Taxonomy

In early papers on Spirula, up to five species were described (Owen, 1879; Huxley and Pelseneer, 1885; Lonnberg, 1896). Only one species was accepted by Chun (1915), Naef (1923), and Bruun (1943). Nesis (1987) and Norman (2000) also described one living species of Spirula. A major problem in the description of more than one species of Spirula is that different "species" are represented by only a few, often incomplete specimens. Moreover, most type repositories are unknown (Young and Sweeney, 2002). At present, the taxonomic status of Spirula is still called into question. Indeed, Young and Sweeney (2002) listed most species of Spirula as either undetermined or nomina nuda. Young and Sweeney (2002) considered only Spirula spirula as a valid species (Table 7.1). Nonetheless, the type repository of this holotype remains unknown and the type locality is extremely vague.

No doubt, Spirula is widely distributed. Live specimens occur in the waters of Indonesia, Melanesia, Australia, southeastern Africa, between the Canary Islands and northwestern Africa (Fig. 7.1), in the Caribbean Sea, and in the Gulf of Mexico (Bruun, 1943; Clarke, 1966; Dauphin, 1979a, b; Nesis, 1987).

Apparently the geographic range of Spirula is disjunct like that of many other epi- and mesopelagic, circumtropical species that are widely distributed in the Atlantic and Indo-West Pacific. Probably there is no gene flow between the Atlantic and Indo-Pacific populations living around South Africa (Nesis, 1998). Thus, one can infer the occurrence of geographic subspecies, one in the Atlantic and the other in the Indo-West Pacific (Nesis, 1998). Subspecies are rarely used in cepha-lopod systematics (Voss, 1977). However, Bruun (1943) already considered the

Table 7.1 Status of Spirula species after Young and Sweeney (2002).

Species name

Determination

Type locality

Comments

Spirula peronii

[ forma] Girard,

Algarve

Undetermined

atlantica

1890: 250.

(Portugal); Azores; etc.

Spirula australis

Lamarck, 1816: pl 465,

Not designated

Undetermined

Figs. 5a, b.

Spirula blakei

Lonnberg, 1896: 100.

West Indies

Undetermined

Spirula fragilis

Lamarck, 1801: 102.

Nomen nudum

Spirula peronii

[ forma] Girard,

New Caledonia;

Undetermined

indopacifica

1890: 250.

Indian Ocean; etc.

Spirula peronii

Lamarck, 1822 in

"l'Océan austral

Undetermined

1815-1822: 601.

et celui des Moluques"

Spirula prototypus

Lesueur and Petit, 1807:

Not designated

Undetermined

pl 30, Fig. 4.

Spirula reticulata

Owen, 1848: 14, pl. 4,

Off Timor [ fide Lönnberg

Undetermined

Figs. 3, 9.

(1896: 99)]

Loligo spiralis

d'Orbigny, 1826: 153

-

Nomen nudum

Nautilus spirula

Linné, 1758: 710

"America"

Valid species

(Spirula spirula)

[ fide Bruun (1943: 3)]

Fig. 7.1 LivingSpirula spirula (left, female [mantle length = 4cm], right, male [mantle length = 5cm) caught between the Canary Islands and the coast of Morocco. The animals were caught with an Isaacs Kidd mid-water trawl and placed in an aquarium to take photos.

possibility of subspecies or races of Spirula based on morphological characters. He compared preserved soft parts from the Atlantic and the Indo-Pacific and analyzed them with regard to pigmentation, size, sexual arm differentiation, similarity of external characters, and some further morphometric measurements, but he did not find any definite morphological difference between them.

Nesis (1998) again emphasized the potential importance of biochemical or molecular data to distinguish intra- and interspecific differences, especially regarding species with a distribution pattern like that of Spirula.

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