Shumway Lab Research

Shumway Lab – Research Evolution of Brain and Behavior in African Cichlid Fishes
BRAIN STRUCTURE
How does Habitat Complexity and Social Behavior affect the Brain? Which factors led to the increased size of our own forebrain during evolution? A debate has raged in the primate literature about whether social or environmental forces were more influential in brain expansion, particularly neocortical expansion. The answer is difficult to resolve in primates because there are limited numbers of species for comparison and because the species have differing degrees of relatedness. We can answer this question in African cichlid fishes because of the tremendous diversity of species, diversity of behaviors, and because we can compare species that are closely related, within a monophyletic group, or clade. We compare the gross and internal morphology of brains from closely related species that differ in either habitat or mating behavior. We also look at the presence/abundance of specific neurotransmitters that are associtated with social behaviors.		Lateral view of a cichlid brain Brain sectioned through telencephalon

Two brains of similar species: Note the differences Measurements of Brain Features Habitat comparison of Telencephalon Size Social Comparison	How does Habitat Complexity and Social Behavior affect the Brain? Part 1: Gross Brain Morphology We compared the gross brain morphology of closely related species of Tanganyikan Cichlids living in diverse habitats. We investigated whether there were any differences in brain structure between species that lived in different habitats, or had different social organizations or strategies. Research was done in collaboration with the Hofmann Laboratory at Harvard University After accounting for phylogenetic confounds with independent contrasts, we find that environmental and social factors differentially affect the brain, with environmental factors showing a broader effect on a range of brain structures compared to social factors. Brain size and cerebellum are positively correlated with species number (which is correlated with habitat complexity) The medulla and olfactory bulb are negatively correlated with habitat measures. The telencephalon shows a trend toward a positive correlation with rock size. Only two brain structures, the telencephalon and hypothalamus, are correlated to social factors. Telencephalic size is larger in monogamous species compared to polygamous species, as well as with increased numbers of individuals Social organization is also negatively correlated with hypothalamic size Publication: Pollen, A.A., A.P. Dobberfuhl, J.G. Scace, M.M. Igulu, S.C.P. Renn, , C.A. Shumway, and H.A. Hofmann. (2006, in press). Environmental complexity and social organization sculpt the brain in Lake Tanganyikan cichlid fish. Brain Beh. Evol.

How does Habitat Complexity and Social Behavior affect the Brain? Part 2: Internal Structure Dl We sectioned the brains of the rock dwelling monogamous A. leptura and the sand dwelling X. flavipinnis at 50u and stained them with cresyl violet. Cresyl violet stains the ribosomal matter in the cells purple and allows us to discern the regions of the brain. We measured an area of the telencephalon called the lateral division of the area dorsalis or simply Dl (area highlighted in red on the brains to the right). Dl is believed to be the homologue to the mammalian hippocampus, which is implicated in spatial memory. We calculated the ratio of Dl volume to the volume of the telencephalon and we found that Dl is significantly larger in the rock dwelling fish. We are currently working on another pair of sister species within the Ectodini clade where one species, X. papilio, lives in rock habitats and the other, X. boulengeri, lives in sand. In addition we will compare sister species of marine gobies. Dm We sectioned the brains of the monogamous X. flavipinnis and polygamous X. ochrogenys at 25μ. We measured the area called the medial division of the area dorsalis or simply Dm (see figures). Dm is believed to be the homologue to the amygdala, which is implicated in social recognition. We calculated the ratio of Dm volume to the telencephalon volume and found that the Dm was significantly larger in the monogamous fish than in the polygamous fish. We will compare Dm in another monogamous and polygamous pair in the future.	A. leptura Brain X. flavipinnis Brain The area Dl is outlined in red and divided into 3 subdivisions (Dld1, Dld2 and Dlv) Error Bars +/- SE X. flavipinnis X. ochrogenys The area Dm is outlined in red Error Bars +/- SE

Preoptic area with AVT-immunoreactive cells visualized with DAB (brown cells)	How does Social Behavior affect the Brain AVT Recently, it has been demonstrated that the neurotransmitter arginine-vasopressin (AVP) plays a critical role in social and pair-bonding behavior in voles (Young et al., 2001; Lim et al., 2004). The phylogeny of these voles is not well resolved and the monogamous and polygamous species live in different habitats. Because cichlids from Lake Tanganyika exhibit a diverse array of social behaviors, we are able to study how arginine-vasotocin (AVT) mediates social behaviors within a single habitat and known phylogeny. AVT is a homologue to the mammalian neurotransmitter AVP. Using immunohistochemistry, we compared the pre-optic areas (POA) of the sand-dwelling monogamous X. flavipinnis and the sand-dwelling polygamous X. ochrogenys. We found that the monogamous X. flavipinnis had twice as many AVT-ir cells in the POA as the polygamous X. ochrogenys, after normalizing for brain volume. Dobberfuhl AP, Scace JG, Shumway CA (2005). Monogamy and pair-bonding is correlated to an increase in vasotocin-immunoreactive cells in cichlid fishes. Soc Neurosci Abstr 205.3. Washington.

More Research at New England Aquarium!

HOME CONSERVATION CONTACTS

Evolution of Brain and Behavior in African Cichlid Fishes

BRAIN STRUCTURE

How does Habitat Complexity and Social Behavior affect the Brain?

Which factors led to the increased size of our own forebrain during evolution? A debate has raged in the primate literature about whether social or environmental forces were more influential in brain expansion, particularly neocortical expansion. The answer is difficult to resolve in primates because there are limited numbers of species for comparison and because the species have differing degrees of relatedness. We can answer this question in African cichlid fishes because of the tremendous diversity of species, diversity of behaviors, and because we can compare species that are closely related, within a monophyletic group, or clade.

We compare the gross and internal morphology of brains from closely related species that differ in either habitat or mating behavior. We also look at the presence/abundance of specific neurotransmitters that are associtated with social behaviors.

Lateral view of a cichlid brain

Brain sectioned through telencephalon

Two brains of similar species: Note the differences

Measurements of Brain Features

Habitat comparison of Telencephalon Size

Social Comparison

How does Habitat Complexity and Social Behavior affect the Brain?
Part 1: Gross Brain Morphology

We compared the gross brain morphology of closely related species of Tanganyikan Cichlids living in diverse habitats. We investigated whether there were any differences in brain structure between species that lived in different habitats, or had different social organizations or strategies.

Research was done in collaboration with the Hofmann Laboratory at Harvard University

After accounting for phylogenetic confounds with independent contrasts, we find that environmental and social factors differentially affect the brain, with environmental factors showing a broader effect on a range of brain structures compared to social factors.

Brain size and cerebellum are positively correlated with species number (which is correlated with habitat complexity)
The medulla and olfactory bulb are negatively correlated with habitat measures.
The telencephalon shows a trend toward a positive correlation with rock size.

Only two brain structures, the telencephalon and hypothalamus, are correlated to social factors.

Telencephalic size is larger in monogamous species compared to polygamous species, as well as with increased numbers of individuals
Social organization is also negatively correlated with hypothalamic size

Publication: Pollen, A.A., A.P. Dobberfuhl, J.G. Scace, M.M. Igulu, S.C.P. Renn, , C.A. Shumway, and H.A. Hofmann. (2006, in press). Environmental complexity and social organization sculpt the brain in Lake Tanganyikan cichlid fish. Brain Beh. Evol.

How does Habitat Complexity and Social Behavior affect the Brain?
Part 2: Internal Structure

Dl
We sectioned the brains of the rock dwelling monogamous A. leptura and the sand dwelling X. flavipinnis at 50u and stained them with cresyl violet. Cresyl violet stains the ribosomal matter in the cells purple and allows us to discern the regions of the brain. We measured an area of the telencephalon called the lateral division of the area dorsalis or simply Dl (area highlighted in red on the brains to the right). Dl is believed to be the homologue to the mammalian hippocampus, which is implicated in spatial memory. We calculated the ratio of Dl volume to the volume of the telencephalon and we found that Dl is significantly larger in the rock dwelling fish. We are currently working on another pair of sister species within the Ectodini clade where one species, X. papilio, lives in rock habitats and the other, X. boulengeri, lives in sand. In addition we will compare sister species of marine gobies.

Dm
We sectioned the brains of the monogamous X. flavipinnis and polygamous X. ochrogenys at 25μ. We measured the area called the medial division of the area dorsalis or simply Dm (see figures). Dm is believed to be the homologue to the amygdala, which is implicated in social recognition. We calculated the ratio of Dm volume to the telencephalon volume and found that the Dm was significantly larger in the monogamous fish than in the polygamous fish. We will compare Dm in another monogamous and polygamous pair in the future.

A. leptura Brain X. flavipinnis Brain

The area Dl is outlined in red and divided into 3 subdivisions (Dld1, Dld2 and Dlv)

Error Bars +/- SE

X. flavipinnis X. ochrogenys

The area Dm is outlined in red

Error Bars +/- SE

Preoptic area with AVT-immunoreactive cells visualized with DAB (brown cells)

How does Social Behavior affect the Brain

AVT
Recently, it has been demonstrated that the neurotransmitter arginine-vasopressin (AVP) plays a critical role in social and pair-bonding behavior in voles (Young et al., 2001; Lim et al., 2004). The phylogeny of these voles is not well resolved and the monogamous and polygamous species live in different habitats. Because cichlids from Lake Tanganyika exhibit a diverse array of social behaviors, we are able to study how arginine-vasotocin (AVT) mediates social behaviors within a single habitat and known phylogeny. AVT is a homologue to the mammalian neurotransmitter AVP. Using immunohistochemistry, we compared the pre-optic areas (POA) of the sand-dwelling monogamous X. flavipinnis and the sand-dwelling polygamous X. ochrogenys. We found that the monogamous X. flavipinnis had twice as many AVT-ir cells in the POA as the polygamous X. ochrogenys, after normalizing for brain volume.

Dobberfuhl AP, Scace JG, Shumway CA (2005). Monogamy and pair-bonding is correlated to an increase in vasotocin-immunoreactive cells in cichlid fishes. Soc Neurosci Abstr 205.3. Washington.

More Research at New England Aquarium!

HOME CONSERVATION CONTACTS