Early Development and Post Embryonic Skeletal Morphology of the Progeny of Spined Loach <I>Cobitis taenia</I> L. (Teleostei, Cobitidae) and its Naturally Occurring Allotriploids

Abstract

JUCHNO D., BOROÑ A., SZLACHCIAK J., KUJAWA R. 2016. Early development and post embryonic skeletal morphology of the progeny of Cobitis taenia (Teleostei, Cobitidae) and its naturally occurring allotriploids. Folia Biologica (Kraków) 64: 153-162.Polyploid fishes of the genus Cobitis represent a valuable model system to study the origin and consequences of hybridization and polyploidization within vertebrates. These naturally accessible polyploids are an excellent subject to determine the advantages or disadvantages of polyploidy. We investigated the embryonic and larval development with skeletal morphology of diploid and polyploid Cobitis progeny, obtained from crosses between females and males of Cobitis taenia and between allotriploid Cobitis females and C. taenia males. Observations were made during first fourteen days post fertilization. The pattern of development of all investigated individuals was the same. However the diploids developed synchronically, achieving successive stages faster than the polyploid ones; hatching was observed at 50 and 63 hours post fertilization, respectively. Statistically significant differences in hatching success and survival rate between diploid and polyploid progeny were not observed. All newly hatched larvae were characterized by a large amount of yolk, forty myomeres, body pigmentation and four external gills. Skeletal elements of the chondrocranium in the first days post hatching consisted of the otic capsule, ethmoid plate, trabeculae cranii and Meckel's cartilage. In contrast to the diploids, the polyploid larvae were characterized by a higher number of deformities. This study gives new comparative data on the features of early development of diploid and polyploid Cobitis progeny.

Histological evidence that diploid hybrids of Cobitis taenia and C. elongatoides (Teleostei, Cobitidae) develop into fertile females and sterile males

“…Interestingly, the external features of sexual dimorphism, such as lamina circularis 'expressing' male maturity, do not indicate their reproductive capacity. The duration of embryonic development of hybrids (this paper) was similar (c. two hours shorter) to C. taenia (Juchno et al, 2016). However, the percentage of hatching hybrid larvae was lower (15% of TE and 32% of ET) in comparison with that in C. taenia (46%) but the survival rate of all these larvae (Juchno et al, 2016) was similar.…”

“…a decrease in mean survival, health and fertility (Gharrett et al, 1999). The Cobitis hybrids in the present study had lower reproductive success than C. taenia as a parental species (Juchno et al, 2016).…”

“…The developmental stages and the hatching success were defined as described for Danio rerio by Kimmel et al (1995) and were compared with the developmental stages described for C. taenia and its polyploids (Juchno et al, 2016). The survival rates of larvae at 14 and 21 days post hatching (dph) were calculated and statistically analyzed using Pearson's Chi-squared test for each treatment.…”

“…Artificial spawning was done in June, during the natural time for reproduction, but collected parental individuals were hormonally stimulated before crossing according to the routine fertilization method described in detail by Juchno et al (2014). Similar to the method described by Juchno et al (2016), the developing eggs were initially incubated in Petri dishes, and then in separate small aquaria with running water at 24°C under artificial light with a photoperiod similar to natural light conditions. A special electronic controller was used to maintain a stable temperature.…”

Co-feeding period on the survival and growth of larvae (Botia lohachata) during the feeding transition

“…At this stage, the newly hatched larvae are dependent on yolk reserves, and when the yolk sac is exhausted they need to ingest exogenous food to satisfy their increasing energy demands (MENOSSI et al 2012;FOSSE et al, 2018). For most species that have been studied, the digestive tract of larvae shortly after hatching appears histologically as a straight, undifferentiated tube and must undergo further development and differentiation before exogenous food is provided so that it can be efficiently ingested and digested (LAZO et al, 2011) Depending on the size of the larva and the specialization of its digestive tract at the beginning of exogenous feeding, live food is essential to ensure the growth and survival of many fish species (JOMORI et al, 2008;MENOSSI et al 2012). The supply of Artemia nauplii as live food during the early stages of development has already been successfully studied for larvae of other freshwater fish species, such as beta Betta splendens (FOSSE et al, 2013), tambacu Colossoma macropomum × Piaractus mesopotamicus (LOMBARDI & GOMES, 2008), the black catfish Rhinelepis aspera (LUZ & SANTOS, 2010), and common carp Cyprinus carpio (FOSSE et al, 2018).…”