Building a Better June Sucker: Characterization of Mouth Shape in the Captive Brood Stock

Abstract

June sucker, Chasmistes liorus, is an endangered lake sucker endemic to Utah Lake, Utah, USA. Over the last two decades, captive-raised June suckers have been stocked into Utah Lake to augment the wild population. However, it has become apparent that the fish stocked from captive stock may not always represent the typical June sucker morphology. To determine the utility of current captive brood lots to produce June sucker phenotypes, we characterized shape of the lip lobes on the lower jaw of each brood lot. We obtained offspring from within-lot crosses and characterized shape of the lower lips using geometric morphometrics. We compared shape of brood lots to reference samples of June sucker and reference samples of the co-occurring sister species, Utah sucker (Catostomus ardens). Mean shape of the lower lips among brood lots varies from typical June sucker morphology to shapes typical of Utah sucker. Three brood lots had mean shape scores somewhat similar to the reference June sucker mean, and five brood lots had mean shape scores more similar to the reference Utah sucker mean. All other brood lots were intermediate representing hybrid phenotypes. Utilization of all brood lots on a roughly equal basis for augmentation in Utah Lake will likely result in the loss of typical June sucker morphology in the lake within a few decades. We recommend use of brood lots that exhibit June sucker morphology and discontinuance of use of brood lots that represent Utah sucker morphology. In addition, selection on lower lip shape in captive brood lots may be required to recreate June sucker phenotypes from captive brood stock.

Heterochronic shift in gene expression leads to ontogenetic morphological divergence between two closely related polyploid species

“…During the 1990’s and early 2000’s, captive brood lots were created from forced spawning of wild June sucker to augment natural reproduction while critical spawning habitat was restored. 73 Belk et al. 73 formally evaluated lower lip morphology of these brood lots and determined that lower lip morphology ranged between that of pure June sucker (crosses between wild June sucker from Utah Lake; thin, separated lower lip lobes with few papillae) and pure Utah sucker (crosses between wild Utah sucker from an introduced population in Strawberry Reservoir, Utah, USA; broad lower lip lobes with no gap between them, that are highly papillose), with most brood lots exhibiting intermediate phenotypes.…”

“… 73 Belk et al. 73 formally evaluated lower lip morphology of these brood lots and determined that lower lip morphology ranged between that of pure June sucker (crosses between wild June sucker from Utah Lake; thin, separated lower lip lobes with few papillae) and pure Utah sucker (crosses between wild Utah sucker from an introduced population in Strawberry Reservoir, Utah, USA; broad lower lip lobes with no gap between them, that are highly papillose), with most brood lots exhibiting intermediate phenotypes. 49 For our analysis, we acquired samples from two of these brood lots from Utah Lake: a lot identified as the most June-sucker-like (June sucker) and another lot identified as the most Utah-sucker-like (Utah Lake Utah sucker).…”

Allometric Changes and Shape Comparisons of Two Southwestern Sucker Species and Their Hybrids Using a Geometric Morphometric Approach

“…Another characteristic that could aid in distinguishing among the fish types is mouth shape. Mouth shape is commonly used as an identification method for suckers (Belk et al 2016), and mouth shape differs among Razorback Suckers, Flannelmouth Suckers, and their hybrids. We attempted to conduct shape analysis on the lips of fish that were 60-100 mm TL.…”