Embryo developmental events and the egg case of the Aleutian skate Bathyraja aleutica (Gilbert) and the Alaska skate Bathyraja parmifera (Bean)

Abstract

Embryo development events were correlated with egg-case changes for the Aleutian skate Bathyraja aleutica and the Alaska skate Bathyraja parmifera. Yolk absorption underwent two phases: that of steady absorption during early development and that of rapid yolk absorption during the final development stages. Total length (L(T)) for 50% of the pre-hatching embryos egg-case jelly disappearance was 92.04 mm (range 81-102 mm) and 99.36 mm (range 81-100 mm) for B. aleutica and B. parmifera, respectively, allowing the inner chamber to open to seawater flow. The tail filament underwent three phases of growth: rapid elongation during early development (<100 mm embryo L(T)), stasis of tail filament length during the remainder of embryo development and rapid absorption soon after hatching. Complete tail filament development coincided with the disappearance of egg-case jelly. Clasper buds first developed at embryos >70 mm L(T) for both species and the sex ratio was 1:1 well before hatching. Egg cases that were devoid of an ova or developing embryo were c. 5.0 and 6.5% of the egg cases examined for B. aleutica and B. parmifera, respectively. Measurements showed that egg cases containing only egg jelly were smaller in both width and length than those possessing an ova. Embryo stages were punctuated with distinct events that correlated with egg case changes controlling the internal environment of the developing embryo.

Identification of skate nursery habitat in the eastern Bering Sea

“…4). Most sites possessed eggs that were recently deposited (stage 1 = little development) and in early stages of embryo development (< 40 mm), and those near hatching size (approximately 250 mm for the Aleutian and Alaska skates, 160 mm for the Bering skate) (for description of embryo stages see Hoff 2008Hoff , 2009a. …”

“…Unique habitats can be formed at the heads of canyons due to currents Table 1 Table 1 ). These areas possess physical features that may produce optimal conditions for the long development time required by embryos in sub-arctic waters (Hoff 2007(Hoff , 2008(Hoff , 2009a. EBS canyons can be highly productive with northerly slope currents causing upwelling and high primary production (Springer & McRoy 1996), which in turn can support high biomass of birds (Piatt et al 2006), mammals (Loughlin et al 1999) and fish and invertebrate species (Brodeur 2001, Stevenson et al 2008.…”

Reproductive biology of Psammobatis rutrum (Chondrichthyes: Arhynchobatidae) in south Brazil, south‐west Atlantic

“…Lateral fibrils were observed in P. scobina (Concha et al, 2009), R. agassizi (Oddone et al, 2006) and A. castelnaui (Oddone et al, 2008c). These structures are responsible for camouflage and anchorage of the egg capsule in marine substrata (Hoff, 2009). The presence of lateral fibrils in P. rutrum may be related to the low development level of posterior and anterior horns, as observed in other species (Concha et al, 2009) and these structures play important role in attaching the egg capsule to the substratum.…”

Identification of multiple nursery habitats of skates in the eastern Bering Sea

“…parmifera and B. aleutica hatch at c . 22–25 cm L T (Teshima & Tomonaga, ; Hoff, 2009 a ) and both are estimated to be 1 year post‐hatching at 35 cm L T based on previous studies (Matta & Gunderson, ; Hass, ). Therefore, data from both species that were considered to be YOY juveniles (<36 cm L T ) were used.…”