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European Journal of Applied Sciences – Vol. 10, No. 1
Publication Date: February 25, 2022
DOI:10.14738/aivp.101.11714. Maxwell, S. J. (2022). A New Putative Hybrid in Conomurex Fischer, 1884 (Mollusca, Neostromboidae, Strombidae) with Notes on
the Types of Hybrids. European Journal of Applied Sciences, 10(1). 401-408.
Services for Science and Education – United Kingdom
A New Putative Hybrid in Conomurex Fischer, 1884 (Mollusca,
Neostromboidae, Strombidae) with Notes on the Types of Hybrids
Stephen J. Maxwell
College of Science and Engineering, James Cook University
Cairns Qld 4870, Australia
ABSTRACT
The propensity for hybridisation is well established in Strombidae. I propose that
there are three forms of hybridisation: first the true hybrids; second reticulatory
hybrids; and third diversificatory hybrids. The illustrated putative true hybrid
between Conomurex decorus and Conomurex luhuanus is known from a single
example from central Indonesia and represents the first example of intrageneric
hybridization for Conomurex. Furthermore, this paper introduces and illustrates
the novel concept of diktyzonos for regions of morphological reticulation within and
between taxa, and how hybrids can be classified after assessing this dikyzonotic
region.
Keywords: Conomurex, diktyzonos, Hybrid, Species.
INTRODUCTION
In this paper I present a putative hybridisation event in the family Strombidae. While hybrids
fall outside the rules that govern the zoological code for nomenclature [1]; notwithstanding, it
is often worth providing a name as a reference marker rather than for placement at any nominal
taxonomic rank. Not all hybrids should be considered taxonomically valid to be recognised
within the nomenclature, and in terms of circumscribing taxa the assessment of hybrids needs
to be considered carefully [2].
In clades where there is evidence for strong hybridisation in extant taxa, these hybrids will
generate a plethora of forms and varieties in the clade, each of which may indicate processes of
reticulation, where two species are introgressing, and/or speciating, or may just be indicators
of random mating events. While three forms of hybridisation are well recognised in the
literature among a diverse set of organisms, these have not been delineated or defined. To
address this, I propose the following terms (Figure 1): 1) true hybrids, which are isolated
examples of the congruence of two species and not viable; 2) reticulatory hybrids, that are
evidence of the merging of two species; and 3) diversificatory hybrids, which are the product of
hybridisation between two species that results in a new species being formed. The question
then is, when is a hybrid to be recognised in the literature as a new species? I suggest that it is
diversifacatory hybrids, where the hybrid population has established a permanent presence
alongside parental stock giving rise to a new taxonomic entity, which should be given
taxonomic status within the nomenclature [2-8].
Therefore, there also needs to be an understanding of the potential role of hybridisation when
seeking to understand the evolution of a set of organisms. Is the hybridisation a random
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infertile mating event? Do the hybrids represent the reticulation of two species? Or is the
hybridisation the birth of a new species? One way to answer these questions is to visualise the
hybrids in terms of the diktyzonos the parental and hybrid taxa fill [2; Figure 2). A diktyzonos is
the region in which a set of organisms are morphologically bound, and contains all the
phenotypic variability that the organism exhibits. The classification of hybrids into distinct
classes, each of which has a potential differing outcome for the understanding of hybrids in the
evolution of a set of organisms enables a robust understanding of how hybrids are affecting
current evolutionary trends. This is particularly important when considering taxa which have
a high propensity to hybridise and the morphological variability of the resulting hybrids. In
populations where there is a high degree of variability in the hybrid offspring, and the hybrids
differ in the morphological characters they express leading to some tendency to favour the
morphology of either parent, the diktyzonos between the two parental stock tends to become
blurred. In contrast, where there is low variability in the morphospace occupied by hybrids and
they form and cluster somewhere between the parental stock, this gives rise to three distinct
regions of clustered organisms with differing morphological characteristic, and may lead the
taxonomist to infer that there are three regions of diktyzonism and an inference that there are
three species within the morphospace.
METHODS
This paper is based on morphological comparison of the putative hybrid with type material of
each putative parent, and other regional forms. The morphological characteristics include the
columella, aperture and structures such as the anterior canal. The hybrid material used in this
study was obtained from the collection of Messrs Bradfield, who collected during the last
century while yachting. Comparative material was obtained from fisherman and dealers who
legally obtained the material with appropriate permits.
The putative Conomurex hybrid between C. decorus (Linné, 1758) and C. luhuanus (Röding
1798) is only known from a single example, and there is no evidence to suggest at present that
a population with the characteristics of the putative hybrid has established, thus currently
invalidating it for species consideration [2].
SYSTEMATIC PART
Conomurex Fischer, 1884
Type Species: Strombus luhuanus Linné, 1758, p. 744, no. 432 [9, p. 670], by monotypy.
Original Description: “5° Conomurex, Bayle.1884, Labre non dilaté; coquille conique; spire
courte (S. luhuanus, Linné)” [9, p. 670].
Supplementary Diagnosis: The shell of this genus is cone shaped, with a blunted spire and a
long narrow aperture. The outer lip is not dilated and runs parallel to the inner body whorl. The
spire is rarely with varices.
Remarks: The genus Conomurex is a widely distributed Indo-Pacific genus, with one Lessepsian
migrant, or possibly introduced, member found in the Mediterranean [10]. Two taxa from
which the hybrid is derived can be found converging in Indonesia [11]. At present there is only
Pacific Ocean species C. luhuanus and the Indian Ocean C. decorus from that region described.
The exact distribution of these Conomurex taxa in Indonesia in not known at this time.
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Maxwell, S. J. (2022). A New Putative Hybrid in Conomurex Fischer, 1884 (Mollusca, Neostromboidae, Strombidae) with Notes on the Types of
Hybrids. European Journal of Applied Sciences, 10(1). 401-408.
URL: http://dx.doi.org/10.14738/aivp.101.11714
Conomurex decorus (Röding, 1798)
Figures 3A-C
Type Material: Lectotype – Chemnitz [12] Conchylien Cabinet, volume 10, Fig. 1499-1500 [13
p. 62, no. 777].
Type Locality: Mauritius (designated by Abbott [11]).
Original Description. “Die zierliche Flügel Schnecke, Gmel. Strombus luhuanus. sp.16 γ” [13, p.
62].
Supplementary Description. Shell “solid, heavy, somewhat conic in shape... . Whorls 9-10.
Teleoconch usually moderately raised, rarely high, rarely low. Nuclear whorls 3, glossy, smooth,
rounded. First three postnuclear whorls with 7 to 9 microscopic, incised spiral lines crossing
numerous, small axial riblets, about 24 per whorl. Top of teleoconch with 6 to 8 small, whitish,
rounded, swollen former varices. Whorls rounded in the teleoconch and, in the penultimate
whorl, bearing 14 to16 small, well-rounded axial ribs or knobs, The last whorl may be
smoothish at the shoulder or bear 4 to 6 prominent knobs. Base of shell smoothish. Columella
callus very thin...Interior of aperture light-orange to rose, with a broad white border. Inner wall
of body whorl with exceedingly fine, numerous spiral threads. Stromboidal notch moderately
deep. Posterior siphonal notch moderately developed and bordered above by a ... tongue-like
flap which is adherent to the previous whorl” [11, pp. 137-138].
Distribution: Literary Records – Indian Ocean [14]. India: Port Blair [15]. Thailand: Phuket,
Bay of Bengal [16]. Indonesia: Poelau Berhala, Sumatra [11]; off Deli, Sumatra [11]. Myanmar:
Mergui Archipelago [11].
Remark: The broad white border on the interior of the labrum is distinctive of this species.
Further, the anterior canal is almost straight whereas in C. luhuanus it is bends to the right.
Conomurex luhuanus (Linné, 1758)
Figures 3E-I
Type Material: Syntypes – Linnean Society of London Collection: LSL 430.
Type Locality: Luhu Island, Indonesia (restricted by Abbott [11]).
Original Description: “432. S. testæ labro prominulo, dorso lævi, anfractibus rotundatis
æqualibus” [17, p. 744]
Supplementary Diagnosis: Shell “solid, well shouldered, conic, with a black columella and
orange-red aperture. ... Whorls 8 or 9. Nuclear whorls three, bulimoid, glossy, smooth ... . First
postnuclear whorl with 15-18 microscopic spiral threads which are axially crossed by much
smaller scratches. In later whorls numerous fine, axial riblets develop. Teleoconch with 8-10
small ... swollen, former varices. After the fourth postnuclear whorls (sic), the rounded shoulder
has about 20 short, even-sized, well-rounded, ribs per whorl. These disappear on the last whorl.
Base of shell with about 2 dozen obsolete spiral threads. Interior of body whorl with about 100
very fine spiral striae which do not reach the edge of the sharp outer lip. Basal sinus usually
well-developed. A similar notch occurs at the shoulder, a little below the well-indented, almost
channeled, suture. Columella smooth, glossy... but poorly developed” [11, pp. 135-136].
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Distribution: Indian Ocean [14]. Indonesia: Ambon [14]; Banka [14]; Tjilatjap, Java [14];
Wagéoe [14]; Batjan [14]; Bouro Island, Molluccas [11]; Roti Island, Timor [11, 14]; Wodo
Island, Halmahera [11]; Poeloe Boeton, Celebes [11]; Dutch New Guinea [11]; Bunguran Island,
Natuna Besar Islands [18]; Ansus Island [19]; Jobi [19]; Aru [19]; Kei Bandan [19]; Sorong [19].
Remark: This species is easily identified by the strawberry red aperture in combination with
the black stripe on the columella.
Conomurex decorus (Röding, 1798) x Conomurex luhuanus (Linné, 1758)
Figures 3D
Material: Panjang Island, Lampas, Indonesia, 1990.
Description: Shell solid and conic with a distinctive shoulder and smooth body whorl. Spire
moderately depressed, smooth and rounded. The columella is not well developed and smooth
with black colouration. The inner aperture is reddish and the outer aperture white toward the
border. The outer lip is thicker posteriorly, becoming thin and sharp after the stromboidian
sinus. Further it has the bend anterior canal similar to C. luhuanus, not the straight as in C.
decorus.
Remarks: The shell has the aperture colouration of C. decorus, and is similar in form to that
species from Malaysia (Figure 3A). However, the shell as the distinctive black columella of C.
luhuanus. Other than colouration of the aperture and columella, the who putative parents C.
decorus and C. luhuanus, are difficult to split morphologically. However, as you move away from
the Indonesian archipelago and associated central coral triangle, the two species start to form
distinctive morphological kinds, that may be recognised as species in time. This is the first
reported putative hybrid within Conomurex [2], the other hybrid is intergeneric between C.
decorus and Gibberulus gibberulus (Linné, 1758) [10].
DISCUSSION
Mapping hybridisation across a phylogeny will enable a more accurate assessment of the
reticulatory potential between species and facilitate a more compressive understating of the
relationships between reticulation-driven speciation reflected in the fossil taxa. This will also
enable the distinguishment of new species, with narrow diversicatory diktyzonotic parameters,
from a broader diktyzonos of true hybrids between the putative parental stock, or those that
are undergoing a process of reticulation with a broad spread of hybrid forms without a region
of morphologically stable clustering.
When undertaking a systematic revision into a set of organisms, it is imperative that
consideration is given to the representative taxa in the fossil record to identify diktyzonotic
regions, and also determine the form of hybridisation. Failure to include hybridisation in
speciation modelling for a set of organisms will potentially have a negative impact on the
determination of a phylogeny because of the consequence of trickle-down discordance. When
seeking to estimate the potential impact of hybridisation on a phylogeny, it is worth examining
descendant extant taxa to determine the current level of hybridisation across a clade. Thus,
there is a necessity to consider the reticulatory potential of a set of organisms when defining
clades, and also in the determination of their phylogenetic internal resolution.
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Maxwell, S. J. (2022). A New Putative Hybrid in Conomurex Fischer, 1884 (Mollusca, Neostromboidae, Strombidae) with Notes on the Types of
Hybrids. European Journal of Applied Sciences, 10(1). 401-408.
URL: http://dx.doi.org/10.14738/aivp.101.11714
CONCLUSION
This paper provides the first example of intragenetic hybridisation in Conomurex from
Indonesia. This organism is an illustration of a single putative hybrid that lacks the physical
evidence to support recognition as a species and which does not form part of a diktyzonotic
morphological zone. It is therefore considered a true hybrid. The three forms of hybridisation
that are defined herein provide a classificational framework that enables taxonomists to assess
the status of a set of hybrid organisms with the goal of determining if the hybrids warrant
recognition in the nomenclature.
References
[1]. International Commission on Zoological Nomenclature (ICZN). International Code of Zoological
Nomenclature. The International Trust for Zoological Nomenclature, London, 1999.
[2]. Maxwell, S.J., et al., The birth of a species and the validity of hybrid nomenclature demonstrated with a revision
of hybrid taxa within Strombidae (Neostromboidae). Proceedings of the Biological Society of Washington, 2019.
132(1): 119-130.
[3]. Grant, B.R. and P.R. Grant, Evolution of Darwin’s finches caused by a rare climatic event. Proceedings of the
Royal Society of London, 1993. 251(1331): 111-117.
[4]. Grant, B.R. and P.R. Grant, High survival of Darwin’s finch hybrids: Effects of beak morphology and diets.
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[5]. Kraak, S.B.M., B. Mundwiler, and P.J.B. Hart, Increased number of hybrids between benthic and limnetic three- spined sticklebacks in Enos Lake, Canada; the collapse of a species pair? Journal of Fish Biology, 2001. 58: 1458-
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[6]. Lamont, B.B., et al., Anthropogenic disturbance promotes hybridization between Banksia species by altering
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[8]. Mercaderm, R.J., et al., Dispersal of emerald ash borer, Agrilum planipennsis, in newly colonized sites.
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[9]. Fischer, P., Manuel de conchyliologie et de paléontologie conchyliologique, ou histoire naturelle des mollusques
vivants et fossiles suivi d'un Appendice sur les Brachiopodes par D. P. Oehlert. Avec 23 planches contenant 600
figures dessinées par S. P. Woodward. F. Savy, Paris, 1884. 8: 689-784.
[10]. Dekkers, A.M. and S.J. Maxwell, A putative inter-generic hybrid between Conomurex Fischer and Gibberulus
Josseaume (Gastropods: Strombidae) from South Africa. The Festivus, 2018. 50(3): 158-163.
[11]. Abbott, R.T., The genus Strombus in the Indo Pacific. Indo-Pacific Mollusca, 1960, 1: 35-146.
[12]. Chemnitz, J.H., Neues Systematisches Conchylien Cabinet, X. Nurnberg, Germany, 1788. 31 pp.
[13]. Röding, P.F., Museum Boltenianum sive Catalogus Cimeliorum e Tribus Regnis Naturæ quæ Olium Collegerat
Jon. Fried Bolten, M.D.p.d. per X: Pars Secunda Continens Conchylia sive Testacea Univalvia, Bivalvia and
Multivalvia. Typis Johan. Christi. Trappii; Hamburgi, Germany, 1798. 199 pp.
[14]. Horst, R. and M.M. Schepman, Catalogue Systématique des Mollusques (Gatsropodes Prosobranches et
Polyplacophores). Muséum d’Histoire Naturelle des Pays-Bas, 1908. 13: 1-176.
[15]. Melvill, J.C. and E.R. Sykes, Notes on a second collection of marine shells from the Andaman Islands, with
descriptions of new forms of Terebra. Journal of Molluscan Studies, 1897. 3(1): 35-48.
[16]. Tantanasiriwong, R., An illustrated checklist of marine shelled gastropods from Phuket Island, adjacent
mainland and offshore islands, Western Peninsular Thailand. PMBC Research Bulletin, 1978. 21: 1-22.
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[17]. Linné, C., Systema Naturae per Regna Tria Naturae Secundum Classes, Ordines, Genera, Species, cum
Caracteribus, Differentiis, Synonymis, Locis, 10th edn. Volume 1. Reformata. Laurentii Salvii, Holmiae, 1758. 824
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[18]. Mudjiono, N., Telaah komunitas moluska di rataan terumbu (reef flat) perairan Kepulanuan Natura Besar,
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[19]. Tapparone-Canefri, C.M., Contribuzioni per una fauna malacologica della Isole Papuane. III. Molluschi della
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Zoobank registration: urn:lsid:zoobank.org:act:1CF037ED-D555-462B-BADF-82A3D54BA46C
Figure 1: The diktyzonotic regions of reticulation within a species, and which occurs between
species leading to three forms of hybridisation: A) true hybrids, which are sporadic infertile
outcomes of the mating of two taxa; B) reticulatory hybrids, which are generated when two
species come together and generate viable offspring that then cause the merging of the two
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Maxwell, S. J. (2022). A New Putative Hybrid in Conomurex Fischer, 1884 (Mollusca, Neostromboidae, Strombidae) with Notes on the Types of
Hybrids. European Journal of Applied Sciences, 10(1). 401-408.
URL: http://dx.doi.org/10.14738/aivp.101.11714
parental taxa; and C) diversifactory hybrids, where two species hybridise and produce viable
offspring that then form a taxon (c-us) that is distinguishable from both of the parental taxa
Figure 2: The two forms of expressed hybridisation between species: level of high variability
with a large diktyzonotic region which may blur the character set limits for each of the parental
taxa; and low variability hybrids which may lead the taxonomist to concur that there are three
distinct regions of diktyzonism indicating that there may three species, and a test of
establishment needs to be considered to determine if a speciation event has occurred
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Figure 3: A study in Conomurex [shown to scale]: Variations of C. decorus (Röding, 1798): A –
Palau Pangkora, Malaysia, 1974, 61 mm (SMC 45.003); B – Nacala Bay, Mozambique, 2000, 31
mm (SMC 43.006); C – Mauritius, 1980, 47 mm (SMC 43.002); The C. luhuanus (Linné, 1758) x C.
decorus (Röding, 1798) hybrid: D – Panjang Island, Lampas, Indonesia, 2000, 52 mm (SMC
47.027); Variations in form and colour of C. luhuanus (Linné, 1758): E – Balicasag Island,
Philippines, 2015, 60 mm (SMC 47.040); F – Medang, Papua New Guinea, 39 mm (SMC 47.030);
G – Tokunoshima, Japan, 2008, 58 mm (SMC 47.028); H – Coolgaree Bay, Queensland, 50 mm
(SMC 47.026); I – Cebu Island, Philippines, 46 mm (SMC 47.029)