Wednesday, June 13, 2018

Post #22
Donald A. Windsor

The Strepsiptera is an order of parasitic insects containing about 600 species in 9 families, 3 extinct and 6 extant (1). Bizarre is a good way to describe them because they do not seem to fit in prevailing phylogenetic schemes.

Caenocholax fenyesi is a species in the order Strepsiptera, family Myrmecolacidae. Its males parasitize ants and its females parasitize crickets (2).

Three ant species host male C. fenyesi: Dolichoderus bispinosus, Red Fire Ant Solenopsis invicta, and Camponotus planatus (Order Hymenoptera, Family Formicidae). Two other possible host species were not named.

The cricket species hosting female C. fenyesi is Macroanaxipha mecilenta (Order Orthoptera, Family Gryllidae).

The first-instar larvae are not sexually dimorphic and, apparently, sex is determined by the host species. If a larva enters an ant it becomes a male; if it enters a cricket, it becomes a female. Males undergo a complete metamorphosis from larvae to flying adults. Females go from larvae to a neotenic adulthood (no wings). Males leave their host ants after pupation and live for only a few hours; they do not eat. Females spend their entire lives in their cricket hosts, only poking out their genitalia to receive sperm from the male, who copulates on the abdomen of the hosting cricket. Males find female genitalia by following pheromones exuded by the females. The resulting larvae feed on their mother until they emerge and manage to find and enter a host.

This life cycle is so fraught with disaster that it is a wonder it works. The research described by Kathirithamby in several articles is daunting and frustrating but will probably turn up even more amazing situations.

Strepsipteran parasites seem to have plenty of opportunities to acquire multiple species of hosts and more should be discovered as interest in this order increases. Meanwhile, I wonder if this separation of host species for males and females occurs anywhere else besides in the Myrmecolacidae.

References cited:

1. Strepsiptera. Wikipedia.

2. Kathirithamby, Jeyaraney ; Johnston, J. Spencer. The discovery after 94 years of the elusive female of a myrmecolacid (Strepsiptera), and the cryptic species of Caenocholax fenyesi Pierce sunsu lato. Proceedings of the Royal Society of London B (Supplement) 2004; 271: S5-S8.


Saturday, June 9, 2018


Post # 21
Donald A. Windsor

When a parasite uses another parasite as a tool, what do you call it? A “biotool”? A “biohenchman”? A “bioenforcer”? A “bioally”? I prefer “bioally”.

Consider the amazing case of a parasitic wasp laying its eggs in a lady beetle; then using a virus to convert the beetle to a robotic, zombie-like protector of the resulting wasp pupae.

The parasitic wasp is Dinocampus coccinellae. The host is the lady beetle Coleomegilla maculata. The bioally is a Dinocampus coccinellae paralysis virus DcPV. The life cycle is described by Dhailly et al (1).

Wasp lays an egg in the beetle. Egg hatches and larva develops within the beetle.
Larva emerges 3-weeks later and pupates, spins its cocoon between the beetle’s legs.
The beetle remains static and trembles, protecting the cocoon from predators.
Adult wasp emerges. Sometimes the beetle host recovers.

The guarding behavior of the host beetle is attributed to the DcPV in the beetle’s brain. This virus infects the oviduct cells of the wasp and is transmitted with the wasp egg into the host beetle.

Lacewing fly larvae (Neuroptera) are among the natural predators of this wasp’s pupae (2-3).

This complexity can be depicted as: H + Pw + Pv ====> HPwPv ====> HPv + Pw

I do not know what happens to the virus in the beetle’s brain.

This parasitic team of wasp and virus shows how a biological interaction between a host and a parasite has not just 2 participants, but 3. Four, if the causative predator driving its evolution is included.

I am now investigating how high the number of participants in a basic host-parasite interaction can go. What is the maximum level of complexity that has ever evolved?

References cited:

1. Dheilly, NM ; Maure, F ; Ravallec, M ; Galinier, R ; Doyon, J ; Duval D ; et al. Who is the puppet master? Replication of a parasitic wasp-associated virus correlates with host behaviour manipulation. Proceedings of the Royal Society of London B Biological Sciences 2015; 282: 20142773: 1-10.

2. Libersat, Frederic ; Kaiser, Maayan ; Emanuel, Stav. Mind control: how parasites manipulate cognitive functions in their insect hosts. Frontiers in Psychology 2018 May; 9: article 572: 1-6.

3. Maure, Fanny ; Brodeur, Jacques ; Droit, Anais ; Doyon, Josee ; Thomas, Frederic. Bodyguard manipulation in a multipredator context: Different processes, same effect. Behavioural Processes. 2013 October; 99: 81-86.


Wednesday, June 6, 2018


Post # 20
Donald A. Windsor

An interaction between a parasite and a host is like a chemical reaction.

Parasite + Host ==> ParasiteHost complex P + H ==> PH

A biobroker acts as a catalyst. P + H == biobroker ==> PH

This analogy helps me to understand my basic amazement at the complexities of biology. Nature seems to be a giant nexus of multiple species so tightly bound together that it resembles sticky cotton candy on a hot humid day.

Consequently, I visualize interactions between two species as involving multiple species. Species interactions are not between species, but among species. Many of these interactions have participants that operate behind the scenes.

Some of the behind the scenes mechanisms of biobrokers are especially interesting. A recent article reports that Bacteroides fragilis attaches itself to the gut epithelium of mice by adhering to the mouse’s immunoglobulin A. The bacterium then rules by excluding invasive pathogenic microbes (1). It acts as a gatekeeper, or in my view, a biobroker. The presence or absence of this bacterial species determines whether or not a pathogenic bacterial species (a parasite) can or cannot infect this mouse and use it as a host. The host species has retained Bacteroides fragilis to exclude parasites and to allow commensals.

                                       / ==> P + H Interaction prohibited; parasite excluded.
C + P + H == biobroker
                                       \ ==> CH Interaction accepted; commensal allowed.

To infect this host a parasite would have to overcome the biobroker.

P + H === biobroker ===> PH Interaction overcame biobroker.

In metazoan parasites and hosts this biobroker role could be played by competitive parasites.

References cited:

1. Donaldson, G.P. ; et al Gut microbiota utilize immunoglobulin A for mucosal colonization. Science 2018 May 18; 360(6390): 795-800.