Gaskiya ne ƙwai na kifin kasusuwa kuma mafi zagaye. Akwai membrane na waje wanda zai iya shiga tare da ƙananan pores, wanda ake kira chorion. Wannan membrane gabaɗaya yana da santsi, kodayake a cikin wasu nau'in yana da ƙyalli mai kusurwa shida.
El gwaiduwa daga kwai shi ne ke kula da bayar da makamashi da abubuwan gina jiki abin da amfrayo ke bukata yayin ci gabansa har sai ya iya ciyar da kansa, lokacin da ya riga ya kasance daga cikin plankton. A wasu nau'ikan de peces, gwaiduwa ta mamaye duk sararin da ke akwai kuma ya bar wani yanki na gefe kawai kyauta.
En elasmobranchs, da zarar sun samu haduwar ovules, an rufe su da capsule corneal wanda ke da matakai da girma dabam dabam dangane da nau'in. A cikin wasu sharks na oviparous, alal misali, wannan kwandon yana da kamannin kusurwa huɗu ko ,asa, kuma ana ba shi filaments don gyara a ƙasa.
Dangane da girman ƙwai yana da canji sosai, kodayake sun kai kusan 1 mm a diamita, kuma suna iya kasancewa tsakanin 0,25 zuwa 7 mm a cikin nau'ikan daban -daban. Da mafi kyau duka kwai size Shi ne yake ƙara yawan ƙwai da kuma rayuwa ta gaba da tsutsotsi da ƙananan yara.
da benthic qwai su ne, gabaɗaya, sun fi na planktonic girma, tare da ƙarin gwaiduwa kuma ba su da yawa. Ci gaban amfrayo a cikin kwai ya fi tsayi, kuma tsutsa tana fitowa cikin yanayin ci gaba, tare da idanun launin fata.
A dawo fecundity a cikin pelagic spwning kifi ya fi na waɗanda suke yin ƙwai benthic. Don haka akwai kyakkyawar alaƙa tsakanin girman ƙwai da tsira da tsutsa. Kuma, larvae mafi girma suna da ikon cin abinci iri -iri iri -iri da girma, kuma, a lokaci guda, ba su da rauni ga masu farauta.