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The energy crisis of the 1970s sparked growing concern over minimizing fuel consumption in water, land, and air transportation. Researchers fascinated by sharks' effortless swimming abilities investigated shark skin denticles and uncovered functions beyond drag reduction, such as antifouling, protection, and bioluminescence. Over the past five decades, significant progress has been made in comprehending drag reduction and antifouling functions of denticle structures; however, the investigation of other functions remains limited. Recent discoveries of diverse denticle morphologies have ignited a keen interest in obtaining morphogroups that can aid other functional studies. This work integrates advances in antifouling, hydrodynamics, aerodynamics, bioluminescence, and protective functions to provide a holistic understanding of their diverse roles. Additionally, this work also dictates multi‐functional adaptations of denticles and contributes to the relatively less‐explored but essential aspects, such as protective functions and denticle morphogroups. By examining these functions together, this work aims to uncover potential synergies and interactions, facilitating the development of multifunctional materials inspired by shark skin denticles. [ABSTRACT FROM AUTHOR]

The Zebra Shark, in recent years known as Stegostoma fasciatum (Hermann, 1783), is well known for its dramatic ontogenetic change of color pattern, from striped ("zebra") juveniles to spotted ("leopard") adults. Nevertheless, many aspects of the species' biology, ecology, and morphology are still unknown or inadequately described, and its nomenclature is contentious. This study introduces a hitherto undescribed color morph of the Zebra Shark and provides an updated diagnosis and redescription of the species. Firstly, we establish that the Zebra Shark remains a single species based on genetic data from mitochondrial COI and ND4 markers. Secondly, through morphological analyses, we conclude that there are two morphs of the species, the known, zebra striped morph and a new, sandy colored morph. Both morphs were studied morphometrically to expose any ontogenetic changes, such as a decrease in the relative length of the tail with increasing total length (TL). The external coloration pattern clearly differentiates the two morphs, and both morphs can be further divided into three stages based on color pattern and size: juveniles (255–562 mm TL), transitionals (562–1395 mm TL), and adults (>1300 mm TL). The transitional sandy morph is dorsally covered by a swirly pattern of thin, dark brown bands edged with freckle-like brown spots. The adults are a uniform sandy beige, partially covered with brown freckles. A mature male of the zebra morph displayed a yet unknown feature of the claspers: a small, triangular spike extruding from the dorsal terminal of the clasper glands. Finally, we reviewed the nomenclature of the species and suggest that the original name Stegostoma tigrinumForster, 1781 should be used as the senior synonym for the species. [ABSTRACT FROM AUTHOR]

Androdioecy (co-existence of hermaphrodites and dwarf males) is a fascinating yet poorly understood phenomenon. The pedunculated barnacle Scalpellum scalpellum is an emerging model species for the system. In S. scalpellum, dwarf males and hermaphrodites are very different in adult morphology (e.g., in feeding structures and reproductive organs), but they share the same larval development with nauplii followed by cypris larvae. Recently, it was found that S. scalpellum cypris larvae display both genetic and environmental sex determination, but no detailed morphological study has yet investigated how the settled cypris larvae differ subsequent to settlement. This study investigates the morphological aspects of the onset of sex determination in the cyprids of S. scalpellum by examining their metamorphosis into either dwarf males or hermaphrodites under laboratory conditions. This study emphasizes morphological differences, such as size and shape of primordial shell plates, development of a flexible peduncle and of thoracopods. It was shown that the cypris larvae start to differ already one day after settlement on either a hydroid (leading to hermaphrodites) or an adult hermaphrodite (leading to dwarf males). Dwarf males gradually developed an ovoid body shape and two pairs of circular scutal and tergal primordia. Such cyprids developed neither a carina nor any peduncle or cirri for feeding. The study concludes that the dwarf males of S. scalpellum are not just hermaphrodites arrested early in development. This entails that dwarf males constitute their own separate developmental pathways and points to S. scalpellum dwarf males being more specialized than previously stated. Finally, the study compares differences in dwarf male morphology between S. scalpellum with two other androdioecious species with less specialized dwarf males and use this to discuss evolutionary implications for the adaptive evolution of dwarf males across the Cirripedia. [ABSTRACT FROM AUTHOR]