The reproductive systems of 119 males of the umbrella squid Histioteuthis bonnellii (Férussac, 1835) caught in the Sardinian waters (Central Western Mediterranean) at depths between 400 and 700 m were examined and are described for the first time. Fully mature males were present all year round. The smallest mature male measured 60.0 mm in mantle length (ML) and 113.50 g in body weight, and the sizes at maturity were 100.0 mm ML and 400.00 g TW. The total number of spermatophores was counted in 18 specimens, and varied from 12 to 3097 (977±928), without correlation with body size. Spermatophore total length (SpL) ranged between 3.00 and 15.45 mm (7.11±3.49). SpL gradually decreased towards the distal end of the reproductive system, so that spermatophores found in the proximal part of the Needham’s Sac were larger than those found in the terminal organ, and this difference in length was conspicuous (i.e., up to over 200%). Only the SpL of spermatophores from the proximal part of the Needham’s Sac was correlated with body size. Both indices of the sperm mass and of the ejaculatory apparatus decreased with the increase of spermatophore length, while the cement body index increased. Spermatangia were found in 13 specimens, exclusively in the terminal organ. Up to 64 spermatangia (21±17), measuring between 2.02 and 8.12 mm in length (4.44±1.88 mm), were counted. The large size range of mature males (ML 60.0–198.0 mm; TW 113.50–2409.00 g) and the variation in spermatophore number indicate that in H. bonnellii males the production of sexual products is a process that starts early in the individual life and extends in time, while animals continue to grow and mate, releasing spermatophores at different times. A continuous production of sexual gametes is already known and better investigated in females of deep-sea cephalopods, where it is considered a reproductive adaptation to depth (Rocha et al., 2001). A similar strategy, that increases the time interval in which reproduction can take place, was proposed recently for H. miranda males from the South African waters by Hoving et al. (2010). Indeed, as evidenced by these authors, an early and continuous production of spermatophores allows a maximum time range for mating; this, in deep-sea environments where low density of individuals and scarcity of spawning aggregations may occur, would result in a winner reproductive strategy
Male reproductive system and sexual products in Histioteuthis bonnellii (Cephalopoda: Histioteuthidae)
MEREU, MARCO;AGUS, BLONDINE;CAU, ANGELO;
2012-01-01
Abstract
The reproductive systems of 119 males of the umbrella squid Histioteuthis bonnellii (Férussac, 1835) caught in the Sardinian waters (Central Western Mediterranean) at depths between 400 and 700 m were examined and are described for the first time. Fully mature males were present all year round. The smallest mature male measured 60.0 mm in mantle length (ML) and 113.50 g in body weight, and the sizes at maturity were 100.0 mm ML and 400.00 g TW. The total number of spermatophores was counted in 18 specimens, and varied from 12 to 3097 (977±928), without correlation with body size. Spermatophore total length (SpL) ranged between 3.00 and 15.45 mm (7.11±3.49). SpL gradually decreased towards the distal end of the reproductive system, so that spermatophores found in the proximal part of the Needham’s Sac were larger than those found in the terminal organ, and this difference in length was conspicuous (i.e., up to over 200%). Only the SpL of spermatophores from the proximal part of the Needham’s Sac was correlated with body size. Both indices of the sperm mass and of the ejaculatory apparatus decreased with the increase of spermatophore length, while the cement body index increased. Spermatangia were found in 13 specimens, exclusively in the terminal organ. Up to 64 spermatangia (21±17), measuring between 2.02 and 8.12 mm in length (4.44±1.88 mm), were counted. The large size range of mature males (ML 60.0–198.0 mm; TW 113.50–2409.00 g) and the variation in spermatophore number indicate that in H. bonnellii males the production of sexual products is a process that starts early in the individual life and extends in time, while animals continue to grow and mate, releasing spermatophores at different times. A continuous production of sexual gametes is already known and better investigated in females of deep-sea cephalopods, where it is considered a reproductive adaptation to depth (Rocha et al., 2001). A similar strategy, that increases the time interval in which reproduction can take place, was proposed recently for H. miranda males from the South African waters by Hoving et al. (2010). Indeed, as evidenced by these authors, an early and continuous production of spermatophores allows a maximum time range for mating; this, in deep-sea environments where low density of individuals and scarcity of spawning aggregations may occur, would result in a winner reproductive strategy
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