Dorsal Fin

Their dorsal fins enlarge and the young adults migrate to the ocean, where they spend 18–24months living as parasites sucked onto fish, feeding on blood and lymph fluid.

From: Neural Regeneration , 2015

BRAIN AND NERVOUS SYSTEM | Motor Control Systems of Fish

S. Grillner , in Encyclopedia of Fish Physiology, 2011

Dorsal fins

The dorsal fins increase the lateral surface of the body during swimming, and thereby provide stability but at the expense of increasing drag ( see also BUOYANCY, LOCOMOTION, AND MOVEMENT IN FISHES | Maneuverability). Their position in relation to the body during movement is stabilized by an exclusive set of fin motor neurons that are activated in antiphase with the motor neurons controlling the trunk muscles during locomotion. This is required to stabilize the vertical position of the dorsal fins in relation to the body movement.

In some teleost species, the dorsal fin extends along most of the body (e.g., Gymnarchus niloticus), and an undulatory wave can actually be transmitted along the entire dorsal fin, in either a backward or a forward direction, moving the fish in the corresponding direction. Instead of having only one undulatory wave, as in trunk locomotion, there are many small amplitude waves transmitted along the fin.

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Neural Crest–Determined Evolutionary Novelties

Nelson R. Cabej , in Epigenetic Principles of Evolution, 2012

Neural Crest and Vertebrate Morphogenesis

From the neural crest that forms on the neural tube starts a mass migration of neural crest cells. They are at the origin of many cell types and contribute to the formation of a great number of tissues and organs. A group of them from the developing brain and spinal cord go in direction of ectoderm to be differentiated into pigment cells (melanocytes). The rest of them follow an internal path between the neural tube and somites to reach down to the deepest layers and form sensory and sympathetic ganglia (Figure 16.4). The pluripotent neural crest cells differentiate into nerve cells, glial cells, adrenergic cells, pigment cells (leukophores, erythrophores, melanophores, iridiophores, and xanthophores), and chondrocytes.

Figure 16.4. Staggered, lateral views of all internal tissue layers in an early avian embryo. These illustrate the changes in locations of each population and the spatial relations among them. Neural crest progenitors, cranial nerves, and myogenic primordia for each branchial arch all arise at the same axial level and maintain this close registration throughout their dorsoventral movements. For example, crest cells that will populate the second branchial arch arise from the same axial location (rhombomere 4) as the seventh cranial nerve and the second arch muscles it will innervate. By contrast, the periocular neural crest, the extraocular muscles, and the motor nerves that innervate them all arise at separate axial locations and do not establish stable relations until all have reached their sites of terminal differentiation.

 Source: From Noden and Trainor (2005).

Once the hindbrain neural crest cells exit the neural tube, they are maintained in segregated streams (Noden and Trainor, 2005). In mice, the hindbrain-derived neural crest cells migrate in three segregated streams adjacent to the even-numbered rhombomeres, compartments of developing hindbrain (Trainor et al., 2002b), but odd and even rhombomeres produce equal number of neural crest cells. The neural crest cell free zones are at the level of rhombomeres 3 and 5 (physically restricted by the invaginating otic placode). Creation of neural crest cell free zones is necessary for maintaining the separation of neural crest cells of different origin and function (Trainor et al., 2002a). The pluripotent neural crest cells contribute to the development and morphology of regions where they migrate not only by transforming themselves into different types of cells, but also by transforming the local cells in appropriate types of cells. So, for example, initiation of chondrogenesis in the pharyngeal endoderm requires direct contact with the neural crest cells (Hall, 1999, p. 137).

Migrating neural crest cells themselves serve as precursors of neuroblasts, from which neurons of the spinal ganglia, nerve cells of the autonomic vegetative system, peripheral ganglia neurons, and ganglia cells that accompany nervous processes differentiate, such as Schwann cells, but also nonneural cells of some of the faster evolving/recurring parts of the vertebrate body, such as the visceral skeleton, which previously was believed to derive from mesoderm.

Of neural crest origin are also cartilaginous elements of the jaws and pharyngeal arches and their sound-transmitting derivatives of the inner ear: incus, malleus, and stapes, as well as the laryngeal and tracheal skeleton, the dental papilla, producing bone-like material to the tooth germs. Of similar neural crest origin are most bones of the face and of the brain case, pigment cells of the skin, feathers, and hairs (Figure 16.5).

Figure 16.5. Neural crest cell derivatives. Derived from the neural tube, neural crest cells are a pluripotent, mesenchymal population that migrates extensively and gives rise to a vast array of cell types, tissues, and organs. Given the wide variety of differentiative fates and a limited capacity for self-renewal, neural crest cells are often considered to be a stem cell–like population.

 Source: From Trainor et al. (2003).

Neural crest cells also produce the dorsal fins of fish ( Müller, 1996b) and, in all likelihood, the reemerged dorsal fins in aquatic mammals and ichthyosaurus as well as characteristic crests developing in numerous reptiles, including dinosaurs. The neural crest also provides neurons, mesenchymal cells, cells of the aortic pulmonary conotruncal septa, valves, and major vessels to the developing heart in chick (Hall, 1999). They also determine formation of neurohormonal cells, such as cells of the adrenal medulla and neuroendocrine cells of the digestive tract. The unique role of migrating neural crest cells in different regions of the animal body to form there some of the most typical vertebrate features clearly suggests that:

1.

Neural crest cells possess positional–structural information for the organs or parts, whose formation they are involved in.

2.

Neural crest cells induce differentiation and proliferation of neighboring cells to participate in formation of those parts or tissues.

3.

Evolution of neural crest–induced structures is based on the intrinsic properties of neural crest cells, which are provided with the necessary epigenetic information before leaving the neural tube/CNS.

Now let us illustrate, with some representative examples, the rapid evolutionary changes in vertebrate morphology, in response to changes in conditions of living, in which the neural crest was essentially involved.

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The Shark

Gerardo De Iuliis PhD , Dino Pulerà MScBMC, CMI , in The Dissection of Vertebrates (Second Edition), 2011

Key Terms: Skeleton

abducens foramen

acetabular surface

adductor mandibulae process

anterior dorsal fin

antorbital process

antorbital shelf

basal plate

basal pterygiophore

basapophysis

basibranchials

basihyal

basitrabecular processes

branchial arches

carotid foramen

caudal fin

centrum (vertebral body)

ceratobranchials

ceratohyal

ceratotrichia

chondrocranium

clasper

coracoid bar

endolymphatic foramina (sing., foramen)

endolymphatic fossa (plur., fossae)

epibranchials

epiphyseal foramen

fin spine

foramen magnum

glenoid surface

glossopharyngeal foramen

hemal arch

hemal canal

hemal plate

hemal spine

hook of clasper

hyoid arch

hyomandibular

hyomandibular foramen

hypobranchials

iliac process

intercalary plates (interneural arch)

labial cartilage

mandibular arch

Meckel's cartilage (mandibular cartilage)

mesopterygium

metapterygium

nares (sing., naris)

nasal capsules

neural arch (vertebral arch)

neural canal (vertebral canal)

neural plate

neural spine

notochord

occipital condyle

oculomotor foramina (sing., foramen)

optic foramen

optic pedicle

orbital process

otic capsules

palatoquadrate cartilages

pectoral fins

pectoral girdle

pelvic fins

pelvic girdle

perilymphatic foramina

pharyngobranchials

posterior dorsal fin

postorbital process

precerebral cavity

precerebral fenestra

propterygium

puboischiadic bar

radial pterygiophores

rib

rostral carina

rostral fenestra (plur., fenestrae)

rostrum

scapular process

spine of clasper

splanchnocranium

superficial ophthalmic foramina

supraorbital crest

suprascapular cartilage

trigeminofacial foramen

trochlear foramen

vagus foramen

vertebral column

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The Lamprey

Gerardo De Iuliis PhD , Dino Pulerà MScBMC, CMI , in The Dissection of Vertebrates (Second Edition), 2011

Key Terms: Lamprey

afferent branchial arteries

annular cartilage

anterior cardinal veins

anterior dorsal fin

anus

archinephric duct

arcualia

atrium

brain

branchial basket

buccal papillae

caudal artery

caudal fin

caudal vein

chondrocranium

cloaca

coelom

common cardinal vein

dorsal aorta

efferent branchial arteries

"esophagus"

external pharyngeal slits

eyes

fin rays

gonad

head

heart

hepatic portal vein

hypophyseal pouch (nasohypophyseal pouch)

inferior jugular vein

intestine

kidney

lateral line pores

lingual cartilage (piston cartilage)

liver

mouth

myomere

myoseptum (plur. myosepta)

naris (nostril)

notochord

olfactory sac

oral cavity

oral cecum

oral disk

oral funnel

ovary

pericardial cartilage

pineal eye complex

pleuroperitoneal cavity

posterior cardinal veins

posterior dorsal fin

respiratory tube ("pharynx")

sinus venosus

spinal cord

tail

teeth

testis

tongue (piston)

transverse septum

trunk

typhlosole

urogenital papilla

urogenital pore

velum

ventral aorta

ventricle

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Intralocus Tactical Conflict and the Evolution of Alternative Reproductive Tactics

Molly R. Morris , ... Oscar Rios-Cardenas , in Advances in the Study of Behavior, 2013

4.2.4 Potential for Further Study

The evidence suggests that vertical bars, courtship behavior and potentially sword and dorsal fin size associated with the ARTs in X. multilineatus could be experiencing IATC, warranting further more specific testing of the three IATC criteria in this species. Given the two species of northern swordtails that have independently lost the large male size classes and have evolved irreversible sneaker males (X. continens and X. pygmaeus), the northern swordtail clade presents an excellent system in which to test the mechanistic components of the hypothesis that release from IATC is involved in the association between ARTs and speciation. The evolution of a threshold trait could explain the irreversible use of courtship in the larger size classes of X. multilineatus (threshold too high to ever use sneak-chase) as well as the irreversible use of sneak-chase (threshold too low to ever use courtship) by males in the related species X. pygmaeus and X. continens once the larger male size classes were lost (i.e. genetic assimilation). While intralocus conflict could constrain the evolution of ARTs within a species, it has been argued that its presence could also facilitate rapid evolution once one of the ARTs is lost (Smith, 1962; West-Eberhard, 1986). In addition, further identification of the genetic influences on the traits in this system could increase our understanding of the resolution of conflict. Variation in body size in X. multilineatus is influenced by copies of the mc4r gene on the Y chromosome (Lampert et al., 2010), suggesting one could examine the role of gene duplication in resolving IASC and IATC in this system (Gallach & Betrán, 2011). And finally, a better understanding of which traits are sex-linked could provide insights into how both sexual and tactical conflicts may be driving the evolution of sex chromosomes, which are highly variable within Xiphophorus fishes (Lindholm & Breden, 2002).

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FISH | Important Elasmobranch Species

J.P.H Wessels , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Utilization of Shark Fins for Soup

One set of shark fins usually consists of two pectoral fins, the first dorsal fin (and in large sharks with two dorsal fins, the second) and the lower lobe of the tail fin. These fins are either dried or salted and dried and used in the Orient and by Chinese communities elsewhere to produce shark fin soup. Small sharks do not yield suitable fins, while some larger species do not produce fins of desirable quality. In general, however, the fins of any shark longer than 1.5 m can be used.

Of the sharks of suitable size, only nurse shark (Ginglymostoma cirratum) fins and the sawshark (Pristiphorus mudipiunis) pectoral fins appear to be of no commercial value.

The preferred shark species are the hammerhead, the mako, and the blue, mentioned above, and the tope or soupfin, Galeorhinus galeus. Fins from many of the large and the very large sharks are used, however, including those of the great white shark (Carcharodon carcharias), the fibrous meat of which, incidentally, is eaten in part of northern Japan. The very large tiger shark (Galeocerdo cuvieri) is also listed as a source of good-quality shark meat. Several Carcharinus species provide fins for processing in Pakistan.

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THE SKIN | Bioluminescence in Fishes

A.F. Mensinger , in Encyclopedia of Fish Physiology, 2011

Anglerfish

Anglerfish also culture bacteria in an esca, a fleshy growth at the end of a modified dorsal fin spine ( Figure 3 ). The spine is movable and the esca is used as a luminescent lure to attract prey to the fish. The bacteria appear to glow continually. However, flashes or pulses of light have been observed from live fish. The control mechanism is not understood, but blood flow and concomitant oxygen availability to the organ may be involved in regulation. Only female anglerfish are luminescent, which is consistent with their unusual natural history. The much smaller, nonluminescent males permanently attach to the female, who provides nutrients to the male throughout its life. Esca are species specific and range from simple bulbs to elaborate protuberances that may assist in the male locating the correct mate.

Figure 3. The anglerfish Chaenophryne longiceps. Anglerfish culture bacteria in an esca, which is a fleshy growth at the end of a modified dorsal fin spine. The spine is movable and the esca is used as a luminescent lure to attract prey to the fish (fish length approximately 4   cm).

 Photograph by Steve Haddock.

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FISH MIGRATIONS | Tracking Oceanic Fish

B.A. Block , in Encyclopedia of Fish Physiology, 2011

Satellite Tags on Fishes and Sharks

The first directly attached fin tag was developed by Dr. Francis G. Carey, who designed a fixed position, dorsal fin-mounted, satellite tag that was placed on blue sharks ( Prionace glauca) in 1993 in collaboration with the Sea Mammal Research Unit of the UK. The experiment was highly successful with high-quality locations obtained from sharks surfacing regularly enough to track the sharks along the Gulf Stream. The tag was robust and straddled the dorsal fin. The tags measured pressure (and thus calculated depth), speed, and position on a half dozen sharks in the North Atlantic. The longest track was over 2 months.

Direct telemetry off the dorsal fin of sharks provides an opportunity to enhance the capability of near real time tracking, data collection, and ocean observation. Most recently, this technique was applied to five species of sharks in the Tagging of Pacific Pelagics program (TOPP). Salmon sharks (Lamna ditropis) are large in body size and surface regularly due to behavioral thermoregulation in cold subpolar seas, making it easy to attach satellite tags. Tracks of over 3 years are routine on this shark, and makos have been followed for over 2 years.

Salmon sharks are apex predators in Alaskan ecosystems, yet little is known about their movements or population dynamics in Alaskan waters. Tagging through TOPP has been critical for documenting the extensive oceanic migrations of salmon sharks and enabled the characterization of their habitat use on oceanic scales ( Figure 4 ). Tagging has demonstrated that salmon sharks utilize the inshore and nearshore waters of Prince William Sound, Cook Inlet, the Alaskan Peninsula, and southeastern Alaska shelf habitat throughout the year.

Figure 4. Single Position Only tags (SPOT) provide positions of salmon sharks, Lamna ditropis, carrying the tags. Sharks were tagged in Alaskan waters while foraging. Sea-surface temperature data experienced by the sharks are shown in color.

 From Weng KC, Castilho PC, Morrissette J, et al. (2005) Satellite tagging and cardiac physiology reveal niche expansion in salmon sharks Science 310: 104–106.

The same techniques utilized for studying the salmon shark were rapidly integrated with multiple species within the TOPP program. To date, over 10 species of sharks have been tagged with the single position only transmitting or SPOT tags with extremely successful tracking in species such as shortfin mako sharks (Isurus oxyrinchus), blue sharks and juvenile white sharks (Carcharodon carcharias). have also been tracked with limited success (Galapagos sharks Carcharhinus galapagensis, silky sharks C. falciformis and oceanic whitetip sharks C. longimanus).

Most teleost fish do not have appendages that break the surface of the water and can serve as a fixed attachment point for a tag as is possible with a shark's first dorsal fin. However, recently Holdsworth and colleagues obtained high-resolution satellite locations from striped marlin (Tetrapturus audax) using Argos transmitters attached to the upper lobe of the caudal fin. Twenty-six striped marlin were tagged off New Zealand (2005–07) and tracked as far as the central Pacific Ocean. Remarkably, the caudal fin mounted Argos tags generated a significant number of high accurate positions of ±1   km or better. The caudal fin attachment methodology and antenna configuration were adjusted each season to improve transmission life and data quality, with the best results obtained in the last year of deployments (2007). The longest track duration was 102 days, with a total displacement of 4959   km and a total track distance from all locations received of 6850   km. Tag shedding and antenna failure appear to have limited the duration of SPOT tracks on fish. The high temporal and spatial resolution data revealed behaviors not previously observed in striped marlin, including associations to subsurface bathymetric features. High-resolution location data will be valuable for generating robust behavioral state-space and habitat selection models.

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Environmental Causes of Dermatitis

Joao Paulo Niemeyer-Corbellini , ... Stephen K. Tyring , in Tropical Dermatology (Second Edition), 2017

Catfish (Siluridae)

The catfish are the most common fish associated with human injuries, in both marine and freshwater environments. 4,5 Marine catfish cause injuries through serrated bony sting organs localized on the anterior dorsal and pectoral fins and covered by an integumentary sheath with glandular venomous tissue. 30 Freshwater catfish are siluriform fish, common in rivers and lakes. There are various venomous genera, such as the South American Pimelodus and Pimelodella and the North American Ictalurus and Noturus. The main populations at risk are amateur and professional fishermen. The mechanism of envenomation is similar to those of marine catfish. 30,31

Patients present with intense pain, blanching in the point of the puncture, malaise, vomiting, and possible local skin necrosis. The envenomation is considered of mild severity, but it can present serious complications, such as breaking and retention of fragments of the stingers and severe bacterial infections. 4,30

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Rhabdoviridae

In Fenner's Veterinary Virology (Fifth Edition), 2017

Clinical Features and Epidemiology

Clinical sigs of acute viral hemorrhagic septicemia may be nonspecific and include lethargy, darkening of the skin, anemia (evidenced by pale gills), and hemorrhages in many locations including the skin at the base of fins, muscles (dorsal musculature), gills, internal organs, meninges, and eyes. Abdominal distention due to ascites and exophthalmia can also occur. A neurologic form of disease presents as abnormal swimming behavior (spiraling or flashing). External signs or lesions may not be evident in the chronic stages of infection.

Viral hemorrhagic septicemia virus infection that results in significant mortality may occur in fish of any age. However, mortality is generally greatest in naïve populations and young fish, in which it can reach 100%. Fish that survive disease may become virus carriers. Epizootic outbreaks and fish losses occur at water temperatures from 4°C to 14°C. Both mortality and the proportion of fish that become virus carriers decrease as water temperatures approach or exceed 15°C. Outbreaks are more common in spring when water temperatures are rising or fluctuating.

Nucleic acid sequencing of the N-gene confirm genetic differences of strains of viral hemorrhagic septicemia virus that are related to geographical location (molecular topotype) and, to a lesser extent, host specificity. These studies confirm four major virus genotypes with; genotype I found in wild marine fish and diseases outbreaks in rainbow trout in continental Europe; genotype II found in clinically normal Atlantic herring (Clupea harengus), Atlantic cod (Gadus morhua), and sprat (Sprattus sprattus) from the Baltic Sea; genotype III from subclinical infection and disease epizootics involving sea-reared rainbow trout and turbot (Scophthalmus maximus) in marine waters around the United Kingdom and Norway; and genotype IV found in fish in North America, Japan, and Korea. The genotype IV viruses are further segregated into three subtypes (IVa, IVb, and IVc). Subtype IVa is found in marine and anadromous fish populations such as Pacific herring (Clupea pallasii), Pacific sardine (Sardinops sagax), Pacific hake (Theragra chalcogramma), and Japanese flounder (Paralichthys olivaceus) from western North America and Asia, where it can be highly virulent. Genotype IVb invaded the North American Great Lakes in 2003 causing large-scale mortality events in muskellunge (Esox masquinongy), freshwater drum (Aplodinotus grunniens), and round goby (Neogobius melanostomus) among other species. Genotype IVc has been isolated from disease epizootics in mummichog (Fundulus heteroclitus), stickleback (Gasterosteus aculeatus aculeatus), brown trout (Salmo trutta), and striped bass (Morone saxatilis) in the Atlantic coastal regions of North America.

Transmission of viral hemorrhagic septicemia virus occurs horizontally through water, with excretion of virus in the urine and reproductive fluids from infected fish (both diseased and virus-carrier fish). Given the large number of fish species that are susceptible to viral hemorrhagic septicemia virus, active infections are maintained within wild fish populations and are the major concern for its introduction into aquaculture production facilities. Piscivorous birds can act as mechanical vectors of the virus.

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