Zoological Letters最新文献

The needle nematode genus Paralongidorus Siddiqi, Hooper & Khan, 1963 currently comprises 76 species of polyphagous plant ectoparasites with global distribution. Here, we revise the taxonomic ambiguities within the genus and update the polytomous key to facilitate species identification. Integrating ribosomal (D2-D3 expansion segments of 28S, ITS, partial 18S) and mitochondrial (partial COI mtDNA) markers, we reassess phylogenetic relationships within Paralongidorus and Longidorus. Our analyses reveal that Paralongidorus is paraphyletic, consistently resolving into two distinct subclades. We describe Paralongidorus cantabronavarrus sp. nov. from northern Spain, a species characterized by both molecular placement and morphological traits, including a uniquely anterior vulval position (V = 26-29%), the most extreme reported within the genus. This feature may represent a derived developmental adaptation, with potential ecological significance. Amphidial fovea morphology also shows evidence of convergent evolution, complicating generic boundaries. These findings challenge the validity of Longidoroides, reinforce the separation between Paralongidorus and Longidorus, and highlight the value of integrative approaches in resolving long-standing taxonomic uncertainties. The phylogenetic placement of P. cantabronavarrus sp. nov. is consistent across markers and aligns with previous studies. Overall, this work expands our understanding of Paralongidorus biodiversity in the Iberian Peninsula and underscores the need for further intensive nematological surveys in this area.

The needle nematode genus Longidorus comprises approximately 194 species of polyphagous plant ectoparasites distributed worldwide, some of which serve as vectors for plant viruses. However, the high species diversity and conserved morphology of these nematodes pose significant challenges for accurate identification of species. To address this issue, we conducted an integrative taxonomic study across 264 sites in major olive-growing regions (Greece, Morocco, Italy, Portugal, and Spain) of the Mediterranean Basin, including nearby patches of natural vegetation. Herein, we describe two new species, Longidorus olearum sp. nov. and Longidorus morocciensis sp. nov., and report Longidorus oakgracilis in Portugal for the first time. We performed a comprehensive study that integrates morphological and morphometric traits with molecular data from nuclear ribosomal RNA (rRNA) genes (D2-D3 expansion segments of 28 S, ITS1, and partial 18 S) and a mitochondrial DNA (mtDNA) marker, specifically the Cytochrome c oxidase subunit I (COI). The results of our phylogenetic analyses provided robust support for the delimitation of the newly described species, L. olearum sp. nov. and L. morocciensis sp. nov., and further clarified of three previously recognized species within the genus: L. magnus, L. oakgracilis, and L. vineacola. Phylogenetic relationships inferred from ribosomal and mitochondrial markers revealed that the majority of Longidorus species from the Mediterranean Basin clustered within subclades of Clade I. The phylogenetic placement of these species demonstrated strong congruence across lineages, corroborating previous studies on the genus. These findings contribute to a broader understanding of Longidorus biodiversity in the Mediterranean region and highlight the need for further intensive and wide-ranging nematological surveys.

Background: The transparent jellyfish body is often difficult to see underwater, as its refractive index is similar to that of seawater, resulting in a low light reflectance on the body surface. Nevertheless, the outlines of jellyfish can be recognized by the slight reflection of light from their body surfaces. In some jellyfish species, the epidermis covering the body surface has an array of microvilli, nanostructures that can potentially reduce light reflection. However, the anti-reflective effect is minimal in water, as the difference in the refractive indices of tissue and seawater is so small that reflectance is low, even on flat surfaces. In jellyfish that have pneumatophores, structures used in floating and drifting on the sea surface, light reflection on the surface is expected to be large and noticeable owing to the large differences in refractive indices between the pneumatophore exposed above the water surface and air. In the current study, we examined the epidermal ultrastructure and refractive index of the pneumatophores of a Portuguese man o' war (Physalia physalis) and a by-the-wind sailor (Velella velella).

Results: The refractive index of P. physalis pneumatophores measured with an Abbe refractometer was approximately 1.344. Microvillar arrays were found in epidermal cells of both P. physalis and V. velella. Based on the length, thickness, and pitch of the microvilli, we constructed simplified structural models for the simulation of light reflection using rigorous coupled wave analysis (RCWA). Our simulations showed that reflectance on the microvillar models could be greater or less than that on the flat surface, depending on light conditions (wavelength and angle of incidence), but with an overall effect of reduced reflection. Reflection reduction in microvillar models was particularly significant at large incident angles, where reflectance was extremely high on the flat surface.

Conclusions: Microvillar arrays found on the epidermis potentially reduce surface reflections of the pneumatophore and contribute to the reduction in visibility of the pleustonic hydrozoans above the sea surface. Moreover, less reflection at the pneumatophore surface indicates greater transmission of light through transparent bodies, potentially providing a counter-illumination effect that obscures the shadow of the hydrozoan bodies, depending on the intensity of ambient light.

Rhizocephalans (Thecostraca: Cirripedia) are parasitic crustaceans that infect a wide range of decapod hosts, including hermit crabs, crabs, and shrimps. These parasites exert profound effects on their hosts, inducing parasitic castration, suppressing the development of secondary sexual characteristics, feminizing male crabs, and altering male behavior to resemble that of females. In the present study, we examined the secondary sexual characteristics of two hermit crab species- Pagurus lanuginosus from Asari (Hokkaido, Japan) on the Sea of Japan coast and Pagurus filholi from Chikura (Chiba, Japan) on the Pacific coast-parasitized by Peltogasterella gracilis and Peltogaster sp., respectively. Specifically, we assessed the presence of secondary pleopods and the length of the right large cheliped. Our findings demonstrate that male P. lanuginosus and P. filholi parasitized by P. gracilis and Peltogaster sp. exhibit morphological changes and characteristics of females, confirming morphological feminization. The magnitude of parasitic effects on morphological feminization varies between the two host species depending on the rhizocephalan genus. Thus, the extent of feminization varies depending on the parasite genus. Notably, different parasite genera induced varying degrees of host modification, even within the same host species. Similarly, the level of feminization caused by a single parasite genus differed between host species. These results highlight the importance of understanding the characteristics of both the hermit crab host and rhizocephalan parasite in developing insights into parasitically induced morphological feminization.