New Paper in Science on the Lake Victoria Cichlid Extinction

Today our paper came out in Science investigating the actual causes of the Lake Victoria cichlid extinction event. Lake Victoria was home to around several hundred endemic cichlid species. However, introductions of the Nile perch (Lates niloticus) into Lake Victoria in the 1950’s caused a mass extinction of roughly 200 species of cichlids. As the Nile perch is a voracious predator that grows to six feet in length, it was long thought  high predation on the Lake Victorian cichlids (the largest of which only grow slightly over 12 inches in length)  by Nile perch best explained the extinction of so many species.

Our research group found that predation alone doesn’t explain the Lake Victorian cichlid extinction as we found that there was a non-random pattern of which cichlid species went extinct. Specifically, we found that the cichlids that were most impacted by the Nile perch were piscivorous (fish eating) species. The reason for this is that cichlids have highly modified pharyngeal jaws in their throat that function as a second set of jaws. These pharyngeal jaws are essentially a fused gill arch supported by muscles. Cichlids and other fish with this trait are known as “pharyngognathous fishes”. It has long been thought that pharyngognathy is evolutionary innovation as it allows the oral jaws to specialize in prey capture and the pharyngeal jaws in prey processing. When measuring the diameter of the oral jaws and the pharyngeal jaws we saw that the pharyngeal jaws were much smaller and imposed a limit on the prey size that could be swallowed by cichlids due to their bulkiness. Nile perch, which lack these specialized pharyngeal jaws had much larger gapes, meaning that they could swallow much larger prey.

PJAsize

Pharyngeal jaw gape of piscivorous cichlids from Lake Victoria and other geographic regions in comparison to Nile perch. Nile perch have much larger gapes than cichlids do.

 

Additionally, when we performed prey processing trials to see how long it took Lake Victorian cichlid piscivores and Nile perch to swallow fish prey, it took Victorian cichlids hours to process and swallow a fish that of comparable size would take Nile perch only several minutes! This indicates that when competing for the same prey resources, Nile perch are far superior to the native cichlids.

So what then explains the Lake Victorian extinction? While predation by Nile perch certainly played a role, our study highlights that competition for prey between Lake Victorian cichlid piscivores and Nile perch also played a critical role. So why then were so many cichlids in Lake Victoria piscivores if pharyngeal jaws limit them? There is pretty good evidence that the ancestor to all Lake Victorian cichlids was either a generalist or insectivore. Piscivory likely evolved in the lake because it was an open niche that had an abundance of prey resources. As the lake is dominated by cichlids, the main competitor to other cichlid piscivores before the Nile perch invasion was other piscivorous cichlids, so it was a leveled playing field in relation to prey processing. We show  support for this when looking at marine reef systems and evolutionary transitions to piscivory verses processing intensive prey (algae, mollusks, echinoderms) between other pharyngognathous fishes (wrasses, parrotfish, surf perches, damselfishes) and non-pharyngognathous fishes. We find that  non-pharyngognathous fish have far more transitions to piscivory than pharyngognathous fishes, indicating that pharyngognathy does restrict piscivory in marine systems as well. However, pharyngognathous fishes more commonly transition to processing intensive prey, highlighting that the pharyngeal jaws are extremely useful for processing these hard and tough to process items.

PJA_Marine

Transition into piscivory are uncommon in pharyngognathous fishes (red) relative to non-pharyngognathous fishes (blue). However, transitions to feeding on process intensive prey occur more often in pharyngognathous fishes.

Paper Citation & Link : McGee MD, Borstein SR, Neches RY, Buescher HH, Seehausen O, and Wainwright PC. 2015. A pharyngeal jaw evolutionary innovation facilitated extinction in Lake Victoria cichlids. Science 350:1077-1079. http://science.sciencemag.org/content/350/6264/1077

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Speaking at the GCCA Cichlid Classic May 23rd and 24th

I’ll be presenting two talks at the GCCA Cichlid Classic in Chicago May 23rd-24th. One will focus on broadscale evolutionary patterns in cichlids while the other will revolve around research my collaborators and I have done on the Nile perch invasion of Lake Victoria. Come check out the show and the talks, it should be a good time and I hope to see you there. More info on the convention and my talks are below:

http://www.gcca.net/docs-events/classic

Friday May 23rd 8:30 pm- Current Cichlid Research: Focus on new findings about cichlid evolution.

Saturday May 24th 1pm- The Lake Victorian Extinction Revisited.

“Cichlasoma” grammodes also known as the Sieve Cichlid for the lines and dots on its face.

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Speaking at The Atlanta Area Aquarium Association Nov. 2nd

I will be speaking on my fieldwork with Costa Rican cichlids at the Atlanta Area Aquarium Association on November 2nd at 1:30 pm at the Fernbank Science center. Come check it out and learn a bit about  the biology and keeping these cool fish. Address to for the meeting location is below:

FERNBANK SCIENCE CENTER
156 Heaton Park Drive N.E.
Atlanta, GA 30307

Tomocichla tuba male in the Rio Frio, CR

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Speaking at Sacramento Aquarium Society Saturday 7/6/13

I will be presenting to the Sacramento Aquarium society this Saturday about keeping the smaller species of Central American cichlids in the captivity. The talk will discuss the ecology, husbandry, and evolutionary relationships of these fish.

Talk will begin at 7pm at the Round Table Pizza at the below address. Feel free to stop by even if you are not a member of the club.

Round Table Pizza
9500 Greenback Lane
Folsom, CA
(916) 989-1133

Pair of Cryptoheros septemfasciatus in the Rio San Jose, CR

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Speaking 2 GCCA May 19, 2013: Keeping the Cichlids of Costa Rica

I will be speaking tomorrow at the Greater Chicago Cichlid Association meeting on the fishes of Costa Rica. The meeting begins at 6pm at the Double Tree in Downers Grove. Feel free to stop by and check out the talk. Address details below:

Doubletree Hotel Downers Grove
2111 Butterfield Rd.
Downers Grove, Illinois, 60515

Female Cryptoheros septemfasciatus from the Rio Corinto, Costa Rica

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Heros notatus- The Spotted Severum

I recently was able to get a wild group of Heros notatus, the Spotted Severum, from Guyana. I’ve never kept a Heros species before, so I was quite excited to give this South American heroine cichlid a try.

Heros notatus occurs in Brazil, French Guinea, and Guyana and has gained popularity in recent years as imports of this species have been more frequent. I could definitely see this species becoming more popular in the hobby as the fish is a beautiful olive color with orange-red fins and a bright red eye. Males also get a orange cheek and many bronze highlights along the body while females are less colorful. While both male and female have spots along the flank, leading to the name Spotted Severum, the spotting is much more pronounced on the males of this species. Males also have intense spotting and som squamation on the cheek which is much less and sometimes entirely absent on females.

A large male Heros notatus photographed at ACA 2012. One can see the nice spotting and bronze and orange highlights of this attractive species.

I’ve not found Heros notatus to be a difficult fish to keep. They are a little shy and take some time to acclimate to new conditions, but once they come around are quite a robust and easy to keep species. They are not fussy when it comes to water chemistry or diet and are easily weened onto prepared foods. Overall, it is a very peaceful and mild fish, with occasional squabbles occurring, but nothing that occurs in injury. I am able to maintain a breeding group of five in a 55 gallon. This species does need clean water, so 50% water changes a week is recommended.

The Heros notatus I got were decent size, around 3.5-4″. Overall this species can grow to 7-8″. I was quite surprised when they spawned as I didn’t quite think they were at maturity yet, but I was wrong. I was also surprised that they spawned in regular tap water! I was certain that I would have to lover the hardness to get them to spawn, but fortunately I didn’t have to play with the water chemistry.

Pair of Heros notatus (male in background) guarding fry.

While I decorated the tank with driftwood and plants (I know, I actually had a planted tank  for once!) the Heros notatus where quite happy spawning on the flower pot. While these are young fish, they still had a fairly large spawn of over 100 eggs. I’ve found that Heros notatus are fairly reliable parents and even though this was the first spawn for these individuals they successfully raised their offspring to the free swimming stage and guarded them diligently against the other three Spotted Severum in the tank.

While the fry are tiny, they are capable of consuming baby brine shrimp on their first day free swimming and grow fairly quickly. At first, I was amazed of was how quickly this species spawns, but as my young fish have grown a bit, it became evident that it really wasn’t that quickly, I just had one male and he was switching females every two weeks! Talk about a lucky guy.

My male Heros notatus is living the dream as he is the lone male of my group of 5.

Overall, I would recommend you try Heros notatus if you see it for sale. If you’ve kept and enjoyed a Heros species before, this may be one you haven’t had a chance to keep yet and should give a try. I’m fairly sure this fish will see a rise in popularity in the near future as it is easy to keep and breed and is a nice mild mannered species that would mix well in a South American community tank.

Heros notatus female guarding fry.

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Presentation at WCBSURC in San Diego April 20th

I will be speaking at the West Coast Biological Sciences Undergraduate Research Conference (WCBSURC for short, even though this is the longest acronym ever!) April 20th at Point Loma Nazerene University in San Diego. I will be discussing my research on the rates of evolution in Tanganyikan cichlids. My presentation is at 2:45 in the BAC102 room. As always your presence and heckling are welcomed!

Male Callochromis melanostigma, a Tanganyikan cichlid

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