Bio E179 Lecture 8 Notes .doc

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University of California - Irvine
Biological Sciences
Rahul Warrior

Limnology and Freshwater BiologyNotes on PupfishPupfish in the genus Cyprinodon are in the killifish family Cyprinodontidae and are closely related to the California killifish Fundulus parvipinnis present in Newport Back BayPupfish are descendants of an ancestral species group that once had a broader range in what are now Californian and Mexican desert areasToday pupfish occur in three deserts the Mojave Sonoran and Chihuahan deserts There is a beautiful website with pictures of pupfish and many other desert fishes at httpdesertfishesorgtopindexhtml There are roughly 20 distinct populations in an area 3000 square milesThey are very tolerant of a wide range of temperatures and salinitiesFor example in Death Valley there are five species of pupfishTemperatures there are greater than 49 degrees C from May to SeptemberPupfish became isolated in desert springs during the Pleistocene as uplift by the Sierras caused a climate change that dried up former lakes in which pupfish livedthereby forcing them to be restricted to the small springs which survivedPupfish can survive phenomenally low dissolved oxygen levelsPupfish are able to withstand the lowest minimum level of dissolved oxygen in water of all fishes 01302 mg oxygenl whereas normally water supporting fishes contains 5070 times this concentration of dissolved oxygenSome pupfish like the Amargosa pupfish are able to dive into the oxygen deficient mud and bury themselves though they often keep their heads or mouths exposed to obtain oxygenOthers dont do that and are clearly tolerant of very very low oxygen concentrationsPupfish have the greatest tolerance of salinity of all fishesThey are able to adjust to direct transfer from seawater to freshwaterThis explains why they are able to invade newly inundated terrain and or temporary pools and establish breeding populationsThe eggs of one species Cyprinodon macularius can hatch and develop in distilled water with 0 salinity and in water with up to 70 grams per liter saltCan survive very high temperaturesPupfish are tolerant of high temperaturesIn nature fish have been found at temperatures as high as 45 degrees CThey also have been observed able to withstand brief periods under iceIn the desert water temperatures can fluctuate 15 degrees C on a daily basisthus these fish are truly living on the edge of survivalThe fish use behavior as a means of thermoregulatingThe ability of pupfish to detect and avoid critically high temperatures enables them to live for weeks and even reproduce in thermal pools in which they are literally inches from death water too hot for them surviveFish often hide under algal mats to stay cooler and track temperature as they feed and move about during the dayFor example in the Salton Sea they move into shallow water where they feed in the early morning as the temperature rises they move into deeper water and remain motionless perhaps minimizing metabolic demand as food is processed then they move back to the shallow to feed in the afternoon after dark they once again become motionlessAt least some species can also tolerate low temperatures and they have been observed to live under ice for short periodsPupfish live in isolated populations in small desert springsBecause they are isolated in the springs there may be related but different species in springs quite close to each other sometimes separated by only a few hundred yardsExotic fishes have been introduced as aquarium releases into many of the springs and they interfere with pupfish breeding biology as well as actually eating them in the case of bassSimilar to the pupfish small desert springs often have endemic species occurring only in one or a few springs of hydroid snailsas an exampleBreeding biology using C maculariusBreeding commences in April or May and continues till Augustin constant water habitats it continues year roundThey can spawn in a wide range of temperatures ranging from 13 to 44 degrees C with 28 degrees being the optimalThe dominant male patrols
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