The digestive tract sections of the sea cucumber Isostichopus badionotus reveal differences in composition, diversity, and functionality of the gut microbiota

For the first time, this study analyses the composition and diversity of the gut microbiota of Isostichopus badionotus in captivity, using high-throughput 16S rRNA sequencing, and predicts the metagenomic functions of the microbiota. The results revealed a different composition of the gut microbiota for the foregut (FG) and midgut (MG) compared to the hindgut (HG), with a predominance of Proteobacteria, followed by Actinobacteria, Bacteroidetes, and Firmicutes. The FG and MG demonstrated a greater bacterial diversity compared to the HG. In addition, a complex network of interactions was observed at the genus level and identified some strains with probiotic and bioremediation potentials, such as Acinetobacter, Ruegeria, Streptococcus, Lactobacillus, Pseudomonas, Enterobacter, Aeromonas, Rhodopseudomonas, Agarivorans, Bacillus, Enterococcus, Micrococcus, Bifidobacterium, and Shewanella. Predicting metabolic pathways revealed that the bacterial composition in each section of the intestine participates in different physiological processes such as metabolism, genetic and environmental information processing, organismal systems, and cellular processes. Understanding and manipulating microbe--host-environment interactions and their associated functional capacity could substantially contribute to achieving more sustainable aquaculture systems for I. badionotus.

Seasonal shifts of arbuscular mycorrhizal fungi in Cocos nucifera roots in Yucatan, Mexico

The diversity and community structure of arbuscular mycorrhizal fungi (AMF) associated with coconut (Cocos nucifera) roots was evaluated by next generation sequencing (NGS) using partial sequences of the 18S rDNA gene and by spore isolation and morphological identification from rhizosphere soil. Root samples from six different Green Dwarf coconut plantations and from one organic plantation surrounded by tropical dry forest along the coastal sand dunes in Yucatan, Mexico, were collected during the rainy and dry seasons. In total, 14 root samples were sequenced with the Illumina MiSeq platform. Additionally, soil samples from the dry season were collected to identify AMF glomerospores. Based on a 95-97% similarity, a total of 36 virtual taxa (VT) belonging to nine genera were identified including one new genus-like clade. Glomus was the most abundant genus, both in number of VT and sequences. The comparison of dry and rainy season samples revealed differences in the richness and composition of AMF communities colonizing coconut roots. Our study shows that the main AMF genera associated with coconut tree roots in all samples were Glomus, Sclerocystis, Rhizophagus, Redeckera, and Diversispora. Based on glomerospore morphology, 22 morphospecies were recorded among which 14 were identified to species. Sclerocystis sinuosa, Sclerocystis rubiformis, Glomus microaggregatum, and Acaulospora scrobiculata were dominant in field rhizosphere samples. This is the first assessment of the composition of AMF communities colonizing coconut roots in rainy and dry seasons. It is of importance for selection of AMF species to investigate for their potential application in sustainable agriculture of coconut.

Diversidad de macro-artrópodos en sistemas silvopastoriles del sur de Quintana Roo

Introducción: La diversidad de macro-artrópodos está relacionada con el estado de conservación del suelo, por lo tanto, el cambio de uso del suelo afecta su integridad. Una estrategia para la conservación de estos organismos es la implementación de sistemas de producción diversificados como los sistemas silvopastoriles; no obstante, en el sureste de México la información aún es limitada. Objetivo: El propósito del presente estudio fue evaluar y comparar la riqueza y la abundancia de macro-artrópodos en cuatro agro-ecosistemas contrastantes: dos sistemas silvopastoriles conformados por Leucaena leucocephalay pastos asociados (i.e. Panicum maximumcv mombaza y Cynodon plectostachyus), un pastizal convencional de Brachiaria brizanthacon árboles dispersos y una selva mediana subperennifolia. Métodos: Se utilizaron trampas pit-fall de un litro de capacidad y un diámetro de 14.4 cm. Los muestreos se realizaron en dos periodos: uno en el mes de febrero y otro en el mes de mayo del 2018, en cada mes se hicieron cinco colectas espaciadas, lo que hizo un total de 100 muestras. Resultados: Se recolectaron un total de 1 737 organismos pertenecientes a 14 especies de 11 órdenes. Los sistemas con mayor abundancia de macro-artrópodos fueron, el sistema de selva media subperennifolia (923 individuos) y el sistema silvopastoril de L. leucocephalacon C. plectostachyus(354 individuos). Los órdenes más abundantes fueron: Hymenoptera, Coleoptera, Aracnidos y Orthoptera.La mayor diversidad de macro-artrópodos se presentó en los sistemas silvopastoriles de L. leucocephalacon P. maximum(H’=1.586) y L. leucocephalacon C. plectostachyus(H´=1.441). Conclusiones: Los resultados encontrados muestran que los sistemas pecuarios manejados con componentes leñosos (árboles/arbustos) pueden equipararse, en términos de abundancia y diversidad de órdenes de macro-artrópodos, con sistemas como las selvas o bosques, lo cual contribuye a la integridad y funcionalidad de los agro-ecosistemas.

Behavioral Responses and Pupa Development Patterns After Hypoxia or Anoxia in a Desiccation-Resistant Anastrepha ludens Strain

The aim of this study was to experimentally test for adult cross-resistance to hypoxia or anoxia in a desiccation-resistant population of Anastrepha ludens Loew. We compared desiccation resistant flies with unselected (control) flies by measuring the effect of pre-emergence hypoxia on some fitness parameters (emergence, flight ability, copulation success, latency to copulation, copulation duration, ovary size). Anoxia effects were determined using eye color changes during pupa development and fly emergence after re-oxygenation. Both strains were negatively affected in all measured parameters when exposed to hypoxia for more than 48 h. However, after hypoxia, control flies showed, in general, shorter latency to mate and longer copula duration than desiccation-resistant flies. Anoxia-induced arrest of pupa development, whereas returning to normoxia conditions induced resumption of development. Anoxia period length (longer than 72 h) increased mortality to 100% in the control line, whereas the desiccation-resistant line survived even at 120 h of anoxia. Thus, pre-release hypoxia must not exceed 24 h in order to maintain insect quality independently of fly type.

The male ejaculate as inhibitor of female remating in two tephritid flies

The inhibition of female receptivity after copulation is usually related to the quality of the first mating. Males are able to modulate female receptivity through various mechanisms. Among these is the transfer of the ejaculate composed mainly by sperm and accessory gland proteins (AGPs). Here we used the South American fruit fly Anastrepha fraterculus (where AGP injections inhibit female receptivity) and the Mexican fruit fly Anastrepha ludens (where injection of AGPs failed to inhibit receptivity) as study organisms to test which mechanisms are used by males to prevent remating. In both species, neither the act of copulation without ejaculate transfer nor sperm stored inhibited female receptivity. Moreover, using multiply mated sterile and wild males in Mex flies we showed that the number of sperm stored by females varied according to male fertility status and number of previous matings, while female remating did not. We suggest female receptivity in both flies is inhibited by the mechanical and/or physiological effect of the full ejaculate. This finding brings us closer to understanding the mechanisms through which female receptivity can be modulated.

Colonización y estructura de la comunidad de hongos micorrízicos arbusculares en Alsophila firma (Cyatheaceae) en bosque mesófilo de montaña en Veracruz, México

<p><em>Alsophila firma</em> is a tree fern that is distributed mainly in tropical montane cloud forest (TMCF) and is considered as a threatened species. Arbuscular mycorrrhizal fungi (AMF) have been proposed as an alternative in rescue programs of endangered species. However, our knowledge about diversity of AMF and mycorrhizal status of the species of TMCF is limited. In Mexico TMCF shows different degrees of conservation because of fragmentation and land use change. In this study, we evaluated the level of colonization, richness and abundances of spores of AMF in three fragments with different conservation status: conserved (100 years), secondary vegetation (17 years) and disturbed. For this, soil samples and roots were collected from five individuals of <em>A. firma</em> per site, with at least 100m away from each other; a total of 100cm of roots were analysed per site. Root samples showed AMF and occasionally dark septate fungi (DSF) colonizations. For the overall study, 19 species of AMF were recorded: <em>Gigaspora</em> (7), <em>Acaulospora</em> (4), <em>Glomus</em> (4), <em>Funneliformis</em> (2),<em> Sclerocystis</em> (1) and <em>Scutellospora</em> (1). The dominant species in the three sites were<em> Funneliformis geosporum </em>and<em> Acaulospora scrobiculata. </em>The highest diversity (H’) and evenness (J’) (p&lt;0.05) were found in the conserved site (H’=1.7, J’=0.66), when compared to the secondary vegetation (H’=1.5, J’=0.61), and the disturbed site (H’=0.74, J’=0.41). Statistical analysis showed that the AMF degree of colonization was significantly higher (p&lt;0.05) in the conserved site; although, the disturbed site showed low richness and abundances of AMF, the degree of root colonization did not differ statistically (p&lt;0.05) with the secondary vegetation site. Chao2 (Richness estimation model) showed that the number of analysed samples were sufficient to represent the structure of the AMF communities with values &gt;90%. The present study confirmed that <em>A. firma</em> is a mycorrhizal species that exhibits high levels of colonization even in disturbed sites. We suggest that <em>F. geosporum</em> and <em>A. scrobiculata</em> may have the potential to inoculate the gametophyte and young sporophyte of <em>A. firma, </em>to support restoration programs, because of their abundances and high tolerance to disturbed sites.</p>