Distribution and female reproductive state differences in orexigenic and anorexigenic neurons in the brain of the mouth brooding African cichlid fish, Astatotilapia burtoni

Abstract

Integration of reproduction and metabolism is necessary for species survival. While the neural circuits controlling energy homeostasis are well-characterized, the signals controlling the relay of nutritional information to the reproductive axis are less understood. The cichlid fish Astatotilapia burtoni is ideal for studying the neural regulation of feeding and reproduction because females cycle between a feeding gravid state and a period of forced starvation while they brood developing young inside their mouths. To test the hypothesis that candidate neuropeptide-containing neurons known to be involved in feeding and energy homeostasis in mammals show conserved distribution patterns, we performed immunohistochemistry and in situ hybridization to localize appetite-stimulating (neuropeptide Y, NPY; agouti-related protein, AGRP) and appetite-inhibiting (cocaine and amphetamine-regulated transcript, CART; pro-opiomelanocortin, pomc1a) neurons in the brain. NPY, AGRP, CART, and pomc1a somata showed distribution patterns similar to other teleosts, which included localization to the lateral tuberal nucleus (NLT), the putative homolog of the mammalian arcuate nucleus. Gravid females also had larger NPY and AGRP neurons in the NLT compared to brooding females, but brooding females had larger pomc1a neurons compared to gravid females. Hypothalamic agrp mRNA levels were also higher in gravid compared to brooding females. Thus, larger appetite-stimulating neurons (NPY, AGRP) likely promote feeding while females are gravid, while larger pomc1a neurons may act as a signal to inhibit food intake during mouth brooding. Collectively, our data suggest a potential role for NPY, AGRP, POMC, and CART in regulating energetic status in A. burtoni females during varying metabolic and reproductive demands.

Integrating Authentic Scientific Research in a Conservation Course–Based Undergraduate Research Experience

“…By incorporating CUREs into ongoing research, mentors spend less time developing research experiences (Spell et al, 2014), and are better able to provide relevant expertise to participating students, while students benefit from participating in a more comprehensive and applicable research experience (Bakshi et al, 2016). Beyond overcoming logistical barriers, CUREs also benefit research programs by increasing data collection (Dubansky et al, 2013; Porter, 2015), enhancing outreach and community engagement, and developing networks of potential technicians and future collaborators.…”

“…Most reported examples of CUREs take place in the context of biological sciences executed in laboratory settings (Bakshi et al, 2016; Dubansky et al, 2013; Miller et al, 2013; Porter, 2015; Venesky, 2015; Wei and Woodin 2011). There are few examples of CUREs integrated into conservation and natural resource sciences and, to the authors’ knowledge, no reports of CUREs that take place in a field research setting.…”

Expression of tachykinin3 and related reproductive markers in the brain of the African cichlid fish Astatotilapia burtoni

“…Because expression is widely distributed, a fine‐scale neuroanatomical approach should be taken to examine specific tac3 cell‐populations in the brain, not just on a macro level. For example, tac3a cells are found in close proximity to cells expressing appetite stimulating and inhibiting proteins (Porter, Roberts, & Maruska, ) and are located in regions of the brain implicated in parental care and feeding. Since A. burtoni is a maternal mouthbrooding fish, it would be interesting to compare levels of tac3a in these regions between feeding, reproductively active females and nonfeeding females engaged in maternal care.…”

Untitled

“…In a Haplochromine cichlid, Astatotilapia burtoni, six cart isoforms have been described and among them cart/cartpt1 show the greatest similarity to mammalian CART gene (Hu et al, 2016). The brain expression pattern of cart appeared to be similar to its orthologues in other teleosts in the lateral posterior part of the hypothalamus (or lateral tuberal nucleus), which is also similar to the expression of mammalian CART in a comparable region called arcuate nucleus (Porter, Roberts & Maruska, 2017).…”

“…Here we investigated the expression of appetite regulating genes in the brains of cichlids adapted to herbivorous and carnivorous trophic niches and identified two appetite-regulating genes, cart (or cartpt1) and npy2r, to have higher expression in the carnivore brains prior to the initiation of feeding across all three lakes. Both genes are indicated to have anorexigenic function in different groups of teleost fishes (Matsuda et al, 2012;Babichuk & Volkoff, 2013;Wang et al, 2014;He et al, 2015;Volkoff, 2016;Porter, Roberts & Maruska, 2017). The first gene, cart, or cocaineand amphetamine-regulated transcript, encodes a pre-proprotein which proteolyzes to multiple active peptides and participates in biological processes related to regulation of appetite, energy balance, stress response, and reward and addiction responses (Volkoff, 2006(Volkoff, , 2016Koylu, Balkan & Pogun, 2006;Vicentic et al, 2007;Rogge et al, 2008).…”