Does more maternal investment mean a larger brain? Evolutionary relationships between reproductive mode and brain size in chondrichthyans

Mull, Christopher G.; Yopak, Kara E.; Dulvy, Nicholas K.

doi:10.1071/mf10145

Cited by 32 publications

(32 citation statements)

References 57 publications

(105 reference statements)

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“…4(b)] were slightly lower than those reported when using species as independent data points [Fig. 4(a)], indicating that previous estimates have been biased by phylogenetic contrasts, although they were comparable to those values published for chondrichthyans that were similarly independent of phylogeny ( α = 0·38, n = 37, Yopak et al , 2007; α = 0·37, n = 57, Yopak & Montgomery, 2008; α = 0·353, α RMA = 0·39, Yopak & Frank, 2009; α RMA = 0·46, α RMA = 0·41, Mull et al , 2011).…”

Section: Brain Scalingsupporting

confidence: 73%

Neuroecology of cartilaginous fishes: the functional implications of brain scaling

Yopak

2012

Journal of Fish Biology

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It is a widely accepted view that neural development can reflect morphological adaptations and sensory specializations. The aim of this review is to give a broad overview of the current status of brain data available for cartilaginous fishes and examine how perspectives on allometric scaling of brain size across this group of fishes has changed within the last 50 years with the addition of new data and more rigorous statistical analyses. The current knowledge of neuroanatomy in cartilaginous fishes is reviewed and data on brain size (encephalization, n = 151) and interspecific variation in brain organization (n = 84) has been explored to ascertain scaling relationships across this clade. It is determined whether similar patterns of brain organization, termed cerebrotypes, exist in species that share certain lifestyle characteristics. Clear patterns of brain organization exist across cartilaginous fishes, irrespective of phylogenetic grouping and, although this study was not a functional analysis, it provides further evidence that chondrichthyan brain structures might have developed in conjunction with specific behaviours or enhanced cognitive capabilities. Larger brains, with well‐developed telencephala and large, highly foliated cerebella are reported in species that occupy complex reef or oceanic habitats, potentially identifying a reef‐associated cerebrotype. In contrast, benthic and benthopelagic demersal species comprise the group with the smallest brains, with a relatively reduced telencephalon and a smooth cerebellar corpus. There is also evidence herein of a bathyal cerebrotype; deep‐sea benthopelagic sharks possess relatively small brains and show a clear relative hypertrophy of the medulla oblongata. Despite the patterns observed and documented, significant gaps in the literature have been highlighted. Brain mass data are only currently available on c. 16% of all chondrichthyan species, and only 8% of species have data available on their brain organization, with far less on subsections of major brain areas that receive distinct sensory input. The interspecific variability in brain organization further stresses the importance of performing functional studies on a greater range of species. Only an expansive data set, comprised of species that span a variety of habitats and taxonomic groups, with widely disparate behavioural repertoires, combined with further functional analyses, will help shed light on the extent to which chondrichthyan brains have evolved as a consequence of behaviour, habitat and lifestyle in addition to phylogeny.

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Section: Brain Scalingsupporting

confidence: 73%

Neuroecology of cartilaginous fishes: the functional implications of brain scaling

Yopak

2012

Journal of Fish Biology

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“…Ellis and Otway (2011) unveiled new details of the environment in which the embryos of wobbegong sharks develop. Mull et al (2011) revealed one possible advantage of investing in live young -matrotrophic sharks have brains that are 20-70% larger than those of similar-sized leicithotrophic species. These types of discoveries are important because they can have other societal benefits, including development of new materials, biomedical discoveries, understanding of other biological processes, and can also help change the public's understanding of sharks (and hence their receptiveness to conservation management that may affect them).…”

Section: Priority Setting and Communicationmentioning

confidence: 99%

“…This is evidenced by the fact that 38% of the papers published from 'Sharks Down Under Conference' in 1991 (Pepperell 1992) were related to life history, whereas life history-related papers account for only 24% of those published in the current conference volume. The types of research that are needed include reproductive biology (Ainsley et al 2011;Graham and Daley 2011;Mull et al 2011), age and growth (Tanaka 2011) and mortality (Simpfendorfer et al 2005). In particular, research targeted at endangered species (e.g.…”

Section: Biological Dimensionsmentioning

confidence: 99%

The importance of research and public opinion to conservation management of sharks and rays: a synthesis

Simpfendorfer

Heupel

White

et al. 2011

Mar. Freshwater Res.

241

186

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Abstract. Growing concern for the world's shark and ray populations is driving the need for greater research to inform conservation management. A change in public perception, from one that we need to protect humans from sharks to one where we must protect sharks from humans, has added to calls for better management. The present paper examines the growing need for research for conservation management of sharks and rays by synthesising information presented in this Special Issue from the 2010 Sharks International Conference and by identifying future research needs, including topics such as taxonomy, life history, population status, spatial ecology, environmental effects, ecosystem role and human impacts. However, this biological and ecological research agenda will not be sufficient to fully secure conservation management. There is also a need for research to inform social and economic sustainability. Effective conservation management will be achieved by setting clear priorities for research with the aid of stakeholders, implementing well designed research projects, building the capacity for research, and clearly communicating the results to stakeholders. If this can be achieved, it will assure a future for this iconic group, the ecosystems in which they occur and the human communities that rely on them.

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“…Much of the variation in brain organization in these fishes is attributed to differences in telencephalon size and the size and degree of folding (or foliation) of the cerebellum . Hypertrophy of these brain areas is associated with various ecological niche and life-history factors, such as habitat, lifestyle, feeding behavior, and reproductive mode [Northcutt, 1978;Graeber, 1984;Yopak et al, 2007;Lisney et al, 2008;Mull et al, 2011]. In comparison, very little is known about interspecific variation in the organization of other brain areas, such as the midbrain or mesencephalon.…”

Section: Introductionmentioning

confidence: 99%

Allometric Scaling of the Optic Tectum in Cartilaginous Fishes

Yopak

Lisney

2012

Brain Behav Evol

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In cartilaginous fishes (Chondrichthyes; sharks, skates and rays (batoids), and holocephalans), the midbrain or mesencephalon can be divided into two parts, the dorsal tectum mesencephali or optic tectum (analogous to the superior colliculus of mammals) and the ventral tegmentum mesencephali. Very little is known about interspecific variation in the relative size and organization of the components of the mesencephalon in these fishes. This study examined the relative development of the optic tectum and the tegmentum in 75 chondrichthyan species representing 32 families. This study also provided a critical assessment of attempts to quantify the size of the optic tectum in these fishes volumetrically using an idealized half-ellipsoid approach (method E), by comparing this method to measurements of the tectum from coronal cross sections (method S). Using species as independent data points and phylogenetically independent contrasts, relationships between the two midbrain structures and both brain and mesencephalon volume were assessed and the relative volume of each brain area (expressed as phylogenetically corrected residuals) was compared among species with different ecological niches (as defined by primary habitat and lifestyle). The relatively largest tecta and tegmenta were found in pelagic coastal/oceanic and oceanic sharks, benthopelagic reef sharks, and benthopelagic coastal sharks. The smallest tecta were found in all benthic sharks and batoids and the majority of bathyal (deep-sea) species. These results were consistent regardless of which method of estimating tectum volume was used. We found a highly significant correlation between optic tectum volume estimates calculated using method E and method S. Taxon-specific variation in the difference between tectum volumes calculated using the two methods appears to reflect variation in both the shape of the optic tectum relative to an idealized half-ellipsoid and the volume of the ventricular cavity. Because the optic tectum is the principal termination site for retinofugal fibers arising from the retinal ganglion cells, the relative size of this brain region has been associated with an increased reliance on vision in other vertebrate groups, including bony fishes. The neuroecological relationships between the relative size of the optic tectum and primary habitat and lifestyle we present here for cartilaginous fishes mirror those established for bony fishes; we speculate that the relative size of the optic tectum and tegmentum similarly reflects the importance of vision and sensory processing in cartilaginous fishes.

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Does more maternal investment mean a larger brain? Evolutionary relationships between reproductive mode and brain size in chondrichthyans

Cited by 32 publications

References 57 publications

Neuroecology of cartilaginous fishes: the functional implications of brain scaling

Neuroecology of cartilaginous fishes: the functional implications of brain scaling

The importance of research and public opinion to conservation management of sharks and rays: a synthesis

Allometric Scaling of the Optic Tectum in Cartilaginous Fishes

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