A Possible Relationship Between Chitinozoa And Tintinnids

The biological affinity of the extinct microfossil order chitinozoa has been the source of much discussion in the fifty years since they were first discovered. Within this period these flask-shaped, organic-walled organisms have been variously attributed to rhizopods, flagellates, tintinnids, chrysomonads, metazoan eggs, dinoflagellates, and fungi. Most of these suggested relationships were made before it was recognised that chitinozoans were encapsulated and must therefore be resting cysts or eggs and not active individuals. There are no living organisms which combine all the characteristics of the chitinozoa. Of all the possibilities, a grouping of flask-shaped cysts which have been found in present-day marine plankton and sediment comes closest to characterising the morphology of chitinozoa. This grouping of flask-shaped cysts includes forms which have been found within tintinnid loricae. Another modern cyst type Pacillina arctica, which is believed to be a ciliate cyst, comes close to replicating the morphology of the chitinozoan genus Hoegisphaera. This paper discusses the structure of tintinnid, other flask-shaped cysts and Pacillina arctica in relation to chitinozoan morphology, drawing attention to similarities and differences. The occurrence and distribution of these cyst forms in present-day plankton is also described and interpreted.

Defining seasonal marine microbial community dynamics

Here we describe, the longest microbial time-series analyzed to date using high-resolution 16S rRNA tag pyrosequencing of samples taken monthly over 6 years at a temperate marine coastal site off Plymouth, UK. Data treatment effected the estimation of community richness over a 6-year period, whereby 8794 operational taxonomic units (OTUs) were identified using single-linkage preclustering and 21 130 OTUs were identified by denoising the data. The Alphaproteobacteria were the most abundant Class, and the most frequently recorded OTUs were members of the Rickettsiales (SAR 11) and Rhodobacteriales. This near-surface ocean bacterial community showed strong repeatable seasonal patterns, which were defined by winter peaks in diversity across all years. Environmental variables explained far more variation in seasonally predictable bacteria than did data on protists or metazoan biomass. Change in day length alone explains >65% of the variance in community diversity. The results suggested that seasonal changes in environmental variables are more important than trophic interactions. Interestingly, microbial association network analysis showed that correlations in abundance were stronger within bacterial taxa rather than between bacteria and eukaryotes, or between bacteria and environmental variables.

Meiobenthos and macrobenthos are discrete entities and not artefacts of sampling a size continuum: Comment on Bett (2013)

Species size distributions for metazoan benthic invertebrates conform to the highly conservative bimodal pattern, regardless of the sieve mesh sizes or numbers of sieves used in their extraction. This pattern is not an artefact of sampling a size continuum as suggested by computer simulations using just 2 fixed mesh sizes in Bett (2013; Mar Ecol Prog Ser 487:1-6). Meiobenthos and macrobenthos are coherent entities, each with a distinct suite of functional attributes, and should not be regarded as a single unit for ecological modelling purposes.