22
in immature to 7.9 g (±4.2) in mature animals (Rosas and Monteiro-Filho 2002;
Rosas and Barreto 2008).
The newborn average size was estimated in 92 cm. The estimated gonadal maturity occurs between 165 and 170 cm in females and between 170 and 175 cm in
males (Rosas and Monteiro-Filho 2002). In relation to the cetacean morphology, the
skin is mostly evaluated regarding the blubber (e.g. Sokolov 1960; Giacometti
1967; Simpson and Gardner 1972; Pfeifer and Jones 1993). The skin thickness
changes according to age in S. guianensis, with expressive ontogenetic variation in
pigmentation (Randi et al. 2008). Therefore, the pink color that appear in infants
(Fig. 2.6) results of intense vascularization and a thin blubber layer rather than by
red pigmentation on the skin. The only detected pigment was melanin, scarce in
infants and increases with aging. Such increase tend to cover the pink tones of vascularization, making adults mostly grey in the dorsal portion of the body, reducing
towards the flanks.
2.5 Age Evaluation
Successful age estimates were made with S. guianensis carcasses through counting
of dentin growth layers deposited in teeth (Schmiegelow 1990; Ramos 1997, Rosas
2000; Rosas et al. 2003; Sydney and Monteiro-Filho 2011; Wanderley 2013;
Fig 2.7). The term “Growth Layer Group” (GLG) describes the distinct lines formed
by deposition of dentin and cementum in layers. Although different possible techniques may be used to access age in cetacean, Rosas et al. (2003) describe some
guidelines for age estimates with teeth since there was no specific model for dentin
deposition or GLG reading for the species. Researches in Cananéia (SP) and
Paranaguá (PR) registered a variation between 0 (newborn) and 30 years, being
female the eldest representation (Rosas et al. 2003; Wanderley 2013) and immature
(up to 6 years old) present greater mortality frequency, indicating a possible greater
vulnerability to natural and/or anthropic threats due to inexperience of younger animals (Wanderley 2013).
Fig. 2.6 Photography of
two specimens of Sotalia
guianensis. Dolphin on left
is an adult, while the
dolphin on right side is an
infant, which is recognized
by pinkish color of dorsal
fin, back and flanks (Photo:
Caio N. Louzada)
E.L.A. Monteiro-Filho et al.
in immature to 7.9 g (±4.2) in mature animals (Rosas and Monteiro-Filho 2002;
Rosas and Barreto 2008).
The newborn average size was estimated in 92 cm. The estimated gonadal maturity occurs between 165 and 170 cm in females and between 170 and 175 cm in
males (Rosas and Monteiro-Filho 2002). In relation to the cetacean morphology, the
skin is mostly evaluated regarding the blubber (e.g. Sokolov 1960; Giacometti
1967; Simpson and Gardner 1972; Pfeifer and Jones 1993). The skin thickness
changes according to age in S. guianensis, with expressive ontogenetic variation in
pigmentation (Randi et al. 2008). Therefore, the pink color that appear in infants
(Fig. 2.6) results of intense vascularization and a thin blubber layer rather than by
red pigmentation on the skin. The only detected pigment was melanin, scarce in
infants and increases with aging. Such increase tend to cover the pink tones of vascularization, making adults mostly grey in the dorsal portion of the body, reducing
towards the flanks.
2.5 Age Evaluation
Successful age estimates were made with S. guianensis carcasses through counting
of dentin growth layers deposited in teeth (Schmiegelow 1990; Ramos 1997, Rosas
2000; Rosas et al. 2003; Sydney and Monteiro-Filho 2011; Wanderley 2013;
Fig 2.7). The term “Growth Layer Group” (GLG) describes the distinct lines formed
by deposition of dentin and cementum in layers. Although different possible techniques may be used to access age in cetacean, Rosas et al. (2003) describe some
guidelines for age estimates with teeth since there was no specific model for dentin
deposition or GLG reading for the species. Researches in Cananéia (SP) and
Paranaguá (PR) registered a variation between 0 (newborn) and 30 years, being
female the eldest representation (Rosas et al. 2003; Wanderley 2013) and immature
(up to 6 years old) present greater mortality frequency, indicating a possible greater
vulnerability to natural and/or anthropic threats due to inexperience of younger animals (Wanderley 2013).
Fig. 2.6 Photography of
two specimens of Sotalia
guianensis. Dolphin on left
is an adult, while the
dolphin on right side is an
infant, which is recognized
by pinkish color of dorsal
fin, back and flanks (Photo:
Caio N. Louzada)
E.L.A. Monteiro-Filho et al.