Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles
Epibionts are organisms that utilize the exterior of other organisms as a living substratum. Many affiliate opportunistically with hosts of different species, but others specialize on particular hosts as obligate associates. We investigated a case of apparent host specificity between two barnacles t...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2021-12-01
|
| Series: | Frontiers in Ecology and Evolution |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fevo.2021.807237/full |
| _version_ | 1818289091192553472 |
|---|---|
| author | Liberty L. Boyd John D. Zardus Courtney M. Knauer Lawrence D. Wood |
| author_facet | Liberty L. Boyd John D. Zardus Courtney M. Knauer Lawrence D. Wood |
| author_sort | Liberty L. Boyd |
| collection | DOAJ |
| description | Epibionts are organisms that utilize the exterior of other organisms as a living substratum. Many affiliate opportunistically with hosts of different species, but others specialize on particular hosts as obligate associates. We investigated a case of apparent host specificity between two barnacles that are epizoites of sea turtles and illuminate some ecological considerations that may shape their host relationships. The barnacles Chelonibia testudinaria and Chelonibia caretta, though roughly similar in appearance, are separable by distinctions in morphology, genotype, and lifestyle. However, though each is known to colonize both green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) sea turtles, C. testudinaria is >5 times more common on greens, while C. caretta is >300 times more common on hawksbills. Two competing explanations for this asymmetry in barnacle incidence are either that the species’ larvae are spatially segregated in mutually exclusive host-encounter zones or their distributions overlap and the larvae behaviorally select their hosts from a common pool. We indirectly tested the latter by documenting the occurrence of adults of both barnacle species in two locations (SE Florida and Nose Be, Madagascar) where both turtle species co-mingle. For green and hawksbill turtles in both locations (Florida: n = 32 and n = 275, respectively; Madagascar: n = 32 and n = 125, respectively), we found that C. testudinaria occurred on green turtles only (percent occurrence – FL: 38.1%; MD: 6.3%), whereas the barnacle C. caretta was exclusively found on hawksbill turtles (FL: 82.2%; MD: 27.5%). These results support the hypothesis that the larvae of these barnacles differentially select host species from a shared supply. Physio-biochemical differences in host shell material, conspecific chemical cues, external microbial biofilms, and other surface signals may be salient factors in larval selectivity. Alternatively, barnacle presence may vary by host micro-environment. Dissimilarities in scute structure and shell growth between hawksbill and green turtles may promote critical differences in attachment modes observed between these barnacles. In understanding the co-evolution of barnacles and hosts it is key to consider the ecologies of both hosts and epibionts in interpreting associations of chance, choice, and dependence. Further studies are necessary to investigate the population status and settlement spectrum of barnacles inhabiting sea turtles. |
| first_indexed | 2024-12-13T02:06:46Z |
| format | Article |
| id | doaj.art-862046a1a1bb4082b7c14e7343277867 |
| institution | Directory Open Access Journal |
| issn | 2296-701X |
| language | English |
| last_indexed | 2024-12-13T02:06:46Z |
| publishDate | 2021-12-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Ecology and Evolution |
| spelling | doaj.art-862046a1a1bb4082b7c14e73432778672022-12-22T00:03:07ZengFrontiers Media S.A.Frontiers in Ecology and Evolution2296-701X2021-12-01910.3389/fevo.2021.807237807237Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea TurtlesLiberty L. Boyd0John D. Zardus1Courtney M. Knauer2Lawrence D. Wood3Department of Biology, Florida International University, Miami, FL, United StatesDepartment of Biology, The Citadel, Charleston, SC, United StatesDepartment of Biology, Florida International University, Miami, FL, United StatesFlorida Hawksbill Project, National Save the Sea Turtle Foundation, Fort Lauderdale, FL, United StatesEpibionts are organisms that utilize the exterior of other organisms as a living substratum. Many affiliate opportunistically with hosts of different species, but others specialize on particular hosts as obligate associates. We investigated a case of apparent host specificity between two barnacles that are epizoites of sea turtles and illuminate some ecological considerations that may shape their host relationships. The barnacles Chelonibia testudinaria and Chelonibia caretta, though roughly similar in appearance, are separable by distinctions in morphology, genotype, and lifestyle. However, though each is known to colonize both green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) sea turtles, C. testudinaria is >5 times more common on greens, while C. caretta is >300 times more common on hawksbills. Two competing explanations for this asymmetry in barnacle incidence are either that the species’ larvae are spatially segregated in mutually exclusive host-encounter zones or their distributions overlap and the larvae behaviorally select their hosts from a common pool. We indirectly tested the latter by documenting the occurrence of adults of both barnacle species in two locations (SE Florida and Nose Be, Madagascar) where both turtle species co-mingle. For green and hawksbill turtles in both locations (Florida: n = 32 and n = 275, respectively; Madagascar: n = 32 and n = 125, respectively), we found that C. testudinaria occurred on green turtles only (percent occurrence – FL: 38.1%; MD: 6.3%), whereas the barnacle C. caretta was exclusively found on hawksbill turtles (FL: 82.2%; MD: 27.5%). These results support the hypothesis that the larvae of these barnacles differentially select host species from a shared supply. Physio-biochemical differences in host shell material, conspecific chemical cues, external microbial biofilms, and other surface signals may be salient factors in larval selectivity. Alternatively, barnacle presence may vary by host micro-environment. Dissimilarities in scute structure and shell growth between hawksbill and green turtles may promote critical differences in attachment modes observed between these barnacles. In understanding the co-evolution of barnacles and hosts it is key to consider the ecologies of both hosts and epibionts in interpreting associations of chance, choice, and dependence. Further studies are necessary to investigate the population status and settlement spectrum of barnacles inhabiting sea turtles.https://www.frontiersin.org/articles/10.3389/fevo.2021.807237/fullturtle barnacleepibiontassortative epibiosissubstratum specificitybasibiont preferencecarapace |
| spellingShingle | Liberty L. Boyd John D. Zardus Courtney M. Knauer Lawrence D. Wood Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles Frontiers in Ecology and Evolution turtle barnacle epibiont assortative epibiosis substratum specificity basibiont preference carapace |
| title | Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles |
| title_full | Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles |
| title_fullStr | Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles |
| title_full_unstemmed | Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles |
| title_short | Evidence for Host Selectivity and Specialization by Epizoic Chelonibia Barnacles Between Hawksbill and Green Sea Turtles |
| title_sort | evidence for host selectivity and specialization by epizoic chelonibia barnacles between hawksbill and green sea turtles |
| topic | turtle barnacle epibiont assortative epibiosis substratum specificity basibiont preference carapace |
| url | https://www.frontiersin.org/articles/10.3389/fevo.2021.807237/full |
| work_keys_str_mv | AT libertylboyd evidenceforhostselectivityandspecializationbyepizoicchelonibiabarnaclesbetweenhawksbillandgreenseaturtles AT johndzardus evidenceforhostselectivityandspecializationbyepizoicchelonibiabarnaclesbetweenhawksbillandgreenseaturtles AT courtneymknauer evidenceforhostselectivityandspecializationbyepizoicchelonibiabarnaclesbetweenhawksbillandgreenseaturtles AT lawrencedwood evidenceforhostselectivityandspecializationbyepizoicchelonibiabarnaclesbetweenhawksbillandgreenseaturtles |