On the development of the dog-fish Chiloscyllium indicum (Gmel.). Records of the Raffles Museum, No. 31
This short note by N. Smedley documents the developmental stages of the dog-fish Chiloscyllium indicum (Gmel.) based on egg-cases recovered from a cable.
Summary
Smedley describes egg-cases bearing byssus-like thread attachments, noting that three cases were firmly joined by continuous strands, suggesting simultaneous oviposition—an exceptional arrangement compared to the paired or single laying reported by Sundara Raj and Southwell and Prashad. One case was empty, a second contained a young male with a yolk-sac of about 10 mm diameter, and a third held a female nearly ready to hatch with the yolk-sac almost fully reabsorbed (p. 165). Five additional cases had their attachments cut during removal.
The author recognises only C. indicum for the purposes of the note, treating C. griseum and C. plagiosum as synonyms despite Tate, Regan, and Garman’s recognition of three separate species. Developmental stages are described, including an embryo of 20 mm adhering to the case, a 50 mm embryo with a 23 mm yolk-sac, and a 95 mm specimen with an empty yolk-sac and a distinct 10–12 mm duct (p. 165). Smedley notes that in one specimen the head pointed toward the rear of the case, which appears exceptional, and that hydroid colonies on the cases indicate a lengthy incubation period (p. 166).