaca during copulation. The outer body of many fish is covered with scales. Some species are covered instead by scutes. Others have no outer covering on the skin; these are called naked fish.

Most fish are covered in a protective layer of slime mucus. File:Lampanyctodes hectoris Hector's lanternfish 2. File:Thunnus obesus Bigeye tuna diagram cropped. We could talk until we're blue in the face about this quiz on words for the color "blue," but we think you should take the quiz and find out if you're a whiz at these colorful terms.

Origin of pectoral fin First recorded in — Words nearby pectoral fin pectinose , pectize , pectolite , pectoral , pectoral cross , pectoral fin , pectoral girdle , pectoralis , pectoralis major , pectoralis minor , pectoral muscle. How to use pectoral fin in a sentence In an ethanol specimen, its pectoral fin s look soft and ghostly, whereas the living larva sports flamboyant, spiky and spotted fins.

During zebrafish embryogenesis, pectoral fin buds grow along their proximal-distal axis, which is parallel to the dorso-ventral body axis [ 11 , 15 ]. As pectoral fin buds grow, they rotate from the initial position in a way that allows their distal margins to point caudally and their anterior side to face upwards with respect to the body axis [ 11 , 15 ].

Immediately before this rotation, chondrogenic condensation begins to form the endoskeletal disc, and the apical ectodermal thickening becomes transformed into the apical fin fold [ 11 , 15 ]. When the rotation of the pectoral fin bud is complete, a single-cell-layered endoskeletal disc and the apical fin fold structure become apparent [ 11 , 15 ]. Similarly, during the embryogenesis of the mudskipper, pectoral fin buds begin to rotate their initial position and point their distal tips caudally Fig.

At the same time, the apical fin folds are seen at the distal tips of pectoral fin buds Fig. Chondrogenic condensation also begins within the pectoral fin buds just before the rotation of the fin Fig.

These results suggest that developmental processes of the mudskipper pectoral fin bud during embryogenesis and larval development are similar to those of zebrafish [ 11 , 15 ], and thus the unique characteristics of mudskipper pectoral fins do not form before the larva-to-juvenile transition. Here we found that the localized cell division of the proximal part of the endoskeletal disc and subsequent cell divisions along the proximal-distal axis specifically in the distal region during metamorphosis lead to the protrusion and elongation of the proximal radials.

Future studies are needed to further explore whether these metamorphic changes are observed during development of the pectoral fins in various mudskippers as well as in the rest of the oxudercine gobies to understand how mudskippers evolved their pectoral fin morphology to adapt to a terrestrial environment.

Sustained periodic terrestrial locomotion in air-breathing fishes. J Fish Biol. Harris VA. On the locomotion of the mud-skipper Periophthalmus koelreuteri Pallas : Gobiidae. Proc Zool Soc Lond. Article Google Scholar.

Murdy EO. A taxonomic revision and Cladistic analysis of the Oxudercine gobies Gobiidae: Oxudercinae. Rec Aus Mus Suppl — Mudskipper pectoral fin kinematics in aquatic and terrestrial environments. J Exp Biol. Eggert B. Bestimmungstabelle und Beschreibung des Arten der family Periophthalmus. Z Wiss Zool. Google Scholar. Mudskippers brood their eggs in air but submerge them for hatching.

Article PubMed Google Scholar. Egg development and rearing experiments of the larvae of the muds skipper, Periophthalmus cantonesis. Bull Fac Fish, Nagasaki Univ. A two-color acid-free cartilage and bone stain for zebrafish larvae. Biotech Histochem. Development of the lateral plate mesoderm in medaka Oryzias latipes and Nile tilapia Oreochromis niloticus: insight into the diversification of pelvic fin position.

J Anat. Thyroid hormones are important for embryonic to larval transitory phase in zebrafish. Grandel H, Schulte-Merker S. The development of the paired fins in the zebrafish Danio rerio. Mech Dev. Brown DD. The role of thyroid hormone in zebrafish and axolotl development. Thyroid hormone-dependent adult pigment cell lineage and pattern in zebrafish. Miwa S, Inui Y. Effects of various doses of thyroxine and triiodothyronine on the metamorphosis of flounder Paralichthys olivaceus.

Gen Comp Endocrinol. Stages of embryonic development of the zebrafish. Dev Dyn. Download references. You can also search for this author in PubMed Google Scholar. EO carried out most experiments except for the following: MVH and AI collected specimens and fixed some of the specimens. All authors read and approved the final manuscript. Correspondence to Mikiko Tanaka. All animal work was performed in accordance with guidelines for animal experiments of the Tokyo Institute of Technology and Nagasaki University.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Figure S1. Development of mudskipper embryos before hatching. Arrowheads in F, M indicate melanophores and in K indicate blood cells.

Open arrowheads in E, F, G, M indicate xanthophores. PDF kb. Table S1. Comparison of the stages of Periophthalmus modestus in this study with those suggested by Kobayashi et al. Figure S2. Development of mudskipper larvae and juveniles after hatching. J, L Magnified images. Arrowheads in D indicate fin rays in the caudal fin.

Arrows in D, E and arrowheads in G, I, K indicate the primordia of the hypural and melanophores, respectively. Reprints and Permissions. Okamoto, E. Modification of pectoral fins occurs during the larva-to-juvenile transition in the mudskipper Periophthalmus modestus. Zoological Lett 4, 23 Download citation. Received : 22 March Accepted : 16 July Published : 11 August Anyone you share the following link with will be able to read this content:.

Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Photographs were taken from dissected specimens in order to accelerate the illustration process. Images from larger structures were taken via digital camera Nikon D whereas small structure images were obtained via digital camera Zeiss Axiocam Color attached to a stereomicroscope Zeiss SteREO Discovery.

Anatomical drawings were based on photographs and direct stereomicroscopic observations of specimens in order to capture fine anatomical details. The black and white illustrations were hand drawn with graphite, while digital bidimensional colour drawings were produced with a Wacom Intuos Comic pen tablet.

Early in development, polynemid larvae have a pectoral-girdle and fin morphology comparable to that of generalized percomorphs, that is, with a pectoral fin undivided and lacking differentiated filaments. Drastic ontogenetic changes in the pectoral rays, pectoral proximal radials, and coracoid are primarily responsible for the differentiation of the pectoral fin of adult polynemids.

We were able to study these changes in an ontogenetic series of Polydactylus approximans , as described below. In earlier ontogenetic stages, a single cartilaginous pectoral radial plate is present and, at approximately 4 mm SL, this plate is already subdivided into a dorsal and a ventral subplate. At around 4. The scapulocoracoid is fully cartilaginous and has an elongate and posteriorly directed postcoracoid process.

No trace of ossification and differentiation in the pectoral-fin rays is observed in these stages. At approximately 8 mm SL, all four pectoral-radial cartilages are distinguishable from one another, and only the first one has started to ossify proximally Fig.

Pectoral radial 3 starts to tilt and shift from horizontal to a more vertical position, and pectoral radial 4 starts to enlarge ventrally. The coracoid shows the first signs of ossification on the posteroventral region of the scapulocoracoid cartilage, anterior to the postcoracoid process cartilage. Although rays and filaments are still contiguous with each other at this stage, a regionalization into a dorsal set of rays and ventral set of early filaments is evident, marking the beginning of the differentiation of the pectoral fin.

The pectoral-fin rays have begun to ossify and articulate with pectoral radials 1 to 3. Ossification in these rays occurs from the dorsal to the ventral rays and from the proximal to the distal region of each ray. At this stage, the early pectoral filaments consist of bundles of actinotrichia lacking any associated ossification lepidotrichia.

These early filaments are considerably thicker and shorter than the ossifying pectoral rays and articulate primarily with pectoral radial 4. Medial views of cleared and stained ontogenetic series of left pectoral girdle in Polydactylus approximans, Polynemidae; a 4. White arrow indicates the foramen on pectoral radial 4. Blue staining on pectoral-fin rays and filaments likely due to affinity of Alcian Blue with collagen rather than indicative of presence of cartilaginous tissue.

X-ray microcomputed tomographies of left pectoral girdle in medial view; a Pentanemus quinquarius , Polynemidae; b Polydactylus opercularis , Polynemidae; c Polynemus multifilis , Polynemidae; d ventral view of pectoral radial 3 of P. Arrow indicates site of articulation between pectoral radial 3 and the dorsalmost pectoral filament in d ; postcoracoid process broken distally in a. The coracoid ossification is well developed, with the postcoracoid process starting to ossify Fig.

Pectoral-fin rays and pectoral filaments have further diverged from each other and are now separated by a considerable gap.

At this stage, all but the two ventralmost pectoral-fin rays are well ossified. The basal portions of all the pectoral filaments are ossified, following a generalized ossification pattern from dorsal to ventral and from proximal to distal. At The third and the fourth pectoral radials start to ossify at their proximal portions.

Pectoral radial 3 still articulates with the ventralmost pectoral-fin rays. The coracoid is well ossified Fig. At this stage the ossified portions of the pectoral filaments have nearly the same length as the ossified portions of the pectoral-fin rays.

At this size, the third radial no longer supports any pectoral-fin rays. The foramen in pectoral radial 4 is formed at These ontogenetic changes result in the highly specialized osteology of the pectoral complex of adult polynemids. All adult polynemids have the first two radials articulating with the unmodified pectoral-fin rays, while an enlarged pectoral radial 4 supports the pectoral filaments Figs.

Pectoral radial 3 does not articulate with any ray or filament, with two exceptions: in Polynemus it articulates with the dorsalmost pectoral filament Fig.

In all adult polynemids, most of the pectoral filaments are thicker than the unmodified fin rays, showing a different pattern of segmentation. While the pectoral-fin rays present a roughly uniform pattern of segmentation along each ray, the pectoral filaments have shortened segments proximately that gradually increase in length towards their tips. There is a considerable variation in the number, thickness, and notably the maximum length of the pectoral filaments, which vary from nearly the same size as the unmodified pectoral-fin rays Eleutheronema and Galeoides to roughly three times the total body length Polynemus kapuasensis 1.

In all adult polynemids the abductor muscle mass serving the pectoral fin is divided into two independent segments herein named segmentum radii genitive of Latin radius , meaning ray and segmentum fili genitive of Latin filum , meaning thread or filament.

The former is responsible for moving the unmodified fin rays, while the latter serves the pectoral filaments Fig. Lateral view of left pectoral girdle of Polydactylus virginicus , Polynemidae.

Towards insertion, the muscle gradually differentiates into small bundles that serve each individual ray, although this differentiation is not complete.

Parapolynemus is unique in having the abductor superficialis radii originating entirely from the lateral surface of the coracoid Fig. Insertion of the muscle is conservative amongst all polynemid genera.

The dorsomedial surface of the muscle is aponeurotic and contacts a similarly aponeurotic area of the adductor profundus radii see below. Lateral view of left pectoral girdle of Parapolynemus verekeri , Polynemidae. The second division of the abductor profundus radii serves all pectoral-fin rays except the first one and is accordingly named pars ceterae genitive of Latin ceterus meaning others, remainder, rest; AbPRc. This muscle section is a single unit at its origin and progressively differentiates into bundles that attach tendinously to each individual ray, although some intermingling of fibers between the bundles may occur Figs.

The partes marginalis and ceterae are completely separate in all examined members of the family, except Pentanemus in which there is only superficial differentiation.

The origin of the pars ceterae is musculous and usually associated with the concave surface of the lateral projection of the cleithrum, coracoid, and third pectoral radial Figs. The scapula is additionally involved in the muscle origin in Eleutheronema , Filimanus , Pentanemus, and most Polydactylus except P.

The pars ceterae of Parapolynemus originates only from the coracoid and pectoral radial 3 Fig. The dorsalmost portion of the pars ceterae of the abductor profundus radii is more elongate and covered by a lateral aponeurosis Fig. The pars marginalis of the abductor profundus radii is a bipinnate muscle partially covered by the pars ceterae and runs parallel to both this section and the arrector ventralis Fig. Parapolynemus is exceptional in having a pars marginalis not bipinnate and positioned in an oblique angle relative to the adjacent muscles Fig.

Most polynemids have a pars marginalis originating primarily from the lateral surfaces of the cleithrum, coracoid, and scapula; in Galeoides and Leptomelanosoma it additionally originates from the lateral face of the third pectoral radial.

Parapolynemus has the pars marginalis originating only from the coracoid and scapula. The arrector ventralis ArV is a long, bipinnate muscle that forms the dorsalmost muscle component serving the lateral portion of the pectoral fin Figs. Most of the muscle is located medial to the segmentum radii of the abductores superficialis and profundus. It originates musculously from the lateral surface of the cleithrum, coracoid and scapula; insertion is via an elongate tendon on the enlarged medial base of the first ray Fig.

Origin is musculous and primarily from the lateral projection of the cleithrum, where the dorsalmost fibers are overlapped by the ventral portion of the abductor superficialis radii Fig.

Parapolynemus , however, has the opposite condition: the segmentum fili covers laterally the ventralmost fibers of the segmentum radii Fig. The abductor superficialis fili inserts tendinously on the dorsal region of the base of the lateral hemitrichia of all filaments. In most polynemids, the segmentum radii is larger than the segmentum fili Fig. The fibers of the abductor superficialis fili are clustered into bundles that serve each filament individually. The degree of differentiation of these bundles varies considerably across the family.

In Parapolynemus , Pentanemus , and Polynemus they are well-developed and well-separated from each other Fig. In Galeoides the fibers additionally arise from the lateral surface of the fourth pectoral radial. Insertion of the abductor profundus fili in all polynemids is invariably tendinous onto the lateral base of each filament. The muscle is also differentiated into bundles corresponding to the number of filaments.

The dorsal bundle usually overlaps part of the subsequent ventral ones, except in Galeoides and Parapolynemus. As seen in the abductor superficialis fili , the bundles of the abductor profundus fili of Parapolynemus , Pentanemus , and Polynemus are well developed and separated from each other compared to other genera Fig. The fibers of the segmentum fili of the abductores superficialis and profundus are usually oriented differently: the former muscle has a posteroventral orientation towards the insertion, whereas the latter is oriented posterodorsally Figs.

As in the case with the abductores of the pectoral fin, the adductor muscle mass is also divided into segmenta radii and fili that serve the unmodified fin rays and the pectoral filaments, respectively Fig. Its origin is usually from the medial surface of the cleithrum and scapula.

The adductor superficialis radii of Galeoides and Leptomelanosoma additionally arises from the coracoid. The origin of the muscle in most polynemids is mixed, with the dorsalmost fibers having an aponeurotic origin and the ventralmost arising musculously. Galeoides, Polydactylus microstomus , and P. The muscle inserts via tendons on the medial region of the rays, relatively distal from their bases.

Except the first ray that is served by the arrector dorsalis see below , all remaining rays are served by the adductor superficialis radii. The fibers serving the ventral rays have a progressively more dorsal origin Fig. The fibers associated with the second and third rays are much more prominent than the remaining fibers and have a well-developed tendinous portion, giving these portions a nearly bipinnate aspect.

Nevertheless, all polynemids lack clear subdivision within the adductor superficialis radii. Medial view of left pectoral girdle. AbPRc, abductor profundus radialis p. Medial view of left pectoral girdle of Eleutheronema tetradactylum , Polynemidae.

In polynemids an adductor medialis radii is not distinguishable from the surrounding medial muscles. The pars ectoprofunda is a robust layer of fibers that originates from the anterior margin of the cleithrum, medial face of the coracoid, and also from the membrane that covers the fenestra between these two bones Fig.

The pars endoprofunda is a deep, thin layer of shorter fibers originating only from the posterodorsal end of the medial face of the coracoid Fig. Some fibers may also arise from the medial face of the scapula and from the adjoining area between this bone and the coracoid.

As the fibers proceed to their insertion, the partes ectoprofunda and endoprofunda gradually merge, and the entire adductor profundus radii inserts on the medial base of all medial hemitrichia Fig.

The arrector dorsalis ArD is not fully separated from the adductor profundus radii , with the two muscles sharing some fibers proximate to their attachment on the pectoral girdle Figs. Close to the tendinous insertion, fibers of each muscle become more distinguishable from one another. Most fibers corresponding to the arrector dorsalis originate musculously from the medial faces of the cleithrum and coracoid and insert on the medial projection of the medial hemitrichium of the first marginal ray.

An adductor radialis AdR is also present and it shares fibers with the adductor profundus radii Fig. The relatively short fibers of the adductor radialis originate musculously primarily from the medial surface of the first three pectoral radials and the medial face of the scapula and insert tendinously on the medial hemitrichium of the ventralmost rays. The segmentum fili , in medial view, is divided into adductores superficialis, medialis, and profundus Figs.

Part of this muscle covers the origin of the adductor superficialis radii. The adductor superficialis fili is subdivided into well-differentiated bundles that serve each individual filament Figs. The muscle originates tendinously from the dorsomedial face of the cleithrum and inserts, also via tendons, onto the medial hemitrichia of each pectoral filament.

The anteriormost fibers are visible in lateral view, anterior to the cleithrum Figs. The thickness of the muscle bundles serving each individual filament varies among genera and, the longer the filament, the thicker the bundle is. Medial view of left pectoral girdle of Galeoides decadactylus , Polynemidae. The fibers of the adductor medialis fili are more horizontal than those of the two other muscles, which have fibers in a more vertical disposition Figs.

None of these muscles share fibers.