Photoreceptor physiology of two species of crab spiders (Araneae: Thomisidae)

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  Photoreceptor physiology of two species of crab spiders (Araneae: Thomisidae) Abstract Spiders are a diverse order of predatory arachnids with more than 53.000 described species, most of which have eight eyes. Many webless hunting spiders, most noticeably the jumping spiders (Salticidae) have been shown to have excellent eyes with high spatial resolution and colour vision. The family of crab spiders (Thomisidae) is also hypothesized to be visual hunters, employing a “sit and wait” or ambush hunting technique; however, little is currently known about their visual capacity. Here we use extracellular electrophysiology to examine the photoreceptor physiology of two crab spiders living in two different ecological niches.  Ozyptila praticola  (C.L. Koch, 1837) hunts on the ground in dim habitats whereas  Xysticus cristatus  (Clerck, 1757) hunts in the typical bright open grasslands. We test the hypotheses that (1) each species has special-purpose eyes, (2) that male...

Morphology and Chemical Composition of the Nuchal Glands of Indonesian Snakes With a Description of a Novel Type of Glands

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Morphology and Chemical Composition of the Nuchal Glands of Indonesian Snakes With a Description of a Novel Type of Glands

ABSTRACT

Several species of natricine snakes sequester bufadienolides from toads, store them in their nuchal glands, and reutilize them for their defense. This study aimed to examine the presence and morphological features of nuchal glands of natricine snakes distributed in Indonesia, containing several lineages of this group. When the presence of the glands was confirmed, the gland fluids were analyzed to identify their chemical components. Secretions from the parotoid glands of several species of toads in Indonesia were also analyzed. Morphological examination of the glands was conducted by observing the presence or absence of structures and recording the spatial pattern of the glands. The glandular fluids of three snake species and four toad species were extracted and analyzed by liquid chromatography/mass spectrometry (LC/MS). Nuchal glands or organs similar to the glands were found on the head or neck region of preserved or freshly dead specimens of Rhabdophis subminiatus, R. flaviceps, R. rhodomelas, and Rhabdophis spp. of Sulawesi, although such a gland was not found in the other genera of natricine snakes. These Rhabdophis species have different spatial patterns of glands, and particularly Rhabdophis spp. of Sulawesi showed an unusual novel gland form in the temporal and occipital regions of the head, possibly comparable to the nuchal glands. Bufadienolides of the bufogenin and bufotoxin types were identified from all toad gland fluids. In contrast, the glandular fluids of snakes, R. subminiatus, R. flaviceps, and Rhabdophis spp. of Sulawesi store only bufogenin-type bufadienolides. Bufadienolide profiles of snakes and toads indicate that the toxin composition is highly diverse among species. The results suggest that snakes would be able to chemically convert dietary bufadienolides from toads and reutilize some bufadienolides readily. This study demonstrated that the form and location of “nuchal glands” in a snake's body are more diverse than previously recognized.

Anita, S., Inoue, T., Inoue, A., Eto, K., Hamidy, A., Mori, N., & Mori, A. (2025). Morphology and Chemical Composition of the Nuchal Glands of Indonesian Snakes With a Description of a Novel Type of Glands. Journal of Morphology, 286(8), e70071. https://doi.org/10.1002/jmor.70071