Forty-year natural history study of Bahalana geracei Carpenter, 1981, an anchialine cave-dwelling isopod (Crustacea, Isopoda, Cirolanidae) from San Salvador Island, Bahamas: reproduction, growth, longevity, and population structure

Almost nothing has been reported on the natural history of any world’s 92 species cave cirolanids, including those from saltwater caves (anchialine). Over 1400 specimens Bahalana geracei Carpenter, 1981 were collected in two 1978–2018; size-frequency data provided insight into population structure. Some maintained alive over multiple years to study rarely activities for cirolanids: feeding, molting, growth, longevity, and reproduction. Photographs document these phenomena. Mating occurred after gravid females shed both halves reproductive molts. Females can have broods (iteroparous) with ~2.0–3.5 per cycle: egg production (~9–24 months), mating, brooding (5–6 release 6–55 mancas (2.3–3.3 mm long), oostegite molt (~2–13 months manca release). Estimated lifetime fecundity is 58 female; probable range 20–120. In Lighthouse Cave, outnumbered males (~4:1), grew larger (16.8 vs. 9.5 mm), lived longer. Growth rates slow: ~1–2 three instars post-marsupial development (from ~2.3–4.0 mm); estimated adult growth rate was 0.8 mm/year (1.6 molts/year) males, 0.5 (1.5 females. Longevity estimates are 25–28 23–30 instars, 6–8 13–15 instars. Males Major’s Cave nearly as numerous large (14.8 mm) females; longevity >20 years. appear be longest isopod species. Female probably increased by being starvation resistant, surviving broods, cannibalizing smaller B. , living a low-stress environment. Populations stable, relatively large, not currently threatened.