Variation of tooth traits in ecologically specialized and sympatric morphs

Arnar Pálsson, 19/12/2024

Variation of tooth traits in ecologically specialized and sympatric morphs

Guðbjörg Ósk Jónsdóttir*, Finnur Ingimarsson, Sigurður Sveinn Snorrason, Sarah Elizabeth Steele, Arnar Pálsson. Submitted to Evolutionary Biology.

GOJ: https://orcid.org/0009-0008-0502-5553
FI: https://orcid.org/0000-0002-0815-7622
SES: https://orcid.org/0000-0001-8404-5537
AP: https://orcid.org/0000-0002-6525-8112

Rotational from top left, premaxilla, maxilla, supramaxilla  (w.o. teeth) and palatine.

Abstract
Differences in dentition between species relate to feeding specialisations, as examples of tetrapod dentition variation show clearly. The association of tooth traits and specialisations in non-mammalian vertebrates is less studied. We examined variation in dental traits in four sympatric morphs of Arctic charr (Salvelinus alpinus) which differ in feeding specialisations, head and jaw bone morphology. We studied tooth numbers in six bones (dentary, maxilla, premaxilla, palatine, vomer and glossohyal) and tooth angles in one bone (maxilla). We found fluctuating asymmetry in tooth numbers and angles and that the allometry of tooth numbers varied by bone but not morphs. The tooth numbers differed by morphs in four bones (dentary, palatine, vomer and glossohyal). In general, the morphs defined as pelagic had more teeth, and this relates partially to changes in bone shape. There was a difference in maxilla tooth angle, with benthic morphs having teeth which were angled more inwards. Dentary and maxilla tooth number correlated moderately with bone shape, maxilla tooth angle and premaxilla tooth number did not. While it is currently unknown what tooth characteristics are ancestral vs derived in these populations, the marked differences in specific bones presents an opportunity to explore rapid adaptive evolution in dentition.

Uppeldissvæði laxfiska í Þingvallavatni og tengdum ám

Arnar Pálsson, 09/12/2024

 

Large benthic charr on the spawning grounds, picture took Kalina H. Kapralova and Quentin Horta.

Now published in the Icelandic Naturalist. Areas used by Salmonid juveniles in Lake Þingvallavatn and connected rivers. Uppeldissvæði laxfiska í Þingvallavatni og tengdum ám (in icelandic, w. English abstract). Guðbjörg Ósk Jónsdóttir, Benóný Jónsson, Magnús Jóhannsson og Arnar Pálsson.  (Náttúrufræðingurinn).

Nursery grounds of juvenile fish provide them shelter and food making them essential for the life of an individual, the population and species as a whole. In Lake Þingvallavatn, Iceland, two species of salmonids inhabit the lake, Brown trout (Salmo trutta) and Arctic charr (Salvelinus alpinus). Extensive biological studies have been conducted on adult fish of both species in the lake and its catchment area, but much less is known about the biology of age-0 fish and the ecology of their first 1−2 years in the life. Given the critical importance of nursery areas for the existence of fish populations and their contribution to biological diversity, research was undertaken to examine the distribution of charr and trout juveniles in the surf zone of Lake Þingvallavatn and in streams connected to the lake. The research questions were,

1) Where in the lake and connected streams are juvenile fish found?

2) Has the density of charr and trout juveniles changed in the last twenty years?

3) Is there a connection between the environmental conditions and the presence of juvenile fish?

Data from Veiðimálastofnun (now Hafrannsóknastofun) surveys of salmonid juveniles in Þingvallavatn and adjacent rivers, spanning 2000 to 2021, were analyzed. In the summer of 2022, ten locations in Þingvallavatn were surveyed, fish were caught and measured, and several environmental factors were assessed using electrofishing. Fish were counted, identified by species, and measured for length and weight. Additionally, environmental factors, including the lake bottom composition and shoreline vegetation, were documented. The results show that the two species utilize different juvenile habitats, trout predominantly occupy river habitats, whereas charr are more abundant in the surf zone of the lake. There was a significant increase in density of the Brown trout over the 19-year period, but density of Arctic charr remained relatively stable with a sign of subtle decline. In 2022, six possible nursery sites were documented in the surf zone, four with majority of Arctic charr and two with mainly Brown trout. There was little overlap in the species distribution. Vegetation on the shoreline was the only environmental factor significantly correlated with the presence or absence of juvenile fish on a given site. Further studies on juvenile fish biology in the lake and adjacent streams and river might explore the interplay of environmental factors and genetics in shaping the size and morphology of adult fish in both species´ populations. This is particularly relevant for Arctic charr, which features four distinct sub-populations (or morphs) differing in size, shape, trophic morphology and ecology.

 

Mývatn conference

Arnar Pálsson, 23/09/2024

Lake Mývatn in north Iceland is unique for its biota and geology. To commemorate 50 years of research on the lake, and the retirement of Árni Einarsson a meeting was held there last week. Multiple scientists came to describe the hydrology, ecology and evolution of the organisms and ecosystem in the lake.

The programme was quite extensive and interesting - Mývatn research conference 2024.

Hot shore spring on the Myvatn east side

Guðbjörg and Kenedy brought some of our fish stuff to the meeting.

Guðbjörg Ósk Jónsdóttir - Divergence of functional phenotypes in feeding elements of Arctic charr along the benthic – pelagic axis

Kenedy A. Williams - Patterns of Feeding Element Specialization in Arctic charr and Brown trout

Arnar Pálsson - Genetic structure and relatedness of anadromous and landlocked populations of Icelandic brown trout

 

Skilningur á rás 1

Arnar Pálsson, 14/08/2024

Fyrir örþættina Uppástand á rás 1.

Umsjón og upptaka Jóhannes Ólafsson. Flutt 24. júní 2024.

Skilningur

Skilningur var ræddur við kvöldverðarborðið. Börnin reyndu að misskilja skilninginn, skilja misskilninginn, sundurliða skil – ninginn, inga við skilin og aðskilja skilninginn og skilningsleysið, og skemmta sér í leiðinni. Leikur að orðum, kasta þeim á milli sín, hvolfa þeim og hnoða, snúa út úr þeim og innúr, er ein dægradvöl fjölskyldunar, sem ég tel hjálpa okkur að skilja og öðlast skilning.

Samtal, þar sem skipst er á orðum, spurningar settar fram, efi læðist um og steinum velt um koll. Grín gert að orðum, og síðan grín gert að gríninu. Með öðrum orðum, við færum rök og mótrök, greinum forsendur og rætur orða. Ja hérna, spjall yfir kvöldverði var etv eins og heimspeki eða vísindi.

Forvitni, spurningar og samtal eru mikilvæg mannlegri tilveru og gefa okkur lífsfyllingu. Sálfræðingurinn Mihaly Csikszentmihalyi – höfundur bókanna Flow og Creativity sagði eitt sinni að

"Búið til fullt af hugyndum. Reynið einnig að koma með ólíklegar hugmyndir"

Í vinnunni minni við HÍ, kenni ég margvísleg viðfangsefni og rannsaka allskonar spennandi hluti. Á haustin kenni ég venjulega mannerfðafræði, nema ekki í haust af því að ráðherra og fjárveitingavaldið skáru niður framlög til háskólanna. Það má spyrja sig hversu mikinn skilning alþingi hafi á mikilvægi skilningsleitarinnar í Háskólum landsins.

Sem dæmi, í mannerfðafræði fjöllum við um áhrif erfða og umhverfis á margvíslega eiginleika mannfólks. Mikilvægasti hluti námskeiðsins eru kynningar nemenda á viðfangsefnum sem þeir velja sér, allt frá erfðum klumbrufóts, sögu þjóða eyjaálfu og breytileika í byggingu erfðamengja manna. Viðfangsefnin sjálf eru mikilvæg, en mestu skiptir er að nemendur þjálfist í vísindalegu samtali. Tökum þessa tvö viðfangsefni fyrir.

Nemendur spyrja hvaða þættir hafa áhrif á tiltekið einkenni? Hvort vegur meira erfðir eða umhverfi, og hversu sterk eru áhrif tilviljunarinnar? Oft er hugsað um erfðafræði sem leitina að genum sem móta einhverjar eiginleika, hversu margir erfðaþættir og hvernig eru áhrif þeirra? En fyrir mörg einkenni eru áhrif umhverfisþátta sterkari og tilviljun mjög mikilvæg. Þau áhrif er aftur á móti erfitt að greina og skilgreina, sérstaklega miðað við erfðabreytileika. Breytileika í genum er auðvelt að mæla, með því að keyra lífsýni (DNA úr blóði) í gegnum stórkostleg apparöt, og greina þær milljónir staða í erfðamenginu sem eru breytilegir. Ekkert sambærilegt tæki dugar til að mæla allt umhverfi sem við hrærumst í. Hversu mörg epli höfum við borðað yfir ævina, hversu margar sýkingar fengum við, hvaða sýkingar og hvenær. Sultum við í bernsku eða urðum fyrir öðru áfalli? Nemendurnir fjalla um slíkar spurningar í kringum viðfangsefni sín.

En þau spyrja líka um eðli þekkingarinnar og þess sem ekki er vitað.

Þau lesa greinar og ræða við sérfræðinga, og reyna að ná utan um viðfangsefnin. (tekst mjög vel í flestum tilfellum).  Þau spyrja; Hvað er vitað um sjúkdóm X? Hversu traustar eru þær upplýsingar? Hvernig var þeirra þekkingar aflað? Er önnur túlkun á gögnunum möguleg? Hvaða eiginleika hefur aðferðin sem var notuð ? Kosti galla, bjaga. Þetta er áþekkt kvöldverðar samtalinu sem við ræddum áðan,  spurt er um forsendur og röksemdir, rökflæði, rök og mótrök sett fram, gæði þeirra og gallar metnir.

Sjálfsöryggi og sannfæringarkraftur er ekki mikilvægasti kostur vísindafólks. Það er nóg af sannfærandi fólki með vísindamenntun, sem hefur aukið á misskilning mannfólks frekar en skilning. Má til með að vísa í umfjöllun Veru Illugadóttir um lækninn Andrew Wakefield sem leiddi til víðtæks misskilnings um eðli og áhættur af bólusetningum. Mikilvægt er að viðhafa varfærni og hófsemi í ályktunum. Það er mjög gefandi að sjá nemendur byggja upp hæfileika sína á þessum sviðum. Maður vonar auðvitað að þeirra persónulega leit að þekkingu og skilningi haldi áfram eftir útskrift,  hvort sem þau fari formlega menntabraut eða leit á aðrar slóðir.

Mihaly Siksentmihaly – lagði einmitt áherslu á að allir geta öðlast lífsfyllingu með því að spyrja spurninga og kafa í málin, leita að skilningi.

Ég ljúka þessum pistli á annari tilvitnun í hann:

„Ef þú hefur áhuga á einhverju, þá veitiru því athygli

Og ef þú veitir einhverju athygli, þá er líklegt að þér muni finnast það áhugavert.

Margt af því sem okkur finnst áhugavert er það ekkert endilega í sjálfu sér, heldur vegna þess að við lögðum það á okkur að veita því athygli.“

Athygli er gjaldmiðill mannslegs samfélags, sérstaklega í nútíma. Vonandi var þessi pistill nógu áhugaverður fyrir hlustendur, eða a.m.k. vakti áhuga ykkar á því að hafa áhuga á einhverju. Og leiða þannig til skilnings.

Skírnir

Arnar Pálsson, 14/08/2024

In January 2023 I was asked to give a historical account of the discovery of DNA helix in a local medical conference. From that I wrote a little piece about the discovery and discussed how DNA is seriously overinterpreted in modern society, as synonymous with Fate and a determinant stronger than environmental factors.

Sorry, no translation available.

(Icelandic) Vespur sem temja veirur, samtal á RÚV

Arnar Pálsson, 29/05/2024

Sorry, this entry is only available in Icelandic.

Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Arnar Pálsson, 22/05/2024

Guðbjörg´s first paper is now published in PLoS-One.

Jónsdóttir GÓ, von Elm L-M, Ingimarsson F, Tersigni S, Snorrason SS, Pálsson A, et al. (2024) Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus). PLoS ONE 19(5): e0300359.

Abstract

The diversity of functional feeding anatomy is particularly impressive in fishes and correlates with various interspecific ecological specializations. Intraspecific polymorphism can manifest in divergent feeding morphology and ecology, often along a benthic–pelagic axis. Arctic charr (Salvelinus alpinus) is a freshwater salmonid known for morphological variation and sympatric polymorphism and in Lake Þingvallavatn, Iceland, four morphs of charr coexist that differ in preferred prey, behaviour, habitat use, and external feeding morphology. We studied variation in six upper and lower jaw bones in adults of these four morphs using geometric morphometrics and univariate statistics. We tested for allometric differences in bone size and shape among morphs, morph effects on bone size and shape, and divergence along the benthic-pelagic axis. We also examined the degree of integration between bone pairs. We found differences in bone size between pelagic and benthic morphs for two bones (dentary and premaxilla). There was clear bone shape divergence along a benthic–pelagic axis in four bones (dentary, articular-angular, premaxilla and maxilla), as well as allometric shape differences between morphs in the dentary. Notably for the dentary, morph explained more shape variation than bone size. Comparatively, benthic morphs possess a compact and taller dentary, with shorter dentary palate, consistent with visible (but less prominent) differences in external morphology. As these morphs emerged in the last 10,000 years, these results indicate rapid functional evolution of specific feeding structures in arctic charr. This sets the stage for studies of the genetics and development of rapid and parallel craniofacial evolution.

Wonderful for Guðbjörg and Sarah who made this such a stellar paper, with amazing visuals. For me it feels good to publish in PLoS One again, 10 years after my favorite paper on Eve and Hunchback (Naturally Occurring Deletions of Hunchback Binding Sites in the Even-Skipped Stripe 3+7 Enhancer. 2014. Palsson A, Wesolowska N, Reynisdóttir S, Ludwig MZ, Kreitman M. PLoS ONE 9(5): e91924. doi:10.1371/journal.pone.0091924.)

(Icelandic) Maurar í Perlunni

Arnar Pálsson, 03/05/2024

Sorry, this entry is only available in Icelandic.

Arnar Pálsson, 15/04/2024

Sorry, this entry is only available in Icelandic.

The prey availability and diet of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northern Europe

Arnar Pálsson, 02/04/2024

The prey availability and diet of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northern Europe

accepted for publication in the Journal of Fish Biology. http://doi.org/10.1111/jfb.15757 

Authors:

Sum Yi Lai1,2,  Arnar Pálsson2, Guðni Guðbergsson1, Ingi Rúnar Jónsson1, Jón S. Ólafsson1, Hlynur Bárðarson1

1. Marine and Freshwater Research Institute, Hafnarfjördur, Iceland

2. University of Iceland, Reykjavík, Iceland

Corresponding author: Name: Sum Yi Lai Address: Marine and Freshwater Research Institute, Fornubúdir 5, 220 Hafnarfjördur, Iceland,

Email: sammi.lai@hafogvatn.is

Abstract:

The availability of resources varies across a species distributional range, and a low productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low productivity rivers at Northeast Iceland, which is one of the species´ most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S. salar was the Chironomidae. The type of food items consumed varied across different weight groups of S. salar, with smaller juveniles having more diverse diet. S. salar did not have a selection preference for chironomids, which indicate that they were eating the highly available prey in their environment, rather than hunting high biomass items such as terrestrial invertebrates and large Dipterans. Estimates of dietary niche showed that S. salar in these low-productivity rivers relied on consuming what was most readily available, the chironomids, and that they must share resources with other salmonid species. This may be due to the low diversity of freshwater invertebrates (fewer prey options), whereas S. salar in nutrient-rich rivers could rely more on terrestrial invertebrates as an additional subsidy in their diet. In conclusion, with limited prey choices, juvenile S. salar in nutrient-poor rivers, especially in a biogeographically isolated region with low species diversity, may increase in vulnerability and decrease in adaptability to environmental change. Management methods that increase benthic prey abundance and diversity are recommended for conserving S. salar population in a nutrient-poor river

Log10 average number of prey items found in stomachs of juvenile Atlantic salmon (Salmo salar) was differed significantly across rivers (p<0.001) and by weight ranges (p<0.001).
The number of prey items consumed increased with weight (p<0.05). Log10 abundance also varies between taxonomic groups for all rivers (p<0.001) with abundances of Chironomidae higher in comparison.