Editing Paddlefish (section)

== Morphology ==
[[File:General Morphology of Paddlefish.png|thumb|270px|General [[Morphology (biology)|morphology]] of paddlefish]]
Paddlefish as a group are one of the few organisms that retain a [[notochord]] past the embryonic stage. Paddlefish have very few [[bone]]s and their bodies mostly consist of cartilage with the notochord functioning as a soft spine. During the initial stages of development from embryo to fry, paddlefish have no [[Rostrum (anatomy)|rostrum]] (snout).  It begins to form shortly after hatching.<ref name=LSU>{{cite report | title=Biology of the Paddlefish | publisher=Lamer-Louisiana State University | series=NFC Section&nbsp;I  | url=http://www.lamer.lsu.edu/pdfs/NFC_Section1.pdf | access-date=June 9, 2014 | url-status=dead | archive-url=https://web.archive.org/web/20140714195741/http://www.lamer.lsu.edu/pdfs/NFC_Section1.pdf | archive-date=2014-07-14 }}</ref> The rostrum of the [[Chinese paddlefish]] was narrow and sword-like whereas the rostrum of the American paddlefish is broad and paddle-like. Some common morphological characteristics of paddlefish include a spindle-shaped, smooth-skinned scaleless body, [[Heterocercal|heterocercal tail]], and small poorly developed [[eye]]s.<ref name=FAO/><ref name=LSU/> Unlike the filter-feeding American paddlefish, Chinese paddlefish were [[piscivores]], and highly predatory.  Their jaws were more forward pointing which suggested they foraged primarily on small fishes in the water column, and occasionally on shrimp, [[benthic]] fishes, and crabs.<ref name=FAO/><ref name=Miller>{{cite book | last=Miller |first=Michael J. | date=2006-01-20 | chapter=Chapter&nbsp;4 – The ecology and functional morphology of feeding of North American sturgeon and paddlefish | title=Sturgeons and Paddlefish of North America | publisher=Springer Science & Business Media | isbn=9781402028335 | pages=87–101 |editor1-first=G.T.O |editor1-last=le&nbsp;Breton |editor2-first=F. William H. |editor2-last=Beamish  |editor3-first=Scott R. |editor3-last=McKinley |series = Fish & Fisheries Series |volume=27 |url=https://books.google.com/books?id=M-2cxIjeuMIC | chapter-url=https://books.google.com/books?id=M-2cxIjeuMIC&q=Chinese+paddlefish+have+electroreceptors&pg=PA87 | access-date=June 10, 2014 | url-status=live | archive-url=https://web.archive.org/web/20140728044150/http://books.google.com/books?id=M-2cxIjeuMIC&pg=PA87&lpg=PA87&dq=Chinese%2Bpaddlefish%2Bhave%2Belectroreceptors%3F&source=bl&ots=1KDmJpKIFj&sig=h7tdiFolHfCG4QsOer5TQPGU2hU&hl=en&sa=X&ei=G0aXU6S2M6HG0AXK1YAI&ved=0CDkQ6AEwAw#v=onepage&q=Chinese%20paddlefish%20have%20electroreceptors%3F&f=false | archive-date=July 28, 2014 }}</ref> The jaws of the American paddlefish are distinctly adapted for filter feeding only. They are [[Aquatic feeding mechanisms#Ram feeding|ram suspension filter feeders]] with a diet that consists primarily of [[zooplankton]], and occasionally small insects, insect larvae, and small fish.<ref name=Wilkens-Hofmann-2007/>
[[File:DSC08833 - Open Wide (36823357680).jpg|thumb|270px|Closeup of the head, showing the presence of [[Electroreception and electrogenesis|electrorecepting]] organs ([[ampullae of Lorenzini]])]]
The largest Chinese paddlefish on record measured {{convert|23|ft|m|abbr=on}} in length, and was estimated to weigh a few thousand pounds.<ref name=IUCN-Chinese/> They commonly reached {{convert|9.8|ft|m|abbr=on}} and {{convert|1100|lb|kg|abbr=on}}.<ref name=IUCN-Chinese/><ref name=FAO/><ref name=BBC>{{cite news | last=Bourton |first=Jody | date=September 29, 2009 | title=Giant fish 'verges on extinction' | website=[[BBC News]] | department=Earth News | url=http://news.bbc.co.uk/earth/hi/earth_news/newsid_8269000/8269414.stm | access-date=June 9, 2014 | url-status=live | archive-url=https://web.archive.org/web/20141006072635/http://news.bbc.co.uk/earth/hi/earth_news/newsid_8269000/8269414.stm | archive-date=October 6, 2014 }}</ref> Although the American paddlefish is one of the largest [[freshwater fish]]es in North America, their recorded lengths and weights fell short in comparison to the larger Chinese paddlefish. American paddlefish commonly reach {{convert|5|ft|m|abbr=on}} or more in length and can weigh more than {{convert|60|lb|kg|abbr=on}}. The largest American paddlefish on record was caught in 1916 in Okoboji Lake, Iowa.{{efn|"Okoboji Lake" could refer to either of two attached lakes: [[West Okoboji Lake]] and [[East Okoboji Lake]]. The source does not state which one is meant.}}<ref name=Nichols>{{cite journal |last=Nichols |first=J.T. |date=24 August 1916 |title=A large ''Polyodon'' from Iowa |journal=Copeia |volume=34 |issue=34 |page=65 <!-- |publisher=JSTOR --> |jstor=1436920 }}</ref> The fish was taken with a spear, and measured {{convert|7|ft|1|in|m|abbr=on}} long and {{convert|45.5|in|m|abbr=on}} in the girth.<ref name=Nichols/> A report published by J.R. Harlan and E.B. Speaker (1969) in ''Iowa Fish and Fishing'' states that the fish weighed over {{convert|198|lb|kg|abbr=on}}.<ref name=AFS-7>{{cite book |last=Gengerke |first=Thomas W. |date=August 1986 |section=The paddlefish: Status, management and propagation |title=Distribution and Abundance of Paddlefish in the United States |id=AFS-7 }}</ref> The world record paddlefish caught on rod and reel weighed {{convert|144|lb|kg|abbr=on}} and was {{convert|54.25|in|m|abbr=on}} long. The fish was caught by Clinton Boldridge in a 5&nbsp;acre pond in [[Atchison County, Kansas]] on 5&nbsp;May 2004.<ref name=Kansas>{{cite web | title=State Record Fish | department=Kansas angler online edition | date=May 2004 | publisher=[[Kansas Department of Wildlife, Parks and Tourism]] | url=http://ksoutdoors.com/Fishing/State-Record-Fish | url-status=live | access-date=June 9, 2014 | archive-url=https://web.archive.org/web/20150326215821/http://www.kansasangler.com/archive/0502riley.html | archive-date=March 26, 2015 }}</ref><ref name=KWPT>{{cite web |title=State record fish |publisher=Kansas Wildlife Parks & Tourism |via=ksoutdoors.com |url=http://ksoutdoors.com/Fishing/State-Record-Fish |access-date=September 8, 2017}}</ref> However, the record would be broken an additional two times in 2020: On 28&nbsp;June 2020, an Oklahoma man caught a 146&nbsp;pound paddlefish in [[Keystone Lake]], west of [[Tulsa]]. Later on 23&nbsp;July 2020, the record was broken again when another Oklahoma man caught a 151&nbsp;pound, nearly 6&nbsp;foot long paddlefish in the same lake.<ref>{{cite news | last=Wilkinson |first=Joseph | date=July 31, 2020 | title=Oklahoma man catches world-record 150&nbsp;pound paddlefish — breaking record set last month in the same lake |newspaper=[[The New York Daily News]] | via=NYDailyNews.com | url=https://www.nydailynews.com/news/national/ny-oklahoma-man-paddlefish-world-record-cory-watters-20200731-3j7ueb3fhjczfaychucyegviva-story.html | access-date=August 3, 2020 }}</ref>

Scientists once believed paddlefish used their rostrums to excavate bottom substrate,<ref name=LSU/><ref name=Nachtrieb>{{cite journal |last=Nachtrieb |first=Henry F. |year=1910 |title=The primitive pores of ''Polyodon spathula'' (Walbaum) |journal= Journal of Experimental Zoology |volume=9 |issue=2 |pages=455–468 |doi=10.1002/jez.1400090211 |url=https://zenodo.org/record/1426858 |via=zendo.org }}</ref> but have since determined with the aid of [[electron microscopy]] that paddlefish rostrums are covered in [[electroreception and electrogenesis|electroreceptors]] called [[Ampullae of Lorenzini|ampullae]].<ref name=Jorgensen>{{cite journal |last1=Jørgensen |first1=J. Mørup |last2=Flock |first2=Å. |last3=Wersäll |first3=J. |date=September 1972 |title=The Lorenzinian ampullae of ''Polyodon spathula'' |journal=Zeitschrift für Zellforschung und Mikroskopische Anatomie |issue=3 |volume=130 |pages=362–377 |doi=10.1007/BF00306949 |pmid=4560320 |s2cid=28712903 }}</ref> These ampullae are densely packed within star-shaped bone projections that branch out from the rostrum.<ref name=Grande1991>{{Cite journal |last1=Grande |first1=Lance |last2=Bemis |first2=William E. |date=1991-03-28 |title=Osteology and phylogenetic relationships of fossil and recent paddlefishes (Polyodontidae) with comments on the interrelationships of Acipenseriformes |journal=Journal of Vertebrate Paleontology |volume=11 |issue=sup001 |pages=1–121 |doi=10.1080/02724634.1991.10011424 |issn=0272-4634 |lang=en |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.1991.10011424 |url-access=subscription }}</ref> The electroreceptors can detect weak electrical fields which not only signal the presence of prey items in the water column, such as [[zooplankton]] which is the primary diet of the American paddlefish, but they can also detect the individual feeding and swimming movements of zooplankton's [[appendages]].<ref name=Wilkens-Hofmann-2007/><ref name=LSU/> Paddlefish have poorly developed eyes, and rely on their electroreceptors for foraging. However, the rostrum is not the paddlefish's sole means of food detection. Some reports incorrectly suggest that a damaged rostrum would render paddlefish less capable of foraging efficiently to maintain good health. Laboratory experiments, and field research indicate otherwise. In addition to electroreceptors on the rostrum, paddlefish also have sensory pores covering nearly half of the skin surface extending from the rostrum to the top of the head down to the tips of the [[operculum (fish)|operculum]] (gill flaps). Paddlefish with damaged or abbreviated rostrums are still able to forage adequately.<ref name=Wilkens-Hofmann-2007/><ref name=LSU/>