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Dentinal layering observed in the half-etched teeth of long-beaked common dolphins (Delphinus capensis); sample of four different individuals from the present study. Each line marks a Growth Layer Group (GLG). PD = prenatal dentine, NL = neonatal line, AL = accessory layer, PC = pulp cavity, inc = incomplete GLG. a) Individual ITESM- CIAD880426: estimated age: 3 + 1 inc GLG, estimated age: 3.8 years old (mid-longitudinal section). b) Individual I T E S M -C I A D 9 0 0 3 2 6 : estimated age: 6 + 1 inc GLG, known age: 6.2 years old (mid-longitudinal section, upper part " offcenter " ). c) Individual ITESM-CIAD860429-5: estimated age: 12+1 inc GLG. d) Individual ITESM- CIAD840429-8: estimated age: 15 GLG, known age: 14-16 years old (slightly " off-center " section).
Source publication
Introduction: We estimated the age of 41 long-beaked common dolphins, Delphinus capensis, found
stranded in Sonora and Baja California beaches in the Gulf of California from 1981 to 2000. The aim of
our work was to know the age and if possible the size of stranded dolphins and the possible causes of their
stranding.
Methods: Dentinal growth layers...
Citations
... We analyzed the teeth' dentin and cementum growth layers following Gallo-Reynoso et al. (2014). A tooth from the middle region of the right jaw was removed, and two longitudinal cuts were made, leaving the middle portion of the tooth. ...
Strandings provide valuable information about rare marine organisms and their relationship with their environment. In the southern Gulf of México, specifically on the central coast of Campeche, Mexico, strandings of oceanic cetaceans have rarely been recorded, therefore, biological information has also been scarce. One of such rare stranding cases occurred on September 7, 2022, on the coast of Seybaplaya, Campeche. The specimen was identified as a female of Tursiops truncatus with the morphology features of the oceanic ecotype. The carcass was examined shortly after death, and samples for different analyses were obtained fresh. Tissue samples were collected, and some particular observations were made to define the individual's general health status. Results of the analyses revealed damage in the liver, lungs, and kidneys, probably related to 1) the advanced age of the organism (>35 years), and 2) the presence of persistent organic pollutants. Most importantly, this study contributed two new findings, the first record of the parasite Anisakis and the presence of renal calculi in the oceanic ecotype of T. truncatus in the southern Gulf of Mexico.
Neritic, long‐beaked common dolphins have been described as species distinct from the more oceanic and globally distributed short‐beaked species, Delphinus delphis , although recent molecular studies have challenged this view. In the eastern North Pacific (ENP), the taxonomic status of the long‐beaked ( bairdii ) form has been controversial since its original description in 1873, and has vacillated between species, subspecies, and geographic forms several times. It is currently provisionally viewed as a subspecies of Delphinus delphis , D. d. bairdii . To clarify this situation, we reviewed the literature and conducted additional analyses using both newly obtained genetic and cranial morphometric data sets. The results indicate that there are diagnostic differences in skull morphology and coloration between the eastern Pacific long‐and short‐beaked forms, and near‐perfect diagnosability in mitochondrial DNA. These differences, along with indications of ecological distinctions, including important differences in life history parameters and reproductive timing, indicate that these forms are well on their way down separate evolutionary pathways. As such, we consider them to be distinct species in the eastern Pacific. The long‐beaked species is referable to Delphinus bairdii Dall, 1873, and is redescribed as such herein.
