A Homerian Silurian Arthropod had a Unique Brood Caring Mode

Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care

Authors:

Briggs et al

Abstract:

The ∼430-My-old Herefordshire, United Kingdom, Lagerstätte has yielded a diversity of remarkably preserved invertebrates, many of which provide fundamental insights into the evolutionary history and ecology of particular taxa. Here we report a new arthropod with 10 tiny arthropods tethered to its tergites by long individual threads. The head of the host, which is covered by a shield that projects anteriorly, bears a long stout uniramous antenna and a chelate limb followed by two biramous appendages. The trunk comprises 11 segments, all bearing limbs and covered by tergites with long slender lateral spines. A short telson bears long parallel cerci. Our phylogenetic analysis resolves the new arthropod as a stem-group mandibulate. The evidence suggests that the tethered individuals are juveniles and the association represents a complex brooding behavior. Alternative possibilities—that the tethered individuals represent a different epizoic or parasitic arthropod—appear less likely.

Luprisca incuba: Oldest Fossil Evidence of Paternal Care From Katian Ordovician

A portrait of prehistoric parenthood captured deep in the fossil record has been uncovered by an international team of scientists led by University of Leicester geologist Professor David Siveter.

The 'nursery in the sea' has revealed a species new to science – with specimens preserved incubating their eggs together with probable hatched individuals. As a result, the team has named the new species Luprisca incuba after Lucina, goddess of childbirth, and alluding to the fact that the fossils are ancient and in each case the mother was literally sitting on her eggs.

The find, published in the journal Current Biology, provides conclusive evidence of a reproductive and brood-care strategy conserved for at least 450 million years. It also represents the oldest confirmed occurrence of ostracods in the fossil record.

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Autism Risk Linked to Mother's Age

Advanced maternal age is linked to a significantly elevated risk of having a child with autism, regardless of the father's age, according to an exhaustive study of all births in California during the 1990s by UC Davis Health System researchers. Advanced paternal age is associated with elevated autism risk only when the father is older and the mother is under 30, the study found.

Published online today in the February issue of the journal Autism Research, the study, "Independent and Dependent Contributions of Advanced Maternal and Paternal Ages to Autism Risk," is one of the largest population-based studies to quantify how each parent's age — separately and together — affects the risk of having a child with autism.

The study found that the incremental risk of having a child with autism increased by 18 percent — nearly one fifth — for every five-year increase in the mother's age. A 40-year-old woman's risk of having a child later diagnosed with autism was 50 percent greater than that of a woman between 25 and 29 years old.

Advanced parental age is a known risk factor for having a child with autism. However, previous research has shown contradictory results regarding whether it is the mother, the father or both who contribute most to the increased risk of autism. For example, one study reported that fathers over 40 were six times more likely than fathers under 30 to have a child with autism.

"This study challenges a current theory in autism epidemiology that identifies the father's age as a key factor in increasing the risk of having a child with autism," said Janie Shelton, the study's lead author and a doctoral student in the UC Davis Department of Public Health Sciences. "It shows that while maternal age consistently increases the risk of autism, the father's age only contributes an increased risk when the father is older and the mother is under 30 years old. Among mothers over 30, increases in the father's age do not appear to further increase the risk of autism."

Autism is a pervasive developmental disorder of deficits in social skills and communication, as well as repetitive and restricted behaviors, with onset occurring prior to age 3. Abnormal brain development, probably beginning in the womb, is known to be fundamental to the behaviors that characterize autism. Current estimates place the incidence of autism at between 1 in 100 and 1 in 110 children in the United States.

During the 1990s, the number of California women over 40 giving birth increased by more than 300 percent. But only about 5 percent of the 600-percent increase in the number of autism cases in the state can be attributed to women waiting longer to have children, the study suggests.

To conduct their investigation, the researchers obtained the electronic records for all births in California between Jan. 1, 1990 and Dec. 31, 1999. The records incorporated detailed demographic information, including the ages of both parents. To identify which children would develop autism, the researchers obtained electronic records identifying children born during the study period who later received an autism diagnosis from state Department of Developmental Services. In this study autism was defined as a diagnosis of full-syndrome autism at a California Regional Center.

The researchers also excluded a small number of births where demographic information about parents, such as their ages and levels of education, was not available. Instances of multiple births were analyzed separately. The exclusions brought the total size of the study sample to approximately 4.9 million births and 12,159 cases of autism.

For older mothers, the step-wise progression in the risk of having a child who later would be diagnosed with autism was apparent among every age group of fathers. When the father was older and the mother was younger — under 30 — the child's risk for developing autism also was elevated. For example, among births to mothers under 25, children fathered by a man over 40 were twice as likely to develop autism as those whose father was between 25 and 29. Among mothers over 30, the increased risk associated with older fathers dissipated, the study found.

Because of the large study size, the researchers were able to show how risk for autism was affected by each parent's age by holding one parent's age constant and then comparing autism incidence across the age of the other parent across five-year increments. The subtle interaction of how each parent's age affects the risk of autism then became quantifiable even when it was reliant on the other parent's age. This methodology is more efficacious and requires fewer assumptions than the mathematical modeling used by earlier studies, the researchers said.

The researchers note that understanding the relationship between increased parental age and autism risk is critical to understanding its biological causes. Earlier studies have observed that advanced maternal age is a risk factor for a variety of other birth-related conditions, including infertility, early fetal loss, low birth-weight, chromosomal aberrations and congenital anomalies.

I have to admit that when I first started reading about autism and getting a bit scared with the potential that one of my kids could end up with it, I came to the conclusion - or perhaps jumped to it! - that paternal age was linked to the problem. We already knew about the problems of having kids at age 35 for women (increased risk of Down's Syndrome, frex). The thought immediately crossed my mind that the primary difference between times prior and now was the increased age - fertility postponement - of parenthood. No proof then. This certainly adds credence to my hunch, that's for sure!

Post 2401: Parenting Question

I have an oddball question for the parents out there that read the blog. How many of you have ambidextrous kids? Avrora appears to be exactly that. I have concerns about screwing it up. Why? Because I was ambi when I was her age and up through kindergarten...and then the teachers made a concerted effort to get me to use only my right hand. Now, after years of using it that way, I'm pretty much right handed, but can still use the left better than average. Slightly.

So, advice? Anyone?