Embryonic development of the pelvic girdle and hindlimb skeletal elements in Anilius scytale (Linnaeus, 1758) (Serpentes: Aniliidae).

Anilius scytale is the sister lineage of all other alethinophidian snakes. Morphology of the hind limb complex in adult A. scytale (Aniliidae) has been documented. We herein, for the first time, describe the embryology of the skeletal elements of its hind limb and pelvic girdle and contextualize the evolution of these structures. We identified pregnant females of A. scytale in the Herpetology Collection of the Museu Paraense Emílio Goeldi and separated 40 embryos. The embryos were sequentially staged using external and internal anatomy, collectively comprising a developmental series representing six stages. We cleared-stained one specimen of stages 31, 34, 36, and 37. Using the embryological information gleaned from A. scytale, we reinterpret evidence relating to the ossification of the pelvis and hindlimbs. In A. scytale hindlimb buds develop as transient structures that developed before Stage 30 and regresses in subsequent stages. There is no external or internal evidence of the forelimb or scapular girdle. From Stage 31 onwards the ischium, pubis, ilium, femur and zeugopodial cartilages are visible. Pubis and femur ossify towards the end of embryonic life, and cloacal spurs do not develop in the embryo. Skeletal elements of the hindlimb and pelvic girdle develop initially in the ventral zone of the cloaca-tail region. In subsequent stages the hindlimb and pelvic girdle elements migrate dorsally, with the pubis/ischium positioned medial to the ribs. A similar process may be associated with the achievement of the condition of the pelvic girdle in adults of scolecophidians, pythonids and boids.

Sexual dimorphism and allometry in malacophagus snakes (Dipsadidae: Dipsadinae).

Sexual dimorphism in snakes is generally described in association with body or tail size and scale counts, with relatively few studies addressing intrasexual divergence in the skull. Here, we analyzed sexual dimorphism in the size and shape of skull and body in three malacophagous dipsadine snakes, Dipsas mikanii, Dipsas neuwiedi and Dipsas turgida, as well as allometric effect on these components. We used linear and geometric analysis to assess: (1) if there is sexual dimorphism in cranial components; (2) if there are differences between the sexes regarding body and tail size, number of ventral and subcaudal scales; (3) whether there is covariation between cranial components and body size; (4) if there are changes in cranial shape associated with increased size; and (5) whether there is an allometric relationship between body and tail size. Our results showed that all three species are dimorphic in cranial shape and size (except D. turgida for cranial size), with females having longer and thinner skulls than males. In the three species, the female skull was negatively allometric, whereas the male skull was isometric. Allometry related to cranial shape was significant only in males of D. turgida, which showed greater snout robustness and eye size associated with enlargement of the skull. Females of D. mikanii and D. neuwiedi were significantly larger than males. Only males of D. neuwiedi showed positive allometry for the tail, while dimorphism related to scale counts followed the pattern found in most snakes, with females having a greater number of ventrals and males subcaudals (except D. neuwiedi in the latter case). Based on our results, we hypothesize that patterns of sexual dimorphism and skull allometry in malacophagous snakes may be explained both by aspects related to diet and reproduction. Meanwhile, patterns associated with body size reflect advantages related to fecundity favoring greater reproductive success of females.

Dataset from the Snakes (Serpentes, Reptiles) collection of the Museu Paraense Emílio Goeldi, Pará, Brazil.

BACKGROUND: We present a dataset with information from the snake collection of the Museu Paraense Emílio Goeldi, known as the "Ophidia Collection". This collection currently has 26,728 specimens of snakes, including 9 families, 66 genera and 220 species. For the most part, it represents material from the Amazon Region. Specimens are preserved mostly in wet (alcohol) preparation, with some samples preserved in dry form, as is the case of the shells and skeletons of turtles. The dataset is now available for public consultation on the Global Biodiversity Information Facility portal (https://doi.org/10.15468/lt0wet). NEW INFORMATION: The Herpetological collection of Museu Paraense Emílio Goeldi comprises the largest collection of its kind in the Amazon region with about 100,000 specimens of amphibians and reptiles (chelonians, alligators, lizards, snakes and amphisbaenians). This collection currently has 26,728 specimens of snakes, including 9 families, 66 genera and 220 species, some of which are endemic to the Amazon rainforest region. The Museu Paraense Emílio Goeldi is the second oldest institution of science in Brazil in activity, founded in 1866.

Unusual labial glands in snakes of the genus Geophis Wagler, 1830 (Serpentes: Dipsadinae).

Geophis belongs to the goo-eating dipsadine assemblage of snakes that are known to feed exclusively on earthworms, snails, and slugs. Although the unusual feeding strategies of the goo-eating dipsadines are well known (but poorly documented), little attention has been paid to their internal anatomy. Here, we describe a new and noteworthy morphological and histochemical condition of the infralabial glands in three species of Geophis (G. brachycephalus, G. nasalis and G. semidoliatus), all earthworm feeders. Their infralabial glands are constituted of two distinct parts: an anterolateral portion composed of mucous and seromucous cells that stretches from the tip of the dentary to the corner of the mouth, and a tubular posteromedial portion that is exclusively seromucous. The anterolateral portion receives fibers of the levator anguli oris muscle that attaches on its posterodorsal extremity while the posteromedial portion extends posteriorly to the corner of the mouth where it receives fibers of the adductor mandibulae externus medialis muscle. Furthermore, the posteromedial portion of the infralabial gland is constituted by large acini filled with secretion that is periodic acid-Schiff positive. These acini release their secretion directly into a large lumen located in the middle of the glandular portion. In the three species examined, the supralabial glands show a traditional configuration, being constituted of mucous and seromucous cells and retaining an enlarged part in its caudal region that resembles a Duvernoy's gland. The presence in Geophis of an expanded lumen in part of the infralabial gland that is compressed by an adjacent muscle suggests a more specialized role for the secretion produced by these glands that may not be related to envenomation but rather to prey transport and mucus control.

Oral glands in dipsadine "goo-eater" snakes: morphology and histochemistry of the infralabial glands in Atractus reticulatus, Dipsas indica, and Sibynomorphus mikanii.

Although snake infralabial glands are generally constituted of mucous cells, among dipsadines, they are much more developed and predominantly serous in nature, possibly due to the peculiar feeding habits of some species of this group, the "goo-eaters", which feed on soft and viscous invertebrates. We compared the morphology and histochemistry of the infralabial glands of three goo-eater species of Southeast Brazil, Atractus reticulatus, Dipsas indica and Sibynomorphus mikanii. In A. reticulatus the glands are formed by mixed acini composed of mucous and seromucous cells and in D. indica, they are composed of mucous tubules and seromucous acini. In S. mikanii the glands are organized in seromucous acini; mucous cells are restricted to the gland anterior region and to the duct lining epithelium. Ultrastructurally, secretory granule electron density varies from low to moderate, depending on their mucous or seromucous nature. The results indicate a large morphological and histochemical variation in the infralabial glands, probably reflecting differences in the secretion chemical composition and in feeding specialization among the three species. The protein content in the secretory cells can be related with the presence of toxins that can be used in chemical prey immobilization or detaching of snails from their shells.