Diapause in the Gemmules of the Marine Sponge,haliclona Loosanoffi, With a Note on the Gemmules Ofhaliclona Oculata

The gemmules of Haliclona loosanoffi are present throughout the year in the Mystic Estuary, but active specimens of this sponge are found only during the period extending from late May to late October or early November. Germination of the gemmules occurs primarily during May and June, and new gemmules are produced from late June through early October. The gemmules of this species evidently are a means for surviving adverse environmental conditions.2. Both gemmules and active specimens of Haliclona oculata are found through-out the year in Fishers Island Sound. The gemmules of this species may repopulate the substrate when the parent sponges degenerate or are ripped loose during storms.3. Gemmules of Haliclona loosanoffi collected in the fall do not germinate readily when they are cultured at 20° C. There is frequently only limited germination after 1 to 2 months at this temperature. However, if the gemmules are first put at 5° C for 4 or more weeks, they usually germinate within a few days after being placed at 20° C. Thus low temperature appears to enhance germination of these gemmules which undergo diapause.4. Although low temperature appears to accelerate maturation of the gemmules of Haliclona loosanoffi, it also inhibits actual germination. Gemmules do not germinate at either 5 or 10° C. However, germination occurs within 2 to 4 weeks at 15° C and within 1 to 2 weeks at 20° C. At 25° C germination appears to be accelerated by approximately 24 to 48 hours compared to that occurring at 20° C.5. The gemmules of Haliclona loosanoffi may be stored in the dark at 5° C for at least 10 months without any detectable reduction in their capacity to germinate at higher temperatures. However, such gemmules can not be stored indefinately. Gemmules kept at 5° C for from 16.5 to 19.5 months did not germinate when they were subsequently placed at either 20 or 25° C.6. Gemmules of Haliclona loosanoffi germinate at 30° C, but this temperature appears to be less favorable than 20 or 25° C. Slightly higher temperatures inhibit germination, and continuous exposure to 34° C apparently is lethal.7. The reproductive period of Haliclona loosanoffi in the Mystic Estuary extends from late May through July and that of Haliclona oculata in Fishers Island Sound extends from March through June.