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Overview

Brief Summary

You wouldn't think so, but there are thousands of dolphins swimming in the southern North Sea. There used to be a lot of bottlenose dolphins as well, but now you see white-beaked dolphins more often. Every once in awhile, a short-beaked common dolphin or a white-sided dolphin is spotted. Even more rare are Risso's dolphins, striped dolphins, orcas or pilot whales. Beaked whales form a separate group and include the bottlenose whale. These are ocean animals, which occasionally swim into the North Sea.
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Physical Description

Diagnostic Description

Description

The family Delphinidae has been called a 'taxonomic trash basket', because many small to medium-sized odontocetes of various forms have been lumped together in this group for centuries. Consequentely, the so-called delphinids are diverse in form. They range in size from 1 to 1.88 m dolphins of the genera Sotalia and Cephalorhynchus, to the killer whale, in which males can reach lengths of at least 9.8 m. However, most delphinids share the following characteristics: a marine habitat, a noticeable beak, conical teeth, and a large falcate dorsal fin set near the middle of the back. There are exceptions to everyone of these rules, except the presence of basically conical teeth. <123>
  • MASDEA (1997).
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Biosonar gives an accurate imaging: dolphin
 

High resolution biosonar of dolphins, bats and mole rats gives an accurate imaging by using real-time data processing.

   
  "Biosonar animals send ultrasonic sounds called 'pings' into the  environment. The shape of the returning signals, or echoes, determines  how these animals 'see' their surroundings, helping them to navigate or  hunt for prey. In a matter of tens of milliseconds, the neurons in the  animal's brain are capable of a full-scale analysis of their  surroundings represented in three dimensions, with little energy  consumption. Even with the aid of a supercomputer, which consumes  thousands of times more energy, humans cannot produce such an accurate  picture, Prof. Intrator says...'Animals explore pings with multiple filters or receptive fields, and we  have demonstrated that exploring each ping in multiple ways can lead to  higher accuracy,' he explains. 'By understanding sonar animals, we can  create a new family of ultrasound systems that will be able to explore  our bodies with more accurate medical imaging.'" (Hunka 2011:1)
  Learn more about this functional adaptation.
  • Hunka G. 2011. Bats, dolphins, and mole rats inspire advances in ultrasound technology. EurekAlert [Internet], Accessed November 14.
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Functional adaptation

Chirps carry through water: dolphins
 

Chirps of dolphins carry through water because they are multi-rate, ultra-short wave forms.

   
  "Dr. Mohsen Kavehrad, director of the Center for Information and Communications Technology Research at Penn State, is using multi-rate, ultra-short laser pulses or wavelets that mimic dolphin chirps to make optical wireless signals that can penetrate fog, clouds, and other adverse weather conditions. The multi-rate feature increases the chances that some of the pulses will get through the obstacle. The new approach could help bring optical bandwidth, capable of carrying huge amounts of information, to applications ranging from wireless communication between air and ground vehicles on the battlefield to short links between college campus buildings to metropolitan area networks that connect all the buildings in a city." (Courtesy of the Biomimicry Guild)
  Learn more about this functional adaptation.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:378Public Records:228
Specimens with Sequences:238Public Species:25
Specimens with Barcodes:236Public BINs:21
Species:30         
Species With Barcodes:25         
          
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Barcode data

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Delphinidae

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Wikipedia

Oceanic dolphin

Oceanic dolphins are members of the cetacean family Delphinidae. These marine mammals are related to whales and porpoises. They are found worldwide, mostly in the shallower seas of the continental shelves. As the name implies, these dolphins tend to be found in the open seas, unlike the river dolphins, although a few species such as the Irrawaddy dolphin are coastal or riverine.

Six of the larger species in the Delphinidae, the killer whale (orca), pilot (long-finned and short-finned), melon-headed, pygmy killer and false killer whales, are commonly called whales, rather than dolphins; they are also sometimes collectively known as "blackfish".

Characteristics[edit]

The Delphinidae are the most diverse of the cetacean families, with numerous variations between species. They range in size from 1.2 metres (3.9 ft) and 40 kilograms (88 lb) (Haviside's dolphin), to 9 metres (30 ft) and 10 tonnes (orca). Most species weigh between approximately 50 and 200 kilograms (110 and 440 lb). They typically have curved dorsal fins, clear 'beaks' at the front of their heads, and forehead melons, although exceptions to all of these rules are found. They have a wide range of colors and patterns.[1]

Most delphinids primarily eat fish, along with a smaller number of squid and small crustaceans, but some species specialise in eating squid, or, in the case of the orca, also eat marine mammals and birds. All, however, are purely carnivorous. They typically have between 100 and 200 teeth, although a few species have considerably fewer.

Delphinids travel in large pods, which may number a thousand individuals in some species. Each pod forages over a range of a few dozen to a few hundred square miles. Some pods have a loose social structure, with individuals frequently joining or leaving, but others seem to be more permanent, perhaps dominated by a male and a 'harem' of females.[1] Individuals communicate by sound, producing low-frequency whistles, and also produce high-frequency broadband clicks of 80-220 kHz, which are primarily used for echolocation. Gestation lasts from 10 to 12 months, and results in the birth of a single calf.

Taxonomy[edit]

Etruridelphis giulii skull in Bologna

Recent molecular analyses indicate that several delphinid genera (especially Stenella and Lagenorhynchus) are not monophyletic as currently recognized.[3] Thus, significant taxonomic revisions within the family are likely.[4]

References[edit]

  1. ^ a b Evans, Peter G.H. (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 180–185. ISBN 0-87196-871-1. 
  2. ^ Bianucci, G., Vaiani, S. C. & Casati, S. (2009): A new delphinid record (Odontoceti, Cetacea) from the Early Pliocene of Tuscany (Central Italy): systematics and biostratigraphic considerations. N. Jb. Geol. Paläont. Abh., 254: 275–292.
  3. ^ LeDuc, R.G.; Perrin, W.F.; Dizon, A.E. (July 1999). "Phylogenetic relationships among the delphinid cetaceans based on full cytochrome b sequences". Marine Mammal Science 15: 619–648. doi:10.1111/j.1748-7692.1999.tb00833.x. ISSN 0824-0469. 
  4. ^ Hassanin, A., et al. (2012). "Pattern and timing of diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as revealed by a comprehensive analysis of mitochondrial genomes". Comptes Rendus Biologies 335 (1): 32–50. doi:10.1016/j.crvi.2011.11.002. 

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