The Mariana Islands consist of two volcanic island arc chains, one volcanically inactive frontal arc in the Southern Marianas and a younger, volcanically active arc in the Northern Marianas. Given their extreme remoteness, the hermit crab fauna of the uninhabited northern islands are little-known. In this study we collected and examined hermit crabs from two scientific cruises to the Northern and Southern Marianas conducted in 2003 and 2015. We report 39 species from these field efforts, including 5 new records and 6 undescribed species. The updated checklist of the hermit crabs of the Marianas now includes 79 species.

Using scanning electron microscopy, egg morphology was determined for five sea urchin species collected from Saipan, Commonwealth of the Northern Mariana Islands in June 2014: Echinometra mathaei, Parasalenia poehlii, Eucidaris metularia, Colobocentrotus mertensii, and Mespilia globulus. Gross morphological observations of these species’ eggs generally coincided with previous descriptions. However, due to preservation methods, size discrepancies were present. Eggs collected in 2014 after fixation measured at a smaller diameter than reported in previous studies except for M. globulus, which measured between the two previously reported mean diameters. In order to compare measurements with those in previously published studies, additional samples were collected in June 2017 for measurement of fresh unpreserved eggs. Samples of three of these original five species were successfully collected – and all showed shrinkage after fixation and SEM prep. Fresh egg diameter measurements collected in 2017 were comparable to those reported in previous studies, except M. globulus which at 149.02 μm was much larger than the previously reported mean diameters of 80 μm and 110.8 μm. Variation in egg microvilli density, size, and shape was observed between all species as viewed using scanning electron microscopy. The present study provides an analysis of the egg surface morphology utilizing scanning electron microscopy of five species of sea urchin collected in Micronesia, three species of which egg surface morphology was previously undescribed. Findings of this study also describe a previously unreported mean diameter of M. globulus which could support a latitudinal gradient in egg size of this species.

Serianthes nelsonii Merr. is an endemic leguminous tree found in limestone forests of Guam and Rota in the Mariana Islands. It is an endangered species. Plant recovery efforts have focused on plant surveys, phenological studies, seed propagation, and field out- plantings. This study was conducted to understand the genetic structure of S. nelsonii populations on Guam and Rota for the conservation program utilizing genetically unique germlines of the species. Samples were obtained from wild Rota trees, outplanted Rota trees, the lone Guam S. nelsonii mother tree and its seedlings. A genome-wide multiplexed inter-simple sequence repeat (ISSR) genotyping by sequencing (MIG-seq) analysis was used for single-nucleotide polymorphisms (SNPs) detection. The STRUCTURE analysis showed a clear genetic differentiation between plants from the two islands, between Rota wild trees and Rota out-planted tree populations, and among individuals from Rota out-planted trees. Lower genetic diversity in the Guam seedlings population was observed, which might have been due to the selfing of the Guam mother tree. This study provides the first genetic information on S. nelsonii in Guam and Rota. In-situ protection and ex-situ establishment of S. nelsonii populations should consider genetic data in developing a conservative management plan.

Quantification of bird morphology is valuable for evaluating population structure and for investigating environmental drivers of such major energy expenditures as breeding and molt. I made morphological measurements primarily on two lesser known species on the Mariana Island of Saipan, the Bridled White-eye (Zosterops conspicillatus) and Saipan Reed-warbler (Acrocephalus hiwae), although I measured incidentally captured Rufous Fantails (Rhipidura rufifrons), Micronesian Myzomelas (Myzomela rubrata) and Golden White-eyes (Cleptornis marchei). As is typical for passerines, males of all five species averaged larger than females particularly in wing chord, although for the Bridled White-eye differences were small and somewhat conflicting. Discriminant function analysis demonstrated that Bridled White-eye and Saipan Reed-warbler sexes differed significantly, with sexes of these species and those of the Micronesian Myzomela best separated by measurements of wing chord. Both the Bridled White-eye and Saipan Reed-warbler showed evidence of molting particularly toward the end of the wet season and having breeding peaks during the dry season, thereby seasonally segregating these energetically expensive activities. Further study of seasonal resource availability may clarify the mechanisms involved in driving the choice of season for molt and peak breeding.