Littorally adaptive? Testing the link between habitat, morphology, and reproduction in the intertidal sculpin subfamily Oligocottinae (Pisces: Cottoidea)

Abstract

While intertidal habitats are often productive, species-rich environments, they are also harsh and highly dynamic. Organisms that live in these habitats must possess morphological and physiological adaptations that enable them to do so. Intertidal fishes are generally small, often lack scales, and the diverse families represented in intertidal habitats often show convergence into a few general body shapes. However, few studies have quantified the relationship between phenotypes and intertidal living. Likewise, the diversity of reproductive traits and parental care in intertidal fishes has yet to be compared quantitatively with habitat. We examine the relationship of these characters in the sculpin subfamily Oligocottinae using a phylogenetic hypothesis, geometric morphometrics, and phylogenetic comparative methods to provide the first formal test of associations between fish phenotypes and reproductive characters with intertidal habitats. We show that the ability to live in intertidal habitats, particularly in tide pools, is likely a primitive state for Oligocottinae, with a single species that has secondarily come to occupy only subtidal habitats. Contrary to previous hypotheses, maximum size and presence of scales do not show a statistically significant correlation with depth. However, the maximum size for all species is generally small (250 mm or less) and all show a reduction in scales, as would be expected for an intertidal group. Also contrary to previous hypotheses, we show that copulation and associated characters are the ancestral condition in Oligocottinae, with copulation most likely being lost in a single lineage within the genus Artedius. Lastly, we show that body shape appears to be constrained among species with broader depth ranges, but lineages that occupy only a narrow range of intertidal habitats display novel body shapes, and this may be associated with habitat partitioning, particularly as it relates to the degree of wave exposure.

Have Niche, Will Travel. New Means of Linking Diet and Ecomorphology Reveals Niche Conservatism in Freshwater Cottoid Fishes

“…The diet of these fishes is dominated by algae (constituting up to 100% of the stomach contents (see Johnston 1954 ) and their jaws are greatly reduced in length (see Fig. 5 and discussion in Buser et al. 2017 , 2018 ).…”

Mating Season, Egg-Laying Season, and Internal Gametic Association in the Sympatrically Occurring Fluffy Sculpin (Oligocottus snyderi) and Rosy Sculpin (O. rubellio)

“…S1). Buser et al (2017) identified morphological variation between the species, such as body depth, eye size, and shape, but these morphological characteristics are difficult to discern in the field, especially in females.…”

“…Species with IGA share several characteristics with true internal fertilizers. For example, most IGA species have a well-developed genital papilla for mating (Evans and Meisner, 2009) and have sperm with elongated head, in comparison with external fertilizing species that lack copulatory anatomy and exhibit round sperm head morphology (Koya et al, 2011;Buser et al, 2017;Ito and Awata, 2019;Ito et al, 2022). While IGA is interesting in the evolution of reproductive strategy, it is currently unknown how widespread this strategy is within Agonidae and Psychrolutidae.…”

“…Marine sculpins in the subfamily Oligocottinae (Psychrolutidae) are represented by 16 species including both external fertilizers and internal inseminators (Buser et al, 2017). They are all found in shallow waters of the west coast of North America and possess a suite of traits that enable them to exploit intertidal habitats (Ramon and Knope, 2008;Buser and López, 2015).…”

External reproductive structures of male Surfperches (Embiotocidae): Urogenital papilla

“…A less studied intromittent organ is the ventrally located papillae of male marine, internally inseminating fish species, and to our knowledge, has only been studied in clinid fishes (Clinidae, Blennioidei;Fishelson et al, 2006). Additionally, despite their documentation, marine fish papillae have not been thoroughly investigated in some sculpins in the family Cottidae (Buser et al, 2017), rockfishes in the genus Sebastes (F. R. Shaw et al, 2012), clingfishes in the family Gobiesocidae (Conway et al, 2019), or surfperches (Embiotocidae; Carlisle et al, 1960;Nakazono et al, 1981;E. Shaw, 1971;F.…”