Loliolus Steenstrup, 1856

Introduction

These are generally small squids with heart-shaped fins.

Brief diagnosis:

A loliginid ...

• with short mantle, rounded posteriorly; fins wider than long but without posterior lobes.
• with ventral crest on hectocotylus formed by fusion of the protective membrane with the ventral row of papillae.
• with an Indo-Pacific distribution.

Characteristics

1. Arms
   1. Arm sucker rings with square plate-like teeth on margin.
      

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      Figure. Oral view of large arm III suckers of L. hardwickei, 33 mm ML, male. The left sucker is from the dorsal series and the right sucker from its pair in the ventral series. Drawings from Lu, et al. (1985).

   2. Hectocotylus:
      1. Ventral crest present, formed by fusion of protective membrane with ventral row of papillae such that original form of conical papillae completely obscured (see below).
      

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      Figure. Top - Aboral-medial view of the hectocotylus of Loliolus (Loliolus) hardwickei showing the crest that reaches the full length of the arm, male, off Madras, India, preserved. Photograph by R. Young. Bottom - Oral-lateral view of the hectocotylus of L. (L.) hardwickei showing the crest, male, 33 mm ML, Indian Ocean south of Calcutta. Drawing from Lu et al. (1985).

2. Tentacles
   1. Tentacular clubs expanded, suckers in four series.
      
      
3. Mantle
   1. Mantle rounded posteriorly; without tail-like elongation.
      
      
4. Fins
   1. Fins extend to posterior tip of mantle.
      

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      Figure. Dorsal view of L. (L.) hardwickei, 33 mm ML, male. Drawing from Lu, et al. (1985).

5. Photophores
   1. Photophores absent.
      
      
6. Viscera
   1. Eggs small.
   2. Spermatophore cement body short.

comments

Hectocotylization includes a crest along a portion of the ventral surface of the arm and a modification of part of the dorsal row of suckers into papillae. Modification of the proximal portion of the hectocotylus varies between subgenera. In Loliolus (Loliolus) the modified portion of the hectocotylus occupies the entire length of the arm whereas in Loliolus (Nipponololigo) some proximal suckers are unmodified.

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Figure. Oral view of the hectocotylus of Loliolus (Nipponololigo) japonica showing the crest restricted to the distal region of the arm, male, Hakkodate fish market. Photograph by R. Young.

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Figure. Oral (top) and medial (bottom) views of a portion of the hectocotylus crest of L. (N.) japonica, same hectocotylus as pictured above. Photographs by R. Young.

Nomenclature

Steenstrup (1856) erected the genus Loliolus for his new species typus. Lu et al. (1985) showed that L. typus is a junior synonym for Loligo hardwickei Gray, 1849, making the latter species the type for the genus Loliolus.

Because the percentage of the arm hectocotylized is considered to be a cline within this group of species with otherwise similar hectocotyli and arm-sucker dentition, Loliolus and Nipponololigo were combined by Vecchione et al. (1998) into a single genus that, by priority, is named Loliolus.

Discussion of Phylogenetic Relationships

Loliolus was originally erected to include species of small loliginids with heart-shaped fins in which the entire left ventral arm of the males is modified. However, as discussed by Brakoniecki (1986), clines exist in the percentage of the arm hectocotylized within species groups with similar hectocotyli. Thus, this character state is not sufficient for generic status. The presence, though, of a distinctive character, a ventral crest on the hectocotylus formed by fusion of the protective membrane with the ventral row of papillae such that the original form of the conical papillae is completely obscured, indicates a close relationship among these species (Natsukari, 1983).

Distribution

References

Brakoniecki, T.F. 1986. A Generic Revision of the Family Loliginidae (Cephalopoda; Myopsida) Based Primarily on the Comparative Morphology of the Hectocotylus. Ph.D. Dissertation, University of Miami, Miami, FL, USA. 163 pages.

Lu, C.C., C.F.E. Roper, and R.W. Tait. 1985. A Revision of Loliolus (Cephalopoda; Loliginidae), including L. noctiluca, a new species of squid from Australian waters. Proceedings of the Royal Society of Victoria, 97(2):59-85.

Natsukari, Y. 1983. Taxonomical and morphological studies on the loliginid squids--III. Nipponololigo, a new subgenus of the genus Loligo. Venus, The Japanese Journal of Malacology, 42(4):313-318.

Vecchione, M., T. F. Brakoniecki, Y. Natsukari and R. T. Hanlon. 1998. A provisional generic classification of the family Loliginidae. Smithson. Contr. Zool., 586.

Vecchione, M., E. Shea, S. Bussarawit, F. Anderson, D. Alexeyev, C.-C. Lu, T. Okutani, M. Roeleveld, C. Chotiyaputta, C. Roper, E. Jorgensen and N. Sukramongkol. 2005. Systematics of Indo-West Pacific loliginids. Phuket Mar. Biol. Cent. Res. Bull. 66: 23-26.